Patent Application
20180055969
The invention relates to synthetic bone grafts and their use in bone regeneration. More particular, the invention shows how a biphasic ceramic bone substitute can act as a carrier of both a bone active protein that can induce and/or stimulate bone growth, e.g. bone morphogenic proteins (BMP), and an anti-catabolic drug, e.g. a bisphosphonate, thereby being inductive and useful in improved active bone regeneration.
Fracture healing and bone remodeling can be seen as a form of tissue regeneration, and living bone is subject to constant remodeling with a complete turnover of bone mass in adults every 4-20 years. Bone remodeling is a cycle involving the 4 phases: activation, resorption, reversal and formation. Activation is probably started by the death or reformation of osteoclasts around a fracture or bone malignancy which recruit and induce new osteoclasts to start resorption of dead bone. After some time, resorption slows down and osteoblasts are recruited and activated in the reversal phase. Activated osteoblasts adhere to the surface after resorption of dead bone and start to produce new bone matrix-osteoid tissue, followed by a mineralization of the matrix. The action of the different bone cell types and their activators and inhibitors is balanced in a sensitive way normally leading to replacement of dead or fractured bone over time.
Restoration of serious bone defects such as loss of bone due to, i.a. trauma, eradication of infection, resection of tumor lesions, nonunion surgery and in primary or revision arthroplasties bone healing is often supported by surgical intervention where new bone formation is supported and accelerated, for example by use of bone grafts.
Autologous bone grafts are the ideal choice, because living cells and proteins within the graft is capable of inducing osteogenesis, i.e. de novo synthesis of bone. However, a limited supply and the risk of donor site morbidity after harvesting fresh bone have led to the use of bone allografts instead (for example bone from femoral heads resected at primary arthroplasty). Bone allografts, i.e. dead bone from subjects of the same species, which function as an osteoconductive scaffold are limited in supply and furthermore present a potential risk of inducing blood-born diseases, and even prohibited in some ethnical groups.
In several animal studies using cancellous bone grafts, the speed of remodeling and the volume of remodeled graft/substitute were found to be increased by bone morphogenic proteins (BMP), but most of the newly formed bone formed by BMP driven osteoinduction was resorbed almost as fast as formed. The reason for the resorption of the newly formed bone appears to be BMP activation of the Rank ligand system with enhanced recruitment of osteoclasts leading to premature catabolism. In clinical studies, the premature catabolism has led to loss of fixation in fractures, premature allograft resorption and failure and loosening in hip revision arthroplasty (Nicole Y. C. Yu, Aron Schindler, Magnus Tagil, Andrew J. Ruys, David G. Little. Frontiers in Bioscience E4, 2647-2653, Jun. 1, 2012).
Bisphosphonates is a group of anti-catabolic drugs that inhibit bone resorption and they are clinically used in prevention and treatment of i.a. osteoporosis and bone metastases. Intravenously or orally administered bisphosphonates target and bind to bone mineral and such systemic applied bisphosphonates thus mainly accumulate in areas of active bone remodeling. During osteoclastic resorption, bisphosphonates bound to bone mineral are released and internalized in the osteoclasts followed by apoptosis of these cells. In animal studies, it has been shown that bisphosphonates applied intravenously or locally may inhibit resorption of newly formed bone induced by autografts or a combination of allografts and BMP (Yu et al. ibis). Toshihiko Nishisho et al. have disclosed a local administration of zoledronic acid together with artificial bone (hydroxyapatite or β-tricalcium) in the treatment of giant cell tumor of bone (Orthopedics Vol. 38, Issue 1: e25-e30 (2015).
During the last decade, large bone defects have been treated with artificial grafts such as biomaterials that act as osteoconductive bone substitutes (Oryan A, Alidadi S, Moshiri A, Maffulli N. Bone regenerative medicine: classic options, novel strategies, and future directions. Journal of orthopaedic surgery and research. 2014; 9:18). These materials are polymeric, ceramic or of composite nature (Habibovic P, de Groot K. Osteoinductive biomaterials—properties and relevance in bone repair. Journal of tissue engineering and regenerative medicine. 2007; 1:25-32).
Other studies in bone tissue engineering involve incorporation of bone active proteins like bone morphogenic proteins (BMPs) and anti-catabolic drugs like bisphosphonates in porous polymers, sugar based high viscosity carriers or collagen. WO 2012/094708 discloses incorporation of BMP alone or combined with zoledronic acid (ZA) in biodegradable or biocompatible polymers. Hydroxyapatite may be doped with ZA and incorporated into the polymer when formed. WO 2014/032099 discloses compositions comprising a sugar based high viscosity carrier, BMP, bisphosphonate and optionally hydroxyapatite. Murphy C M, Schindeler A, Gleeson J P, Yu N Y C, Cantrill L C, Mikulec K, et al. Acta Biomaterialia. 2014; 10:2250-8, discloses a collagen-hydroxyapatite scaffold which allows binding and co-delivery of recombinant BMPs and bisphosphonates. Studies involving a combination of BMP and bisphosphonates with carriers such as allografts or porous polymers have shown more or less synergistic results between BMP and the bisphosphonate. The polymers are pre-made standard products produced prior to insertion in a patient and therefore not easily adaptable for effectively use in filling individual bone voids for an efficient regeneration of bone without leaving empty spaces, which increases the risk of infection. The polymers are neither osteoconductive nor osteoinductive per se and therefore do not take active part in bone regeneration.
Injectable biphasic ceramic bone substitutes with the capability of being hardened in vivo to act as a synthetic graft, comprising a resorbable calcium sulphate hemihydrate component and a stable calcium phosphate component, such as for example hydroxyapatite, have been developed over the last years, for example by the Swedish company Bone Support AB (see: EP 1301219, EP 1465678, EP 1601387, EP 1829565, WO 2011/098438; WO 2014/128217). These publications suggest that the bone substitutes may contain an additive taken from a long list of biologically active agents. The list includes among others antibiotics, bone active proteins like bone morphogenic proteins (BMPs) and bisphosphonate. However, only antibiotics have so far been included in commercial bone substitutes. Bone Support AB has the three biphasic ceramic products on the market: CERAMENT™ IBONE VOID FILLER, CERAMENT™ ISPINE SUPPORT and CERAMENT™ IG (CERAMENT™ with gentamicin), and a fourth product, CERAMENT™ IV (CERAMENT™ with vancomycin) is now CE approved and ready for launch.
Despite the many promising results in the use of more or less osteoconductive bone substitutes, an osteoinductive bone substitutes that could speed up the bone regeneration would be highly desirable.
In the present invention, bone active protein(s) and anti-catabolic agent(s) are delivered together in an improved bone substitute to the bone defects by an osteoconductive carrier composed of a biphasic cement/ceramic material comprising at least one phase containing an anabolic agent that provides an initial microporosity and mechanical stability, and is resorbed in vivo, and at least one other phase that is stable and only slowly remodeled in vivo and preferably has as high affinity for an anti-catabolic agent.
The carrier material by itself is mainly osteoconductive, but the microporous and fast resorbable phase provides a controlled delivery of various added therapeutic agents and increases the macro porosity of the material allowing a fast ingrowth of new bone cells induced by bone growth factors, while the stable phase with its closely bound anti-catabolic agent is very slowly remodeled by new bone cells intruding through the porous material, whereby the anti-catabolic agent is slowly released over time and thus provides an ongoing local balancing of fast bone growth and resorption of new bone for the benefit of a formation of more dense and strong new bone.
The biphasic ceramic bone substitute according to one embodiment of the present invention, i.e. the ceramic material in a set state, comprises a) a calcium sulphate phase; b) a calcium phosphate phase; c) at least one bone active protein; and d) at least one anti-catabolic agent. The at least one bone active protein is preferably present in the fast resorbable calcium sulphate phase and the at least one anti-catabolic agent is preferably present in the stable calcium phosphate phase. The anti-catabolic agent is preferably an agent that inhibits bone resorption and has an affinity for the calcium phosphate.
The calcium sulphate phase preferably consists essentially of calcium sulphate dihydrate (CSD), also known as Gypsum. Needle-shaped calcium sulphate dihydrate particles are formed when calcium sulphate hemihydrate (CSH), also known as plaster of Paris, is reacted with water and the resulting CSD needles interlock to create a solid CSD matrix with a microporosity of about 20-40%. CSD is relative soluble in water and body fluids and therefore relatively quickly dissolved and fully resorbed in the body (within 6-12 weeks). Until being dissolved, the calcium sulphate phase provides a desirable mechanical strength to the bone support, which is often crucial for stability of the artificial graft after being implanted in the patient and for the hydroxyapatite particles not to migrate. In the process of CSD being dissolved and resorbed, the micropores are gradually enlarged in the bone substitute to form a matrix allowing stem cells (e.g. mesenchymal progenitor cells), activated osteoblasts, extracellular matrix (ECM) proteins and other bone cells to migrate from the lining between bone, bone marrow and the bone substitute deeper into the bone substitute, where new bone formation and remodeling can take place. The properties of calcium sulphate phase thus allow a progressive ingrowth of bone cells in the ceramic bone substitute while maintaining mechanical stability until newly formed bone secure mechanical stability.
