Conditions that affect acquisition of developmental competence by mouse oocytes in vitro: FSH, insulin, glucose and ascorbic acid

The simplest unit required for the support of oocyte growth and development is the oocyte-granulosa cell complex. Therefore, a culture system was esta blished that utilizes these complexes to assess mechanisms promoting nuclea r, cytoplasmic and genomic maturation in mammalian oocytes. Deletion of ser um from the culture, results in increased apoptosis in oocyte-associated gr anulosa cells (OAGCs), however, addition of ascorbic acid (0.5 mM) signific antly reduced the level of apoptosis in the OAGCs, although no improvement of oocyte developmental competence was detected. The effects of reducing gl ucose during oocyte growth were studied since, under some culture condition s, glucose has deleterious effects on early preimplantation development. Re ducing the glucose concentration to 1 mM resulted in the production of oocy tes with greatly reduced developmental competence. Deleterious effects of F SH plus insulin during oocyte growth in vitro on preimplantation developmen t are reviewed and discussed in terms of the communication of oocytes with inappropriately developing granulosa cells. Evidence that oocytes promote t he appropriate differentiation of OAGCs in intact follicles in vivo is also discussed. It is hypothesized that oocytes control the differentiation of these cells, in order to promote intercellular signaling essential for the acquisition of competence to undergo normal embryogenesis. (C) 2000 Elsevie r Science Ireland Ltd. All rights reserved.