TGF-β signaling is involved in the migration and differentiation of MSCs and the regulation of collagen formation and tissue remodeling through the activation of its canonical pathway and Smad2/3 phosphorylation.45,71,72 We previously demonstrated that TGF-β1 could recruit MSCs to injury sites to induce enthesopathy and heterotopic ossification in tendons.43,47 In this study, we found a similar mechanism in PAF, and excessive levels of active TGF-β1 recruited MSCs to the adhesion sites and facilitated their differentiation into myofibroblasts. The gene discussed is SMAD2; the disease is enthesopathy.