In an embodiment of the present invention, the solid CSD is formed in a setting process, where calcium sulphate hemihydrate powder is mixed with water. Often it is necessary to add an accelerator for the process to occur within a desired and controllable time. If the substitute is to be injected or otherwise applied in liquid form (e.g. as a paste), for example in an in vivo treatment, a convenient setting time is between 10 and 30 minutes. As accelerant may be used calcium sulphate dihydrate or saline (NaCl solution).
The bone active proteins, and other bioactive agents if present (e.g. antibiotics), are preferably placed in and thus released from the calcium sulphate phase through the micropores of the calcium sulphate phase upon contact with body fluids. The fast release of the active agents after implantation in the patient leads to an initial high local concentration of bone active proteins and optionally other bone active factors in the bone substitute matrix and vicinity shortly after implantation, resulting in a strong initial stimulation of bone cell activation and growth.
In one embodiment of the invention, the bone active proteins and optionally any other bioactive agents are pre-mixed with the CSH powder prior to mixing with the calcium phosphate and liquid. In another embodiment, the bone active proteins and optionally any other bioactive agents are pre-mixed with the liquid before being mixed with the calcium sulphate and calcium phosphate. In a further embodiment the bone active proteins and optionally any other bioactive agents are pre-mixed with the calcium phosphate prior to mixing with the calcium sulphate and liquid. In yet another embodiment the bone active proteins and optionally any other bioactive agents are mixed with the paste right after mixing the calcium sulphate powder and the calcium phosphate powder with the liquid in a process known as “delayed mixing” (see WO 2011/098438). The latter may be relevant if the bone active proteins and optionally any other bioactive agents are disturbing the setting or setting time, for example if the setting time becomes too long for use in surgery of a patient. In any mixing event, the bone active proteins and optionally any other bioactive agents will preferably end up in the calcium sulphate phase in the biphasic ceramic bone substitute of the present invention.
The calcium sulphate phase of the biphasic ceramic bone substitute of the present invention provides a unique carrier and delivery matrix for the bone active proteins, both allowing a controlled but relatively fast release of the bone active proteins and at the same time creating a beneficial porosity for fast bone cell ingrowth together with initial mechanical stability.
The calcium phosphate phase preferably consists essentially of calcium phosphate ceramics selected from the group consisting of α-tricalcium phosphate, hydroxyapatite, tetracalcium phosphate and β-tricalcium phosphate (see EP 1 301 219 which is hereby incorporated by reference). A mixture of different calcium phosphate ceramics may be applied if desired.
The calcium phosphate phase consists of amorphous and/or crystalline calcium phosphate particles. The particle size is preferably less than 200 μm, such as less than 100 μm, less than 50 μm, less than 35, less than 20 μm or less than 10 μm. (preferable between 0.1 and 50 μm). In one embodiment, the calcium phosphate is provided as calcium phosphate particles (e.g. sintered hydroxyapatite particles) to be mixed with the calcium sulphate powder and water for the calcium sulphate to set, whereby the calcium phosphate particles becomes embedding in the calcium sulphate phase after setting. In another embodiment, the calcium phosphate is provided as a hardenable calcium phosphate powder prepared for a setting reaction to form calcium phosphate cement upon mixing with water (see EP 1 301 219, which is hereby incorporated by reference). The setting reaction of calcium phosphate may be accelerated by particulate calcium phosphate or a phosphate salt, for example disodium hydrogen phosphate (Na2HPO4).
In one particular embodiment of the present invention, the calcium phosphate phase consists essentially of hydroxyapatite particles. The hydroxyapatite particles may be in an amorphous or crystalline state. In a preferred embodiment the calcium phosphate phase consists essential of sintered crystalline hydroxyapatite particles. In one embodiment, the sintered crystalline hydroxyapatite particles are prepared in accordance with the method disclosed in WO 2014/128217 (hereby incorporated by reference), where sintered crystalline hydroxyapatite particles are inactivated by heating leading to improved setting properties of the calcium sulphate phase in a biphasic ceramic composition comprising crystalline hydroxyapatite and calcium sulphate. This is preferable when the composition comprises additional agents such as antibiotics.
In one embodiment of the present invention, the bone active proteins useful in the biphasic ceramic bone substitute of the invention are anabolic factors active in bone formation, i.e. preferably bone growth proteins selected from the group comprising bone morphogenic proteins (BMPs), insulin-like growth factors (IGFs), transforming growth factor-βs (TGFβs), parathyroid hormone (PTH), sclerostine, and the like. The bone active proteins may also be provided in the form of a composition comprising cell factory-derived bone active proteins, and ECM proteins (WO 2008/041909). Alternatively strontium as a bone growth factor may be used in addition to or as a substitute of the bone active proteins.
In a preferred embodiment, the bone active protein could be bone growth proteins selected from the long list of BMPs, but most preferably BMP-2 or BMP-7 or a combination thereof. BMPs may be isolated from donor cells (e.g. from a bone cell factory) or prepared recombinantly. For human patients recombinant human BMPs, such as rhBMP-2 or rhBMP-7 are preferably used. rhBMPs are commercially available or may be produced by known techniques.
Bone active proteins may be provided as such and added to any of the powders, the aqueous liquid or the paste. Alternatively, the bone active proteins may be encapsulated in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like before use. Encapsulated active additives have the advantage of being protected during storage and mixing in addition to the possibility of being prepared well in advance before use. The encapsulated active additives may be released before or in the paste or during dissolution and resorption of the calcium sulphate phase.
In another embodiment of the present invention, the anti-catabolic agents useful in the biphasic ceramic bone substitute of the present invention are agents which inhibit bone resorption. Examples of inhibitors with bone resorption properties are bisphosphonates, selective estrogen receptor modulators (SERM) (e.g. raloxifene, tamoxifen, lasofoxifene and bazedoxifene); denosumab (a monoclonal antibody against RANKL developed by Amgen) and statins. In case no active binding takes place to the hydroxyapatite, a slow delivery system with encapsulation of the agent is preferable.
In a preferred embodiment the anti-catabolic agent is a bisphosphonate. The bisphosphonates have a strong affinity for bone minerals, i.e. calcium phosphates such as hydroxyapatite, and they can be divided into simple bisphosphonates (e.g. etidronate) and nitrogen-containing bisphosphonates (e.g. alendronate and zoledronate). The potency of the different bisphosphonates should be considered when selecting a bisphosphonate for use in the biphasic ceramic bone substitute according to the present invention. Alendronate is 10-100 times more potent than etidronate and zoledronate up to 10.000 times more potent than etidronate.
Bisphosphonates target and bind to bone mineral due to their molecular structure and their ability to chelate calcium ions. Due to their strong affinity to minerals in bone, they accumulate in areas of active remodeling and minimally to other cell types and they practically remain bound until they are released during bone resorption where they are internalized in osteoclasts. However, as the bisphosphonates are toxic to osteoclasts, these go into apoptosis whereby the bone resorption is inhibited or sustained.
The calcium phosphate phase of the biphasic ceramic bone substitute of the present invention provides a unique carrier and delivery matrix for the anti-catabolic agents, preferably bisphosphonates, both allowing a controlled and slow release of the agents at the same rate as newly formed bone cells are created and differentiated into osteoclast, i.a. as a result of BMP activation, and at the same time forming a stable matrix which is very slowly resorbed (4-12 months) or incorporated into the newly formed bone after the calcium sulphate has been resorbed. Compared to some of the known polymeric carriers, the calcium phosphate phase will be resorbed or incorporated as a natural mineral over time, leaving no artificial polymer in the patient. The anti-catabolic agents (e.g. bisphosphonates) present in the biphasic ceramic bone substitute according to the present invention suppress premature resorption of newly formed bone by osteoclasts in and connected to the biphasic bone substitute at a pace following the ingrowth of new bone, because the anti-catabolic agents bound to the calcium phosphate particles in the matrix becomes exposed as a consequence of dissolution and resorption of the calcium sulphate phase. Newly formed bone cells thus meet the anti-catabolic agent when expanding into the matrix from the graft being inserted in the bone defect until and beyond full mineralization of the newly formed bone. The suppression of premature resorption leads to a more dense formation and mineralization of new bone as seen in an animal muscle model and will help cure patients with bone defects in a better and faster time than previously seen. The whole or part of the calcium phosphate may be pretreated with bisphosphonate and thereby bound for an optimal balance and bone ingrowth starting immediately but extending over a longer period of 12-24 months
While known polymeric carriers may only comprise a small amount of hydroxyapatite (2% (w/v) in WO 2012/094708 and 1-5% (w/v) in WO 2014/032099), the biphasic ceramic carrier of the present invention may comprise up to about 95% (w/w) calcium phosphate (e.g. hydroxyapatite) (about 40% hydroxyapatite in the Cerament™ products on the market), thus allowing the bisphosphonates to be dispersed at a much higher density in the carrier of the present invention. The higher density secures a more effective local inhibition of bone cell resorption by intruding osteoclasts, leaving the scene to the osteoblasts. Furthermore, while only some polymers provide a mechanical support and none of the polymers are ideal as bone grafts as they are not very osteoconductive, the biphasic ceramic bone substitute carrier (e.g. a Cerament™ product) used in the present invention is microporous, mechanical supportive, osteoconductive and osteoinductive. Porous polymers which provide mechanical support, e.g. poly((lactic-co-glycolic) acid) (see WO 2012/094708), require solvents and/or temperatures or has an exothermic polymerization process that make them unsuited for in vivo polymerization and thus insertion by injection. Injectable polymers, e.g. sugar based high viscosity polymers (see WO 2014/032099) provide low porosity and no mechanical support.
