Patent Application
20230148082
The present invention relates to jellyfish collagen for use in the treatment of wounds and the manufacture thereof.
Wound healing is a complex process that involves coordinated interactions between diverse immunological and biological systems. Long-term wounds remain a challenging clinical problem, affecting approximately 6 million patients per year, with a high economic impact.
Wound healing is a process whereby the skin (or another organ-tissue) repairs itself after injury. In normal skin, the epidermis (outermost layer) and dermis (inner or deeper layer) exist in a steady-state equilibrium and shielded from the external environment. When the skin is broken, the normal (physiologic) process of wound healing begins. The classic model of wound healing comprises three or four sequential, yet overlapping, phases:
Phase 1: Haemostasis.
Phase 2: Inflammation.
Phase 3: Proliferation.
Phase 4: Remodelling.
Upon injury to the skin, a set of complex biochemical events takes place in a closely orchestrated cascade to repair the damage. Due to a number of potential stimuli (local tissue ischaemia, bioburden, necrotic tissue, repeated trauma, etc.), wounds can stall in the inflammatory phase contributing to the chronicity of the wound. One key component of chronic wounds is an elevated level of matrix metalloproteinases (MMPs). At elevated levels, MMPs not only degrade nonviable collagen but also viable collagen. In addition, fibroblasts in a chronic wound may not secrete tissue inhibitors of MMPs (TIMPs) at an adequate level to control the activity of MMPs. These events prevent the formation of the scaffold needed for cell migration and ultimately prevent the formation of the extracellular matrix (ECM) and granulation tissue. In the case of chronic wounds including diabetic foot ulcers, a combination of the associated chronic microbial infection and inflammation can lead to blood capillary degradation (reduced blood flow) and amputation. Thus, new medicaments targeting diabetic foot ulcers (DFU) may advantageously provide the ability to stimulate blood flow to the affected region and promote wound healing.
Collagen-based wound dressings have been shown to be uniquely suited to address the issue of elevated levels of MMPs by acting as a ‘sacrificial substrate’ in the wound. It has also been demonstrated that collagen breakdown products are chemotactic for a variety of cell types required for the formation of granulation tissue. In addition, collagen based dressings have the ability to absorb wound exudates and maintain a moist wound environment.
A number of different collagen dressings are available, which employ a variety of carriers/combining agents such as gels, pastes, polymers, oxidized regenerated cellulose (ORC), and ethylene diamine tetraacetic acid (EDTA). The collagen within these products tends to be derived from bovine, porcine, equine, or avian sources, which is purified in order to render it nonantigenic. However, there are a number of disadvantages associated with the use of these collagen types, including poor angiogenic properties, enhanced risk of disease and virus transmission, and the considerable cost associated with obtaining these collagens.
Accordingly, a source of collagen which would be suitable for use in the treatment of wounds, without displaying the disadvantages above, would be particularly advantageous.
The present invention relates to a jellyfish collagen for use in the treatment of a wound. As will be evident from the in vivo and in vitro data presented below, the inventors have surprisingly found that compositions comprising jellyfish collagen are useful in the treatment of wounds as an alternative to mammalian collagens (for example, bovine), whilst displaying equivalent results and providing a number of superior qualities, such as angiogenic properties, increased stability, low immunogenicity and a lower risk of virus transfer and disease/prion transmission. This is an entirely unexpected finding given the vastly different physicochemical and amino acid properties of jellyfish collagen compared to mammalian collagen.
Accordingly, a first aspect of the invention relates to a composition for use in the treatment of a wound, wherein the composition comprises jellyfish collagen.
A second aspect of the invention relates to a method of manufacturing the aforementioned jellyfish collagen, comprising at least the steps of:
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which:
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be understood by those of ordinary skill in the art that embodiments of the present invention may be practiced without these specific details while still remaining within the scope of the claims.
In a first aspect, the present invention provides for a composition for use in the treatment of a wound, wherein the composition comprises jellyfish collagen.
The phrase ‘treatment of a wound’ or the term ‘wound treatment’ refers to any treatment which aids the complex process by which the skin and any associated tissues repair themselves after injury. Examples of wounds which may benefit from the use of jellyfish collagen include, but are not limited to, pressure sores, transplant sites, surgical wounds, ulcers, burns (thermal, chemical or electrical), lacerations, abrasions, punctures, avulsions, seromas and/or hematomas. In a preferred embodiment, the wound is not associated with Epidermolysis Bullosa.
In some embodiments, the jellyfish collagen is not in a hydrolysate form. By “hydrolysate form” we include the meaning of a collagen that has been degraded by heat or by protease/collagenase activity to produce collagen fragments defined as collagen peptides and gelatin-like molecules.
The jellyfish collagen for use in the treatment of a wound may be in its atelo form. By “atelo form” we include the meaning of a low-immunogenic derivative of collagen obtained by removal of N- and C-terminal telopeptide components, which are known to induce antigenicity in humans. Telopeptides are generally removed by treatment of collagen with type I pepsin.
The jellyfish collagen for use in the treatment of a wound may be in its telo form. By “telo form” we include the meaning of a collagen extracted in acid conditions producing a soluble collagen that includes telopeptides.
The jellyfish collagen for use in the treatment of a wound may be thiolated. The term ‘thiolated’ is intended to refer to a jellyfish collagen which has been reacted with a thiol, resulting in the introduction of a —SH group, or ‘thiol’ group.
The jellyfish collagen for use in the treatment of a wound may be cross-linked. In the context of the present invention, the term ‘cross-linked’ refers to the linkage of two independent collagen molecules via a covalent bond. Preferably, the collagen molecules to be cross-linked are in the form of collagen fibres, resulting in inter-fibril cross-linking occurring. In order to create the cross-linked thiolated jellyfish collagen, a ‘cross-linking agent’ or ‘cross-linker’ may be used. The term ‘cross-linking agent’ or ‘cross-linker’ refers to an agent that can, under certain conditions, form covalent linkages between two independent molecules. In the context of the present invention, a cross-linking agent is used to covalently link two independent collagen molecules. Preferably, the collagen molecules to be cross-linked are in the form of collagen fibres. Preferably inter-fibril cross-linking takes place. In some instances, the cross-linking agents are typically composed of two or more reactive functional groups linked together by a hydrocarbon chain. The two or more functional groups do not necessarily have to be the same. The length of the hydrocarbon chain can also be varied to control the distance between the functional groups. The exact length of the hydrocarbon chain in the context of the present invention is not intended to be limiting.
The jellyfish collagen for use in the treatment of a wound may be non-cross-linked.
The source of the jellyfish collagen may be from the sub-phylum Scyphozoa. The source of the jellyfish collagen for use in the treatment of a wound may be selected from the group consisting of: the order Rhizostomeae, including, but not limited to, Rhizostomas pulmo, Rhopilema esculentum, Rhopilema nomadica, Stomolophus meleagris, Cassiopea sp. (upside-down jellyfish), including but not limited to Cassiopea andromeda, the order Semaeostomease, including Aurelia sp., and other species such as Nemopilema nomurai, Rhopilema esculentum, Rhopilema nomadica, Stomolophus meleagris, or any combination thereof. Preferably the source of the jellyfish collagen is Rhizostomas pulmo. Accordingly, the collagen may comprise at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 91%, at least 92%. At least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% Rhizostomas pulmo collagen.
