Induction of Smooth Muscle Differentiation in Fibroblasts by Modulation of Cytoplasmic Actin Ratio

Myogenic differentiation is a powerful mechanism for generating diverse cell types from fibroblasts. Here, we show that targeted suppression of β-actin by RNA interference in human fibroblasts triggers coordinated molecular and structural changes consistent with trans-differentiation toward SMC-like phenotype. This conversion is marked by upregulation of smooth muscle differentiation markers (α- and γ-smooth muscle actins, SM22, smooth muscle myosin, desmin, vinculin) at mRNA and protein levels, together with distinct morphological alterations: increased cell area, loss of polarity, and reorganization of the actin cytoskeleton. Notably, β-actin-downregulated fibroblasts exhibited a focal adhesion architecture that differed from parental fibroblasts. These findings indicate that β-actin downregulation may provide a novel in vitro method to induce SMC-like differentiation, with potential implications for vascular biology and tissue engineering.