MEIOSIS-ACTIVATING STEROLS - BACKGROUND, DISCOVERY, AND POSSIBLE USE

Several years ago we discovered that spent media from cultured human a nd bull testes contain components that initiate meiosis in germ cells from fetal mouse which have been cultured for 6 days in the spent medi um. The active substance(s) was termed meiosis-inducing substance. We later found that human follicular fluid harvested after stimulation wi th gonadotropins has a similar effect. These meiosis-activating substa nces have now been identified and characterized in extracts from bull testes and human preovulatory follicular fluid as naturally occurring sterols (meiosis-activating sterols, MAS). MAS are intermediates in th e cholesterol biosynthetic pathway and are thus present in all cells w hich produce cholesterol de novo and from lanosterol. However, MAS acc umulate only in the gonads. We discuss the possible physiological role of these sterols in initiating meiosis and in oocyte resumption of me iosis, and their potential use in promoting and preventing fertility.