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Three Distinct Cell Types Express Extracellular Matrix Proteins In Different Niches During Skeletal Muscle Fibrosis

ABSTRACT: Tissue extracellular matrix provides structural support and creates unique niches for resident cells . However, the identities of cells responsible for creating specific ECM niches have not been determined. In striated muscle, the identity of these cells becomes important in disease when ECM changes result in fibrosis and subsequent increased tissue stiffness and dysfunction. Here we describe a novel approach to isolate and identify cells that maintain ECM niches in both healthy and fibrotic muscle. Using a collagen I reporter mouse, we show that there are three distinct cell populations that express collagen I in both healthy and fibrotic skeletal muscle. Interestingly, the number of collagen I expressing cells in all three cell populations increase proportionally in fibrotic muscle indicating that all cell types participate in the fibrosis process. Furthermore, it is shown that the ECM gene expression profile is not qualitatively altered in fibrotic muscle. This suggests that muscle fibrosis in this model results from an increased number of collagen I expressing cells and not the initiation of a specific fibrotic gene expression program. Finally, in fibrotic muscle, we show that these collagen I expressing cell populations differentially express distinct ECM proteins – fibroblasts express the fibrillar components of ECM, fibro/adipogenic progenitors cells differentially express basal laminar proteins and skeletal muscle progenitor cells differentially express genes important for the satellite cell niche.

ORGANISM(S): Mus musculus

PROVIDER: GSE89633 | GEO | 2016/12/04

SECONDARY ACCESSION(S): PRJNA352828

REPOSITORIES: GEO

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Project description:Tissue fibrosis is a significant health issue associated with organ dysfunction and failure. Increased deposition of collagen and other extracellular matrix (ECM) proteins in the interstitial area is a major process in the formation of tissue fibrosis. The microRNA-29 (miR-29) family has been demonstrated as anti-fibrotic microRNAs. Our recent work also showed that dysregulation of miR-29 contributes to the formation of cardiac fibrosis in animal models of uremic cardiomyopathy and replenish of miR-29 attenuated cardiac fibrosis in these animals. However, due to the multi-targeting effect, overexpression of miR-29 could result in unexpected side effect. In the current study, we constructed a novel col1a1-miR-29b vector using collagen 1a1 promoter, which can strategically express miR-29b-3p (miR-29b) in cells with high expression of collagen and thus minimize the side effect of excessive miR-29b. Because of the similarity between the col1a1 promoter in the plasmid and the endogenous col1a1 promoter in the cell, pro-fibrotic factors that stimulate endogenous collagen expression will simultaneously activate the col1a1 promoter in the plasmid vector and thus stimulate the anti-fibrotic miR-29b expression. The increased miR-29b will then contra-regulate the collagen synthesis and maintain a dynamic balance of collagen. To evaluate the anti-fibrotic effect of miR-29b overexpression, we performed RNA sequencing in MEF cells transfected with the col1a1-miR-29b vector with or without TGF-β treatment. A CMV-miR-29b vector was used as positive control. The RNA-sequencing data showed that TGF-β treatment upregulated a broad spectrum of extracellular matrix (ECM) genes. In accordance, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis using GAGE package showed that the top 5 upregulated pathways after TGF-β treatment were mostly fibrosis-related, including focal adhesion, ECM reaction, and TGF-β signaling pathways, while transfection of miR-29b expression vectors attenuated the activation of these pathways, suggesting their anti-fibrotic effect. However, despite that the expression of miR-29b in CMV-miR-29b transfected cells were about 1000 times higher compared to the col1a1-miR-29b transfected cells, there was no significant difference in the anti-fibrotic effect in these cells. In summary, our work demonstrated that the col1a1-miR-29b vector expresses much lower miR-29b compared to the CMV-miR-29b vector, but it is as effective as the CMV-miR-29b vector in blocking the fibrosis-related signaling pathways in response to TGF-β treatment. Our results also suggest that miR-29b has a moderate effect on each of its targeting genes, and its anti-fibrotic effect may result from perturbation of a broad spectrum of fibrosis-related signaling pathways.

Project description:Dupuytren's disease (DD) is a classic example of pathological fibrosis which results in a debilitating disorder affecting a large sector of the human population. It is characterized by excessive local proliferation of fibroblasts and over-production of collagen and other components of the extracellular matrix (ECM) in the palmar fascia. The fibrosis progressively results in contracture of elements between the palmar fascia and skin causing flexion deformity or clawing of the fingers and a severe reduction in hand function. While much is known about the pathogenesis and surgical treatment of DD, little is known about the factors that cause its onset and progression, despite many years of research. Gene expression patterns in DD patients now offers the potential to identify genes that direct the pathogenesis of DD. In this study, we used primary cultures of fibroblasts derived from excisional biopsies of fibrotic tissue from DD patients to compare the gene expression profiles on a genome-wide basis with normal control fibroblasts. Our investigations have identified genes that may be involved with DD pathogenesis including some which are directly relevant to fibrosis. In particular, these include significantly reduced expression levels of three matrix metallopeptidases (MMP1, MMP3, MMP16), follistatin, and STAT1, and significantly increased expression levels of fibroblast growth factors (FGF9, FGF11), a number of collagen genes and other ECM genes in DD patient samples. Many of these gene products are known to be involved in fibrosis, tumour formation and in the normal processes of tissue remodelling. In addition, alternative splicing was identified in some DD-associated genes. These highly sensitive genomic investigations provide new insight into the molecular mechanisms that may underpin the development and progression of DD. Four exon arrays of DD primary fibroblasts derived from fibrotic tissue were compared to fibroblasts derived from skin punch biopsies from individuals who did not show DD symptoms.

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Three Distinct Cell Types Express Extracellular Matrix Proteins In Different Niches During Skeletal Muscle Fibrosis

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