Bmi1 Induces Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells Under Inflammatory Environment

Abstract

Bmi1 is a polycomb histone that regulates stem cells, but the role and mechanism of Bmi1 in bone marrow mesenchymal stem cells (BMSCs) differentiation has not been elucidated. Rat BMSCs were cultured in vitro and randomly divided into control group and inflammation group (treated with LPS). Bmi1 and Bmi1 siRNA were transfected into inflammatory BMSCs, followed by analysis of Bmi1 expression by Real time PCR, cell proliferation by MTT assay, Caspase3 activity, ALP activity, expression of Runx2, OP and PPARγ 2 by Real time PCR, as well as secretion of TNF-α and IL-1β by ELISA. In inflammatory environment, Bmi1 expression was significantly decreased, cell proliferation was significantly inhibited, along with increased Caspase3 activity, decreased ALP activity and the expression of Runx2 and OP, increased PPAR 2 expression and secretion of TNF-α and IL-1β (P < 0 05). Transfection of Bmi1 siRNA into inflammatory BMSCs further significantly aggravated the above changes (P < 0 05). Bmi1 plasmid transfected into inflammatory BMSCs significantly promoted Bmi1 expression and cell proliferation, decreased Caspase3 activity, increased ALP activity and expression of Runx2 and OP, decreased PPAR γ2 expression and TNF-α and IL-1β secretion (P < 0 05). Bmi1 expression is reduced in BMSCs under inflammation. Up-regulation of Bmi1 can inhibit the secretion of inflammatory factors, regulate the proliferation and apoptosis of BMSCs, and promote the proliferation and osteogenic differentiation of BMSCs.