The jellyfish collagen for use in the treatment of a wound may have a concentration of at least 1 mg/mL. It is envisaged that the maximum concentration of jellyfish collagen which may be used is 50 mg/mL. Accordingly, the concentration of jellyfish collagen may be between 1 mg/mL to 50 mg/mL, 2 mg/mL to 50 mg/mL, 3 mg/mL to 50 mg/mL, 4 mg/mL to 50 mg/mL, 5 mg/mL to 50 mg/mL, 6 mg/mL to 50 mg/mL, 7 mg/mL to 50 mg/mL, 8 mg/mL to 50 mg/mL, 9 mg/mL to 50 mg/mL, 10 mg/mL to 50 mg/mL, 11 mg/mL to 50 mg/mL, 12 mg/mL to 50 mg/mL, 13 mg/mL to 50 mg/mL, 14 mg/mL to 50 mg/mL, 15 mg/mL to 50 mg/mL, 16 mg/mL to 50 mg/mL, 17 mg/mL to 50 mg/mL, 18 mg/mL to 50 mg/mL, 19 mg/mL to 50 mg/mL, 20 mg/mL to 50 mg/mL, 25 mg/mL to 50 mg/mL, 30 mg/mL to 50 mg/mL, 35 mg/mL to 50 mg/mL, 40 mg/mL to 50 mg/mL, or 45 mg/mL to 50 mg/mL.
The jellyfish collagen for use in the treatment of a wound may be stable at a temperature at up to at least 37° C. The term ‘stable’ is intended to refer to the ability of the jellyfish collagen to not substantially denature under the given environmental conditions and to maintain its desirable properties. This is an advantageous property given that the intended use of the present invention involves physical contact of the product with a subject. It is envisaged that the subject is a human, however the present invention may also be utilised in the veterinary industry, for example, for use for wound treatment on dogs, cats, horses, cows, goats, sheep and the like.
The jellyfish collagen for use in the treatment of a wound may be a hydrogel, a paste, a powder, preferably a micronised powder, a membrane, a scaffold, a solution, a sponge matrix, a nano-fibre electrospun matrix, or in a lyophilised form.
A ‘hydrogel’ is a network of polymer chains that are hydrophilic, resulting in a highly absorbent material. The term ‘paste’ is intended to refer to a semisolid preparation, usually intended for external application to the skin. Typically, when used in a pharmaceutical setting, they consist of a fatty base (for example, petroleum jelly) and are at least 25% solid substance (for example, zinc oxide). A skilled person will recognise that the chosen form of the jellyfish collagen may depend on the specific wound to be treated. For example, a burn may require a hydrogel or fine collagen mesh formulation.
The compositions for use according to the invention may comprise additional pharmaceutically active ingredients. Additional pharmaceutically active ingredients include growth factors, anti-inflammatory agents, and antimicrobial drugs. Examples of anti-inflammatory agents may include nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin salsalate, diflunisal, ibuprofen, ketoprofen, nabumetone, piroxicam, naproxen, diclofenac, indomethacin and sulindac. The concentration of the chosen anti-inflammatory drug is understood to be dependent on the type and severity of the wound to be treated. Examples of antimicrobial agents which may be used include, but are not limited to, nano siliver, penicillin, ofloxacin, tetracycline, aminoglycosides and erythromycin. Mixtures of two or more of the aforementioned pharmaceutically active ingredients, with or without the above listed excipients and carriers, are envisaged.
In some embodiments, compositions for use according to the invention, further comprise at least one growth factor. In preferred embodiments, the at least growth factor is Platelet Rich Plasma (PRP), Epithelial Growth Factor 38 (EGF), Transforming Growth Factor-Beta (TGF-B, TGF-B2, TGF-B3), Hepatocyte Growth Factor (HGF), Keratinocyte Growth Factor (KGF), Granulocyte-Monocyte Colony Stimulating Growth Factor, Platelet Derived Growth Factor, Insulin-like Growth Factor 1 (IGF1), basic Fibroblast Growth Factor (bFGF), and/or Vascular 5 Endothelial Growth Factor (VEGF), or any combination thereof.
The compositions for use according to the invention may further comprise at least one antimicrobial compound. Preferably, the at least one antimicrobial compound is nano siliver, penicillin, ofloxacin, tetracycline, aminoglycosides and erythromycin, flucloxacillin, clarithromycin, doxycycline, gentamicin, metronidazole, co-amoxiclav, co-trimoxazole (in penicillin), ceftriaxone, piperacillin with tazobactam, clindamycin, ciprofloxacin, vancomycin, teicoplanin, linezolid, and/or the standard of care antimicrobial agent, or any combination thereof.
The compositions for use in the treatment of a wound may be formulated for topical application to a wound. The term ‘topical application’ in the context of the present invention, is intended to refer to the application of the jellyfish collagen, to the specific site of the wound to be treated. The wounds to be treated may be present on the skin of a subject or on the mucosal membranes of a subject, for example, the interior of the mouth. The compositions for use according to the invention may be formulated for administration by any other route known in the art. For example, the compositions for use according to the invention may be formulated for administration by Negative Pressure Wound Therapy (NPWT) (also known as Vacuum Assisted Closure (VAC)), which involves the controlled application of subatmospheric pressure to the local wound environment using a sealed wound dressing connected to a vacuum pump.
In some embodiments, compositions for use according to the invention comprise collagen at a dose from 0.01 g/L to 200 g/L, preferably 1 g/L to 50 g/L per administration.
The compositions for use according to the invention may be, formulated as a cream, bi-gel, ointment, mask, serum, milk, lotion, paste, foam, aerosol, stick, shampoo, conditioner, patch, hydroalcoholic or oily aqueous solution, an oil-in-water or water-in-oil or multiple emulsion, an aqueous or oily gel, a liquid, pasty or solid anhydrous product, an electrospun collagen nano-fibre matrix, a membrane and/or an oil dispersion in an aqueous phase using spherules, these spherules being polymeric nanoparticles such as nanospheres and nanocapsules or lipid vesicles of ionic and/or non-ionic type, more preferably an electrospun collagen nano-fibre matrix and/or a membrane.
The composition comprising jellyfish collagen for use according to the invention may further comprise a pharmaceutically acceptable excipient and/or carrier, and/or a pharmaceutically active ingredient. The excipients and carriers may enhance stability and/or improve the biopharmaceutical profile of the pharmaceutically active ingredient or the jellyfish collagen, which may or may not have an active substance conjugated. Examples of suitable pharmaceutically acceptable excipients and carriers may include sterile water, olive oil, ethyl oleate, glycols, monosaccharides such as fructose, glucose and galactose; non-reducing disaccharides such as sucrose, lactose and trehalose; non-reducing oligosaccharides such as raffinose and melezitose; non-reducing starch derived polysaccharide products such as maltodextrins, dextrans and cyclodextrins; and non-reducing alditols such as mannitol and xylitol. Further suitable excipients include cellulose preparations such as maize starch, wheat starch, rice starch, potato starch, gelatin, gum tragacanth, and/or polyvinylpyrrolidone. Mixtures of two or more of any of the above excipients or carriers (or any other suitable equivalent) are also envisaged. It is understood that any other substance with a similar effect would also be suitable.
In a preferred embodiment, the pharmaceutically active ingredient may be 1% lidocaine. Lidocaine, or lidocaine hydrochloride, is an anesthetic, commonly used as a numbing agent. The lidocaine may be up to 5% lidocaine, for example between 0.1% and 5% lidocaine, 0.5% and 5% lidocaine, 1% and 5% lidocaine, 1.5% and 5% lidocaine, 2% and 5% lidocaine, 2.5% and 5% lidocaine, 3% and 5% lidocaine, 3.5% and 5% lidocaine, 4% and 5% lidocaine and 4.5% and 5% lidocaine. Preferably, the lidocaine is at a concentration of 0.1 to 2%. Examples of further anesthetics which would be appropriate for the same purpose include, but are not limited to, benzocaine, butamben, dibucaine, lidocaine, oxybuprocaine, pramoxine, proparacaine, proxymetacaine and tetracaine.
The compositions for use according to the invention may be used to treat a wound selected from the list consisting of: a pressure sore, a transplant site, a surgical wound, an ulcer, preferably a diabetic ulcer, a thermal burn, a chemical burn, an electrical burn, a laceration, an abrasion, a puncture, an avulsion, a seroma, and/or a hematoma.
