Dose-dependent effects of triiodothyronine on the osteogenic differentiation of rat bone marrow mesenchymal stem cells.

Background/aims: The aim of this study was to investigate the dose-dependent effects of triiodothyronine (T3) on the osteogenic differentiation of mesenchymal stem cells(MSCs).

Methods: MSCs that express CD73, CD54 (intercellular adhesion molecule-1) and CD90 were cultured in triplicate (1 x 10(5)/well) in osteogenic medium with T3 (1, 10, 10(3) or 10(5) pM) or without T3 (control) for 7, 14 and 21 days. Alkaline phosphatase activity, conversion of MTT into formazan crystals, collagen synthesis, collagen maturation, the number of mineralized nodules and their diameters were all determined, and the means were compared by the Student-Newman-Keuls test.

Results: A dose of 10(5) pM T3 resulted in a negative effect on MSC osteogenic differentiation, with less collagen synthesis. The 1 pM T3 dose resulted in greater collagen synthesis and alkaline phosphatase activity and more mineralized nodules than in the control group, similar to the 10 pM dose. Nevertheless, the 10 pM dose demonstrated better results than the 1 pM dose with regard to MSC osteogenic differentiation, with greater MTT reduction, better collagen maturation and a larger mean diameter of mineralized nodules.

Conclusions: The effect of T3 on MSC differentiation is dose-dependent, with the 10 pM dose promoting better bone marrow MSC osteogenic differentiation.