Patent Application
20170183658
The present invention relates to the field of fibroproliferative disorders, particularly idiopathic pulmonary fibrosis (IPF), and the role of microRNA (miRNA) in the tissue fibrosis process.
The present invention relates more specifically to the use of microRNA (miRNA), particularly miR-199a-5p, targets and/or inhibitors thereof for the diagnosis, the prognosis and treatment of fibroproliferative disorders, namely idiopathic pulmonary fibrosis.
In the description hereinafter, the references between square brackets ([ ]) refer to the list of references given at the end of the text.
Tissue fibrosis, defined as the excessive persistent formation of non-functional connective scar tissue in response to a chronic tissue lesion, is a major cause of morbidity and mortality associated with loss of function of the damaged organ in various disorders such as those affecting the pulmonary interstitium [Wynn, J. Clin. Invest., 117: 524-529, 2007] [1]. Fibroproliferative disorders are a major public health problem. Indeed, in the United States alone, 45% of deaths are attributed to fibroproliferative disorders and the prevalence thereof is constantly increasing [Wynn, Nat. Rev. Immunol., 4: 583-594, 2004] [2].
Of the pulmonary interstitial disorders of unknown origin, idiopathic pulmonary fibrosis (IPF) is the most frequent and lethal form with an average survival rate of 3 to 5 years post-diagnosis [Wilson and Wynn, Mucosal. Immunol., 2: 103-121, 2009] [3]. IPF is a chronic and frequently fatal lung disease characterised by fibroblast proliferation and excessive extracellular matrix protein deposition. IPF is a rare disorder with a prevalence of 13 to 20 cases per 100,000 inhabitants and whose causes remain poorly understood, and for which no effective treatment is currently available.
Observations based on animal pulmonary fibrosis models and lung sections of patients with IPF suggest a dynamic biopathological process involving excessive scar tissue formation with chronic inflammation, epithelial and endothelial cell apoptosis, mesenchymatous cell proliferation and activation with fibroblast/myofibroblast site formation, and finally excessive extracellular matrix deposition resulting in the destruction of the lung structure and loss of lung function. In physiopathological terms, at the present time, repeated alveolar epithelium damage is considered to be responsible for lesions on the pulmonary epithelium promoting alveolar plasma exudate formation and clotting process activation, secretion of growth factor such as TGFβ by pneumocytes enabling pulmonary fibroblast recruitment, proliferation and activation and abnormal and excessive extracellular matrix deposition [Wilson and Wynn, 2009, cited above] [3]. During the fibrosis process, the fibroblasts have a myofibroblast phenotype and are organised into fibroblastic foci. Other mechanisms may also be involved in the fibrosis process such as mesenchymal epithelial transition of epithelial, endothelial or mesothelial cells and pulmonary medullary circulating fibrocyte recruitment [Wilson and Wynn, 2009, cited above] [3].
MicroRNAs (miRNAs) are a class of small non-coding RNA with approximately 22 bases and having a key role in a wide range of cell phenomena such as development, differentiation, survival, response to stress, apoptosis, proliferation, homeostasis or differentiation [Ambros, Nature, 431: 350-355, 2004] [4]. Recent studies have identified specific miRNA expression profiles associated with the initiation and progression of various disorders including cancer and inflammatory and autoimmune disorders. Moreover, miRNA function gain and loss studies have revealed pathogenic miRNA functions accentuating the major role thereof in vivo. Preferably, the term “microRNA” or “miRNA”, in the context of the present invention, means an RNA oligonucleotide consisting of between 18 to 25 nucleotides in length. In functional terms miRNAs are typically regulatory endogenous RNA molecules.
The mechanism of action thereof involves the formation of a complex between a plurality of miRNA bases and the 3′-non-coding part of the target mRNA [Brennecke et al., PLoS. Biol., 3: e85, 2005] [5]. This interaction gives rise to destabilisation of the target mRNA and/or protein synthesis inhibition [Brennecke et al., 2005, cited above] [5]. Recognition between miRNA and the target thereof is essentially controlled by a sequence of approximately 7 bases, situated in the 5′ part of the miRNA (recognition sequence or seed) [Brennecke et al., 2005, cited above] [5]. For this reason, each miRNA would appear to be capable of regulating the stability of a broad range of distinct mRNAs. The terms “target gene” or “target mRNA” refer to regulatory mRNA targets of microRNAs, in which said “target gene” or “target mRNA” is regulated post-transcriptionally by the microRNA based on near-perfect or perfect complementarity between the miRNA and its target site resulting in target mRNA cleavage; or limited complementarity, often conferred to complementarity between the so-called seed sequence (nucleotides 2-7 of the miRNA) and the target site resulting in translational inhibition of the target mRNA.
About 2000 miRNAs have been identified in humans to date (miRBase release 19 http://www.mirbase.org) where they would appear to regulate more than 30% of transcripts. MiRNA regulation is thus considered as a major form of gene expression regulation, the impact of which has been largely underestimated until now [Xie et al., nature, 434: 338-345, 2005; Berezikov et al., Cell, 120: 21-24, 2005] [6, 7].
MiRNAs are transcribed in the nucleus in the form of long precursors (pri-miRNA) and undergo a first maturation step in the nucleus to produce pre-miRNA having a smaller hairpin structure. This miRNA precursor is thus exported from the nucleus to the cytoplasm where it undergoes a final maturation step with Dicer enzyme generating two single-stranded miRNAs (one 5p strand and one 3p strand): the “mature” strand is taken on by a multi-protein complex (RNA Induced Silencing Complex or RISC) interacting with the 3′-non-coding part of the target mRNA, whereas the “star” complementary strand undergoes degradation (annotation: miR-xx*).
In clinical terms, numerous studies suggest possible use of miRNAs as a diagnostic tool. Indeed, miRNAs display good stability in biological fluids such as serum [Mitchell et al., Proc. Natl. Acad. Sci. U.S.A., 105: 10513-10518, 2008] [8] or urine [Weber et al., Clin. Chem., 56: 1733-1741, 2010] [9]. For this reason, studying the expression thereof in these biological media offers new non-invasive prospects for the development of new diagnostic or prognostic biomarkers. Moreover, miRNA tissue expression profiles could also offer new prognostic or diagnostic tools as already demonstrated in cancer treatment [Lu et al., Nature, 435: 834-838, 2005] [10]. For example, miR-199a-5p, one of the two mature miRNA species derived from the miR-199a precursor, has been associated with malignancy not only in hepatocellular carcinoma [Jiang et al., Clin. Cancer Res., 14(2): 419-427, 2008] [11] but also in bronchial tumours [Mascaux et al., Eur. Respir. J., 33(2): 352-359 (Epub 2008), 2009; Puisségur et al., Cell death Differ., 18(3): 465-478, 2011] [12, 13].