The anti-catabolic agent may be provided as a powder or solution and/or may be encapsulated in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like. Encapsulated active additives have the advantage of being protected during storage and mixing in addition to the possibility of being prepared and stored well in advance before use. When added as an encapsulated ingredient, bisphosphonates are released from their encapsulation and bound to the neighboring calcium phosphate particles, such as for example when the encapsulations are contacted with water, for example when preparing the paste or in vivo when body fluids get access to the capsulations. The anti-catabolic agent and the bone active protein may be provided in the same or different encapsulations.
In an embodiment of the present invention, the biphasic ceramic bone substitute further comprises one or more additional bioactive agent selected from antibiotics (including antifungal drugs), bone healing promotors, chemotherapeutics, cytostatics, vitamins, hormones, bone marrow aspirate, platelet rich plasma and demineralized bone. In a preferred embodiment, the biphasic ceramic bone substitute comprises one or more antibiotics (e.g. gentamicin and/or vancomycin). The additional bioactive agent(s) may be mixed with the calcium sulphate powder, the calcium phosphate powder/particles or with the liquid, or may be mixed with the paste comprising the calcium sulphate powder, the calcium phosphate powder/particles and the liquid in a delayed mixing process as has described above. Also the additional bioactive agents may be encapsulated in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like. The additional bioactive agent(s) may be provided in the same or different encapsulations optionally together with the anti-catabolic agent and/or the bone active protein and released before or in the paste or by in vivo contact with body fluids.
In yet another embodiment of the present invention, the biphasic ceramic bone substitute also comprises an X-ray contrast agent selected from water soluble non-ionic X-ray contrast agents (e.g. iohexol) and/or biodegradable X-ray contrast agents. The X-ray contrast agent may be mixed with the calcium sulphate powder, the calcium phosphate powder, other additives or with the liquid, or may be mixed with the paste comprising the calcium sulphate powder, the calcium phosphate powder and the liquid in a delayed mixing process as described above. X-ray contrast agents may also be encapsulated in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like, if desirable. The X-ray agent(s) may be provided in the same or different encapsulations optionally with the anti-catabolic agent and/or the bone active protein and/or other additives and released before or in the paste. A premixed X-ray solution comprising iodine (iohexol) for enhancing x-ray capacity ready for mixing with ceramic powders is available from BONESUPPORT AB under the trade name CERAMENT™ IC-TRU.
In a specific embodiment of the present invention biphasic ceramic materials from BONESUPPORT AB, such as CERAMENT™ I BONE VOID FILLER, CERAMENT™ I SPINE SUPPORTCERAMENT™ IG and CERAMENT™ IV may act as a carrier for bone active agent(s) like bone morphogenic proteins (BMPs) and anti-catabolic agent(s) like bisphosphonates. Table 1 shows the content of commercial Cerament™ products. It has been demonstrated in the present invention that the hydroxyapatite present in the Cerament™ products can act osteoinductive on stem cells and that it has a low immunogenicity.
For the purpose of the present text, “Cerament™ products” means one or more of the powder compositions present in CERAMENT™ I BONE VOID FILLER, CERAMENT™ I SPINE SUPPORT, CERAMENT™ IG and CERAMENT™ IV and denoted CERAMENT™ IBVF or CERAMENT™ BVF or Cerament™ BVF; CERAMENT™ SS or Cerament™ SS; CERAMENT™ G or Cerament™ G; and CERAMENT™ V or Cerament™ V, respectively. Pastes and set solid bone support produced from these powder compositions by mixing with a liquid may be mentioned by the same names throughout the text. The state and content of a “Cerament™ product” will be clear from the context.
It has been shown that high initial release of bone active proteins (e.g. BMP-2) and a sustained release of bisphosphonates (e.g. ZA) from Cerament™ products makes it an excellent carrier platform. The initial high release of bone active proteins as seen in-vitro is attributed to the biphasic material with resorbable calcium sulphate and initial microporosity. The increased availability of such proteins to the inducible cells leads to early onset of differentiation that in turn can provide accelerated bone growth. In contrast, the sustained but low release of bisphosphonates from the carrier platform seen in-vitro is caused by strong binding of bisphosphonates to the surface of the calcium phosphate (e.g. hydroxyapatite) particles. The sustained release and exposure of bisphosphonates to new bone cells inhibits premature resorption of newly formed bone and thus allows maturation and mineralization of new bone cells to result in a fast formation of strong remodeled bone.
In one embodiment of the present invention, the biphasic ceramic bone substitute may be prepared as beads in mold(s) and/or sculptured in any desired form prior to implantation in a patient. Setting time for the material may not be critical in preset beads or sculptured preparations. In another embodiment of the present invention, the biphasic ceramic bone substitute is the result of an in vivo setting process where a biphasic ceramic bone substitute paste according to the present invention is injected or otherwise placed at the site of the bone defect in the patient. In such an in vivo setting process, the setting time is often critical. The right combination of setting components, additives and accelerators is prerequisite for an optimal, consistent and reliable setting of the bone substitute. The paste may be prepared immediately prior to use by mixing the dry powders with an aqueous liquid, which may comprise some or all of the water soluble additives. Some or all of the additives may be premixed with one or different dry powders before mixing with the aqueous liquid. Some or all of the additives may be added to and mixed with the paste before being used and before setting. Some or all of the additives may in an encapsulated form for later release as described above.
In a further embodiment of the present invention, the powders and additives may be provided in a kit ready for mixing, where the different powders and additives are provided individually or pre-mixed in any desirable way or combination in different containers. The kit may also comprise an aqueous liquid for preparing the paste and the liquid may contain one or more of the additives.
Additionally, the kit may contain instructions for mixing and use and/or mixing and injecting devices, including a syringe, such as for example disclosed in WO 2005/122971.
The biphasic ceramic bone substitute according to the present invention may be used in the treatment of most bone defects where surgical intervention and filling of voids are needed and/or beneficial, such as loss of bone due to i.a. trauma, debriding of infected areas, resection of pathological lesions (e.g. bone cancer), nonunion surgery and in primary or revision arthroplasties. Bones to be treated include, but are not limited to, the spinal cord, bones of the hands, fingers, arms, feet, toes, lower or upper legs, knee, hip, ankle, elbow, wrist, shoulders, skull, jaw and teeth of any animal or a human.
The present invention concerns new biphasic ceramic bone substitute for use in the treatment of disorders of supportive tissue such as regeneration of bone defects, in particular serious bone defects where a graft is needed. The two phases in the ceramic bone substitute consists of a relatively fast resorbable calcium sulphate phase and a very slowly resorbable calcium phosphate phase. The biphasic ceramic bone substitute further comprises at least one bone active protein that served as an osteoinductive factor for regeneration of new bone, and at least one anti-catabolic agent that inhibits bone resorption. The combination of bone active proteins, specific inhibitors of bone resorption and a biphasic ceramic bone substitute carrier comprising a microporous and relatively fast resorbable phase and a very slow resorbable phase has proven to be surprisingly beneficial.
The calcium sulphate phase of the biphasic ceramic bone substitute essentially consists of calcium sulphate dihydrate that is formed in a setting process where calcium sulphate hemihydrate is reacted with water, whereby calcium sulphate dihydrate crystals are formed over time and interlock with each other to for a microporous matrix. The setting reaction may be accelerated by addition of 0.1-10, such as 0.2-5 weight % calcium sulphate dihydrate or a suitable salt, e.g. in the form of a solution, for example saline (NaCl-solution). During the setting process, calcium phosphate particles in the calcium phosphate phase (e.g. hydroxyapatite particles) are embedded in the voids of microporous calcium sulphate dihydrate matrix (the calcium sulphate phase). The calcium sulfate phase provides an initial mechanically solid property to the bone substitute. The microporosity and the relatively fast resorption of the calcium sulphate phase in the body liberates additive present in the calcium sulphate phase at an initial high rate and the artificial material is transformed into a very porous skeleton along with the resorption of calcium sulphate resulting in an increased access of body fluids and cells to the calcium phosphate particles in the calcium phosphate phase. This has shown to be highly beneficial in (fast) bone cell ingrowth. In an in-vitro assay it is shown that BMP-2 is released from solid Cerament™ bone support at a constant rate over a period of 7-days with nearly 90% of BMP-2 released after 7-days.
