Hypoxia limits mouse follicle growth in vitro.

Ovarian follicle culture is useful for elucidation of factors involved in the regulation of follicular function. We examined the effects of gas phase oxygen concentration, an oil overlay, serum type and medium supplementation with FSH, insulin-transferrin-selenium (ITS) and l-ascorbic acid on cultured preantral mouse follicle growth in a spherical, non-attached follicle culture system. Follicle growth in 5% oxygen was significantly (PPP>0.05) affected by an oil overlay, ITS supplementation or serum type. Culture in medium with 5% mouse serum, 1IUmL-1 FSH, 25?gmL-1 l-ascorbic acid and 20% oxygen without an oil overlay supported the growth of follicles to a maximum diameter of 380?m in 6 days. Compared with mature preovulatory mouse follicles in vivo that often have diameters >500?m within the same time frame, in vitro-grown follicles clearly exhibit limited growth. Thus, adequate oxygenation is an essential factor in the process of optimising follicle growth.