INITIATION OF GROWTH OF BABOON PRIMORDIAL FOLLICLES IN-VITRO

Factors that cause some primordial follicles to enter the growth phase while the others remain quiescent are unknown, The hypothesis was tes ted that primate primordial follicles can survive and initiate growth in vitro in serum-free medium, Superficial pieces of ovarian cortex, c ontaining mostly primordial follicles, were obtained from baboon fetus es during late gestation and cultured for 0, 2, 4, 7, 10 or 20 days in Waymouth MB 752/1 medium supplemented with insulin, transferrin, sele nium, linoleic acid, and bovine serum albumin (ITS+), Histological exa mination of cortical pieces revealed that after 2 and 4 days in cultur e, the total number of primordial follicles had decreased by 55 and 76 % (P < 0.01) respectively, relative to day 0 of culture, This was asso ciated with a sustained, 5- to 8-fold increase in total primary follic les (P < 0.01) beginning on day 2 of culture, There was also a gradual increase in the total number of early secondary and secondary follicl es, The average diameter of follicles and oocytes increased gradually throughout culture for all follicular categories (P < 0.01), except se condary follicles and oocytes. Immunohistochemical localization of pro liferating cell nuclear antigen (PCNA), a marker for cell proliferatio n and growth, showed that PCNA was generally absent in primordial foll icles on day 0, but was observed after 2 or 4 days in culture in both granulosa cells and oocytes of most growing follicles. Comparison of c ortical pieces cultured for 10 or 20 days with ITS+ versus 10% fetal b ovine serum (FBS) showed a more pronounced decrease in the numbers of primordial follicles and more primary, early secondary and secondary f ollicles in ITS+ compared to FBS-treated cortical pieces (P < 0.01 at 20 days), These results show that primordial follicles from non-human primates can survive and develop to the secondary stage in vitro in se rum-free conditions.