It is envisaged that the present invention may be constitute at least part of a wound dressing, with or without the additional presence of the aforementioned pharmaceutical agents. The wound dressing may contain additional ingredients, such as alginates and cellulose derivatives that can enhance absorbency, flexibility, and comfort, and help maintain an environment conducive to healing.
In one embodiment, compositions for use according to the invention may comprise jellyfish collagen in the form of micronised powder. Preferably, the micronised powder has a particle size of 1 μm to 1000 μm, more preferably, the micronised powder has a particle size of 200 μm to 500 μm.
In a particular embodiment, compositions for use according to the invention may comprise jellyfish collagen in the form of a collagen 3D sponge scaffold.
In some embodiments, compositions for use according to invention promote improved angiogenesis in a treated wound. Preferably, the improved angiogenesis is relative to an untreated wound and/or a wound treated with bovine collagen.
In a second aspect of the present invention, a method of manufacturing the aforementioned jellyfish collagen, comprising at least the steps of:
A ‘solution of purified jellyfish collagen’ refers to a solution of isolated jellyfish collagen that is substantially monomeric or, alternatively, substantially free from collagen fibrils. In this context, ‘substantially free’ refers to a solution of collagen with less than 2 wt % of the collagen being composed of fibrils. In order to maintain a collagen solution under these conditions, the isolated collagen can be stored under conditions which disfavour collagen fibril formation. This may mean the collagen is stored under acidic conditions, wherein acidic means any solution with a pH of from pH 1 to pH 6.5, or alternatively under basic conditions, wherein basic means any solution with a pH of from pH 8 to pH 14. By way of non-limiting example, the collagen may be stored in a 0.1 M solution of weak acid. The weak acid may be acetic acid or hydrochloric acid. The concentration of collagen in the collagen solution may be in the range of from 0.1 mg/ml to 30 mg/ml. Preferably, the concentration of the collagen solution is from 1 mg/ml to 10 mg/ml.
There are multiple methods for ‘isolating’, or ‘purifying’, jellyfish collagen from the anatomical milieu. Many of these will be well known and routine to the skilled person. For example, collagen can be purified from jellyfish by acid extraction, whereby different anatomical parts of the jellyfish are bathed in an acidic solution. ‘Bathing’, or ‘bathed’, refers to the process of incubating the jellyfish in the acid solution for a sufficient amount of time in order to liberate the collagen molecule. An alternative method of collagen purification is enzyme extraction, whereby the jellyfish is incubated with at least one proteolytic enzyme for a sufficient amount of time and under conditions that favour the degradation of the anatomical milieu in order to liberate the collagen molecule. The exact temperature, pH and incubation time of the enzyme extraction method will vary depending on the proteolytic enzyme used. The most suitable conditions will be well known to the skilled artisan. By way of non-limiting example, the enzyme pepsin can be incubated with jellyfish under acidic conditions in order to liberate the collagen molecule. It is envisaged that any enzyme can be used in the enzyme extraction method, and the above examples are intended to be in no way limiting.
The collagen can then be further isolated, or purified, from the undesired contaminants of the acid or enzyme extraction method by a number of different means. For example, insoluble contaminants can be removed by centrifugation. If a more pure source of collagen is required, the isolated collagen can be subjected to gel filtration, or an alternative chromatographic method that would enable the purification of the collagen molecule for other soluble contaminants of the extraction process. The exact method of further purification is not particularly limiting. Any method well known and routinely used by a protein biochemist could be adapted for the purpose of obtaining purified, or isolated, jellyfish collagen. This step can also enable the transfer of the jellyfish collagen into the desired storage buffer in order to obtain the desired solution of purified jellyfish collagen. This can be achieved by first equilibrating the chromatographic apparatus with the desired storage buffer before purification. There exist many alternative, well known methods that could be used for this purpose. Preferably, the collagen solution used in the invention is from 70% to 99% pure, wherein pure refers to the % wt in solution attributable to the collagen molecule. More preferably, the collagen solution is at least 95%, 96%, 97%, 98%, or 99% pure.
In some embodiments, the methods of manufacturing further comprise the step of:
In some embodiments, the cross-linking agent is EDC, Genipin, or Poly ethehylene glycol (PEG). Preferably, the cross-linking agent is EDC. The EDC may be at a concentration of 0.01% to 5%, 0.05% to 5%, 0.1% to 5%, 0.2% to 5%, 0.3% to 5%, 0.4% to 5%, 0.5% to 5%, 0.6% to 5%, 0.7% to 5%, 0.8% to 5%, 0.9% to 5%, 1% to 5%, 1.5% to 5%, 2% to 5%, 3% to 5%, 3.5% to 5%, 4% to 5%, or 4.5% to 5%. Preferably, the concentration of EDC is 0.5% to 1%.
In some embodiments, the methods of manufacturing the jellyfish collagen further comprise digesting the extracted jellyfish collagen with a peptidase to provide an atelo jellyfish collagen. Preferably, in the step of digesting the collagen with a peptidase, the peptidase is a pepsin. The pepsin may be of mammalian origin, non-mammalian origin (for example, papain), or microbial origin. In some embodiments, the step of digesting the collagen with a peptidase is after the step of extraction and before the purification step
The method of manufacturing the jellyfish collagen described above may further comprise the steps: i) providing a jellyfish collagen comprising a S—S bond; and ii) introducing a —SH group in said jellyfish collagen comprising a S—S bond by reduction of the S—S bond to provide a collagen thiol comprising a —SH group.
In order for the jellyfish collagen to comprise a —SH group, the jellyfish collagen must first comprise a S—S bond, or a ‘disulphide’ group. Naturally occurring collagen does not typically comprise a S—S bond. Disulphide groups may be incorporated into collagen by a number of routes. The jellyfish collagen comprising a S—S bond may be obtainable by the jellyfish collagen having one or both lysine and hydroxylysine residues. Collagen is formed of a triple-helix of polypeptide chains, one or more of which commonly comprise one or both of lysine and hydroxylysine residues. Lysine and hydroxylysine are α-amino acids having ε-amino groups. As used herein, the term ‘residue’ refers to the portion of a chemical compound remaining after incorporation into, for instance by chemical reaction and bond formation, another substance. Thus, amino acid ‘residue’ refers to the polymerised form of an amino acid monomer present in a polypeptide. Although 4-5 times less plentiful in collagen than lysine residue, hydroxylysine residue is also present in amounts sufficient to be of use in the method disclosed herein. Thus, a collagen comprising a lysine or hydroxylysine residue, prior to treatment as described herein, may comprise a residue of formula (XI):
The jellyfish collagen comprising one or both of lysine and hydroxylysine residues is preferably solubilised jellyfish collagen comprising one or both of lysine and hydroxylysine. The solubilisation may be achieved by pepsin digestion or acid digestion to provide pepsin solubilised jellyfish collagen comprising one or both of lysine and hydroxylysine or by acid digestion to provide acid solubilised jellyfish collagen comprising one or both of lysine and hydroxylysine.
The jellyfish collagen, such as a pepsin solubilised or acid solubilised jellyfish collagen, comprising one or both of lysine and hydroxylysine residues, can be reacted with an activated dicarboxylic acid derivative comprising a disulphide (i.e. S—S) group to provide collagen comprising a S—S bond. In this reaction, the carbonyl group of the activated dicarboxylic acid derivative can react with the ε-amino group of the lysine or hydroxylysine residues present in the jellyfish collagen to form an amide bond.
