Selenoprotein O deficiencies suppress chondrogenic differentiation of ATDC5 cells

Selenoprotein O (Sel O) is a selenium-containing protein, but its function is still unclear. In the present study, we observed that the mRNA and protein expression levels of Sel O increased during chondrogenic induction of ATDC5 cells. The effects of Sel O on chondrocyte differentiation were then examined through shRNA-mediated gene silencing technique. The expression of Sel O was significantly suppressed at both mRNA and protein levels in a stable cell line transfected with a Sel O-specific target shRNA construct. Thereafter, we demonstrated that Sel O deficiencies suppress chondrogenic differentiation of ATDC5 cells. Sel O deficiencies inhibited expression of chondrogenic gene Sox9, Col II, and aggrecan. Sel O-deficient cells also accumulated a few cartilage glycosaminoglycans (GAGs) and decreased the activity of alkaline phosphatase (ALP). In addition, Sel O deficiencies inhibited chondrocyte proliferation through delayed cell cycle progression by suppression of cyclin D1 expression. Moreover, Sel O deficiencies induced chondrocyte death through cell apoptosis. In summary, we describe the expression patterns and the essential roles of Sel O in chondrocyte viability, proliferation, and chondrogenic differentiation. Additionally, Sel O deficiency-mediated impaired chondrogenesis may illustrate the mechanisms of Se deficiency in the pathophysiological process of the endemic osteoarthropathy.