Regulation of vascular endothelial growth factor production in mouse thymic epithelial cell lines

Abstract

Vascular endothelial growth factor (VEGF) in adults is synthesized in small amounts by thymic epithelial cells and is important for the maintenance of vascular homeostasis. However, its role dramatically increases during the process of thymic reconstitution after damage caused by radiation, chemo-, or hormonotherapy. The aim of the study was to evaluate the influence of different factors on VEGF production by mouse thymic epithelial cells in vitro. As a model, two cell lines were used: cortical cTEC1-2 and medullar mTEC3-10 cells. These cells were characterized by their ability to synthesize VEGF mRNA and VEGF protein, as well as by the presence of VEGF receptors. No VEGFR1 or VEGFR2 mRNA expression was observed in these cells, while NRP-1 mRNA was expressed at a low level. An ELISA test showed that cTEC1-2 cells produced VEGF about 30 times more than mTEC3-10 cells. These cell lines, when exposed to cytokines, hormonal factors, or thymocytes, responded differently. Keratinocyte growth factor (KGF) enhanced VEGF mRNA expression, as well as VEGF protein production, in medullar cells, but down-regulated VEGF mRNA synthesis in cortical cells. Dexamethasone suppressed the levels of VEGF mRNA expression and its protein production in cortical cells, while in medullar cells only VEGF production was reduced. Introduction of IL-7, IL-1β, or murine thymocytes increased, while administration of semaphorin-3A, SDF-1α, or ACTH decreased, VEGF production by cortical epithelial cells with no influence on medullar cells. We suggest that our data, obtained in vitro, can serve for further development of special strategies directed for regulation of VEGF synthesis in the thymic epithelial cells in vivo.