The activated dicarboxylic acid derivative is preferably a compound of the formula:
ZN—C(O)—R3—C(O)—NH—R1—S—S—R2—NH—C(O)—R3—C(O)—NZ (I)
wherein R1, R2 and R3 independently represent divalent linking groups, preferably divalent organic linking groups, more preferably divalent hydrocarbon linking groups, such as an alkanediyl group having from 1 to 6 carbon atoms or alkendiyl or alkyndiyl groups having from 2 to 6 carbon atoms. Still more preferably, R1, R2 and R3 independently represent ethanediyl or propanediyl groups, most preferably ethanediyl i.e. —CH2CH2—. The groups R1, R2 and R3 may independently be optionally substituted by replacing one to four hydrogen atoms with a hydroxyl group or a halogen, such as F or Cl. In a preferred embodiment, R1 and R2 are identical; and ZN together represent a nitrogen containing heterocyclic group, preferably a nitrogen containing heterocyclic group having 5-6 atoms in the heterocyclic ring, in which the N atom is directly bonded to the carbonyl group of the compound of formula (I) such that Z represents a divalent linking group in which the two valences are bonded to the nitrogen. The heterocyclic group may be saturated or unsaturated, such that Z may represent an alkanediyl, alkendiyl or alkyndiyl, particularly having 2 to 4 carbon atoms. Z may optionally comprise 1 or 2 heteroatoms selected from O, S and N.
More preferably, ZN is a nitrogen containing heteroaryl group having 5-6 atoms in the aryl ring of which from 1-3 atoms are heteroatoms selected from O, N and S at least 1 of which is N which is directly bonded to the carbonyl group of the compound of formula (I). Still more preferably the heteroaryl group has 5-6 atoms in the aryl ring of which 2 atoms are N. Alternatively, ZN is a nitrogen containing heterocyclic group having 5-6 atoms in the heterocyclic ring having 1 N atom which is directly bonded to the carbonyl group of the compound of formula (I) and Z is a α, ω-organodionediyl. For example, the α, ω-organodionediyl may be represented as —C(O)R4C(O)— in which R4 is an alkanediyl or alkendiyl having from 2 or 3 carbon atoms.
The group ZN may be optionally substituted by replacing from one to four hydrogen atoms with a hydroxyl group or a halogen, such as F, Br or Cl or by replacing two hydrogen atoms bonded to the same carbon with an oxygen atom to form a carbonyl group, wherein the latter substitution may occur once or twice.
Most preferably, the group ZN is:
1-imidazole i.e.
or 1-pyrrolidine-2,5-dione i.e.
Preferred activated dicarboxylic acid derivatives may be selected from:
The activated dicarboxylic acid derivative (I) may be synthesised in two steps. Firstly, a diamino disulphide of formula (IV) may be reacted with at least two molar equivalents of a dicarboxylic acid anhydride of formula (V) to provide a dicarboxylic acid diamide of formula (VI):
in which R1, R2 and R3 are as defined above. It will be apparent that when R1 and R2 are identical, the diamino disulphide of formula (IV) is a symmetrical molecule, which will result in a symmetrical activated dicarboxylic acid derivative (I).
The first reaction step may be carried out by dissolving the diamino disulphide of formula (IV) in a solvent, such as water, and adding the dicarboxylic acid anhydride of formula (V). It is preferred that the reaction is carried out under basic conditions, such that prior to the addition of the acid anhydride, a base can be added. For instance, aqueous sodium hydroxide can be added to adjust the pH to 10. After addition of the dicarboxylic acid anhydride, the pH may decrease, and it is preferred to maintain the pH in the range of from 7 to 10 during the reaction by the addition of further base. The reaction may be carried out at room temperature under stirring and may be complete within 30 minutes to 2 hours. The dicarboxylic acid diamide product of formula (VI) may be precipitated by lowering the pH, for instance to a pH of 1, by the addition of acid, such as aqueous hydrochloric acid. The precipitated dicarboxylic acid diamide (VI) can be isolated by filtration, washed with water and then dried under reduced pressure.
In the second step of the synthesis the dicarboxylic acid diamide (VI) is activated by the addition of a nitrogen containing heterocyclic compound to provide the activated dicarboxylic acid derivative (I):
HO—C(O)—R3—C(O)—NH—R1—S—S—R2—NH—C(O)—R3—C(O)—OH(VI)→ZN—C(O)—R3—C(O)—NH—R1—S—S—R2—NH—C(O)—R3—C(O)—NZ (I)
in which R1, R2, R3 and NZ are as defined above.
In one embodiment, the nitrogen containing heterocyclic compound may be a carbodiimide, such as a compound of formula (VII):
in which Z is as defined above. Preferably, ZN together are a nitrogen containing heteroaryl group having 5-6 atoms in the aryl ring of which from 1-3 atoms are heteroatoms selected from O, N and S at least 1 of which is N. The carbodiimide (VII) is more preferably 1,1′-carbonyl-diimidazole or the like.
At least 2 molar equivalents of the carbodiimide should be used per mole of dicarboxylic acid diamide (VI). Theoretically, the reaction will produce 2 molar equivalents of carbon dioxide and 2 molar equivalents of imidazole, per mole of dicarboxylic acid diamide (VI). The evolution of carbon dioxide gas indicates that the reaction is proceeding. The reaction may be carried out under reduced pressure.
In another embodiment, the nitrogen containing heterocyclic compound may be a N-hydroxy heterocyclic compound of formula (VIII):
in which ZN together is a nitrogen containing heterocyclic group having 5-6 atoms in the heterocyclic ring of which 1 is N and Z is a α, ω-organodionediyl. For example, the α, ω-organodionediyl may be represented as —C(O)R4C(O)— in which R4 is an alkanediyl or alkendiyl having from 2 or 3 carbon atoms. The N-hydroxy heterocyclic compound (VIII) is most preferably N-hydroxy succinimide.
The second reaction step may be carried out by dissolving the dicarboxylic acid diamide (VI) in a solvent, such as anhydrous dimethylformamide and then adding the nitrogen containing heterocyclic compound (VII) or (VIII). The activated dicarboxylic acid derivative (I) precipitates from the solution. The product can be collected by filtration, washed with anhydrous ethyl acetate, and dried under reduced pressure.
Returning to the first step of the method of the invention, a source collagen comprising one or both of lysine and hydroxylysine residues can be reacted with an activated dicarboxylic acid derivative comprising a disulphide group, such as the activated dicarboxylic acid derivative of formula (I) to provide collagen comprising a S—S bond, such as collagen of one or more of Type I, II, III, IV, V, VI, IX, X and XI comprising a S—S bond. In this reaction, a carbonyl group of the activated dicarboxylic acid derivative can react with the ε-amino group of the lysine or hydroxylysine residues present in the collagen to form an amide bond, thereby incorporating the disulphide group. The reaction can be represented by:
ZN—C(O)—R3—C(O)—NH—R1—S—S—R2—NH—C(O)—R3—C(O)—NZ(I)+collagen-NH2→ZN—C(O)—R3—C(O)—NH—R1—S—S—R2—NH—C(O)—R3—C(O)—NH-collagen+HNZ
This reaction may continue to provide a cross-linked collagen when both activated carboxyl groups of the activated dicarboxylic acid derivative react with collagen, particularly different collagen triple helices or fibrils:
ZN—C(O)—R3—C(O)—NH—R1—S—S—R2—NH—C(O)—R3—C(O)—NH-collagen+collagen-NH2→Collagen-HN—C(O)—R3—C(O)—NH—R1—S—S—R2—NH—C(O)—R3—C(O)—NH-collagen+HNZ
The reaction can be carried out by dissolving the source collagen in a solvent. The dissolution of the source collagen can be carried out in a two-step process. In the first step, the source collagen may be mixed with methanol. In the second step, a polar aprotic solvent is added. For instance, the source collagen can be added to a mixture of methanol and dimethylsulfoxide, and allowed to swell. Additional dimethylsulfoxide can be added with stirring until dissolution of the source collagen is complete. Methanol can then be removed from the solution by evaporating under reduced pressure. This solubilising process can be used with both atelocollagen and telocollagen.