In therapeutic terms, miRNA expression modulation could also enable the development of new treatments [Krutzfeldt et al., Nature, 438: 685-689, 2005] [14]. For example, the use of miR-122 inhibitor in the development of new hepatitis C treatments has made it possible to obtain a significant reduction in the viral load of this virus [Lanford et al., Science, 327: 198-201, 2010] [15].
Despite increasing evidence of the involvement of miRNAs in the tissue fibrosis process, the precise role thereof and mechanism(s) of action thereof have yet to be explored extensively [Jiang et al., FEBS J., 277: 2015-2021, 2010] [16]. Although the cause of IPF is unknown, a central role of miRNAs was recently suggested in the pathogenesis thereof. However, the role of miRNAs in fibrotic disorders, particularly in pulmonary fibrosis, is poorly documented and only a few miRNAs such as miR-21 or let7-d have been studied to date [Liu et al., J. Exp. Med., 20: 1589-1597, 2010; Pandit et al., Am. J. Respir. Crit. Care Med., 182: 220-229, 2010] [17, 18]. Therefore, miRNAs for which the expression is associated with pulmonary fibrosis could offer particularly promising tools for the development of new diagnostic and prognostic markers of IPF and new therapeutic strategies for this disorder which continues to be incurable and have a poor prognosis [Pandit et al., Transl. Res., 157: 191-199, 2011] [19].
The inventors demonstrated, for the first time and completely unexpectedly, the role of miRNAs, particularly miR-199a-5p, and the targets thereof in pulmonary, hepatic and renal fibrosis.
The inventors more specifically used an experimental pulmonary fibrosis model to identify, in the lung, i) miRNAs differentially expressed only in C57BL/6 mice sensitive to bleomycin-induced pulmonary fibrosis and ii) correlated miRNAs during the progression of the fibrotic process. For this purpose, the inventors used various experimental approaches combining miRNA biochips, in situ hybridisation, and quantitative RT-PCR.
In this way, they identified an expression profile of 22 specific miRNAs with respect to the pulmonary response of C57BL/6 mice sensitive to bleomycin-induced pulmonary fibrosis.
Among the 22 miRNAs of the identified expression profile, they demonstrated, for the first time, the unique role of miR-199a-5p in the pulmonary fibrosis process. In this way, they identified significant miR-199a-5p up-regulation in the lungs of mice with bleomycin-induced fibrosis. Indeed, miR-199a-5p would appear to be the most discriminatory miRNA between sensitive C57BL/6 mouse strains and resistant Balb/c mouse strains in respect of bleomycin-induced pulmonary fibrosis, thus enabling a distinction between pathological and normal cases.
Significant miR-199a-5p up-regulation was also identified in the lungs of patients suffering from IPF. More specifically, the miR-199a-5p levels increased selectively in the myofibroblasts of damaged lungs.
Consequently, the profibrotic effects of miR-199a-5p were studied further in pulmonary fibroblasts. In this way, they demonstrated pulmonary fibroblast activation to a profibrotic phenotype after miR-199a-5p overexpression. Finally, the inventors demonstrated that miR-199a-5p overexpression partially mimicked the transcriptional signature and cellular effects of TGFβ, one of the main factors involved in fibrotic mechanisms, which is also capable of increasing miR-199a-5p expression.
They also demonstrated that the role of miR-199a-5p can be extrapolated to other fibrotic disorders in mammals since this miRNA is common to the various forms of pulmonary, hepatic and renal fibrosis; and could thus become a universal marker thereof. Indeed, they demonstrated abnormal miR-199a-5p expression in mouse renal and hepatic fibrosis models, demonstrating that miR-199a-5p deregulation represents a general mechanism contributing to the fibrosis process.
Furthermore, the inventors combined in silico approaches (target prediction bioinformatics software) and experimental approaches (transcriptome chips, ectopic miRNA expression and reporter vectors containing the 3′-UTR part of a gene of interest fused with luciferase) in order to determine and characterise the target genes specifically regulated by miR-199a-5p. In particular, variation in expression of the gene coding for caveolin-1 (CAV1), a critical mediator in pulmonary fibrosis, according to the level of miR-199a-5p expression, was observed. In this way, they identified CAV1 as a genuine target of miR-199a-5p.
The present invention thus relates to an in vitro diagnostic method for a fibroproliferative disorder in a subject characterised in that it comprises the following steps:
(i) quantitative measurement of the level of miRNA expression in a biological sample from said subject;
(ii) optionally determining the miRNA expression profile of said biological sample from said subject;
(iii) comparing the miRNA expression profile of the biological sample from said subject with the same miRNA expression profile of a reference biological sample, said expression profile consisting of mir-146b, miR-34a, miR-21, miR-449a, miR-449b, miR-20a, miR-18a, miR-223, miR-449c, miR-147b, miR-152, miR-181ac, miR-451, miR-351, miR-133ac, miR-214, miR-199a-5p, miR-132, miR-222, miR-342-3p, miR-345-5p and miR-221;
(iv) identifying at least one miRNA for which the level of expression by said biological sample from said subject differs with respect to the level of expression of the same miRNA by said reference sample.
According to one particular embodiment, the 22 miRNAs of the specific expression profile for the pulmonary response to bleomycin-induced pulmonary fibrosis are represented by the following accession numbers:
The term “fibroproliferative disorder” according to the present invention refers to disorders characterised by a parenchymal organ lesion and fibrosis. For example, it refers to pulmonary, hepatic and renal fibrosis, particularly idiopathic pulmonary fibrosis (IPF).
The term “subject” according to the present invention refers to a vertebrate, particularly a mammal, more particularly a human.
The term “biological sample” according to the present invention refers to a bronchial, liver or kidney biopsy. For example, it refers to epithelial tissue, particularly from the respiratory, hepatic or renal epithelium.
The term “reference biological sample” according to the present invention refers to a biological sample as defined above obtained from a healthy subject, i.e. not presenting fibrosis, or a subject in whom the miR-199a-5p expression is known and associated with a particular clinical stage. For example, it refers to the level of miR-199a-5p expression obtained after analysing human biopsy samples (see table 1 hereinafter) or mouse lung samples (see table 2 hereinafter) with “miRNA” biochips (Agilent technology) in healthy subjects (control) or subjects suffering from idiopathic pulmonary fibrosis (IPF).
aID Agilent SurePrint G3 hsa chip probe
blog2 median expression
cIPF vs control
dWilcoxon test
amiRBase ID (http://www.mirbase.org)
blog2 median expression
cbleomycin vs PBS control
dWilcoxon test
The level of miRNA expression in a cell or tissue is determined by measuring the miRNAs present in said cell or said tissue. The level of miRNA expression may be measured using any technique known to those skilled in the art. For example, after RNA extraction, high-speed miRNA sequencing, NASBA (Nucleic Acid Strand Based Amplification) sequencing, primer extension sequencing, “miRNA” DNA chips, quantitative RT-PCR methods applied to miRNA or in situ hybridisation.
