Rapamycin Promotes the Osteoblastic Differentiation of Human Embryonic Stem Cells by Blocking the mTOR Pathway and Stimulating the BMP/Smad Pathway

作者：Kyu-Won Lee, Jin-Yong Yook, Mi‐Young Son, Minjeong Kim, Deog‐Bon Koo, Yong‐Mahn Han, Yee Sook Cho · 发表于：Stem Cells and Development · 年份：2009 · DOI：10.1089/scd.2009.0147 · 被引用次数：164 · 研究领域：Pluripotent Stem Cells Research、Renal and related cancers、Developmental Biology and Gene Regulation

Studies revealed that PI3K/AKT/mTOR signaling is important in the regulation of human embryonic stem cell (hESC) self-renewal and differentiation. However, its action on osteogenic differentiation of hESCs is poorly understood. We tested the effects of pharmacological PI3K/AKT/mTOR inhibitors on their potential to induce osteogenic differentiation of hESCs. Under feeder-free culture conditions, rapamycin (an mTOR inhibitor) potently inhibited the activities of mTOR and p70S6K in undifferentiated hESCs; however, LY294002 (a PI3K inhibitor) and an AKT inhibitor had no effects. Treatment with any of these inhibitors down-regulated the hESC markers Oct4 and Nanog, but only rapamycin induced the up-regulation of the early osteogenic markers BMP2 and Runx2. We also observed that hESCs differentiated when treated with FK506, a structural analog of rapamycin, but did not exhibit an osteogenic phenotype. Increases in Smad1/5/8 phosphorylation and Id1-4 mRNA expression indicated that rapamycin significantly stimulated BMP/Smad signaling. After inducing both hESCs and human embryoid bodies (hEBs) for 2-3 weeks with rapamycin, osteoblastic differentiation was further characterized by the expression of osteoblastic marker mRNAs and/or proteins (osterix, osteocalcin, osteoprotegerin, osteonectin, and bone sialoprotein), alkaline phosphatase activity, and alizarin red S staining for mineralized bone nodule formation. No significant differences in the osteogenic phenotypes of rapamycin-diffe...