The calcium phosphate phase of the biphasic ceramic bone substitute essentially consists of calcium phosphate particles selected from the group consisting of α-tricalcium phosphate, hydroxyapatite, tetracalcium phosphate and β-tricalcium phosphate. The calcium phosphate component may be added as preset particles or added as hardenable precursors (powder) for a setting process within the biphasic material upon addition of water. Accelerators of such setting processes, e.g. particulate calcium phosphate particles and phosphate salts, are known in the art and may be added in the process. The calcium phosphate particles may be amorphous or crystalline in structure. A desired structure may be obtained by e.g. heat-treatment, re-crystallization and/or dissolution processes known in the art. EP 1 301 219, EP 1 465 678 and EP 1 601 387 disclose calcium phosphates, their preparation and their use in ceramic bone substitutes.
In a preferred embodiment of the invention, the calcium phosphate phase is essentially composed of hydroxyapatite, in particular crystalline hydroxyapatite particles. Anti-catabolic agents such as bisphosphonate have a strong affinity to calcium phosphates, such as hydroxyapatite, which constitutes the calcium phosphate phase in the commercially available Cerament™ products.
WO 2014/128217 discloses passivated crystalline hydroxyapatite particles and their use in ceramic bone substitutes. Crystalline hydroxyapatite powder is heated after being sintered and grinded or milled, which surprisingly leads to passivation (inactivation) of the crystalline hydroxyapatite particles that otherwise may interfere with the setting process of the calcium sulphate phase, especially when the bone substitute powder comprises additives such as an antibiotic agent. Passivated crystalline hydroxyapatite particles may advantageously be used in the present invention.
Bone active proteins included as an additive in the biphasic ceramic bone substitute are preferably selected from bone growth proteins such as from the group comprising bone morphogenic proteins (BMPs), insulin-like growth factors (IGFs), transforming growth factor-βs (TGFβs), parathyroid hormone (PTH), sclerostine, and the like. Alternatively, one or more bone active proteins can be provides as a composition of cell factory derived bone active proteins and/or extracellular matrix proteins (ECM). More alternatively, strontium may be used in addition to or substitute the bone active proteins. In one embodiment, the bone active proteins are mixed with the calcium sulphate hemihydrate powder before mixing the sulphate hemihydrate and calcium phosphate powders. Alternatively, the bone active proteins are mixed with the mixed sulphate hemihydrate and calcium phosphate powder or the aqueous liquid or added to the paste. The bone active proteins may be provided as encapsulated in water-soluble and/or biodegradable polymer(s).
In one embodiment the bone active protein is the bone growth protein, preferably a bone morphogenic protein (BMP). Preferably the BMP is BMP-2 or BMP-7. In a specific embodiment the BMP is a recombinant BMP, preferably recombinant human BMP, such as rhBMP-2 or rhBMP-7. BMP is used in a concentration of 0.2 to 500 μg/g dry powder, more preferably 1.0-250, or 2--200, or 5-1500, or 10-120 μg BMP/g dry powder. Other bone active proteins may be used in a similar or corresponding concentration or a concentration necessary for obtaining the desired effect.
The bone active proteins are incorporated into the bone substitute by addition to and mixing with either the bone substitute powder or the aqueous liquid. Alternatively, the bone active proteins may be added to the paste before casting. In a preferred embodiment, the bone active proteins are pre-mixed with the calcium sulphate powder before mixing with the calcium phosphate powder.
Bone active proteins may be provided as such and added to any of the powders, the aqueous liquid or the paste. Alternatively, the bone active proteins may be encapsulated in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like before use.
One or more anti-catabolic agent(s) for inclusion in the biphasic ceramic bone substitute of the present invention is/are preferably selected from either bisphosphonates; selective estrogen receptor modulators (SERM) (e.g. raloxifene, tamoxifen, lasofoxifene or bazedoxifene), denosumab (a monoclonal antibody against RANKL developed by Amgen); or statins or any combination of two or more of these anti-catabolic agents. Preferably the anti-catabolic agent is one or more bisphosphonates.
Bisphosphonates are divided into non-nitrogenous (or simple) bisphosphonates and N-containing bisphosphonates. The N-containing bisphosphonates are more potent than the simple bisphosphonates.
The simple bisphosphonates are metabolized in the cell to compounds that replace the terminal pyrophosphate moiety of ATP, forming a nonfunctional molecule that competes with adenosine triphosphate (ATP) in the cellular energy metabolism. The osteoclast initiates apoptosis and dies, leading to an overall decrease in the breakdown of bone. Examples of simple bisphosphonates are etidronate, clodronate and tiludronate. Clodronate and tiludronate are 10 times as potent as etidronate.
Nitrogenous bisphosphonates act on bone metabolism by binding and blocking the enzyme farnesyl diphosphate synthase (FPPS) in the HMG-CoA reductase pathway (also known as the mevalonate pathway). Examples of N-containing bisphosphonates are (potency relative to etidronate are given in parenthesis): pamidronate (100), neridronate (100), olpadronate (500), alendronate (500), ibandronate (1000), risedronate (2000) and zoledronate (10000).
The bisphosphonates may be added in solution to the calcium phosphate particles/powder (e.g. hydroxyapatite) where it strongly binds to calcium phosphate prior to mixing with the calcium sulphate powder. The amount/concentration of bisphosphonates necessary for obtaining a desired effect depends, i.a. on the potency of the bisphosphonate selected. The concentration of bisphosphonate in “doped” calcium phosphate particles may be controlled by selecting the bisphosphonate concentration in the solution and/or the time the particles are placed in the bisphosphonate solution. Alternatively, the amount/concentration of bisphosphonates in the powders and the paste may be controlled by using a mixture of calcium phosphate particles (e.g. hydroxyapatite) doped with a known (high) amount/concentration of bisphosphonate and un-doped calcium phosphate particles in a desired ratio.
In a preferred embodiment, the selected bisphosphonate is zoledronate/zoledronic acid (ZA).
ZA is used in a concentration of 0.2 to 500 μg/g dry powder, more preferably 1-300 μg/g, or 10-200 μg/g, or 10-120 μg/g. Other bisphosphonates may be used in a similar or corresponding concentration or a concentration necessary for obtaining the desired effect. The dosages of BMP used in local application in accordance with the present invention may be as low as 20% of what is needed in systemic infusion or even lower. Too high dosages of bisphosphonates (e.g. ZA) are toxic and will alone lead to an inflammatory reaction and also not only kill osteoclast but also impair the osteoblasts. In addition high dosages of BMP alone can lead to a strong reaction and a too extensive bone formation.
Bone active proteins may be provided as a powder or a solution and added to any of the powders, the aqueous liquid or the paste. Alternatively, the bone active proteins may be encapsulated in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like before use.
Discs for use in an in-vitro ZA release assay were prepared by mixing ZA with a ceramic powder (Cerament™ BVF), a liquid and cast in molds. Saline was added to the discs and at different time points, a sample of the medium was harvested and analysis. The release of ZA from each Cerament™ BVF discs can be calculated in the harvested supernatants by adding lung cancer cells (cell line A549) wherein ZA is known to induce apoptosis. After a period of 7-days, the amount of ZA released from Cerament™ BVF was about 10% of the total ZA loaded.
Selective estrogen receptor modulators (SERM), e.g. raloxifene, tamoxifen, lasofoxifene and bazedoxifene have proven to have an effect on postmenopausal osteoporosis and may therefore be selected as an anti-catabolic agent for use in the present invention.
Denosumab is fully human monoclonal antibody designed to inhibit RANKL (RANK ligand), a protein that acts as the primary signal for bone removal. In many bone loss conditions, RANKL overwhelms the body's natural defenses against bone destruction. Denosumab was developed by the biotechnology company Amgen and is used in treatment of osteoporosis, treatment-induced bone loss, bone metastases, multiple myeloma, and giant cell tumor of bone.
Statins are another class of drugs that inhibit the HMG-CoA reductase pathway. Unlike bisphosphonates, statins do not bind to bone surfaces with high affinity, and thus are not specific for bone. Nevertheless, some studies have reported a decreased rate of fracture (an indicator of osteoporosis) and/or an increased bone mineral density in statin users.
The biphasic ceramic bone substitute according to the invention may also comprise at least one further bioactive agent. Such bioactive agents are selected from antibiotics (including antifungal drugs), bone healing promotors, chemotherapeutics, cytostatics, vitamins, hormones, bone marrow aspirate, platelet rich plasma and demineralized bone.
