Abstract:
The fetal and post-natal development of the pig ovary involves bothproliferation and apoptotic loss of germ cells, follicle formation and growth,and the initiation of oocyte meiotic maturation. The present study measuredthe expression of the proto-oncogene Bcl-2 immunohistochemically on paraffinsections of pig ovaries to determine its relationship with folliculogenesis onDays 50 and 80 post coitum (p.c.) and on Days 1, 21, and 56 post partum(p.p.). The expression of the steroidogenic enzyme 3β-hydroxy-steroiddehydrogenase (3βHSD) was used to determine the lineages of the cellsforming the ovarian follicles, and the expression of the cellproliferation-associated nuclear antigen Ki-67 was used to determine germ cellproliferation and the initiation of follicle growth. Expression of Ki-67showed that many oogonia were proliferating on Days 50 and 80 p.c. Granulosacells were more proliferative on Day 56 p.p. than at any other stage; Ki-67was expressed in 70% of growing follicles and granulosa cells had a3% mean staining index per section. