REGULATION OF ANGIOGENESIS BY HYPOXIC STRESS - FROM SOLID TUMORS TO THE OVARIAN FOLLICLE

The preovulatory follicle provides a unique physiological example of r apid growth accompanied by neovascularization, two processes that are generally characteristic of pathologies such as wound repair or malign ancy. During the hours preceding ovulation, follicular growth is accom panied by elevated levels of messenger RNA for vascular endothelial gr owth factor (VEGF). Angiogenic activity, mediated by VEGF, is manifest ed in the peripheral blood vessels surrounding the follicle, that show capillary sprouting and increased vascular permeability. Following ov ulation, rapid infiltration of capillaries through the follicular wall is essential for the formation of the corpus luteum. In this review w e compare the preovulatory follicle with a popular model of avascular solid tumour growth, namely the multicellular tumour spheroid, in part icular the role of hypoxic stress in the regulation of angiogenesis in both systems.