The in vitro diagnostic method according to the invention may comprise the additional step for (v) identifying at least one target gene for which the level of expression is regulated by the level of miR-199a-5p expression identified in step (iii).
The level of expression of a target gene in a cell or a tissue is determined by measuring the transcript expressed in said cell or said tissue. The level of target gene expression may be measured using any technique known to those skilled in the art. For example, it may be carried out after quantitative RT-PCR RNA extraction, or on tissue sections by means of immunocytochemistry or immunocytology.
Preferably, said at least one miRNA identified in step (iv) is miR-199a-5p.
Preferably, said at least one target gene identified in step (v) codes for caveolin-1 (Gene ID: 857/http://www.ncbi.nlm.nih.gov/gene/857).
The present invention also relates to a method for identifying a subject liable to develop a fibroproliferative disorder characterised in that it comprises or consists of the following steps:
(i) quantitative measurement of the level of miR-199a-5p expression in a biological sample from said subject;
(ii) comparing the level of miR-199a-5p expression in said biological sample from said subject with the level of miR-199a-5p expression in a reference biological sample;
(iii) detecting an increase in the level of miR-199a-5p expression.
The present invention also relates to the use of a miR-199a-5p inhibitor for preventing and/or treating a fibroproliferative disorder, preferably idiopathic pulmonary fibrosis.
The present invention also relates to the use of a miR-199a-5p inhibitor for stimulating wound repair.
The term “miRNA inhibitor” according to the present invention refers to DNA analogues or “oligomer”, consisting of a contiguous sequence of from 7 to at least 22 nucleotides in length. The term “nucleotide” as used herein, refers to a glycoside comprising a sugar moiety, a base moiety and a covalently linked group (linkage group), such as a phosphate or phosphorothioate internucleotide linkage group. It covers both naturally occurring nucleotides and non-naturally occurring nucleotides comprising modified sugar and/or base moieties, which are also referred to as “nucleotide analogues” herein. Non-naturally occurring nucleotides include nucleotides which have sugar moieties, such as bicyclic nucleotides or 2′ modified nucleotides or 2′ modified nucleotides such as 2′ substituted nucleotides. “Nucleotide analogues” are variants of natural oligonucleotides by virtue of modifications in the sugar and/or base moieties. Preferably, without being limited by this explanation, the analogues will have a functional effect on the way in which the oligomer works to bind to its target; for example by producing increased binding affinity to the target and/or increased resistance to nucleases and/or increased ease of transport into the cell. Specific examples of nucleoside analogues are described by Freier and Altman (Nucl. Acid Res., 25: 4429-4443, 1997) [35] and Uhlmann (Curr. Opinion in Drug Development, 3: 293-213, 2000) [36]. Incorporation of affinity-enhancing analogues in the oligomer, including Locked Nucleic Acid (LNA™), can allow the size of the specifically binding oligomer to be reduced and may also reduce the upper limit to the size of the oligomer before non-specific or aberrant binding takes place. The term “LNA™” refers to a bicyclic nucleoside analogue, known as “Locked Nucleic Acid” (Rajwanshi et al., Angew Chem. Int. Ed. Engl., 39(9): 1656-1659, 2000) [37]. It may refer to an LNA™ monomer, or, when used in the context of an “LNA™ oligonucleotide” to an oligonucleotide containing one or more such bicylic analogues.
Suitably, the oligomer of the invention is capable of specifically inhibiting (silencing) the activity of miR-199a-5p (“anti-miR-199-5p”) or preventing the binding of miR-199a-5p to specific miR-199a-5p binding sites in target RNAs (“miR-199a-5p Target Site Blocker”). Preferably, a “anti-miR-199a-5p” refers to antisense oligonucleotides with sequence complementary to miR-199a-5p (e.g., anti-miR-199a-5p LNA™ miRNA inhibitor; Product No.: 426918-00, Product name: hsa-miR-199a-5p, Description: miRCURY LNA™ microRNA Power Inhibitor, EXIQON). These oligomers may comprise or consist of a contiguous nucleotide sequence of a total of 7 to at least 22 contiguous nucleotides in length, up to 70% nucleotide analogues (LNA™). The shortest oligomer (7 nucleotides) will likely correspond to an antisense oligonucleotide with perfect sequence complementarity matching to the first 7 nucleotides located at the 5′ end of mature miR-199a-5p, and comprising the 7 nucleotide sequence at position 2-8 from 5′ end called the “seed” sequence (i.e., “ccagugu” for miR-199a-5p, see Seq ID No 13) involved in miRNA target specificity (Lewis et al., Cell. 2005 Jan. 14; 120(1):15-20) [38]. A “miR-199a-5p Target Site Blocker refers to antisense oligonucleotides with sequence complementary to a miR-199a-5p binding site located on a specific mRNA. These oligomers may be designed according to the teaching of US 20090137504. These oligomers may comprise or consist of a contiguous nucleotide sequence of a total of 8 to 23 contiguous nucleotides in length. These sequences may span from 20 nucleotides in the 5′ or the 3′ direction from the sequence corresponding to the reverse complement of miR-199a-5p “seed” sequence. For example, “CAV1 Target Site Blockers comprise or consist of a contiguous sequence of a total of 8 to 23 contiguous nucleotides in length which corresponds to the reverse complement of a specific nucleotide sequence present in the CAV1 mRNA (NM_001753.4, NM_001172895.1, NM_001172896.1, NM_001172897.1 or naturally occurring variants thereof and RNA nucleic acids derived therefrom, preferably mRNA) and defined as miR-199a-5p site (
The present invention also relates to the use of a miR-199a-5p inhibitor for obtaining a medicinal product. For example, it consists of the use of a miR-199a-5p inhibitor by the aerosol route for inhibiting fibrogenesis in the pathological respiratory epithelium in subjects suffering from pulmonary fibrosis and thus restoring the integrity of the pathological tissue so as to restore full functionality.
According to one particular embodiment of the invention, said medicinal product is intended to prevent and/or treat a fibroproliferative disorder, preferably idiopathic pulmonary fibrosis.
The examples of embodiments of the present invention hereinafter, along with the appended figures, illustrate the invention and are given as non-limiting examples.
MRC-5 and hFL1 5CCL-153) normal human lung fibroblasts and the A549 human lung cancer cell line were acquired from the American Type Culture Collection (ATCC, Manassas, Va., USA) and cultured in DMEM medium containing 10% foetal calf serum, at 37° C. with 5% CO2 v/v.
Recombinant TGFβ was acquired from Sigma-Aldrich.
