Loss of MFAP5 and Its Effect on Skin Homeostasis and Wound Healing

MFAP5, also known as microfibrillar-associated glycoprotein-2 (MAGP2), may influence parameters of skin wound healing related to scar formation. To further elucidate its role in skin wound healing, we assessed skin wound repair in Mfap5^-/- mice. Loss of MFAP5 reduced external wound closure, angiogenesis, and enhanced neutrophil and macrophage wound influx. Loss of MFAP5 also reduced the deposition of total and mature collagen in uninjured normal skin (NS), but not in wounds. Furthermore, NS dermis of Mfap5^-/- mice was thinner without any reduction in tensile strength. Single-cell RNA-sequencing of NS and wounds from Mfap5^+/+ and Mfap5^-/- mice revealed two fibroblast subclusters that express MFAP5 more highly than other subclusters. Enrichment analysis of the differentially expressed genes (DEGs) in these two subclusters suggests these fibroblasts engage in extracellular matrix (ECM) deposition and angiogenesis. Mfap5^+/+ and Mfap5^-/- fibroblasts also exhibit transcriptomic differences throughout in vivo wound healing, though as healing progressed, fewer differences were evident. To examine the direct effect of MFAP5 on fibroblasts outside of the wound space, fibroblasts were isolated from Mfap5^+/+ and Mfap5^-/- mice for in vitro analysis. mRNA-sequencing of Mfap5^+/+ and Mfap5^-/- fibroblasts found genes involved in cellular migration and proliferation, ECM synthesis, and angiogenesis to be downregulated in Mfap5^-/- fibroblasts vs. Mfap5^+/+ fibroblasts. Functionally, Mfap5^-/- fibroblasts exhibited reduced migration, contractility, proliferation, and ECM deposition. Our findings suggest MFAP5 is a multifunctional glycoprotein in skin wound healing, as it has a role in regulating wound closure, angiogenesis, collagen deposition, inflammatory cell influx, and fibroblast behaviors related to scar formation.