Endocrine Abstracts

There is compelling evidence that certain families of endothelial cell-specific tyrosine kinases and their ligands (e.g. VEGFR/VEGF, Tie2/Ang) are essential for embryonic development and for angiogenesis in a wide variety of physiological and pathological circumstances. There is also evidence for a tissue-specific and tumor-specific regulation of endothelial cell growth and phenotype.
We recently identified EG-VEGF, an endothelial cell mitogen with a unique selectivity, essentially limited to endothelial cells derived from endocrine organs. Human EG-VEGF expression is virtually restricted to steroidogenic tissues, with highest expression in ovary and testis, followed by adrenal cortex and placenta. Another member of the EG-VEGF family is the 'BV8' protein, which displays a high degree of homology to EG-VEGF. In situ hybridization shows that EG-VEGF mRNA expression is localized to the steroid hormone-producing cells, i.e. Leydig cells of the testis and the specialized stroma in the ovary. BV8 expressions occur predominantly in the testis. Strong EG-VEGF mRNA expression was detected in a series of human Polycystic Ovary Syndrome specimens. Recent evidence indicates that the EG-VEGF receptor(s) belongs to the family of GPCRs. In vivo experiments, using adenovirus-delivered EG-VEGF, demonstrated a strong angiogenic response in endocrine tissues such as ovary, testis, but no apparent effect in the skeletal muscle and cornea.
These findings indicate that the EG-VEGF family represents a novel type of endothelial cell-specific effector that acts in a tissue-specific manner to determine the phenotype and promote the growth of the resident endothelial cells.