The following monoclonal and polyclonal antibodies were used for the immunohistochemistry and Western blot analyses: rabbit anti-CAV1 polyclonal antibody (sc-894, Santa Cruz Biotechnology Inc.), rabbit anti-β-actin monoclonal antibody (13E5, cell signaling), mouse anti-α-SMA monoclonal antibody (1A4, Dako).
Male C57BL/6 and BALB/c strain mice, aged from 9 to 12 weeks, were acquired from Charles River, France. To induce the fibrotic changes, the mice were instilled by the intratracheal route with bleomycin or PBS for the controls. For this purpose, the mice were anaesthetised by sevorane (Abbott) inhalation and placed in the supine position. Transtracheal insertion of a 24-G supply needle was used for instilling bleomycin (0.75 units/ml) or excipient (PBS), in an 80 μl volume. The mice were sacrificed 7 and 14 days after instillation and the lungs were removed for subsequent analysis.
Male C57BL/6 and BALB/c strain mice, aged from 9 to 12 weeks, were acquired from Charles River, France. The mice were anaesthetised by means of intraperitoneal injection of pentobarbital (50 mg/kg of body weight). After standard laparotomy, the left proximal ureter was exposed and ligated at two points with 4-0 silk. The “simulation or control” procedure consisted of a similar identification of the left ureter, but the ureter was not ligated.
Male C57BL/6 and BALB/c strain mice, aged from 6 to 8 weeks, were acquired from Jackson Laboratory (Bar Harbor). To induce hepatic fibrosis, the mice received 0.6 ml/kg of body weight of CCl4 (Merck) mixed with corn oil (Sigma life science) by the intraperitoneal route as described above [Roderbrug et al., Hepatol., 53: 209-218, 2011] [24]. The bile duct was ligated by exposing the common hepatic duct and conducting a double-ligation thereof, and subsequently cutting between the ligations as described by Roderburg et al. [2011, cited above] [24]. To induce fibrosis regression, the mice were treated for 6 weeks with CCl4 as described above and sacrificed 2 or 4 weeks, respectively, after the end of the treatment.
Primary stellate cells were isolated from 40-55 week old C57BL/6 mice and stimulated with 20 ng/ml of TGF-β1 (Sigma Aldrich) for 48 hours as previously described by Roderburg et al. [2011, cited above] [24].
Frozen lung tissues from subjects with IPF and free from chronic lung disease were obtained from the “Lung Tissue Research Consortium (LTRC)”. The diagnoses were based on ATS/ERS guidelines [Demedts and Costabel, Eur. Respir. J., 19: 794-796, 2002; Steele et al., Am. J. Respir. Crit. Care Med., 172: 1146-1152, 2005] [32, 33] based on the clinical history, pathology and radiology. All the tests were approved by the local Institutional Review Board at the University of Pittsburgh. The clinical data were made fully available to the investigators for examination.
Paraffin-treated lung sections from patients with IPF were obtained from Lille hospital. The tests were approved by the Lille hospital institutional research commission.
Mouse kidneys and lungs were fixed overnight with neutral buffered formalin and then included in paraffin. μm thick tissue sections were mounted and stained with haematoxylin and eosin and with Masson's trichrome to evaluate the degree of fibrosis. The histological sections were examined by an experienced pathologist.
The total RNA was extracted from lung cell and tissue samples using Trizol Reagent (Invitrogen) according to the manufacturer's recommendations. The purity and concentration of the total RNA samples were first evaluated using the Nanodrop spectrophotometer. The 260/280 and 260/230 ratios were checked and should have a value close to 2. The RNA was then loaded onto a chi nano chip and the quality thereof (RNA integrity and degradation level) was analysed using the Bioanalyzer System (Agilent Technologies, France).
Mouse Lung miRNA Biochips
The oligonucleotide sequences corresponding 2054 mature miRNAs found in the miRNA registry are available at http://www.microarray.fr:8080/merge/index (follow the link to “microARN”: platform references on the NCBI GEO database in GPL4718). Three biological reproductions were produced for each comparison. The experimental data and the biochip design were registered on the NCBI GEO database (http://www.ncbi.nlm.nih.gov/geo/) under series GSE34812. The experimental design used a “dye-swap” approach, such that each mouse probe, imprinted 8 times on the biochip was measured 16 times independently for each sample. The target preparation and biochip hybridisation were carried out as previously described [Pottier et al., PLoS. One, 4: e6718, 2009; Triboulet et al., Science, 315: 1579-1582, 2007; Puisségur et al., 2011, cited above] [25, 26, 13].
Human Lung miRNA Biochip Analysis
MiRNA biochip analysis was conducted as previously described [Pandit et al., 2010, cited above] [18]. In brief, 100 ng of total RNA was labelled and hybridised on Agilent microRNA Microarray Release 16.0, 8×60K. After washing, the chips were scanned using an Agilent Microarray scanner. The scanned images were processed with Agilent's Feature Extraction software version 9.5.3. The miRNA biochip data were analysed using GeneSpring v11.5 and BRB-ArrayTools v.1 developed by Dr. Richard Simon and the BRB-ArrayTools development team. The data were standardised per quantile. The miRNA biochip data are available to the public via the Lung Genomics Research Consortium (LGRC) website (lung-genomics.org).
The RNA samples were labelled with Cy3 stain using the low RNA input QuickAmp kit (Agilent) according to the manufacturer's recommendations. 825 ng of labelled cRNA probe was hybridised on mouse or human Agilent 8×60K high density SurePrint G3 gene expression biochips. Two (in vitro human tests) or five (in vivo-derived samples) biological reproductions were produced for each comparison. The experimental data were registered on the NCBI GEO database (http://www.ncbi.nlm.nih.gov/geo/) under SuperSeries GSE34818 (series GSE34812 and GSE34814 for the miRNA and mRNA responses in the mouse bleomycin model, respectively; series GSE34815 for the miRNA/siRNA transfection tests in hFL1 human fibroblasts). For the human gene expression chips, the data were converted into log 2 and standardised using a cyclic Loess algorithm in the R programming environment as previously described [Wu et al., BMC. Bioinformatics, 6: 309, 2005] [34]. The human biochip data have been made available to the public on the LTRC (ltrcpublic.org) and LGRC websites as part of the LTRC protocol.
The standardisation was carried out using the Limma program available from Bioconductor (http://www.bioconductor.org). The within-chip (two-colour dye-swap tests only) and between-chip standardisation was carried out using the “PrintTip Loess” method and the quantile method, respectively. The mean ratios of all the comparisons were calculated and a B test analysis was conducted. Differentially expressed genes were selected using the Benjamini-Hochberg p-value correction for multiple tests, based on a p-value less than 0.05. The expression biochip data were analysed for biological theme enrichment (canonical pathways and genetic ontology molecular function) and to construct biological networks using Ingenuity Pathway Analysis software (http://www.ingenuity.com/) and Mediante (http://www.microarray.fr:8080/merge/index) [Le and Barbry, Bioinformatics, 23: 1304-1306, 2007] [27], an information system containing various information on probes and data sets. Gene Set Enrichment Analysis (GSEA) software was used to determine whether a gene set defined in principle can characterise differences between two biological states [Subramanian et al., Proc. Natl. Acad. Sci. U.S.A., 102: 15545-15550, 2005] [28]. Hierarchical clusters were produced with MultiExperiment Viewer (MeV) version 4.3, using the Manhattan distance and the mean link.
