Effect of Phosphatase and Tensin Homolog 12 on Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells During Aging by Regulating Transforming Growth Factor Beta/Smad Signaling Pathway

Abstract

Aging affects bone marrow mesenchymal stem cells (BMSC) differentiation. PTEN12 regulates cell proliferation and apoptosis. However, whether PTEN12 affects BMSCs osteogenic differentiation during aging is unknown. Two BMSCs derived from Zempster24−/− (senescence) and Zempster24+/+ (normal) mice were cultured in vitro. Real-time PCR analysis was used to analyze PTEN12 expression. PTEN12 siRNA was transfected into senescent Zempster24-/-BMSCs and after 14 days of osteogenic induction, cell proliferation was analyzed by MTT method along with measuring expression of osteocalcin, type I collagen, RUNX2 and OPN by Real time PCR, ALP activity, and TGFβ/smad signaling protein expression by Western blot. Compared to normal BMSCs, PTEN12 level in aging BMSCs was significantly elevated, osteocalcin, type I collagen, RUNX2 and OPN mRNA level was decreased along with reduced ALP activity and TGFβ1 and Smad2 expression (P < 0.05). PTEN12 siRNA transfection into senescent BMSCs significantly down-regulated PTEN12, upregulated osteocalcin, type I collagen, RUNX2 and OPN mRNA, increased ALP activity and TGFβ1 and Smad2 expression (P <0.05). Aging increases PTEN12 level and inhibits BMSCs osteogenic differentiation. Down-regulation of PTEN12 in BMSCs during aging can promote BMSCs osteogenic differentiation by regulating TGFβ/smad signaling pathway.