Given the importance of the thymus to the immune system and the limited knowledge about its development and involution processes, this study evaluated the expression of the vascular endo-thelial growth factor, a key angiogenic factor for the formation of vascular tissue bed and modulation of functions related to cell proliferation and migration, hormone synthesis, and immunomodulation. In this study, thymus samples of dog fetuses (30, 40, 50 and 60 days old), and young (180 days old) and adult (365 days old) dogs were submitted to real-time PCR and Western blot. Time-dependent changes were observed for proteins and genes associated with the development of the vascular system, such as VEGF-A, VEGF-C, Flt-1, KDR, FLT-4, and EG-VEGF. This result demonstrates that these system components play different roles during development and involution of the thymus. Possible functions, such as the modulatory effect on vasculogenesis and microenvironment, influence the proliferation and differentiation of thymocytes, T cells maturation, cell-cell interaction and hormone secretion.
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