MiRonTop [Le et al., Bioinformatics, 26: 3131-3132, 2010] [29] is an online Java network tool (available at http://www.microarray.fr:8080/miRonTop/index) which integrates DNA biochip data to identify the potential involvement of miRNAs in a specific biological system. In brief, MiRonTop classifies transcripts into two categories (“up-regulated” and “down-regulated”), based on expression level and differential expression thresholds. It then calculates the number of predicted targets for each miRNA, based on the selected prediction software (Targetscan, MiRBase, PicTar, exact progeny search: 2-7 or 1-8 first nucleotides of miRNA, TarBase v1), in each gene set. MiRNA target enrichment in each category is then tested using the hypergeometric function. The absence of a non-siRNA target effect was verified in si-CAV1 transcriptome tests using the Sylamer tool [Van et al., Nat. Methods, 5: 1023-1025, 2008] [30].
Pre-miRNA, LNA-Based miRNA Inhibitors, Target Site Blocker and siRNA Transfection in Lung Fibroblasts
Pre-miR-199-5p, pre-miR-21 and control miRNA (miR-Neg#1) were acquired from Ambion. For the miR-199-5p knock-down tests, anti-miR-199-5p LNA and the anti-miR-159s LNA negative control (miRCURY LNA knock-down probe) were ordered from Exiqon. SiRNA targeted against CAV1 and control siRNA (Silencer Select validated siRNAs) were acquired from Applied Biosystems.
MRC5/hFL1 cells were cultured in DMEM medium containing 10% FCS and transfected to 30-40% confluence in 6- or 12-well plates using Lipofectamine RNAi MAX™ (Invitrogen) with pre-miRNA, siRNA or LNA inhibitors at a final concentration of 10 nM unless indicated.
Pre-miRNA and psiCHECK™-2 Plasmid Construction Cotransfection
Molecular constructions were produced in pSI-CHECK™-2 vector (Promega) by cloning behind Renilla luciferase in the XhoI and NotI restriction sites, CAV1 3′UTR derived hybrid oligonucleotides described hereinafter. HEK293 cells were cultured in DMEM medium containing 10% FCS to confluence. The cells were then distributed into 96-well plates and cotransfected using lipofectamine 2000™ (Invitrogen) with 0.2 μg of psiCHECK™-2 plasmid construction or pre-miR-199-5p or control miRNA at a final concentration of 10, 30 and 50 nM. 48 hours after transfection, the renilla and firefly luciferase activities were evaluated with the Dual Glo Luciferase Assay System kit (Promega) and measured using a luminometer (Luminoskan Ascent, Thermolab system).
MRC5 cells were seeded in 96 well plate and cotransfected 24 h later at 4% confluency using RNAi MAX lipofectamine reagent with 100 ng SMAD reported vector (Cignal Smad Reporter, Qiagen) and 10 nM LNA-control, LNA-199a-5p or CAV1 protector. 24 h after transfection, cells were serum starved 3 h before adding 10 ng/ml TGFβ. Cells were lyzed and Glo luciferase assay (Promega) was performed 24 h following TGFβ exposure.
Mature miRNA Expression
The miR-199a-5p expression was evaluated using the TaqMan MicroRNA Assay kit (Applied Biosystems) as specified in the protocol. Real-time PCR was conducted using the GeneAmp Fast PCR Master Mix product (Applied Biosystems) and the ABI 7900HT real-time PCR machine. The levels of mature miRNA expression were evaluated using the comparative CT method (2-deltaCT).
The pri-miR-199a-1 and pri-miR-199a-2 expressions were evaluated using the TaqMan pri-microRNA Assay system (Applied Biosystems) according to the manufacturer's recommendations. Real-time PCR was conducted using the TaqMan™ Gene Expression Master Mix product (Applied Biosystems) and the ABI 7900HT real-time PCR machine. The levels of pri-miRNA expression were evaluated using the comparative CT method (2-deltaCT).
The levels of human and mouse CAV1 expression were analysed using the TaqMan MicroRNA Assay system (Applied Biosystems) according to the manufacturer's recommendations. Real-time PCR was conducted using the TaqMan™ Gene Expression Master Mix product (Applied Biosystems) and the ABI 7900HT real-time PCR machine. The levels of CAV1 were evaluated using the comparative CT method (2-deltaCT).
The cells or tissues were lysed in a lysis buffer (M-PER protein extraction buffer for cells, T-PER protein extraction reagent for tissues) and a mixture of protease inhibitors (Pierce). The lysates were assayed for protein concentrations using the Bradford assay (Biorad). The proteins (10 μg per sample) underwent electrophoresis in SDS-polyacrylamide gel and transferred into liquid medium on a nitrocellulose membrane (Hybond™ C Extra, Amersham Bioscience) for 1 hr 30 in a transfer buffer (50 mM Tris base, 40 mM Glycine, 1.3 mM SDS and 10% ethanol). After transfer, the membrane was blocked in a 5% milk 0.1% TBS-Tween solution for 1 hour at ambient temperature under stirring. It was then incubated with anti-CAV1 primary antibodies (Santa Cruz) diluted to 1:400, anti-beta actin antibodies (Cell Signaling Technology) to 1:1000 overnight at 4° C. on a rotating plate. After washing 3 times in 0.1% TBS-Tween for 30 minutes at ambient temperature, the membrane was incubated for 1 hour in the presence of mouse anti-IgG secondary antibody coupled with HRP (Horse Radish Peroxidase, Cell Signaling) diluted to 1:5000 5% milk TBS-0.1% Tween under stirring. After washing several times, in 0.1% TBS-Tween for 30 minutes, the proteins of interest were detected by chemoluminescence (ECL substrates, Amersham).
5 μm thick mouse lung sections included in paraffin were deparaffinised in xylene (2×5 minutes) and rehydrated by incubating 2×5 minutes in 100% ethanol, 2×5 minutes in 95% ethanol, and 2×5 minutes in 80% ethanol. After washing with water, the antigen was unmasked by thermal denaturation using a citrate buffer (pH=6.0, DAKO) for 20 minutes. The sections were cooled to ambient temperature and then washed in 0.1% TBS-Tween, and the endogenous peroxidases were inactivated with 3% hydrogen peroxide in TBS for 10 minutes. The sections were also blocked for avidin/biotin activity, blocked with serum-free blocking reagents, and incubated with anti-CAV1 or anti alpha-SMA primary antibody for 1 hour at ambient temperature and overnight at 4° C., respectively. The proteins of interest were then detected with diaminobenzidine (DAB, DAKO) after incubating the secondary antibody.
