The authors state that they have no conflicts of interest.
Activation of Sirt1 Decreases Adipocyte Formation During Osteoblast Differentiation of Mesenchymal Stem Cells†
Article first published online: 15 MAY 2006
Copyright © 2006 ASBMR
Journal of Bone and Mineral Research
Volume 21, Issue 7, pages 993–1002, July 2006
How to Cite
Bäckesjö, C.-M., Li, Y., Lindgren, U. and Haldosén, L.-A. (2006), Activation of Sirt1 Decreases Adipocyte Formation During Osteoblast Differentiation of Mesenchymal Stem Cells. J Bone Miner Res, 21: 993–1002. doi: 10.1359/jbmr.060415
- Issue published online: 4 DEC 2009
- Article first published online: 15 MAY 2006
- Manuscript Accepted: 20 APR 2006
- Manuscript Revised: 17 MAR 2006
- Manuscript Received: 23 SEP 2005
- peroxisome proliferator-activated receptor γ;
- mesenchymal stem cells;
In vitro, mesenchymal stem cells differentiate to osteoblasts when exposed to bone-inducing medium. However, adipocytes are also formed. We showed that activation of the nuclear protein deacetylase Sirt1 reduces adipocyte formation and promotes osteoblast differentiation.
Introduction: Mesenchymal stem cells (MSCs) can differentiate into osteoblasts, adipocytes, chondrocytes, and myoblasts. It has been suggested that a reciprocal relationship exists between the differentiation of MSCs into osteoblasts and adipocytes. Peroxisome proliferator-activated receptor γ2 (PPARγ2) is a key element for the differentiation into adipocytes. Activation of Sirt1 has recently been shown to decrease adipocyte development from preadipocytes through inhibition of PPARγ2.
Materials and Methods: We used the mouse mesenchymal cell line C3H10T1/2 and primary rat bone marrow cells cultured in osteoblast differentiation medium with or without reagents affecting Sirt1 activity. Adipocyte levels were analyzed by light microscopy and flow cytometry (FACS) after staining with Oil red O and Nile red, respectively. Osteoblast and adipocyte markers were studied with quantitative real-time PCR. Mineralization in cultures of primary rat bone marrow stromal cells was studied by von Kossa and alizarin red staining.
Results: We found that Sirt1 is expressed in the mesenchymal cell line C3H10T1/2. Treatment with the plant polyphenol resveratrol as well as isonicotinamide, both of which activate Sirt1, blocked adipocyte development and increased the expression of osteoblast markers. Nicotinamide, which inhibits Sirt1, increased adipocyte number and increased expression of adipocyte markers. Furthermore, activation of Sirt1 prevented the increase in adipocytes caused by the PPARγ-agonist troglitazone. Finally, activation of Sirt1 in rat primary bone marrow stromal cells increased expression of osteoblast markers and also mineralization.
Conclusions: In this study, we targeted Sirt1 to control adipocyte development during differentiation of MSCs into osteoblasts. The finding that resveratrol and isonicotinamide markedly inhibited adipocyte and promoted osteoblast differentiation may be relevant in the search for new treatment regimens of osteoporosis but also important for the evolving field of cell-based tissue engineering.