Function of Microfibril Associated Protein 5 (MFAP5) in Wound Healing

Tissue injury leads to extensive extracellular matrix (ECM) changes throughout the wound healing process. MFAP5 is a 25 kD serine and threonine rich small microfibril-associated protein, involved in the regulation of major ECM pathways and microfibril function. Interestingly, the role MFAP5 plays in the wound healing process is currently unknown. This study was undertaken to identify the genes that are most differentially expressed between skin and oral mucosa as related to wound healing and fibrosis. Previously available human gene array data from scar-forming skin wounds and minimally scarring oral wounds was utilized to investigate the differential expression of genes that are closely related to wound healing and fibrosis in these alternate healing phenotypes. This analysis led to the identification of MFAP5 as a factor that was highly expressed in skin but not oral mucosal wounds, and thus a candidate profibrotic mediator in healing wounds. To directly examine the role of MFAP5 in wound healing, a murine model of full-thickness excisional skin wounds was employed, and the effect of MFAP5 neutralization on healing was assessed. Mice were randomly assigned to three wound treatment groups: phosphate-buffered saline (PBS), immunoglobulin G (IgG), and anti-MFAP5 antibodies. Histologic wound samples were stained with Masson’s Trichrome and Picrosirius stains, and AxioVision software was used to quantify collagen deposition and the ratio of mature/immature collagen, respectively. Data was analyzed by 2-way ANOVA and multiple t-test. It was found that in humans, MFAP5 expression was significantly higher in skin versus oral wounds at baseline and throughout the course of wound healing. Furthermore, in the murine model, antibody neutralization of MFAP5 in vivo led to decreased collagen deposition with lower mature collagen and significantly higher immature collagen when compared to the control groups. These results suggest that MFAP5 promotes collagen deposition during wound healing in skin in vivo. Therefore, the production of MFAP5 may have significant implications for scar formation in skin and other fibrotic conditions

Microfibril-associated protein 5 and the regulation of skin scar formation

Abstract Many factors regulate scar formation, which yields a modified extracellular matrix (ECM). Among ECM components, microfibril-associated proteins have been minimally explored in the context of skin wound repair. Microfibril-associated protein 5 (MFAP5), a small 25 kD serine and threonine rich microfibril-associated protein, influences microfibril function and modulates major extracellular signaling pathways. Though known to be associated with fibrosis and angiogenesis in certain pathologies, MFAP5’s role in wound healing is unknown. Using a murine model of skin wound repair, we found that MFAP5 is significantly expressed during the proliferative and remodeling phases of healing. Analysis of existing single-cell RNA-sequencing data from mouse skin wounds identified two fibroblast subpopulations as the main expressors of MFAP5 during wound healing. Furthermore, neutralization of MFAP5 in healing mouse wounds decreased collagen deposition and refined angiogenesis without altering wound closure. In vitro, recombinant MFAP5 significantly enhanced dermal fibroblast migration, collagen contractility, and expression of pro-fibrotic genes. Additionally, TGF-ß1 increased MFAP5 expression and production in dermal fibroblasts. Our findings suggest that MFAP5 regulates fibroblast function and influences scar formation in healing wounds. Our work demonstrates a previously undescribed role for MFAP5 and suggests that microfibril-associated proteins may be significant modulators of wound healing outcomes and scarring