Transforming growth factor$ (TGF-P) is present in high levels in bone and plays an important role in osteoblast growth and differentiation. In order to dissect the molecular mechanisms of action of TCF-P on osteoblasts, the effects of TGF-P on the steady state mRNA levels of c-fos, c-jun, and jun-B
TGF-β regulates β-catenin signaling and osteoblast differentiation in human mesenchymal stem cells
✍ Scribed by Shuanhu Zhou
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 723 KB
- Volume
- 112
- Category
- Article
- ISSN
- 0730-2312
No coin nor oath required. For personal study only.
✦ Synopsis
Human adult bone marrow-derived skeletal stem cells a.k.a mesenchymal stem cells (hMSCs) have been shown to be precursors of several different cellular lineages, including osteoblast, chondrocyte, myoblast, adipocyte, and fibroblast. Several studies have shown that cooperation between transforming growth factor b (TGF-b) and Wnt/b-catenin signaling pathways plays a role in controlling certain developmental events and diseases. Our previous data showed that agents like TGF-b, cooperation with Wnt signaling, promote chondrocyte differentiation at the expense of adipocyte differentiation in hMSCs. In this study, we tested mechanisms by which TGF-b activation of bcatenin signaling pathway and whether these pathways interact during osteoblast differentiation of hMSCs. With selective small chemical kinase inhibitors, we demonstrated that TGF-b1 requires TGF-b type I receptor ALK-5, Smad3, phosphoinositide 3-kinases (PI3K), and protein kinase A (PKA) to stabilize b-catenin, and needs ALK-5, PKA, and JNK to inhibit osteoblastogenesis in hMSCs. Knockdown of b-catenin with siRNA stimulated alkaline phosphatase activity and antagonized the inhibitory effects of TGF-b1 on bone sialoprotein (BSP) expression, suggested that TGF-b1 cooperated with b-catenin signaling in inhibitory of osteoblastogenesis in hMSCs. In summary, TGF-b1 activates bcatenin signaling pathway via ALK-5, Smad3, PKA, and PI3K pathways, and modulates osteoblastogenesis via ALK5, PKA, and JNK pathways in hMSCs; the interaction between TGF-b and b-catenin signaling supports the view that b-catenin signaling is a mediator of TGF-b's effects on osteoblast differentiation of hMSCs.
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