A combination of insulin and ubiquitin A20 promotes osteocalcin expression in adipose-derived stem cells

Osteocyte generation can be used in bone defect repair; the generation efficiency needs to be further improved. This study aims to evaluate the role of ubiquitin A20 (A20) in facilitating the expression of osteocalcin in adipose-derived stem cells (ADSCs). In this study, adipose tissue was obtained from 10 healthy human subjects; ADSCs were isolated from the adipose samples. The ADSCs were transfected with core binding factor alpha 1 (Cbfa1) and/or insulin-like growth factor-1 receptor (IGF-1R). Expression of osteocalcin, A20 in ADSCs was assessed by quantitative RT-PCR (qRT-PCR) and Western blotting. Apoptosis of ADSCs was analyzed by flow cytometry. The results showed that after the gene transfection and stimulation of insulin, the ADSCs expressed high levels of osteocalcin. However, apoptotic ADSCs were induced by the activation of IGF-1R. Exposure to insulin down-regulated the expression of Bcl-xL and A20, and increased Bax, in ADSCs. The addition of exogenous A20 prevented the ADSC apoptosis. We conclude that activation of IGF-1R can induce apoptosis in ADSCs, which can be prevented by addition of exogenous A20.