PTGER4 and chondrocalcinosis: For example, SRGN inhibited the growth of hydroxyapatite crystals [50]; PTHLH and FGF9 inhibited terminal differentiation of chondrocytes and mineralization [51–53]; mutation of ANKH caused chondrocalcinosis [54, 55]; CTGF-treated mesenchymal stem cells (MSCs) lost the ability to differentiate into chondrocytes and osteoblasts [56]; EGFR signaling suppressed osteoblast differentiation [57, 58]; and PTGER4 mediated the inhibition of mineralization in mature cementoblasts by prostaglandin E2 [59].