Effect of Hepatic Kinase B1 (LKB1) on Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells During Senescence

Abstract

Hepatic kinase B1 (LKB1) is a tumor suppressor and regulates cell proliferation and apoptosis. However, whether LKB1 affects bone marrow mesenchymal stem cells (BMSCs) osteogenic differentiation of during aging remains unclear. Two BMSCs derived from Zempster24−/− (aging) and Zempster24+/+ (normal) mice were cultured in vitro followed by measurement of LKB1 expression by real-time quantitative PCR and Western blot. LKB1 siRNA was transfected into Zempster24−/−BMSCs and LKB1 expression was measured. 14 days after osteogenic induction, mineralized nodule formation was evaluated by alizarin red staining, expression of Calcin, type I collagen, RUNX2 and OPN mRNA expression was measured, together with alkaline phosphatase (ALP) activity and the PI3K/mTOR pathway activity. Compared with normal BMSCs, LKB1 expression was significantly increased, calcified nodules were decreased, with reduced expression of osteocalcin, type I collagen, RUNX2 and OPN mRNA as well as decreased ALP activity and PI3K/mTOR signaling protein expression (P < 0.05). LKB1 siRNA transfection into senescent BMSCs down-regulated LKB1 expression, increased calcification nodule formation, expression of osteocalcin, type I collagen, RUNX2 and OPN mRNA, as well as increased ALP activity and PI3K/mTOR pathway protein expression (P < 0.05). Aging can promote the increase of LKB1 expression and inhibit the osteogenic differentiation of BMSCs. Down-regulation of LKB1 expression in BMSCs during senescence can promote osteogenic differentiation through regulating PI3K/mTOR pathway.