Rapamycin promotes the osteoblastic differentiation of human embryonic stem cells by blocking the mTOR pathway and stimulating the BMP/Smad pathway

Cited 126 time in scopus
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Title
Rapamycin promotes the osteoblastic differentiation of human embryonic stem cells by blocking the mTOR pathway and stimulating the BMP/Smad pathway
Author(s)
K W Lee; J Y Yook; Mi Young Son; Min Joung Kim; D B Koo; Y M Han; Yeesook Cho
Bibliographic Citation
Stem Cells and Development, vol. 19, no. 4, pp. 557-568
Publication Year
2010
Abstract
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-differentiated hESCs and hEBs were detected. Our results suggest that, among these 3 inhibitors, only rapamycin functions as a potent stimulator of osteoblastic differentiation of hESCs, and it does so by modulating rapamycin-sensitive mTOR and BMP/Smad signaling.
ISSN
1525-8165
Publisher
Mary Ann Liebert, Inc
DOI
http://dx.doi.org/10.1089/scd.2009.0147
Type
Article
Appears in Collections:
Division of Research on National Challenges > Stem Cell Convergenece Research Center > 1. Journal Articles
Division of Biomedical Research > Immunotherapy Research Center > 1. Journal Articles
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