An antibiotic agent is preferably selected from gentamicin, vancomycin, tobramycin, cefazolin, rifampicin, clindamycin and the antifungal drug is preferably selected from the group comprising nystatin, griseofulvin, amphotericin B, ketoconazole and miconazole. The ceramic powder product CERAMENT™ IG marketed for use in bone substitution comprises gentamicin. A new ceramic powder product, CERAMENT™ IV, for use in bone substitution comprises vancomycin.
Concentrations in additional bioactive agent depend on the agent and desired effect. For the antibiotics gentamicin and vancomycin, they are used in an amount of 0.5 to 10 weight % of the ceramic powder, preferably between 1 and 6 weight %.
If it is desired to have further bioactive agents in the bone substitute (in addition to bone active protein and anti-catabolic agent), these may be added to and comprised in the powder or in the aqueous liquid. Alternatively, one or more of additional bioactive agents may be added to the paste before setting.
Additional bioactive agents may be provided as such and added to any of the powders, the aqueous liquid or the paste. Alternatively, the bioactive agents may be encapsulated in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like before use.
In implantation situation, it is often important for the surgeon to be able to follow the placement of the biphasic ceramic bone substitute in the patient during and after the surgery. It may also be helpful to be able to follow ingrowth of new bone or failures that need to be corrected. In one embodiment of the present invention an X-ray contrast agent selected from water soluble non-ionic X-ray contrast agents and/or biodegradable X-ray contrast agents may be incorporated into the bone substitute. EP 1 465 678 and WO 2014/128217 disclose incorporation of x-ray contrast agents into ceramic bone support. The X-ray contrast agents may be added to constitute 1-25 weight % of the total powder ingredients, preferable 10-25 weight %.
In a preferred embodiment the water soluble non-ionic X-ray contrast agent is selected from iohexol, iodixanol, ioversol, iopamidol, iotrolane, metrizamid, iodecimol, ioglucol, ioglucamide, ioglunide, iogulamide, iomeprol, iopentol, iopromide, iosarcol, iosimide, iotusal, ioxilane, iofrotal, and iodecol. In another embodiment, biodegradable X-ray contrast agents which may provide additional pores may be used.
The X-ray contrast agent may be provided as such and added to any of the powders, the aqueous liquid or the paste. Alternatively, the X-ray contrast agent may be encapsulated in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like before use.
In a further embodiment, the present invention concerns a hardenable ceramic bone substitute powder comprising:
“Hardenable ceramic bone substitute powder” means that calcium sulphate hemihydrate powder and optionally the calcium phosphate powder will set as a solid material after contact with a liquid.
The biphasic ceramic bone substitute powder (basis powder with or without additives) according to the present invention comprises a calcium sulphate hemihydrate to calcium phosphate ratio (w/w) from 5:95 to 95:5, from 10:90 to 90:10, from 20:80 to 80:20, from 30:70 to 70:30, or from 40:60 to 60:40. Cerament™s on the market comprises 59.6 weight % calcium sulphate hemihydrate and 40 weight % hydroxyapatite.
In a preferred embodiment, the calcium phosphate powder is a preset hydroxyapatite powder, preferable comprised of amorphous and/or crystalline hydroxyapatite particles.
Calcium phosphate particles (e.g. crystalline hydroxyapatite) for use as preset calcium phosphate powder have a particle size of D(v,0.99)<200 μm, preferably <100 μm and more preferably <50 μm, such as less than 35 μm. The specific surface area of the powder should preferable be below 20 m2/g, and more preferably below 10 m2/g, when measured according to the BET (Brunauer, Emmett and Teller) method, which is a method for the determination of the total surface area of a powder expressed in units of area per mass of sample (m2/g) by measurement of the volume of gas (usually N2) adsorbed on the surface of a known weight of the powder sample. Other ways of determining the surface area may be applied in the alternative.
In one embodiment, the anti-catabolic agent is a bisphosphonate that is pre-mixed with (and bound to) the calcium phosphate particles prior to mixing with the calcium sulphate powder. In a further embodiment, the calcium phosphate particles are crystalline hydroxyapatite particles. Alternatively, the anti-catabolic agent is added to and mixed with a pre-mixed calcium sulphate/calcium phosphate powder (a basis powder, e.g. a Cerament™ product).
In one other embodiment, bone active protein present in the powder is selected from the group comprising bone morphogenic proteins (BMPs), insulin-like growth factors (IGFs), transforming growth factor-βs (TGFβs), parathyroid hormone (PTH), strontium, sclerostine, cell factory derived proteins and ECM proteins. The bone active protein may be pre-mixed with the calcium sulphate hemihydrate powder, with the calcium phosphate powder or the basis powder.
The calcium sulphate powder, the calcium phosphate powder or the basis powder may also comprise one or more bioactive agents selected from antibiotics (including antifungal drugs), bone healing promotors, chemotherapeutics, cytostatics, vitamins, hormones, bone marrow aspirate, platelet rich plasma and demineralized bone. The at least one antibiotic agent may be selected from gentamicin, vancomycin, tobramycin, cefazolin, rifampicin, clindamycin and the antifungal drug is selected from the group comprising nystatin, griseofulvin, amphotericin B, ketoconazole and miconazole.
The calcium sulphate powder, the calcium phosphate powder or the basis powder may further comprising an X-ray contrast agent selected from water soluble non-ionic X-ray contrast agents and/or biodegradable X-ray contrast agents. The water soluble non-ionic X-ray contrast agent may be selected from iohexol, iodixanol, ioversol, iopamidol, iotrolane, metrizamid, iodecimol, ioglucol, ioglucamide, ioglunide, iogulamide, iomeprol, iopentol, iopromide, iosarcol, iosimide, iotusal, ioxilane, iofrotal, and iodecol.
Any of the additional bioactive agents/X-ray agents may be provided as powders or solutions and optionally added to any of the powders. Alternatively, the additional bioactive agents/X-ray agents may be encapsulated in synthetic polymeric microcapsules, bovine collagen particles, starch particles, dihydrate nidation particles, or the like before being mixed with any of the powders.
The present invention further concerns a hardenable ceramic bone substitute paste comprising a hardenable ceramic bone substitute powder as defined above and an aqueous liquid. The aqueous liquid may comprise any of the additives, including the bone active proteins and/or anti-catalytic agents (e.g. bisphosphonates) discussed above. X-ray contrast agents and bioactive agents such as antibiotics are preferably dissolved in the aqueous liquid before mixing with the ceramic bone substitute powder. Alternatively, the additives, including the bone active proteins and/or anti-catalytic agents (e.g. bisphosphonates) may be added to and mixed with the paste by delayed mixing as disclosed above. If one or more of the additives are interfering with the setting of the hardenable paste, such additives can advantageously be added to the paste by delayed mixing.
The liquid to dry powder ratio (L/P) in preparing the paste is in the range of 0.2 to 0.8 ml/g, such as 0.3 to 0.6 ml/g and preferably 0.4 to 0.5 ml/g.
In a preferred embodiment of the present invention, the hardenable ceramic bone substitute paste is prepared by mixed the powder(s), additives and liquid in a suitable bowl or in specially designed mixing devise (e.g. a Mixing and Injection Device (CERAMENT™ ICMI) available from BONESUPPORT AB, Sweden or other mixing devices such as Optipac® from Biomet, US, used with or without vacuum) to be made ready for injection through a syringe (e.g. a specific injection device available from BONESUPPORT AB, Sweden). The additives may be part of the powder(s) or liquid or self-contained and added to together with the powder(s) and liquid. In a particular embodiment, one or more additives is/are added to the paste after the initial mixing of powder(s) and liquid in a “delayed mixing” process. It is important that addition and mixing of the additive(s) is/are performed before any setting reactions have started. Preferably, addition of additive(s) to the paste is performed within 2 to 4 minutes after initial mixing.
The present invention also concerns kits for delivering all or some of the ingredients for use in the biphasic ceramic bone substitute according to the present invention. Such kits comprise:
The aqueous liquid may be distilled water, optionally comprising a salt and/or a buffer.
In one embodiment, the kit comprises a basis powder (x) comprising calcium sulphate hemihydrate powder (i) pre-mixed with the calcium phosphate powder (ii).
In another embodiment of the kit, the anti-catabolic agent (iv) is pre-mixed with at least a part of the calcium phosphate powder (ii), at least a part of the calcium sulphate hemihydrate powder (i), the basis powder (x), or the aqueous liquid (ix).
In yet another embodiment of the kit the bone active protein (iii) is pre-mixed with at least a part of the calcium sulphate hemihydrate powder (i), at least a part of the calcium phosphate powder (ii)), the basis powder (x), or the aqueous liquid ii).
In a further embodiment of the kit, the at least one further bioactive agent (v) as defined above is pre-mixed with the calcium phosphate powder (ii), the calcium sulphate hemihydrate powder (i), the basis powder (x), or the aqueous liquid (ix).
