Efeitos in vivo e in vitro dos hormônios tireoidianos na diferenciação osteogênica de células tronco mesenquimais da medula óssea e do tecido adiposo de ratas ovariectomizadas e não ovariectomizadas

Abstract

Four different experiments were performed. Experiment 1 evaluated the role of bone marrow mesenchymal stem cells (BMMSCs) on the genesis of bone alterations caused by hypo and hyperthyroidism in ovariectomized (OVX´d) or non-ovariectomized female rats. Experiment 2 evaluated the effect of in vitro treatment with triiodothyronine (T3) on the reduced osteogenic potential of BMMSCs of the OVX´d rats with osteoporosis, compared to that of BMMSCs of young and adult rats without osteoporosis. Experiment 3 evaluated the effect of T3 on osteogenic differentiation of adipose derived stem cells (ASCs) from adult OVX´d rats with osteoporosis, compared to that of ASCs of young and adult rats without osteoporosis. Finally, experiment 4 compared the osteogenic potential of BMMSCs and ASCs within groups of young rats, adult rats and OVX´d rats with osteoporosis. It was concluded in experiment 1 that the reduction of osteogenic differentiation of BMMSCs is one of the mechanisms involved in osteopenia genesis induced by hypothyroidism and that the increase of MSCs osteogenic differentiation may be one of the mechanisms by which thyroxine increases bone resistance of OVX´d female rats. In experiment 2 it was concluded that T3 improves reduced osteogenic potential of BMMSCs on rats with osteoporosis and it also increases the osteogenic potential with respect to the BMMSCs of adult rats without osteoporosis, where the effect was dose dependent. However, treatment with T3 was not able to reach the osteogenic potential of MSCs in rats with osteoporosis when compared to that of healthy young rats. In experiment 3 it was concluded that ASCs of OVX´d rats with osteoporosis showed reduced osteogenic differentiation and that treatment with T3 has negative effects on some of the factors involved in this differentiation. In experiment 4 it was concluded that ASCs of young rats and OVX´d rats with osteoporosis have higher osteogenic potential that BMMSCs of the same category of animals and that, in the group of adult rats, the osteogenic potential is similar between BMMSCs and ASCs. Furthermore ASCs of OVX´d rats with osteoporosis have an osteogenic potential similar to that of BMMSCs of young rats.