MRTF‐A promotes the myofibroblast contractile phenotype in wound healing

Abstract

Myofibroblasts are contractile smooth-muscle like cells that differentiate from fibroblasts and function to facilitate normal wound closure and healing. Under pathological conditions, such as development of hypertrophic scars, myofibroblasts fail to undergo apoptosis and continue to remodel the extracellular matrix, leading to increased contracture of the connective tissue. Myofibroblasts are characterized as having “super-mature” focal adhesions and expression of smooth muscle alpha-actin (SMAA). Myocardin-related transcription factor A (MRTF-A/MAL/MKL-1) and myocardin-related transcription factor B (MRTF-B/MKL-2) are putative mechanical stress induced coactivators that help to activate transcription of smooth muscle cytoskeletal proteins such as SMAA. A short hairpin RNA (shRNA) mediated knockdown approach, to reduce the levels of MRTF-A and MRTF-B in rat embryonic fibroblasts (REF-52), is being used to study the effects of the knockdown on the myofibroblast contractile phenotype. Preliminary immunocytochemistry analysis has shown a decrease in the size and number of focal adhesions and stress fibers in cells transfected with MRTF-A and B shRNA when compared to myofibroblasts transfected with a control red fluorescent protein (RFP) construct, thus suggesting a role for MRTF-A/B in the contractile phenotype of myofibroblasts. (Funded by NIH 2R01GM60651)