MMP2 and polycystic ovary syndrome: Though the exact mechanisms of increased collagen deposition remained unclear, previous evidence showed that TGF-β RI inhibitor could significantly reduce the pro-fibrotic TGF-β and increase the anti-fibrotic MMP2 level to prevent collagen deposition in a rat model of PCOS (Wang et al., 2018), indicating that the TGF-β signaling pathway may play a key role in the disease etiology (Wang et al., 2018).