The influence of 3,3',5-triiodo-L-thyronine on human haematopoiesis

Thyroid hormones mediate many physiological and developmental functions in humans. The role of the 3,3',5-triiodo-L-thyronine (T3) in normal human haematopoiesis at the cellular and molecular levels has not been determined. In this study, it was revealed that the human haematopoietic system might be directly depended on T3 influence.

We detected the TRalpha1 and TRbeta1 gene expression at the mRNA level in human cord blood, peripheral blood and bone marrow CD34(+)-enriched progenitor cells, using the RT-PCR method. Furthermore, we performed Western blotting to prove TRalpha1 and TRbeta1 expression occurs at the protein level in human cord blood, peripheral blood and bone marrow CD34(+) cells. In addition, the examined populations of cells were exposed in serum-free conditions to increasing doses of T3 and were subsequently investigated for clonogenic growth of granulocyte-macrophage colony-forming unit and erythrocyte burst-forming unit in methylcellulose cultures, and for the level of apoptosis, by employing annexin V staining and the terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling method. We investigated expression levels of apoptosis-related Bax and antiapoptotic Bcl-2 and Bcl-x(L) genes in the examined cells.

We found that exposure to higher and lower than normal concentration of thyroid hormone significantly influenced clonogenecity and induced apoptosis in human haematopoietic progenitor cells.

This study expands the understanding of the role of thyroid disorders in normal human haematopoiesis and indicates a direct influence of T3 on this process.