In yet a further embodiment of the kit the X-ray contrast agent (vi) as defined above is pre-mixed with the calcium phosphate powder (ii), the calcium sulphate hemihydrate powder (i), the basis powder (x), or the aqueous liquid (ix).
In another embodiment of the kit an accelerator for setting of the calcium sulphate (vii) as defined above is premixed with the calcium sulphate hemihydrate powder (i), the basis powder (x), or the aqueous liquid (ix).
In yet another embodiment of the kit an accelerator for setting of the calcium phosphate (viii) as defined above is pre-mixed with the calcium phosphate powder (ii), the calcium sulphate hemihydrate powder (i), the basis powder (x), or the aqueous liquid (ix).
Any of the additional bioactive agents/X-ray agents may be provided as such or in any of the powders or the liquid. Alternatively, the additional bioactive agents/X-ray agents may be encapsulated individually or in any suitable combination in water-soluble and/or biodegradable synthetic polymeric microcapsules, bovine collagen particles, starch particles and/or dihydrate nidation particles, or the like, and optionally mixed with any of the powders or the liquid.
According to the invention, the kit may further comprise mixing and injection devices, optionally including a syringe for injection. The kit may also comprise instructions for use.
In a further embodiment of the present invention, the kit further comprises a lining membrane for enclosing the synthetic grafts or closing the grafts to the outside, e.g. a biodegradable synthetic membrane or a collagen membrane as for example disclosed in WO2013185173. The synthetic graft may also be sealed with a protein in a solution that could be applied, i.a. as a spray, and thus support a surface healing. The covering protein may add additional benefits in preventing surface bacterial adherence and biofilm production.
In another aspect the present invention also concerns a method of treating patients with bone defects such as loss of bone due to, i.a. trauma, eradication of infection, resection of tumor lesions, delayed or nonunions and in primary or revision arthroplasties. In one embodiment, the method includes an insertion of one or more biphasic ceramic bone substitutes (grafts) according to the present invention into the bone lesion to be treated. In another embodiment, the method includes application of a paste of a hardenable biphasic ceramic bone substitute according to the present invention to the bone lesion to be treated. All bones in the animal or human body, including the spinal cord, bones of the hands, fingers, arms, feet, toes, lower or upper leg, knee, hip, ankle, elbow, wrist, shoulder, skull, jaw and teeth. The insertion of a biphasic ceramic bone substitute, for example in the form of a hardenable paste, may follow removal of bone, e.g. removal of broken bone, a bone tumor or infected bone tissue. In the case the substitute needs to be contained in the tissue around the graft or to prevent leakage to the surroundings or to cover an open wound, it may be beneficial or necessary to apply an artificial, e.g. polymeric, membrane. Such a membrane may be porous allowing body liquids and cells to flow to and from the porous graft and/or partially or fully sealed to the outside. After insertion of a biphasic ceramic bone substitute or the paste has hardened, the muscle tissue and skin may be repositioned or grafted over the artificial bone substitute.
To see whether the Cerament™ products are immunogenic per se, a test involving RAW 264.7 macrophages, which are known to activate and secrete large amounts of cytokines when in contact with immunogenic materials, were selected. Ceramic discs prepared from Cerament™ products were seeded with murine macrophage cells RAW 264.7 and secretion of pro inflammatory cytokines like interleukin (IL)-1β, IL-2, IL-6 and tumor necrosis factor (TNF)-α was assessed over a period of 7-days using ELISA. The secretion of all cytokines (IL-1β, IL-2, IL-6 and TNF-α) is comparative with negative controls, and significantly lower than LPS (lipopolysaccharide)-treated positive controls. Application of Cerament™ in patients thus appears to give a very low if any immunological activity.
In some clinical cases extensive bone formation have been observed in the overlaying muscle covering surgically created bone defects treated with the hydroxyapatite/sulphate injectable mixture, CERAMENT™ IBVF.
An in vitro model was designed to investigate the osteoinductive potential at the interface between muscle and bone substitute. Skeletal muscle cells were seeded on discs prepared from Cerament™ BVF and from Cerament™ G. Upon physiochemically characterizing Cerament™ using SEM, the porous structure was verified (
To mimic surgical conditions with leakage of extracellular matrix (ECM) proteins and growth factors from artificial grafts, bone cells ROS17/2.8 were cultured in a bioreactor and the secreted growth factors and ECM proteins were harvested. Harvested cell culture produced bone active proteins were measured using ELISA and bone morphogenic protein-2 (BMP-2, 8.4±0.8 ng/mg) and BMP-7 (50.6±2.2 ng/mg) were found. In vitro, the harvested bone active proteins induced differentiation of skeletal muscle cells L6 towards an osteogenic lineage, which stained positive for bone markers.
Based on the above results, it was found that bone formation can be synergistically enhanced by release of growth factors and/or ECM proteins capable of inducing osteoblast differentiation from and present in biphasic ceramic bone substitute.
A Cerament™ BVF-rhBMP-2 paste was prepared by mixing, transferred to a syringe and solid discs were prepared in a mold. Each disc containing 2 μg rhBMP-2 was immersed in 1 mL saline and placed in an incubator at 37° C. At different time point over a period of 7-days, 50 μl of saline from the supernatant was collected and analysed and the protein concentration calculated. A constant release of BMP-2 from Cerament™ BVF was observed over a period of 7-days with nearly 90% of rhBMP-2 released after 7-days.
Release of bisphosphonate (zoledronic acid (ZA) was used as an example) from a biphasic ceramic bone substitute was investigated in Cerament™ with and without gentamicin. Cerament™ BVF-ZA paste and Cerament™ G-ZA paste were prepared by mixing each of the Cerament™ powders with ZA and a liquid. The discs were produced by transferred the pastes to a mold using a syringe and the solid discs were left to set. Saline was added to the discs and they were incubated at physiological conditions. At different time point over a period of 7-days, a sample of the medium was collected and analysed. To assess the release of ZA from each Cerament™+ZA disc at different time points, the collected supernatants were added to A549 cells and cell viability was calculated after an incubation of 48 h using MTT assay. The concentration of ZA was calculated from a standard curve.
After a period of 7-days, the amount of ZA released from solid Cerament™ discs was nearly 10% of the total ZA loaded. No difference in ZA-release was seen between Cerament™ with and without gentamicin. The cytotoxic effect of ZA released from Cerament™ BVF and Cerament™ G discs on A549 cells indicated a decrease in cell viability at increasing time points.
Discs were produced from Cerament™ products mixed with recombinant human (rh) BMP-2 alone or with rhBMP-2 together with ZA and implanted in 7 week old rats. In a modified ectopic bone model, the implants were inserted in the abdominal muscle by performing a single blunt dissection of the abdominal muscle The modified ectopic bone model is unique in using the unstressed abdominal muscle, which results in an increased resorption of bone cells by osteoclasts compared to an earlier study, where the grafts are placed next to an existing bone in the hip joint on the dorsal side, and thus more likely is influenced by local release and stimulation from the underlying bone which will affect the level bone being built and the tested anti-catabolic agents such as bisphosphonates as well as the growth hormones (WO 2012/094708). In one group the test animals received two discs of only Cerament™ BVF in the left side of the abdominal midline per animal while the right side of the midline was used to implant two discs of Cerament™ BVF+rhBMP-2 per animal. In another group, the animals received two discs of only Cerament™ BVF and two discs of Cerament™ BVF+rhBMP-2+ZA in a similar manner. The scaffolds emerging over time from the discs were left in the animals for 4 weeks. Analysis for bone formation was done using X-ray followed by three-dimensional analysis of mineralized tissue volume using micro computed tomography (micro-CT) and electron microscopy. The type of cells within the scaffold was analyzed using histology (Hematoxylin and eosin (H&E)).
Examination of the animals sacrificed after 4 weeks showed that the scaffolds from Cerament™ BVF discs loaded with rhBMP-2 and ZA are denser than the scaffolds from Cerament™ BVF discs loaded with rhBMP-2 only and scaffolds from Cerament™ BVF discs. Micro-CT results show that the mineralized tissue volume was significantly higher in the Cerament™ BVF disc group loaded with a combination of rhBMP-2 and ZA than in the group loaded with rhBMP-2 and the group with Cerament™ BVF discs. The group loaded with a combination of rhBMP-2 and ZA had significantly higher mineral volume than the Cerament™ BVF+rhBMP-2 group. Histologically, the samples that were loaded with rhBMP-2+ZA had developed a cortical shell around the scaffold with islands of trabecular bone already visible within the scaffold, while the Cerament™ BVF+rhBMP-2 group showed signs of osteoclastic resorption with visible fatty marrow. This is clearly visualized by the electronmicroscopy.
The content of Cerament™ compositions used in the examples is given in Table 1.
In all of the examples “saline” means a NaCl solution containing 9 mg NaCl/mL water unless stated otherwise.
