Osteoadherin serves roles in the regulation of apoptosis and growth in MC3T3‑E1 osteoblast cells.

Abstract

Small leucine‑rich proteoglycans (SLRPs) are a class of proteoglycans that are characterized by small protein cores and structures of leucine‑rich repeats. SLRPs are expressed in most extracellular matrices and share numerous biological functions that are associated with binding of collagens and cell surface receptors. Osteoadherin (also termed osteomodulin) is encoded by the Omd gene and is a keratan sulfate proteoglycan of the class II subfamily of SLRPs. Osteoadherin is highly expressed in mineralized tissues, including bone and dentin; however, it's precise roles remain unknown. The present study determined the Omd expression levels and investigated the effects of over‑ and under‑expression of osteoadherin in osteoblastic cells. Omd mRNA expression increased with osteoblast differentiation in MC3T3‑E1 cells. In C2C12 cells, Omd mRNA expression was induced by bone morphogenetic protein (BMP)2. Reporter assays similarly demonstrated activation of the Omd gene promoter following co‑transfection with Smad1 and Smad4, which are intracellular signaling molecules of the BMP2 signaling pathway. Overexpression of Omd increased the viability and decreased caspase 3/7 activity in MC3T3‑E1 cells. By contrast, following transfection with small interfering RNA for Omd, viable cell numbers were decreased and caspase 3/7 activity was increased. Furthermore, overexpression of Omd reduced the expression of CCN family 2 in these cells. These results demonstrate that Omd expression is regulated during osteoblast differentiation, and that the protein product osteoadherin serves roles in the apoptosis and growth of osteoblast cells.