The activated dicarboxylic acid derivative can then be dissolved in a solvent, particularly an anhydrous polar aprotic solvent, such as dimethylsulfoxide. Since the activated dicarboxylic acid derivative of formula (I) is sensitive to water, the reaction with collagen is preferably carried out in anhydrous polar aprotic solvents, such as dimethylsulfoxide. The activated dicarboxylic acid derivative dissolved in a solvent is then added to the source collagen solution. The carbonyl group of the activated dicarboxylic acid derivative can react with the ε-amino group of the lysine or hydroxylysine residues present in the source collagen to form an amide bond.
The mixture can be stirred at room temperature, for instance 22° C., until a gel is formed. The mixture containing the gel can then be left undisturbed e.g. for 12-18 hr. The dimethylsulfoxide can then be extracted from the gel by blending with an excess of acetone, collecting the collagen gel by decantation and then reblending with more acetone. The mixture can then be stirred e.g. for 0.5 to 1 hr and the collagen subsequently isolated by filtration, washed with acetone, then washed with water-ethanol (30:70 v/v) and dehydrated with ethanol. A jellyfish collagen comprising a S—S bond is thereby provided.
In an alternative embodiment, the jellyfish collagen comprising a S—S bond may be provided by modifying a collagen-binding protein to include a photoreactive cross-linker comprising a disulphide group, combining this with jellyfish collagen to provide a complex and irradiating the complex to cross-link the photoreactive cross-linker to incorporate the disulphide group into the collagen.
This route creates protein-binding sites on the jellyfish collagen by using a site-specific photo-cross-linking strategy allowing the creation of thiol groups in collagen. This involves the introduction of a cysteine residue into the collagen-binding protein by site-directed mutagenesis. A photoreactive cross-linker, preferably APDP, can be introduced into cysteine —SH groups on proteins. The complex of APDP-modified protein and collagen can be cross-linked by ultraviolet (uv) irradiation. The disulfide cross-link can then be cleaved by reduction, and an —SH group is generated on the jellyfish collagen.
In a first step, a collagen-binding protein comprising a cysteine residue is provided. A cysteine residue is necessary because this comprises a sulphydryl group necessary for reaction with the cross-linker. The collagen-binding protein may be, for instance, pigment epithelium-derived factor (PEDF). PEDF is a known anti-angiogenic/neurotrophic factor with a collagen binding site identified by Yasui et al as disclosed in Biochemistry, 2003, 42, pages 3160-3167.
If necessary, cysteine may be incorporated into the collagen-binding protein if not already present or if the collagen-binding protein does not contain sufficient cysteine. Cysteine substitutions can be made via site-directed mutagenesis, for instance where the collagen binding site is localised (F383) and on the opposite surface of the site (Y211). Methods for carrying out such site-directed mutagenesis are found in J. D. J. Biol. Chem. 2002, 277, 4223-4231 and R. R. Biochemistry 1992, 31, 9526-9532.
The sulphydryl groups introduced as a result of the cysteine substitutions can then be reacted with a photoreactive cross-linker. The photoreactive cross-linker should be bifunctional. In particular, the photoreactive cross-linker should comprise a functional group capable of reacting with a sulphydryl group to produce a disulphide bond. One such suitable functional group is a pyridyl-dithio group i.e. C5NH5—S—S—, particularly 2-pyridyl dithio. The photoreactive cross-linker should also comprise a functional group capable of cross-linking with collagen under photo-irradiation. One such suitable functional group is an azide group, particularly an aryl azide group, such as a phenyl azide, especially para —C6H4—N3.
N-[4-(p-azidosalicylamido)butyl]-3′-(2′pyridyldithio) propionamide (APDP) is one example of a preferred photoreactive cross-linker. The disulphide group of APDP can react with the sulphydryl group of the cysteine to produce a disulphide bond between the cysteine and the photoreactive cross-linker, thereby providing a photoreactive cross-linker modified collagen binding protein comprising a S—S group. 2-pyridyl thione is liberated as part of this reaction as a leaving group.
The photoreactive cross-linker modified collagen-binding protein can then be combined with a jellyfish collagen, to provide a complex of the photoreactive cross-linker modified collagen-binding protein and the jellyfish collagen. In this step, the photoreactive cross-linker modified collagen-binding protein binds to the protein binding site of the jellyfish collagen to form the complex. The complex of the photoreactive cross-linker modified collagen-binding protein and the collagen can then be irradiated, for example with ultraviolet (UV) light. Irradiation causes the functional group capable of cross-linking present on the photoreactive cross-linker to form a covalent bond with the adjacent collagen in the complex. For example, when the functional group capable of cross-linking is a phenyl azide, irradiation at a wavelength in the range of from 250 to 280 nm will generate a nitrene, which can then attack nucleophilic or active hydrogen groups, such as C—H or C—NH2 on the collagen to generate a cross-link by insertion across the C—H or N—H bond. In this way, the photoreactive cross-linker modified collagen binding protein comprising a S—S group is incorporated into the collagen to provide collagen comprising a S—S bond. It will be apparent that the disulphide group will be provided in the vicinity of the collagen protein binding site by this route.
A sulphydryl group can then be introduced into the collagen comprising a S—S bond which can be provided by either of the methods discussed above i.e. using the activated dicarboxylic acid derivate or photoreactive cross-linker methods. The jellyfish collagen comprising a S—S bond can be reacted with a suitable reducing agent. The reducing agent reduces the disulphide bond to two sulphydryl groups, thereby cleaving the activated dicarboxylic acid derivative residue or the photoreactive cross-linker residue, in which the disulphide group is located. Such a reduction proceeds by two sequential thiol-disulfide exchange reactions, resulting in the reduction of the disulphide group to produce jellyfish collagen comprising a sulphydryl (—SH) group.
Suitable reducing agents include, for example, dithiothreitol (DTT), (2S)-2-amino-1,4-dimercaptobutane (DTBA) and tris(2-carboxyethyl) phosphine HCl (TCEP hydrochloride). Dithiothreitol is a preferred reducing agent.
The reduction step can be carried out by adding the jellyfish collagen comprising a S—S bond to a buffer solution, such as a glycine/sodium hydroxide buffer solution at a pH of in the range of from 7.5 to 9.5, more preferably about 8 to 9.5, preferably about 8.0. The jellyfish collagen comprising a S—S bond may be inherently acidic, and if so, neutralisation with a base, such as sodium hydroxide, may be required.
Preferably, at least two molar equivalents of DTT reducing agent can be added per mole of disulphide group in the same buffer and the reaction allowed to proceed at 30° C. for 2-6 hr. After completion of the reaction, the pH of the liquid may be decreased to 2, for instance using HCl. The mixture may then be dialysed with dilute HCl solution, centrifuged and freeze-dried to provide the jellyfish collagen thiol having a —SH group.
The reduction may cause a slight degradation of the collagen chains. Consequently, shorter reaction times, lower pH and lower temperature can all be used to minimise any degradation.
It will be apparent that when the jellyfish collagen comprising a S—S bond is provided using a photoreactive cross-linker modified collagen-binding protein, the modified collagen-binding protein will still be attached to the collagen via the photoreactive cross-linker step d prior to the step of forming the collagen thiol. Reduction of the S—S bond will cleave the S—S bond of the photoreactive cross-linker.
When the jellyfish collagen comprises one or both of lysine and hydroxylysine residues, a jellyfish collagen thiol comprising a lysine or hydroxylysine residue of formula (X) is provided:
in which R1, R3 and R5 are as defined above. For instance, R1 and R3 are independently selected from divalent linking groups, preferably divalent organic linking groups, more preferably divalent hydrocarbon linking groups, such as an alkanediyl group having from 1 to 6 carbon atoms or alkendiyl or alkyndiyl groups having from 2 to 6 carbon atoms. Still more preferably, R1 and R3 independently represent ethanediyl or propanediyl groups, most preferably ethanediyl (i.e. —CH2CH2—). R5 is H when the amino acid residue is a lysine residue. R5 is OH when the amino acid residue is a hydroxylysine residue; X is selected from the group OH and a chemical bond and Y is selected from H and a chemical bond, with the proviso that one or both of X and Y are chemical bonds forming peptide bonds within collagen. The peptide chain forming part of the modified collagen is shown bracketed by “[ ]” in formula (X). The residue could be in a terminal position of the peptide, for instance if one or other of X and Y is OH and H respectively. If both X and Y are peptide bonds, the lysine residue is non-terminal within the peptide chain forming part of the collagen.
