Fibrosis involves activated platelets, macrophages, and myofibroblasts, which results in increased collagen deposition.45 Fibrosis and smooth muscle metaplasia are two of the main characteristics of endometriosis in women with fibrosis surrounding endometriotic tissue, and the degree of fibrosis is correlated with the severity of smooth muscle metaplasia.46 Endometriotic lesions are thought to be “wounds” that undergo repeated tissue injury and repair (ReTIAR), leading to TGF-β1/Smad3-mediated EMT and ultimately resulting in fibrosis as the lesions progress. Here, SMAD3 is linked to fibrosis.