The tissue location of miR-199a-5p was detected using the double DIG-labeled LNA probes system (Exiqon, Woburn, Mass.). Mouse tissues included in paraffin were deparaffinised in xylene (2×5 minutes) and rehydrated by incubating 2×5 minutes in 100% ethanol, 2×5 minutes in 95% ethanol, and 2×5 minutes in 80% ethanol. The slides were then washed in PBS (pH 7.5) and permeabilised by incubating for 15 minutes at 37° C. in proteinase K (Ambion). The slides were washed again in PBS, and pre-hybridised in a hybridisation buffer (50% formamide, 5×SSC, 0.1% Tween 20, 9.2 mM citric acid, 50 μg/ml heparin, and 500 μg/ml yeast RNA, pH 6) in a wet chamber. The double DIG-labelled LNA probes were then added at a concentration of 80 nM and incubated for 2 hours at 50° C. in a wet chamber. The slides were rinsed in 5×SSC, 1×SSC and 0.2×SSC solutions at the same hybridisation temperature. This was followed by blocking with 2% sheep serum, 2 mg/ml BSA in PBS+0.1% Tween 20 (PBST) and incubation with anti-DIG-AP Fab fragments (1:800) (Roche Applied Sciences) for 2 hours at ambient temperature. After washing in PBST, the stained reaction was produced by incubating in a 5-bromo-4-chloro-3-indolyl phosphate (BCIP)/nitro blue tetrazolium (NBT) solution (Roche Applied Sciences) with 1 mM levamisole overnight at ambient temperature. The stained reaction was stopped after observing sufficient blue precipitate development by washing with PBST. The slides were then counterstained with Fastred, mounted and topped with a slide cover.
MRC5 cells were grown on a Round Glass Coverslips Ø 16 mm (Thermo scientific) placed inside a 12 Multiwell Plate. Coverslips slides were washed in phosphate-buffered saline and fixed in 4% paraformaldehyde for 15 min, cells were then permeated using 0.1% Triton X-102 (Agilent Technologies) for 10 min and blocked with PBS solution containing BSA (3%) for 30 min. Incubation with primary antibodies was performed in a blocking solution BSA (1%) at 37° C. for 1 h at the following dilutions: α-SMA (1:1000), CAV1 (1:50). After three washes with PBS, cells were incubated with secondary Alexa Fluor 488 goat anti-mouse IgG (Invitrogen) (1:500), Alexa Fluor 647 goat anti-rabbit IgG (Invitrogen) (1:500) and Alexa Fluor® 647 phalloidin (A22287, Life Technologies) (1 unit/slide). 45 min later, Coverslips slides were fixed on microscope slides using Prolong® Gold Antifade Reagent with DAPI (Invitrogen). Fluorescence was viewed with an FV10i Olympus confocal scanning microscope.
The human lung fibroblasts (MRC-5 or hFL-1) were distributed into 6-well plates (150,000 cells per well) in DMEM medium supplemented with 10% FCS. The following day, the culture medium was replaced with serum-free medium and the cells were transfected with pre-miR-199a-5p. The cell proliferation was then evaluated 48 hours after transfection by flow cytometry using the Click-iT™ EdU Cell Proliferation Assay kit (Invitrogen) according to the manufacturer's recommendations.
The human lung fibroblasts (MRC-5 or hFL-1) were placed in 12-well plates (500,000 cells per well). At confluence, the culture medium was replaced with serum-free medium and the cells were transfected with pre-miR-199a-5p or an anti-miR-199-5p inhibitor (LNA anti-miR-199-5p, Exiqon). 24 hours after transfection, the cells were scratched with a pipette tip and treated or untreated with TGFβ (20 ng/ml). The “in vitro” healing mechanism was then filmed for 24 hours after scratching by video microscopy using an Axiovert 200 M inverted microscope (Carl Zeiss) equipped with a regulation insert at 5% CO2 and 37° C. (Pecon GmbH). Images with a light background were taken every 30 minutes through a factor 10 phase contrast lens with a CoolSNAPHQ CCD camera managed using Metamorph software (Roper Scientific). The cell motility was calculated by evaluating the repaired area percentage using ImageJ image analysis software.
Invasion of MRC5 fibroblast overexpressing mR-199a-5p was assessed using commercially available 24-well BioCoat Matrigel Invasion Chamber (BD Biosciences). In brief, pulmonary fibrobasts were transfected either with pre-miR-199a-5p or negative control as described above. 24 h after transfection, cells were harvested with trypsin-EDTA, centrifuged, and resuspended in DMEM medium. Cell suspensions (1×105 cells/well) were added to the upper chamber. Bottom wells of the chamber were filled with DMEM medium containing 10% FBS as chemoattractant, whereas the upper chamber was filled with DMEM only. After incubation for 48 h at 37° C., the non-invading cells on the top of the membrane were removed with a cotton swab. Membrane containing invading-cells were fixed with methanol, washed three times with PBS and mounted with DAPI hard set (Vector Laboratories) onto glass slides for fluorescent microscopy.
The results were given as the mean±standard error of the mean. The statistical analyses were carried out using the Student test as provided by Microsoft Excel™.
Pulmonary Fibrosis-Resistant and Sensitive Mice Display a Distinct miRNA Expression Profile in Response to Bleomycin
Bleomycin is the experimental tool of choice for inducing pulmonary fibrosis on various animal models, including mice. In this way, C57BL/6 type mice are considered to be sensitive to bleomycin-induced pulmonary fibrosis whereas BALB/c type mice are resistant. To identify the miRNAs potentially involved in the pulmonary fibrosis process, the pulmonary miRNA expression profile in response to bleomycin in bleomycin-induced pulmonary fibrosis-sensitive and resistant mice (n=3 mice per group) was studied using a biochip-based platform (data set 1, accession number GSE34812) described elsewhere [25, 26, 13]. In particular, the expression profile study focused on the fibrotic phase of the fibrosis process, i.e. 7 days and 14 days after administering bleomycin. The expression profile identified consists of 22 significantly differentially expressed miRNAs between the lungs of control and bleomycin-treated animals in at least one type, the majority being up-regulated in lungs instilled with bleomycin (
To study the regulation mechanisms underlying miR-199a-5p production, the expression status of two mouse genes was evaluated, miR-199a-1 (on chromosome 9) and miR-199a-2 (on chromosome 1), in response to bleomycin using the Taqman assay designed to discriminate between pri-miR-199a-1 and pri-miR-199a-2. The results demonstrated that, 14 days after instilling bleomycin, the two pri-miR-199a transcripts were up-regulated in the lungs of C57BL/6J mice (
Moreover, in situ hybridisation tests conducted on histological lung sections obtained from C57BL/6 mice, 14 days after administering bleomycin (fibrotic lungs) or PBS (healthy lungs), revealed selective miR-199a-5p expression in myofibroblasts in the damaged areas of the diseased lungs corresponding to the fibroblastic sites (
It is important to note that, in line with previous studies, miR-21 up-regulation was detected in response to bleomycin (
Identification of Specific miR-199a-5p Targets in Lung Fibroblasts
One of the major stakes in miRNA biology is that of being able to identify and characterise regulated target mRNA experimentally. In this context, in silico approaches (target prediction bioinformatics software) and experimental approaches (transcriptome chips), ectopic miRNA expression and reporter vectors containing the 3′-UTR part of a gene of interest fused with luciferase were combined, as previously described [25, 13]. A number of target prediction algorithms have been proposed. They are generally based on i) the complementarity between miRNA and target mRNA 3′-UTR in the 5′ region of miRNA (referred to as the “seed”), and ii) the phylogenetic conservation of this sequence in the target mRNA 3′-UTR.