The present invention further provides for a method of manufacturing the jellyfish collagen disclosed herein, which may or may not be thiolated, which further comprises the steps: i) mixing the solution of purified jellyfish collagen, or the collagen thiol, with an aqueous neutralisation buffer; and ii) incubating the mixture for a sufficient amount of time to enable collagen fibrils to form, wherein a cross-linking agent is added in either step i) or ii) to provide a cross-linked collagen.
The term ‘neutralisation buffer’ refers to any buffer within which a solution of purified jellyfish collagen can be diluted in order to increase or decrease the pH to a pH of from pH 4 to pH 9. The composition of the neutralisation buffer is not particularly limiting, only insofar that it must increase or decrease the pH of the solution of purified jellyfish collagen in order that collagen fibril formation can proceed. Furthermore, the buffer must be substantially free from ions, compounds, or molecules which may interfere with any cross-linking process. Thus, a buffer substantially free from unreacted amines is particularly desirable. By way of non-limiting example only, the neutralisation buffer may be of from 1× to 10× phosphate buffered saline (PBS), where 1× or 10× refer to the concentration of PBS. The composition of 1×PBS will be well known to the skilled person. The exact concentration of PBS (i.e. 1× or, e.g. 10×) will depend entirely on the dilution factor required when mixing with the solution of purified jellyfish collagen, in order that the solution of purified jellyfish collagen is substantially neutralised so that collagen fibril formation can proceed. In some embodiments, the neutralisation buffer is sodium hydroxide.
The term ‘fibril formation’, or ‘fibrillogenesis’, refers to the process by which collagen molecules undergo controlled aggregation to form higher order, well-structured macromolecular assemblies. Collagen in vivo is a predominantly extracellular protein whose aggregation into fibrillar structures provides architectural support for surrounding tissues and/or components of the extracellular matrix. The aggregation of collagens, in particular mammalian collagens, is a well-known phenomenon. Different isoforms of mammalian and marine collagens preferentially aggregate into different macromolecular structures. The unique macromolecular structures formed from each collagen isoform is governed by the physicochemical properties of the collagen polypeptide and the conditions under which fibrillogenesis is promoted. Higher-order collagen structures, i.e. collagen fibrils obtained from mammals or fish, have been exploited in vitro in order to generate mammalian and/or fish collagen hydrogels. Thus, in order to form hydrogels from jellyfish collagens, jellyfish collagens are preferred to assemble into higher order structures. Preferably, the higher order structure is a fibril.
It is envisaged that any cross-linking agent known to cross-link under the conditions within which collagen fibrils are formed would be a suitable cross-linking agent for use in the invention. In certain applications, it may be desirable to use a cross-linking agent that is non-toxic to cells. In certain embodiments, the crosslinking agent may be selected from genipin, 1,4-BDDGE, or mucochloric acid. Preferably, the cross-linking agent is either genipin or 1,4-BDDGE.
The present invention is now further described with reference to the below examples and studies.
Aim
To compare the performance of jellyfish collagen sponge; cross-linked jellyfish collagen sponge; chemically-modified (thiolated) jellyfish collagen paste—to a commercially-available wound product, Puracol®, in a model of excisional, cutaneous wound healing in C57BL/6J mice.
Procedure
Eighty (80) male C57BL/6J mice, aged 5-6 weeks of age, were provided by Epistem in two cohorts of 40 mice each. Each cohort of mice was acclimatized for two weeks and eight mice per cohort were randomized into one of five treatment groups. On day 0 (day of wounding) all animals were anaesthetised, shaved and two 6 mm diameter excisional wounds made at the same relative position, either side of the dorsal mid-line, on each mouse. According to the assigned treatment group one of the following dressings was applied to the wound cavities of each mouse: pre-formed jellyfish collagen sponges, either standard or cross-linked; chemically-modified (thiolated) collagen gel; pre-cut Puracol® dressing; no treatment. Following application of wound treatments, a Tegaderm film dressing was applied to cover each wound. Mice were placed into a warming cabinet after the procedure and allowed to recover from anaesthesia before returning them to their holding room. All mice were housed individually from the time of wounding. Wounds were monitored at least once per day for any sign of infection and detachment of Tegaderm film dressings. Visual assessment of wound condition and measurement of wound width was not possible to perform accurately during the in-life phase of the study, due to the folding of the Tegaderm, caused by normal mouse activity.
From each cohort, four mice per treatment group were euthanised at 3 days post-wounding and four mice at 7 days post-wounding. Mice were humanely killed by cervical dislocation and the strip of dorsal skin containing both wounds was excised. Wound width was determined using digital callipers; wounds were also assigned a subjective visual score (1-5) according to the degree of macroscopic healing. Individual wounds were bisected with half snap-frozen in liquid nitrogen and half fixed in 10% neutral-buffered formalin for histological processing and preparation of Haematoxylin and Eosin (H&E)-stained transverse wound sections. For each wound section, wound width, and degree of re-epithelialisation were determined using computer-assisted morphometry (Zeiss Axiohome system). In addition, a subjective score for granulation tissue maturity was assigned to each wound, and the area of granulation tissue determined.
Results
Each treatment group demonstrated healing of excisional wounds from day 3 to day 7, as evidenced by reduced wound width (
The cross-linked jellyfish collagen sponge group demonstrated the greatest amount of wound closure, with a day 3 mean wound width of (5.11±1.46) mm and a day 7 value of (3.16±0.80) mm (
Re-epithelialisation in the Tegaderm only group progressed from (17.2±10.5) % on day 3 to (59.7±37.9) % on day 7. The Puracol® group demonstrated the most re-epithelialisation on day 7, at (73.2±27.1) %, with the cross-linked jellyfish collagen sponge group showing a similar level of re-epithelialisation at (70.7 t 30.3) % (
Granulation score and the area of granulation (as a percentage of total wound area) increased from day 3 to day 7 for all groups (
Observation of H&E-stained wound cross-sections demonstrated that the obvious structures of both the Puracol® and the cross-linked jellyfish collagen sponges were visible overlaying the wound on day 3. With the cross-linked jellyfish collagen sponges, the migration of the healing epithelium underneath the sponge was readily apparent. Representative images of wounds from each group are shown in
Collagen I immunoreactivity was observed in all wound sections; representative images are shown in
Animals tolerated the different test items well, with no adverse effects. During the seven days after wounding, wounds healed well with evidence of re-epithelialisation in most animals, and both the amount and maturity of granulation tissue increasing over time. Both types of jellyfish collagen sponge were superior to Tegaderm dressing alone, with respect to the extent of tissue granulation in the wound space by day 7, with the cross-linked jellyfish collagen sponge also demonstrating more re-epithelialisation. In contrast, the performance of the jellyfish sponge and the reference product Puracol® dressing was similar.
This study demonstrates that jellyfish collagen is a suitable alternative, with at least an equivalent efficacy, to already known products on the market for treating wounds. These known products are typically of mammalian origin and as such are associated with a number of disadvantages. The provision of an alternative source of collagen suitable for the treatment of wounds is thus extremely advantageous.
Aim
The aim of this study was to section and to immunohistochemically label with anti-mouse CD31, 152 FFPE mouse wounds obtained by study 18/099, a study to determine the effects of test items in a cutaneous wounding healing murine model. CD31 is an endothelial cell marker which is commonly used to determine and measure angiogenesis.
