Quantitative and biomolecular aspects of the thymus vascularization in cat

Author(s)

Camila Ercolini Barroso

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2012-05-31

Examining board members

José Roberto Kfoury Junior; Fernanda Rodrigues Agreste; Marcello Machado; Rose Elí Grassi Rici; Ana Paula Vidotti

• Advisor: Pedro Primo Bombonato

Abstract

The lymphoid system is composed by primary and secondary lymphoid organs. The thymus is a primary lymphoid organ responsible for maturation, differentiation and selection of the lymphoid T cell lineage that is responsible for cellular immunity. To accomplish these functions has a peculiar arrangement with morphologically distinct epithelial cells and vascular structures. The blood vessels have a role in tissue oxygentation and the migration of T cells into the thymic parenchyma, therefore they presents large vessels in cortico-medullary junction and a fine network branches to the cortex. This process has its molecular basis unknown as well as the involution process of the thymus. VEGF is an angiogenic factor that plays a role in the formation and modulation of vascular functions, being an important marker of angiogenesis. We proposed to evaluate the gene and protein of VEGF during the thymus development and involution, stereological quantification and scanning electronic microscopy. Samples of cat´s thymus from 35, 45, 55, 65 days of development and 6 months and 1 year of age. In scanning electronic microscopy different stages maturation thymocytes were observed. Protein expression of VEGF and its receptors were identified in all development stages in epithelial cells, endothelial cells and thymic corpuscles. The VEGF mRNA expression and its receptors in 1 year old animals was significantly increased, coinciding with the decreasing Nvasc and the Nv(vasc) causing a hypoxic condition in the thymus resulting in a compensatory increase of VEGF system. The vascular growth curve follows a pattern of development and involution of the organ. (AU)