PROLIFERATION AND APOPTOSIS IN FOLLICLES OF THE MARMOSET MONKEY (CALLITHRIX-JACCHUS) OVARY

Proliferation and apoptosis were studied in ovarian follicles of immat ure and pubertal marmosets and in mature marmosets during the follicul ar, periovulatory and luteal phases. Proliferation was evaluated using a Ki67 antibody and apoptosis was assessed by in situ detection of DN A fragmentation. In the immature animals only small follicles were pre sent, and the expression of Ki67 was restricted to the granulosa cells of follicles localised near the medulla. There was no evidence of DNA fragmentation. In pubertal and adult animals Ki67 expression was foun d in the granulosa cells of some but not all primordial and primary fo llicles. In the secondary and tertiary follicles immunoreactivity was localised in theca cells and granulosa cells. In atretic follicles (mo rphologically classified) the number of Ki67 positive granulosa cells varied. In corpora lutea as well as in corpora lutea accessoria, stain ing was seen in the nuclei of some luteal cells. During all phases of the cycle, follicles from the secondary stage onwards were proliferati ng, whereas granulosa cells of primary follicles were only stained dur ing the follicular phase. During all phases of the ovarian cycle apopt osis was restricted to the granulosa cells of tertiary follicles. With regard to proliferation and apoptosis, follicles exhibiting morpholog ical signs of atresia can be classified as follows: (1) granulosa cell s showing strong Ki67 expression; (2) granulosa cells with reduced exp ression of Ki67; (3) granulosa cells devoid of Ki67 immunoreactivity a nd of apoptotic signs; (4) granulosa cells heavily stained for DNA fra gmentation and not stained for Ki67; (5) granulosa cells close to the antrum showing DNA fragmentation but luteinizing Ki67 positive granulo sa cells close to the basement membrane. In summary, it was shown that atresia of tertiary follicles is characterised by three consecutive s tages: morphological alterations, cessation of proliferation and final ly apoptosis in tertiary follicles. Thus, our results indicate that ea rly atresia as evidenced by the morphological signs is not necessarily related to DNA fragmentation, since apoptosis is exclusively found in the granulosa cells of advanced atretic tertiary follicles.