Cerament™ BVF paste was prepared according to the manufacturer's instruction and used to prepare discs (diameter: 8 mm; height: 2 mm) which sat before 20 minutes. The discs were seeded with a total of 1×105 murine macrophage cells RAW 264.7 and secretion of pro inflammatory cytokines like interleukin (IL)-1β, IL-2, IL-6 and tumor necrosis factor (TNF)-α was assessed over a period of 7-days using ELISA. As positive control, RAW 264.7 cells were treated with immunogenic lipopolysaccharide (LPS).
The secretion of all cytokines (IL-1β, IL-2, IL-6 and TNF-α) was comparable with the negative control (2D-TCP) and significantly lower than the LPS treated positive control (2D-TCP+LPS) with p-values <0.0001 in all cases (
Two types of bone substitute products, CERAMENT™ IBVF and CERAMENT™ IG, were mixed as per supplier's guidelines (Bone Support AB, Lund, Sweden) to form a homogenous paste. The paste was poured in a disc shape mold with 8 mm diameter and 2 mm height and allowed to set for 30 min.
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MU), Sigmafast pNPP, Dulbecco's Modified Eagle's Medium-High glucose (DMEM-HG), Fetal bovine serum (FBS), antibiotic cocktail, Trizol reagent and primers for real time polymerase chain reaction (RT-PCR) was purchased from Sigma Aldrich, MA, USA. Mouse COLI, OCN, RUNX-2, OPN were purchased from Santa Cruz Biotechnology, Inc., CA, USA and Sigma Chemical company, MA, USA. Rat COLI, OCN, OPN and bone sialoprotein (BSP) antibodies, DRAQ5, alexa flour 488 (AF-488) were procured from Abcam, Cambridge, U.K. RT-PCR reagents were purchased from Thermo scientific, USA. Rat BMP-2 and BMP-7 ELISA kits were purchased from Abnova Inc., Taiwan and Qayee Bio, China respectively. All other reagents were of high purity purchased from recognized suppliers.
Mouse myoblast C2Cl2 cells were cultured in the Dulbecco's Modified Eagle's Medium (DMEM) supplemented with 10% (v/v) fetal bovine serum (FBS) and antibiotics. Cells were kept in an incubator having 95% air and 5% C02. For the proliferation and functionality experiments, 1×105 cells were seeded onto the Cerament™ discs while for immunofluorescence staining and reverse transcription polymerase chain reaction (RT-PCR), 1×106 cells were seeded onto the Cerament™ discs. Rat skeletal muscle myoblast cellline L6 was cultured in DMEM with high glucose with 10% (v/v) FBS and 1% (v/v) antibiotic cocktail consisting of penicillin-streptomycin. Cells were passaged at 80% confluence and were used at 2nd passage after revival. Cell viability before experiments was evaluated using the trypan blue exclusion method.
In order to mimic in vivo conditions that lead to bone formation in the muscle tissue, osteoblast cell factory derived proteins were harvested from an expanded cell culture of ROS 17/2.8 osteoblastic cells. Cells were allowed to proliferate in culture flasks supplemented with complete medium and 5% (v/v) serum for a period of 3 days. The secreted bone active proteins in the medium were collected while the cells were passaged again to repeat the procedure.
In order to ensure transdifferentiation of muscle cells into osteoblast like cells, the rat muscle cell line L6 was used. The cells were allowed to grow to 80% confluence after which they were either supplied with low serum (5% v/v) complete medium or a mixture of complete medium (low serum) and harvested osteoblast cell factory medium in an equal ratio by volume. The cells were allowed to grow for a period of 10 or 12 days and were analyzed using different techniques to confirm a shift in their phenotype.
Data from the MTT and ALP assay were analyzed using unpaired t-test. p<0.05 was considered to be significant. Data from MTT assay and myotube numbers for cell factory experiments were analyzed using non-parametric, multiple t-test and p<0.05 was considered statistically significant. Data is represented in triplicates with mean and standard deviation.
Surface morphology of the materials and adherence of the C2C12 cells on the surface of Cerament™ discs were analyzed using scanning electron microscopy. Materials were dehydrated by gradient ethanol treatment. Further, samples were vacuum dried overnight. For analyzing the cell adherence on the Cerament™ surface, cells were seeded on both the materials i.e., with gentamicin and without gentamicin. The cells were allowed to grow for three days. Thereafter, glutaraldehyde (2.5%) was used to fix all the cells on the surface. Steps following fixation were the same as were used for sample preparation for surface morphology analysis. Furthermore, attachment of cells on the Cerament™ discs were analysed using 4′, 6-diamidino-2-phenylindole (DAPI) staining.
The surface morphology of both Cerament™ discs with and without gentamycin showed porous structure with size of the pores at the material surface in the range of 1-10 μm (
Cell proliferation on both the materials was evaluated using MTT assay at regular time intervals. Briefly, the DMEM media in the wells was removed, and cell seeded inorganic discs were washed using phosphate buffer saline (PBS). Thereafter, DMEM media, without FBS, containing MTT (0.5 mg/ml) was added in the wells and incubation of 5 h was done. Further, this solution was removed and dimethyl sulfoxide (DMSO) was added. The samples were incubated for 20 min at 37° C. The colored solution formed was collected and absorbance was measured spectrophotometrically at 570 nm. Cell proliferation analysis in the cell factory experiments using L6 cells was done in a similar manner and a cell density of 5×104 cells/well was used. The proliferation of myotubes was analyzed by microscopy and multinucleated and elongated cells were considered to be myotubes.
Similar results were observed in both Cerament™ materials with or without gentamicin (
Sigma fast para-Nitrophenylphosphate (pNPP) tablets were used to prepare pNPP substrate solution, using protocol provided by the manufacturer. The media was removed from the wells and samples were washed using PBS buffer. The samples were then incubated with para-nitrophenylphosphate (pNPP) substrate solution for 2 h in the CO2 incubator at 37° C. and absorbance was measured at 405 nm.
The material with and without gentamycin showed increase in ALP amounts by the 14th day of cell seeding (
The differentiation potential of the materials were observed using immunofluorescence staining. The cells were stained to detect the presence of different markers like runx2, osteopontin, osteocalcin and collagen type I (COLI) over the period of 21 days.
Immunofluorescence staining showed the presence of Runx2 by the 7th day of cell seeding on the Cerament™ disc (
To confirm the transdifferentiation of L6 muscle cells into osteoblast like cells, cells in both groups were immunostained for various osteoblastic markers like collagen type I (COLI), osteocalcin (OCN), osteopontin (OPN) and bone sialoprotein (BSP). Cells were allowed to grow in culture flasks for a period of 10 days in complete medium with osteoblast harvested bone active proteins or low serum. The cells were trypsinized and seeded on 4-well chamber slides and allowed to proliferate with same medium further for 48 h. At the day of staining, cells were fixed using 4% formaldehyde for 10 min followed by membrane permeabilization using 0.1% (v/v) triton X-100 for 5 minutes. Later cells were blocked using 5% goat serum for 1 h and incubated with respective primary antibodies for 2 h at room temperature. Slides were washed with PBST five times followed by incubation in secondary antibody (AF-488 labeled) for 1 h. The slides were counterstained using DRAQ5 for 5 min and washed twice for 5 min each. The slides were eventually cleared, mounted and allowed to dry overnight before analysis. The cells were analyzed on Zeiss confocal microscope at different magnifications.
The discs of Cerament™ with and without gentamicin were seeded with C2C 12 cells at a concentration of 1×106 cells/disc. The RNA was extracted using Trizol reagent, after in vitro culturing of cell seeded discs for the time period of 7 and 21 days. Cell seeded discs were transferred from multiwell plate to microtubes after adding 1 ml of Trizol reagent. Thereafter, RNA was isolated by following the protocol supplied by the manufacturer. Complimentary DNA (cDNA) was synthesized by incubating isolated RNA (20 μl) with 1 μl of oligodT at 75° C. for 5 min followed by incubation on ice for 5 min. To this, cDNA mix having 4 μl of buff RT, 1 μl of RTase, 0.5 μl of RI (RNase inhibitor) and 2 μl of dNTP mix was added. RT-PCR was conducted to evaluate the expression of various genes of the osteogenic lineage such as RUNX2, COLI, BSP and OCN. The primer sequences of the genes are obtained from previous work and listed in Table 2. As an endogenous control, expression of Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was determined. Consecutive thermal cycle was used for DNA amplification. Products of RT-PCR were resolved on a 2.0% agarose gel stained using ethidium bromide
Results showed presence of RUNX2 by the 7th day (
The transdifferentiation of muscle cells with the addition of osteoblast harvested bone active proteins was analyzed over a period of several days. Morphological analysis was performed using both light microscopy and H&E staining. Culture flasks were directly monitored using a light microscope at different magnifications. In order to perform H&E staining, cells were grown in 4-well chamber slides and were fixed with 4% (w/v) formaldehyde for 10 min. Cells were hydrated with reducing ethanol gradient and stained with Hematoxylin for 5 min. Excessive stain was washed using running water followed by counterstaining with Eosin for 2 min. The slides were cleared in xylene for 5 min, mounted and dried overnight before imaging.
