Myofibroblast

Myofibroblast is a specialized cell that combines features of fibroblasts and smooth muscle cells. It possesses prominent actin-based contractile fibers and secretes components of the extracellular matrix, enabling wound contraction and tissue remodeling.

Myofibroblasts differentiate from resident fibroblasts in response to signaling molecules such as transforming growth factor-β (TGF-β1) and mechanical tension. They can also arise by transitions from epithelial or endothelial cells (EMT and EndMT), as well as from pericytes and circulating fibrocytes.

The defining marker is alpha-smooth muscle actin (α-SMA); additional markers include vimentin and, variably, desmin. Myofibroblasts produce collagen I and III, fibronectin, and other extracellular matrix proteins, and they generate contractile force via actin-myosin interactions to contract wound edges and remodel tissue.

In normal wound healing, myofibroblasts promote wound closure and ECM remodeling, then typically undergo apoptosis or revert to a quiescent fibroblast phenotype after repair. In chronic injury, persistent myofibroblasts drive fibrosis and scar formation in organs such as the liver, lung, kidney, and heart.

Because of their central role in fibrosis, myofibroblasts are a target in anti-fibrotic strategies, and their presence is assessed by staining for α-SMA in tissue samples.