O efeito do hipotiroidismo experimental sobre os componentes da matriz extracelular de aortas torácicas de ratos.

Abstract

MONTEIRO, P. S. The effect of experimental hypothyroidism on components of the extracellular matrix of rats thoracic aortas. 2012. 60 p. Masters thesis (Morphofunctional Sciences) Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, 2012. The subject of this study was to investigate the effects of experimental hypothyroidism on extracellular matrix deposition in vascular wall of thoracic aorta. Male Wistar rats were thyroidectomized to mimic hypothyroidism, the sham group was submitted to surgery procedure without the thyroid removal. After 6 weeks, histological analyses were performed using hematoxylin-eosin staining (for morphometric measurements), picrosirius and Weigert (for collagen and elastin deposition, respectively). Additionally, Western blotting was used to evaluate collagen I and III, elastin MMP-9, MMP-2, TIMP-1 and TIMP-2 protein expression. Serum T3 and T4 levels as well as heart weight (g)/ tibia’s length (mm) ratio confirmed the characteristic decrease in cardiac mass found in hypothyroidism condition. Hemodynamic parameters (blood pressure and heart rate) showed a decrease in hypothyroid animals, as already reported in the literature. Histological analyses demonstrated a significant diminution in aorta cross-sectional area in hypothyroidism state. Along with this result, protein expression of collagen type I was also decreased while elastin was augmented in hypothyroid aortas. Besides, we observed an increase of nuclei density per mm2 and a decrease in nuclear volume in hypothyroid group. MMP-9 protein expression was decreased and TIMP-2 was increased in hypothyroid aortas. Our data strongly suggest that hypothyroidism alters the extracellular matrix deposition/ degradation in rat aorta, which may indicate a possible fragility of the vascular wall.