Procedure
152 FFPE mouse wounds obtained during study 18/099—a study to determine the effects of test items in a cutaneous wounding healing murine model at day 3 and day 7 time points, were sectioned at 3 μm thickness to provide one slide with two non-serial sections per slide. Sections were mounted on charged slides and dried overnight at 37° C.
The 152 FFPE sections were dewaxed and rehydrated before antigen retrieval was performed using proteolytic digestion with Proteinase K (Dako S3020) for 5 minutes at room temperature. Endogenous peroxidase was blocked for 15 minutes with 0.3% H2O2 in TBST before non-specific binding was blocked with 2.5% goat serum for 30 minutes. The sections were incubated with an anti-mouse CD31, rat monoclonal antibody, clone MEC13.3 (BD Pharmingen 550274) at 0.3125 μg/ml for 1 hour at room temperature. A corresponding rat monoclonal IgG2a isotype control was included at a matched concentration to the primary antibody on one sample. A sample of untreated mouse skin was included as a positive tissue control. Sections were washed in TBST and then incubated with anti-rat, mouse adsorbed polymer (Vector ImmPress MP-7444). All labelling was visualized using DAB (Vector ImmPact SK-4105) and sections were counterstained with haematoxylin before being permanently mounted. Each labelled slide was checked against its corresponding block to confirm a match and examined microscopically as part of the quality control procedure.
Thirty representative images were taken using an AxioVision Imaging System which consists of a Zeiss Axioscope A1 microscope, AxioCam MRc Camera and AxioVision software installed on a computer workstation to capture images. Images were taken using a ×10 objective.
Representative images from each of the treatment wound dressing groups (Tegaderm only, Jellyfish collagen sponge, chemically-modified (thiolated) jellyfish collagen paste, cross-linked Jellyfish collagen sponge and Puracol) were taken at day 3 (
The wound samples taken from study 18/099 were successfully labelled for a mouse-specific endothelial cell marker, CD31, which is indicative of angiogenesis occurring in these samples treated with jellyfish collagen.
As with the in vivo data, the above in vitro data show that jellyfish collagen is an appropriate alternative to bovine collagen for use in the treatment of wounds, one which lacks the disadvantages associated with using a mammalian collagen, such as enhanced risk of disease/prion transmission, increased risk of contamination and the significant cost associated with obtaining collagen from mammalian sources. This finding is a surprising one given the vastly different physicochemical and amino acid properties of jellyfish collagens to mammalian collagen.
Aim
To investigate the impact of three Jellyfish-derived collagen formulations on wound healing in the BKS.Cg-m Dock7m+/+Leprdb/J (db/db) diabetic mouse—a model of delayed cutaneous wound healing.
Procedure
Materials Under Test:
BKS.Cg-m Dock7m+/+Leprdb/J Diabetic Mouse Model
The methods followed are briefly outlined below. The live phase of this study was undertaken between 19 Sep. 2019 and 9 Oct. 2019.
Diabetic mice (BKS.Cg-m Dock7m+/+Leprdb/J, Jackson Labs, Bar Harbour, Me., USA) were brought into the UK aged approximately 9-10 weeks and were allowed to acclimate for one week prior to the start of the study. Animals were maintained according to UK Home Office regulations and the specific requirements of diabetic animals. Animals were randomly allocated to 5 treatment groups (Table 1).
Briefly, mice were anaesthetised using isofluorane and air, and their dorsal flank skin was clipped and cleansed according to protocol. A single standardised full-thickness wound (10 mm×10 mm) was created on the left dorsal flank approximately 5 mm from the spine. Wounds were cleaned with sterile saline-soaked gauze swabs and dried with sterile gauze. 15 μL of sterile physiological saline was then applied to the surface of each wound. The materials under test were then applied directly to the surface of saline-moistened wounds.
Wounds in group 2 received one ˜6 mm diameter (96-well formed) non-crosslinked Jellagen sponge; those in group 5 received a 6 mm disk of the commercial comparator Promogran™ (Acelity, USA), and those in groups 3 and 4 received 5 mg of EDC-crosslinked Jellagen powder (0.5% and 1.0% EDC crosslinked, respectively). Immediately after product application, all wounds were dressed with the semi-occlusive film dressing Tegaderm™ Film, (3M Deutschland GmbH, Germany). The condition of this film dressing was examined daily throughout the study and was replaced if it became detached.
On post-wounding days 4, 8, 12, and 16 all animals were re-anaesthetised, their film dressings and any free debris removed, and their wounds (and marginal skin) were gently cleaned using sterile saline-soaked gauze (without disturbing any existing products within the wound). Wounds were then photographed not shown), moistened with 15 μl of sterile physiological saline, and products re-applied to wounds in selected groups on selected days.
It was originally intended that wounds in groups 2 (non-crosslinked Jellagen sponge) and 5 (Promogran™, Acelity, USA) would receive a second application of product on post-wounding day 4. In view of the observation that neither of these products had experienced significant degradation, it was decided (and agreed with the sponsor) that re-application would not be undertaken at this time point. Product re-application—without prior removal of existing undegraded product—was, however, undertaken on post-wounding days 8, 12, and 16.
After product re-application (where indicated), wounds were re-dressed (as above) with Tegaderm™ Film dressing—and animals were allowed to recover in a warmed environment (˜35° C.). Immediately after wounding, and subsequently after cleaning on days 4, 8, 12, 16, and 20, all wounds were digitally photographed together with a calibration/identity plate.
All animals were culled on post-wounding day 20. One hour prior to termination all animals received an i.p. injection (30 μg/g) of 5-bromo-2′-deoxyuridine (Sigma B5002) in normal saline to facilitate the possibility of detection of cellular proliferation in histological sections. Wound and surrounding marginal tissue was then harvested from all wounds. Tissues were fixed (Neutral Buffered Formalin, Sigma) and embedded in paraffin wax to facilitate histological investigation.
Overview
This study examined the effect of three Jellyfish-derived formulations (non-crosslinked Jellagen sponge, 0.5% EDC crosslinked Jellagen Powder and 1.0% EDC crosslinked Jellagen Powder), applied topically, on the repair of full-thickness excisional skin wounds in the healing-impaired db/db diabetic mouse.
The healing of wounds in receipt of these formulations/products was compared with each other, with that of wounds in receipt of a commercial comparator (Promogran™ Protease Modulating Matrix, Acelity, USA) and, with that of control (film dressing only) treated wounds.
Wound healing was assessed over a 20-day period in terms of (i) initiation of neo-dermal repair responses, and (ii) wound closure. Initiation of neo-dermal tissue formation was expressed as the number of wounds responding in each group at each time point. Wound closure was considered in both overall terms and in terms of its components wound contraction and wound re-epithelialisation. Wound closure (contraction and re-epithelialisation) was determined from digital photographs taken on post-wounding days 0, 4, 8, 12, 16, and 20 post-wounding. At the histological level, H&E-stained sections of wound tissues (harvested on day 20) were briefly considered and compared in terms of granulation tissue formation and re-epithelialisation, and (in the case of the two EDC crosslinked powder formulations) in terms of their potential use as structural scaffolds to support tissue regeneration.