A time course morphological differences were observed in cells treated with bone active proteins and the control groups. The cells in the control groups can be seen as elongated from as early as day 1 until the end of the experiment (
No significant difference in proliferation profile of cells was observed (
With an attempt to detect various pro-osteoblastic proteins in the ROS 17/2.8 cell factory the harvested cell factory proteins were dialyzed against ultrapure water for a period of 48 hr. using a 8 kDa dialysis membrane. After dialyzing, the proteins were concentrated using freeze-drying for a period of 48 hr. The dried protein fraction so obtained was later analyzed using ELISA for the detection and measurement of two important bone active molecules BMP-2 and BMP-7.
The presence of the two most common osteoinductive proteins, BMP-2 and BMP-7 responsible for osteogenic differentiation of various mesenchymal cells into osteoblastic lineages were confirmed. The detection of osteogenic proteins was performed using ELISA and the respective concentrations of BMP-2 and BMP-7 in the cell factory were 8.4±0.8 ng/mg and 50.6±2.2 ng/mg of the harvested protein fraction.
1 g of Cerament™ BVF was mixed with 0.406 ml CERAMENT™ IC-TRU. The Cerament™ BVF paste was mixed rigorously for 30 seconds followed by waiting for 30 seconds and this was continued until 2.5 minutes. A stock solution of rhBMP-2 (Medtronic) containing 40 μg rhBMP-2 was prepared by dissolving it in 40 μL saline (9 mg NaCl/mL). At 2.5 minutes 24 μl of this rhBMP/saline stock solution was rigorously mixed into the pre-mixed Cerament™ BVF paste. After complete mixing of the rhBMP-2 solution into the Cerament™ BVF paste, the rhBMP/Cerament™ BVF paste was transferred to a syringe and 12 discs were made (diameter: 5±0.1 mm; height: 1.5±0.05 mm). All discs were set before 20 min. The weight of the discs was 46±3.2 mg and each disc contained 2 μg rhBMP-2.
Each disc was immersed in 1 mL saline and placed in an incubator at 37° C. At each time point (Day 1, 3, 5 and 7) 50 μl of the supernatant was collected for analysis and 50 μl of fresh saline was added. The protein concentration was calculated using ELISA over a period of 7-days.
For the in-vitro zoledronic acid (ZA) release test a total of 12 discs were prepared; 6 discs were prepared from Cerament™ BVF powder and 6 discs were prepared from Cerament™ G powder:
500 mg of Cerament™ BVF was mixed with 148.64 μl CERAMENT™ IC-TRU. The sample was mixed rigorously for 30 seconds followed by waiting for 30 seconds and this was continued until 2.5 minutes. At 2.5 minutes 67.5 μl zoledronic acid solution (54 μg ZA, Zometa (4 mg/5 ml), Novartis) was added to the Cerament™ BVF paste. The Cerament™ BVF+ZA paste was mixed for 30 more seconds and 6 discs were prepared (diameter: 5±0.1 mm; height: 1.5±0.05 mm; 9 μg ZA). All discs were set before 20 min.
500 mg of Cerament™ G powder was mixed with 148.64 μl saline containing 6.6 mg gentamicin. The sample was mixed rigorously for 30 seconds followed by waiting for 30 seconds and this was continued until 3.5 minutes. At 3.5 minutes 67.5 μl zoledronic acid solutions (54 μg ZA, Zometa, Novartis) was added to the Cerament™ G paste. The Cerament™ G+ZA paste was mixed for 30 more seconds and 6 discs were prepared (diameter: 5±0.1 mm; height: 1.5±0.05 mm; 9 μg ZA). All discs were set before 20 min.
Saline was added to the discs and they were incubated at physiological conditions. At each time point, a sample of the medium was collected and stored for further analysis. To assess the release of ZA from each Cerament™ BVF/G+ZA disc at different time points, the collected supernatants were added to A549 cells and cell viability was calculated after an incubation of 48 hours using MTT assay. The concentration of ZA was then calculated from the obtained standard curve.
In-vitro statistical analysis was performed using multiple t-test (Prism 6) with data represented in triplicates with mean and standard deviation.
After a period of 7-days, the amount of ZA released from the Cerament™ BVF and Cerament™ G discs was nearly 10% of the total ZA loaded (
The study was approved by the local authority for use of laboratory animals (permit M 124-14). Discs of Cerament™ BVF, Cerament™ BVF+rhBMP-2 and Cerament™ BVF+rhBMP-2 and ZA were produced as follows:
1 g of Cerament™ BVF was mixed with 0.43 mL of a iohexol-solution comprising 162 μl saline and 268 μl CERAMENT™ IC-TRU and rigorously mixed for 30 seconds followed by waiting for 30 seconds and this was repeated until 2.5 min. The total liquid used was 430 μl for 1 g Cerament™ powder, which gives 480 μl paste with a liquid/powder ratio of 0.43 ml/g. The paste was used to prepare 12 cylindrically discs (diameter: 5 mm; height: 2 mm; weight: 47.6±3 mg) in a sterile mold (40 μl paste/cylinder). Each disc which contained 83.33 mg Cerament™ BVF, 22.33 μl CERAMENT™ IC-TRU and 13.5 μl saline and sat before 20 minutes.
In the “Cerament™ BVF+BMP” group a stock solution of BMP was initially prepared by dissolving 120 μg of rhBMP-2 (Medtronic) in 162 μl of saline. 1 g of the Cerament™ BVF was mixed with 268 μl CERAMENT™ IC-TRU and rigorously mixed for 30 seconds followed by waiting for 30 seconds and repeated mixing and pausing until 2.5 minutes to obtain a paste. At 2.5 minutes, the 162 μl BMP/saline solution (containing 120 μg rhBMP-2) was added to the paste and rigorously mixed for another 30 seconds. The total liquid used was 430 μl for 1 g Cerament™ BVF powder, which gives a liquid/powder ratio of 0.43 ml/g. A final volume of 480 μl paste was obtained containing 120 μg rhBMP-2 and used to prepare 12 discs of the same size as above, each with a volume of 40 μl BMP/Cerament™ BVF paste. Each disc contained 83.33 mg Cerament™ BVF, 22.33 μl CERAMENT™ IC-TRU, 13.5 μl saline and 10 μg rhBMP-2. The discs sat before 20 minutes.
A solution of rhBMP-2 was prepared by dissolving 120 μg rhBMP-2 (Medtronic) in 12 μl of saline. 150 μl of a ZA-solution (120 μg ZA, Novartis) was added and mixed with the rhBMP-2 solution. A total volume of 162 μl of ZA (120 μg) and rhBMP-2 (120 μg) in saline was achieved. 1 g of Cerament™ BVF was mixed with 268 μl CERAMENT™ IC-TRU and the paste was rigorously mixed for 30 seconds followed by waiting for 30 seconds and mixing and pausing were repeated until 2.5 minutes to prepare a paste. At 2.5 minutes the 162 μl ZA+rhBMP-2 solution was added to the paste and mixed for 30 seconds more to homogenize the contents. A final volume of 480 μl was obtained and used to produce 12 discs as described above, each with a volume of 40 μl ZA/BMP/Cerament™ paste. Each disc contained 83.33 mg Cerament™ BVF, 22.33 μl CERAMENT™ IC-TRU, 13.5 μl saline, 10 μg rhBMP-2 and 10 μg ZA. The discs sat before 20 minutes.
Discs comprising Cerament™ BVF, Cerament™ BVF+rh-BMP-2 and Cerament™ BVF+rh-BMP-2+ZA prepared as described above were implanted in 7 week old Sprague Dawley rats. The implants were inserted in the abdominal muscle by performing a single blunt dissection of the abdominal muscle. In one group, five animals received two discs containing only Cerament™ BVF in the left side of the abdominal midline per animal while the right side of the midline was used to implant two discs containing Cerament™ BVF+BMP-2 per animal. In a second group, 5 animals received two discs containing Cerament™ BVF and two discs containing Cerament™ BVF+BMP-2+ZA in a similar manner. The scaffolds emerging over time from the discs were left in the animals for 4 weeks. Analysis for bone formation was done using X-ray followed by three-dimensional analysis of mineralized tissue volume using micro computed tomography (micro-CT). The type of cells within the scaffold was analyzed using histology (H&E).
In-vivo statistical analysis was performed using student t-test with n=5 (mean and SD). P-value <0.05 was considered to be significant.
As seen in
| Number | Date | Country | Kind |
|---|---|---|---|
| 15160388.3 | Mar 2015 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/056034 | 3/18/2016 | WO | 00 |
