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. Author manuscript; available in PMC: 2014 Jun 1.
Published in final edited form as: Metabolism. 2013 Jan 30;62(6):768–777. doi: 10.1016/j.metabol.2013.01.003

Figure 3. Summary of the interactions among PTH, IGF-I, and 1,25(OH)2D3 on CYP27B1/1α-hydroxylase expression and bone formation in hMSCs.

Figure 3

PTH upregulates IGF-I [12] which stimulates bone formation in hMSCs [8]. PTH upregulates CYP27B1 expression and stimulates 1α,25(OH)2D3 production [12], and at higher concentration, 1α,25(OH)2D3 downregulates CYP27B1 [8]. In addition, IGF-I upregulates CYP27B1 expression and stimulates 1α,25(OH)2D3 biosynthesis [8]. 1α,25(OH)2D3 induces IGF-I and bone formation in hMSCs [8].