Figure 4.

Osteogenic MPC1 and MPC2 cells respond to common endocrine factors. (A) MPC1 (white bars) and MPC2 cells (gray bars) were differentiated for 28 days in osteogenic media and subsequently treated with PTH (50 mM), 1,25D (10 nM), or vehicle control (Con) for 48 h. Sost mRNA was significantly suppressed in both cell types with PTH. Dmp1 mRNA levels decreased with PTH and increased with 125D. Fgf23 mRNA also decreased with PTH and increased with 125D approximately equally with both cell lines. Owing to the induction of Fgf23 mRNA, MPC1 and MPC2 lines were differentiated for 14 or 21 days then exposed to 125D (10⁻⁸ M, white bars) or vehicle (DMSO, gray bars) for 24 h to quantify secreted FGF23 protein. (B) In MPC1 cells, iFGF23 increased with 1,25D treatment at both 14 and 21 days of differentiation. In MPC2 cells, 1,25D upregulated FGF23 secretion in the media in 21-day cultures but not at 14 days. (C) Total or cFGF23 was significantly elevated with 1,25D treatment in MPC1 cells after 14 and 21 days of osteogenic differentiation. In MPC2 cells, 1,25D increased cFGF23 release at 21, but not 14 days. MPC2 cells differentiated for 14 or 21 days had higher cFGF23 secretion compared to MPC1 cells at the same timepoints. *p < 0.05, **p < 0.01, between Veh and 125D at the time point designated; ^ap < 0.05, ^bp < 0.01, ^cp < 0.001, and ^dp < 0.0001 compare PTH or 125D treatment to Con treatment within the same cell line; #p < 0.05 comparing MPC1 and MPC2 at the same treatment and timepoint.