Effect of hypothyroidism in the thyroidectomized rats on immunophenotypic characteristics and differentiation capacity of adipose tissue derived stem cells.

Introduction: Thyroid hormones influence multiple physiological functions, like growth, differentiation, protein synthesis and metabolic rate. The hypothyroid state is a complex hormonal dysfunction rather than a single hormonal defect. The relation between hypothyroidism after thyroidectomy and stem cells is not clear.

Aim: This study was designed to investigate the effect of thyroidectomy on the proliferation, telomerase enzyme activities, immunophenotypic properties and differentiation potentials of adipose tissue-derived (AT-) stem cells (SCs).

Materials And Methods: AT-SCs after 60 and 120 days of thyroidectomized (Tx) rats were compared to normal rats by flow cytometry and immunocytochemistry analyses, and their telomerase activities were estimated.

Results: The telomerase activity was found to be positive for AT-SCs of Tx rats of both 60 and 120 days used in this study, but a decrease was noticed in the cells with the long-term exposure to hypothyroidism. This might indicate the decrease in the regenerative ability of the AT-SCs after 120 days of Tx compared to cells after 60 days of Tx. Both cell lines were induced to differentiate into adipogenic, osteogenic and neurogenic cell lineages, but osteogenic marker expression was not detected in the undifferentiated AT-SCs of the Tx rats. Osteogenic differentiation was also failed in stem cells derived from Tx rats, shown by Alizarin red S staining and alkaline phosphates enzyme assays.

Discussion: These results suggest that hypothyroidism affected SCs, altered stem cell characteristics, like telomerase activity and loss of in vitro bone formation, but not adipogenic or neurogenic differentiation ability.

Conclusions: Hypothyroidism after Tx affects the osteogenic differentiation capacity of stem cells, which might be one of the factors of bone loss due to postnatal hypothyroidism.