To determine the target genes regulated by miR-199a-5p, Agilent® expression chip (Agilent Technology) mRNA profiling was carried out after manipulating the miR-199a-5p expression level by transfection in lung fibroblasts. The influence of miR-199a-5p on the transcriptome of hFL1 human lung fibroblasts was compared to that of miR-21 (data set 2, accession number GEO GSE34815). The ectopic expression of each miRNA induced major modifications in the transcriptome 48 hours after transfection with modulated genes 1261 and 753 in miR-199a-5p and miR-21 contexts, respectively. Whereas these two miRNAs induced very different modulation profiles (
Direct putative targets were then searched in the down-regulated transcript population using the MiRonTop tool. This indicated specific over-representation of predicted targets in the down-regulated transcript population after heterologous miR-199a-5p or miR-21 expression, using a number of prediction tools including an additional direct progeny search or TargetScan (
The analysis then focused on a subset of transcripts containing complementary miR-199a-5p hexamers in the 3′UTR thereof displaying the most expression inhibition. Three different prediction tools, TargetScan, PicTar and miRanda, produced contrasting results, as shown in the Venn diagrams represented in
Homo sapiens acyl-CoA
Homo sapiens A kinase (PRKA)
Homo sapiens adaptor-related
Homo sapiens archain 1
Homo sapiens Rho GTPase
Homo sapiens ATPase, H+
Homo sapiens basonuclin 1
Homo sapiens beta-transducin
Homo sapiens chromosome 17
Homo sapiens chromosome 18
Homo sapiens core 1 synthase,
Homo sapiens chromosome 1
Homo sapiens chromosome 5
Homo sapiens chromosome 5
Homo sapiens chromosome 9
Homo sapiens caveolin 1,
Homo sapiens cell division cycle
Homo sapiens cadherin 2, type 1,
Homo sapiens coiled-coil-helix-
Homo sapiens CCR4-NOT
Homo sapiens canopy 2 homolog
Homo sapiens discoidin, CUB and
Homo sapiens discoidin domain
Homo sapiens disrupted in
Homo sapiens elongation protein
Homo sapiens endothelial PAS
Homo sapiens erythrocyte
Homo sapiens exostoses
Homo sapiens family with
Homo sapiens F-box protein 28
Homo sapiens frizzled homolog 6
Homo sapiens glycerol-3-
Homo sapiens G protein-coupled
Homo sapiens G protein-coupled
Homo sapiens homeobox B6
Homo sapiens hydrogen voltage-
Homo sapiens inhibitor of kappa
Homo sapiens importin 8 (IPO8),
Homo sapiens integrin alpha FG-
Homo sapiens integrin, alpha 3
Homo sapiens kinesin family
Homo sapiens kelch-like 3
Homo sapiens karyopherin alpha
Homo sapiens leprecan-like 1
Homo sapiens mitogen-activated
Homo sapiens mitogen-activated
Homo sapiens MYC associated
Homo sapiens multiple
Homo sapiens membrane protein,
Homo sapiens NGFI-A binding
Homo sapiens neuron navigator 3
Homo sapiens neutral cholesterol
Homo sapiens nicastrin (NCSTN),
Homo sapiens nuclear factor of
Homo sapiens nemo-like kinase
Homo sapiens notch 2 N-terminal
Homo sapiens prenylcysteine
Homo sapiens peroxisomal
Homo sapiens PHD finger protein
Homo sapiens phosphoinositide-
Homo sapiens plasminogen
Homo sapiens plexin D1
Homo sapiens podocalyxin-like
Homo sapiens protein
Homo sapiens protein
Homo sapiens protein kinase,
Homo sapiens prostaglandin-
Homo sapiens paxillin (PXN),
Homo sapiens R3H domain
Homo sapiens RNA binding motif
Homo sapiens ring finger protein
Homo sapiens ring finger protein
Homo sapiens ribosomal protein
Homo sapiens reticulon 4 (RTN4),
Homo sapiens saccharopine
Homo sapiens serpin peptidase
Homo sapiens solute carrier
Homo sapiens solute carrier
Homo sapiens serglycin (SRGN),
Homo sapiens slingshot homolog
Homo sapiens ST6 beta-
Homo sapiens TAF9B RNA
Homo sapiens tetraspanin 6
Homo sapiens thiosulfate
Homo sapiens thioredoxin domain
Homo sapiens U2AF homology
Homo sapiens vacuolar protein
Homo sapiens zinc finger protein
Homo sapiens zinc finger protein
Homo sapiens zinc finger protein
Homo sapiens zinc finger protein
Homo sapiens zinc finger protein
1logarithm (base 2) of the average intensity (AveExpr)
2logarithm (base 2) of the ratio of miR-199a-5p/miR-Neg (logFC)
A genetic network analysis was then focused on these 21 targets, and a more limited list of candidate genes associated with the most significant canonical pathways described above was identified. Finally, the levels of expression of these candidate genes were compared with the mouse orthologues thereof in a bleomycin model using whole genome biochips (C57BL/6J mice 14 days after instilling bleomycin or PBS, data set 3, accession number GEO GSE34814). It was observed that 4 of 21 best putative targets of miR-199a-5p were also down-regulated in fibrotic lung tissue: ARHGAP12, CAV1, MAP3K11 and MPP5 (table 3). Of these, caveolin-1 (CAV1) would appear to represent a key target of miR-199a-5p, based on previous studies demonstrating a significant link between CAV1 down-regulation in lung fibroblasts and adverse TGFβ-mediated effects [Wang et al., J. Exp. Med., 203: 2895-2906, 2006; Xia et al., Am. J. Pathol., 176: 2626-2637, 2010] [23, 31].
