Figure 2.

Expression of S1P receptors and osteoblast differentiation‐related mRNAs in human osteoblasts. (A) Analysis by real‐time PCR of the expression of S1P receptors 1, 2, and 3 (Ai) in correspondence with osteoblast‐related mRNAs expression (Aii), including RUNX2, alkaline phosphatase, type I collagen, and osterix in undifferentiated hOB and after 7, 14, and 21 days in differentiation medium. (B) Effect of 24‐hour treatment with 10 nM estradiol (E2), or 200 nM S1P, on S1PR1‐3 in undifferentiated hOB. Both E2 and S1P increase S1PR1 mRNA expression, decrease S1PR2, and did not change S1PR3. (C) Both S1PR1 and S1PR2 protein production by hOB was increased with S1P treatment at 2 weeks of differentiation. (D) In late differentiation (3 weeks), effects of S1P on receptor mRNAs were limited to minor effects on S1PR2. Relative to control, *p < 0.05; **p < 0.01.