Summary of Results—Wound Closure
Each wound was digitally photographed, along with an identification/calibration plate, immediately after injury and subsequently on days 4, 8, 12, 16, and 20. For a given wound at a given time point, wound closure was expressed as the percentage wound area remaining relative to the initial wound area immediately after injury (i.e. day 0). Mean percentage wound area remaining data for all treatment groups are described in Table 2 below and shown in
When wound closure (in terms of change in ‘% open wound area’ with time) was considered, the following was observed:
Summary of Results—Wound Contraction
Contraction is the centripetal movement of the wound margins, due to the compaction of granulation tissue within the “body” of the wound. The “compactional” forces that drive this process, are thought to reside in cells of the fibroblast lineage. In this study, percentage contraction was calculated as:
Wounds on non-diabetic mice close predominantly by contraction, while those on diabetic mice (such as those used in this study) have a significantly reduced ability to contract (possibly due to impoverished granulation tissue formation). As a result, untreated wounds on diabetic animals tend to close by re-epithelialisation to a greater extent than those on non-diabetic animals. An observation of enhanced contraction suggests improvement in granulation tissue function, which may in turn be explained by an increase in the amount of granulation tissue formed, an increase in the speed at which it is formed, or increased contractile capacity of the tissue. Mean percentage wound contraction data for all treatment groups are described in Table 3 (below) and shown in
When the impact of treatment on wound contraction was considered, the following was observed:
Summary of Results—Wound Re-Epithelialisation
For a given wound, at a given time point, the area of re-epithelialisation was expressed as a percentage of the original area of that wound immediately after injury. Mean percentage wound re-epithelialisation data for all treatment groups are described in Table 4 (below) and shown in
When the impact of treatment on wound re-epithelialisation was considered, the following was observed:
Summary of Results—Initiation of Neo-Dermal Tissue Generation
All wounds in the study were visually assessed on a daily basis until day 8, and subsequently on days 10, 12, 14, 16, and 20 to establish their “healing” status. Each wound was scored as to whether it was displaying “neo-dermal tissue generation activity” within the central wound area. Scoring was undertaken independently by two independent observers and the average % of wounds displaying “neo-dermal tissue generation activity” was compared between treatment groups at each assessment point. The number of wounds responding in each treatment group on each day is displayed in Table 5. The mean time to respond for each group is displayed in Table 6. It should be noted that since 10 out of the 10 wounds in the ‘film dressing only’ treatment group did not respond during the study period, the mean value for ‘time to respond’ for this group is an unknown value greater than 20.
10
10
10
10
10
10
10
10
10
10
10
10
10
Application of all three Jellagen products encouraged initiation of ‘neo-dermal tissue formation’ within the central wound region when compared to ‘film dressing only’ Control treatment. Of the three Jellagen treatments investigated, 1.0% EDC crosslinked powder resulted in the most rapid ‘initiation’, followed by 0.5% EDC crosslinked powder—and finally non-crosslinked sponge. All three products were as effective—if not more effective—than Promogran™.
Summary of Results—Wound Histology
Wound tissue, together with surrounding per-wound skin, was harvested from each animal on conclusion of the study on post-wounding day 20. Tissue samples were fixed, processed and embedded in paraffin wax. Sections (˜6 μm) were taken from the centre of each wound in a cranio-caudal direction. These sections were stained with Haematoxylin and Eosin (H&E), and were digitally scanned. Representative examples of the appearance of wounds in each experimental group are displayed in
Control-treated wounds displayed limited granulation tissue formation and limited re-epithelialisation (both restricted to the edges of wounds).
Application of non-crosslinked sponge resulted in in elevated granulation tissue formation and re-epithelialisation relative to Control. Granulation tissue was formed throughout the wound base, although ‘quality’ was found to be variable. No obvious product residue in the majority of wounds.
Application of both EDC crosslinked powders resulted in elevated granulation tissue formation with minimal re-epithelialisation in the majority of wounds. These products appeared to act as a scaffold for granulation tissue deposition—and when fully cellularised—may support re-epithelialisation. Based on gross wound images and histological appearance, these products appear not to have experienced significant degradation over the 20-day study period.
The EDC crosslinked jellyfish collagen powders appeared to encourage the growth of new blood vessels into it from the wound edges. This was most evident with the 1.0% powder—visible macroscopically as progressive redness from the outer edges of the hydrated mass on the wound surface—and was also apparent on the histological sections (
Study Outcome
All three of the Jellagen products evaluated in this study were found to have a positive impact on the healing of wounds in the db/db diabetic mouse impaired healing model.
The non-crosslinked collagen sponge promoted wound closure by promoting both contraction and re-epithelialisation, and was found to promote granulation tissue formation. The sponge material experienced extensive compaction, limited degradation and appeared not become incorporated into wound tissues.
The crosslinked powders promoted wound closure primarily by promoting the process of wound contraction—which may be explained by the ability of these products to act as a scaffold for granulation tissue formation.
Aim
To investigate the impact of three Jellyfish-derived collagen formulations on wound healing in the BKS.Cg-m Dock7m+/+Leprdb/J (db/db) diabetic mouse—a model of delayed cutaneous wound healing.
Procedure
Materials Under Test:
BKS.Cg-m Dock7m+/+Leprdb/J Diabetic Mouse Model
The methods followed are briefly outlined below.
Diabetic mice (BKS.Cg-m Dock7m+/+Leprdb/J, Jackson Labs, Bar Harbour, Me., USA) were brought into the UK aged approximately 9-10 weeks and were allowed to acclimate for one week prior to the start of the study. Animals were maintained according to UK Home Office regulations and the specific requirements of diabetic animals. Animals were randomly allocated to 5 treatment groups (Table 7).
Briefly, mice were anaesthetised using isofluorane and air, and their dorsal flank skin was clipped and cleansed according to protocol. A single standardised full-thickness wound (10 mm×10 mm) was created on the left dorsal flank approximately 5 mm from the spine. Wounds were cleaned with sterile saline-soaked gauze swabs and dried with sterile gauze. 15 μL of sterile physiological saline was then applied to the surface of each wound. The materials under test were then applied directly to the surface of saline-moistened wounds.
On days of reapplication (see Table 7 above), animals were re-anaesthetised, their film dressings and any free debris removed, and their wounds (and marginal skin) were gently cleaned using sterile saline-soaked gauze (without disturbing any existing products within the wound). Wounds were then photographed not shown), moistened with 15 μl of sterile physiological saline, and products re-applied to wounds in selected groups on selected days. After product re-application (where indicated), wounds were re-dressed with Tegaderm™ Film dressing, and animals were allowed to recover in a warmed environment (˜35° C.). Wounds were digitally photographed together with a calibration/identity plate on immediately after wounding and post-wounding days 4, 8, 12, 16, 20, 24, 28, 35, 42, 49, 56, and 63.
At post wounding day 35, 8 animals from each group were sacrificed. All remaining animals were culled on post-wounding day 63.
Summary of Results—Wound Closure
Each wound was digitally photographed, along with an identification/calibration plate, immediately after injury and subsequently on days 4, 8, 12, 16, 20, 24, 28, 35, 42, 49, 56, and 63. For a given wound at a given time point, wound closure was expressed as the percentage wound area remaining relative to the initial wound area immediately after injury (i.e. day 0). Mean percentage wound area remaining data for all treatment groups are shown in
When wound closure (in terms of change in ‘% open wound area’ with time) was considered, the following was observed:
Summary of Results—Wound Contraction
Contraction is the centripetal movement of the wound margins, due to the compaction of granulation tissue within the “body” of the wound. The “compactional” forces that drive this process, are thought to reside in cells of the fibroblast lineage. In this study, percentage contraction was calculated as:
Wounds on non-diabetic mice close predominantly by contraction, while those on diabetic mice (such as those used in this study) have a significantly reduced ability to contract (possibly due to impoverished granulation tissue formation). As a result, untreated wounds on diabetic animals tend to close by re-epithelialisation to a greater extent than those on non-diabetic animals. An observation of enhanced contraction suggests improvement in granulation tissue function, which may in turn be explained by an increase in the amount of granulation tissue formed, an increase in the speed at which it is formed, or increased contractile capacity of the tissue. Mean percentage wound contraction data for all treatment groups are shown in
When the impact of treatment on wound contraction was considered, the following was observed:
Summary of Results—Wound Re-Epithelialisation
For a given wound, at a given time point, the area of re-epithelialisation was expressed as a percentage of the original area of that wound immediately after injury. Mean percentage wound re-epithelialisation data for all treatment groups are described in Table 4 (below) and shown in
When the impact of treatment on wound re-epithelialisation was considered, the following was observed:
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005141.3 | Apr 2020 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2021/050856 | 4/7/2021 | WO |