Validation of Caveolin-1 (CAV1) as a Target of miR-199a-5p
Caveolin-1 (CAV1) is a 22 kDa membrane protein essential for the formation of small plasma membrane invaginations referred to as caveolae. Caveolae are found in most cell types, in varying quantities according to the tissue. They are particularly abundant in differentiated cells such as adipocytes, endothelial cells, type I pneumocytes, fibroblasts and smooth and striated muscle cells. Caveolae represent a subcategory of lipid rafts, morphologically identifiable due to the invaginated and circular shape thereof, and characterised by the presence of structuring proteins named caveolin-1, caveolin-2 and caveolin-3. Caveolin-1 and -2 have a relatively ubiquitous distribution in most differentiated cells with the exception of skeletal muscle fibres and cardiac myocytes [Scherer et al., J. Cell Biol., 127: 1233-1243, 1994] [20]. The expression of caveolin-3 is restricted to the skeletal muscles, diaphragm and heart [Tang et al., J. Biol. Chem., 271; 2255-2261, 1996] [21]. Interestingly, studies recently demonstrated that transgenic mice in which the caveolin-1 gene has been deleted present various anomalies, particularly in the lungs [Park et al., Biochemistry, 42: 15124-15131, 2003] [22]. These mice in particular develop pulmonary fibrosis and endothelial cell proliferation. In vitro studies have also demonstrated that decreasing caveolin-1 expression in lung fibroblast cells promotes the pro-fibrotic effects of TGFβ on this cell type, particularly the activation, proliferation and differentiation of fibroblasts to myofibroblasts [Wang et al., 2006, cited above] [23].
Using the MicroCible algorithm, a potential binding site for miR-199a-5p was identified in the 3′UTR sequence of CAV1 (
TGFβ Regulates miR-199a-5p and CAV1 Expression in Lung Fibroblasts
It was studied whether the decrease in CAV1 expression following stimulation with TGFβ is associated with an increase in miR-199a-5p expression. In order to test this hypothesis, the MRC5 cell line was exposed to TGFβ, and the levels of CAV1 and miR-199a-5p expression were analysed. As detected by Taqman RT-PCR, treating human fibroblasts with TGFβ for 24 to 48 hours gave rise to a marked reduction in CAV1 mRNA, whereas miR-199a-5p expression was significantly up-regulated (
To further investigate whether miR-199-5p is involved in TGFβ-induced downregulation of CAV1, additional experiments using a LNA-based inhibitor of miR-199a-5p as well as a LNA-based Target Site Blocker preventing miR-199-5p binding on CAV1 3′UTR mRNA (CAV1 protector) were performed to specifically interfere with miR-199a-5p binding on CAV1 3′UTR. As depicted in
Altered CAV1 Expression in Lungs of Mice Suffering from Bleomycin-Induced Pulmonary Fibrosis
CAV1 expression was studied in fibrotic mouse lungs. In line with previous studies, the data show a significant decrease in the level of CAV1 protein and mRNA expression in C57BL/6J mice, 14 days after administering bleomycin (
It should be noted that the BALB/c mice, for which miR-199a-5p expression is not up-regulated in response to bleomycin, did not display a significant decrease in the level of CAV1 mRNA expression 14 days after bleomycin treatment (
Altered CAV1 and miR-199a-5p Expression in Lungs of Patients Suffering from IPF
It was studied whether miR-199a-5p expression is also deregulated in lungs of patients suffering from IPF, using a recently published data set (accession number GEO GSE13316) consisting of 10 IPF samples and control samples. Interestingly, compared to the control, miR-199a-5p expression in the IPF samples increased very significantly (p=0.005, p=0.006, table
These results were then studied on a larger cohort of IPF patients (IPF n=94 and control n=83) where the inverse correlation between CAV1 and miR-199a-5p observed in mice was confirmed in humans (
Given that the level of CAV1 expression is a critical factor involved in the fibrogenic activation of lung fibroblasts, it was studied whether miR-199a-5p overexpression in lung fibroblasts is sufficient to recapitulate the known profibrotic effects associated with a decrease in CAV1 expression (i.e. fibroblast proliferation, migration and differentiation to myofibroblasts). As represented in
It was then studied whether miR-199a-5p has further profibrotic effects regardless of CAV1 regulation. For this purpose, the genetic expression profile obtained in lung fibroblasts transfected with miR-199a-5p precursors was compared with that obtained after transfection with a siRNA specifically targeted against CAV1. Interestingly, some overlap was detected between the two signatures, essentially among the down-regulated transcripts (
For the purposes of familiarisation with the pathways modulated by miR-199a-5p, the Ingenuity Pathways™ canonical pathways of miR-199a-5p were analysed and compared to those of miR-21 and siCAV1 contexts. As shown in the decision tree in
Finally, it was demonstrated that miR-199a-5p is involved in TGFβ signaling. For this, a TGFβ signaling signature was defined experimentally in lung fibroblasts and compared to the signature of miR-199a-5p using the GSEA method. This analysis showed a significant overlap between these two signatures, evaluated with standardised enrichment scores greater than 1 (1.4 and 2.17 for up- and down-regulated genes, respectively, with a nominal p-value and an FDR q value <0.05), demonstrating that miR-199a-5p is, in principle, a TGFβ response mediator in lung fibroblasts (
To further demonstrate the importance of miR-199a-5p in TGFβ response, silencing of miR-199a-5p was performed in lung fibroblasts using LNA-based inhibitors. In particular, it was shown that LNA-mediated silencing of miR-199a-5p strongly inhibited TGFβ-induced differentiation of lung fibroblasts into myofibroblasts (
Remarkably, similar results were obtained using a LNA-based Target Site Blocker (CAV1 protector) demonstrating therefore that miR-199a-5p is a key effector of TGFβ response through CAV1 regulation (
Increasing evidence suggests that miRNA takes part in the fibrotic process in various organs such as the heart, kidneys, liver or lungs. For example, previous studies have shown that miR-21 has an important role in pulmonary and cardiac fibrosis. In this way, it was studied whether miR-199a-5p is also deregulated in one forms of tissue fibrosis, i.e. renal and hepatic fibrosis using well-characterised experimental mouse models. For this purpose, the expression profiles of miRNAs obtained in these fibrosis models were compared using the same platform based on the miRNAs. 5 miRNAs routinely deregulated to a p-value <0.01 were identified (
The increase in miR-199a-5p expression was confirmed in two independent experimental hepatic fibrosis models (
Similarly, the data obtained from the unilateral ureteral obstruction renal fibrosis model demonstrated an increase in miR-199a-5p in damaged kidneys compared to mice undergoing the control procedure (
| Number | Date | Country | Kind |
|---|---|---|---|
| 1251089 | Feb 2012 | FR | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14376569 | Aug 2014 | US |
| Child | 15397351 | US |
