ACTA1 and infarction: During the proliferative phase of cardiac repair, cardiac fibroblasts undergo myofibroblast transformation, incorporating α-SMA into stress fibers and activated myofibroblasts produce extracellular matrix proteins such as collagen I and collagen III, which boosts granulation tissue formation with greater tensile strength as well as more stress fibers to prevent post-infarction cardiac rupture 3.