Identification of a myofibroblast-specific expression signature in skin wounds.

After skin injury fibroblasts migrate into the wound and transform into contractile, extracellular matrix-producing myofibroblasts to promote skin repair. Persistent activation of myofibroblasts can cause excessive fibrotic reactions, but the underlying mechanisms are not fully understood. We used SMA-GFP transgenic mice to study myofibroblast recruitment and activation in skin wounds. Myofibroblasts were initially recruited to wounds three days post injury, their number reached a maximum after seven days and subsequently declined. Expression profiling showed that 1749 genes were differentially expressed in sorted myofibroblasts from wounds seven days post injury. Most of these genes were linked with the extracellular region and cell periphery including genes encoding for extracellular matrix proteins. A unique panel of core matrisome and matrisome-associated genes was differentially expressed in myofibroblasts and several genes not yet known to be linked to myofibroblast-mediated wound healing were found (e.g. Col24a1, Podnl1, Bvcan, Tinagl1, Thbs3, Adamts16, Adamts19, Cxcl's, Ccl's). In addition, a complex network of G protein-coupled signaling events was regulated in myofibroblasts (e.g. Adcy1, Plbc4, Gnas). Hence, this first characterization of a myofibroblast-specific expression profile at the peak of in situ granulation tissue formation provides important insights into novel target genes that may control excessive ECM deposition during fibrotic reactions.