Dihydroxy-cholecalciferol stimulates adipocytic differentiation of porcine mesenchymal stem cells

Dihydroxy-cholecalciferol [1,25(OH)2D3] has been shown to have pleiotropic effects on the differentiation of mesenchymal stem cells (MSC) based on species and culture conditions. We have examined the effects of 1,25(OH)2D3 on the differentiation of porcine MSC under culture conditions designed to promote proliferation in order to attempt to mimic the conditions in young, rapidly growing animals. The MSC were isolated from bone marrow of a young pig and grown in basal media (BM) containing DMEM+10% fetal bovine serum and antibiotics. Cells received either BM, BM+10(-8) M 1,25(OH)2D3 or BM+10(-7) M 1,25(OH)2D3 with complete media changes every 3 days for a total of 12 days of culture. On days 3, 6, 9 and 12, viable cell numbers were determined, and samples were collected for gene expression analysis and cytochemical staining. There was a treatment-based reduction in cell numbers on 6, 9 and 12 days (P<.05). The concentrations of mRNAs encoding peroxisome proliferator-activated receptor gamma, lipoprotein lipase, and adipocyte-binding protein 2 were increased (P<.05) in a manner indicative of adipocytic differentiation by treatment with 1,25(OH)2D3 in a dose-dependent manner. However, the mRNA levels of osteocalcin, a late stage marker of osteoblastic differentiation, was also increased (P<.05) by treatment with 1,25(OH)2D3. An increased percentage of lipid filling, based on Oil Red O staining, and decreased alkaline phosphatase activity, was also seen with 1,25(OH)2D3 treatment. These data suggest that 1,25(OH)(2)D(3) stimulates the differentiation of porcine MSC towards an adipocytic phenotype.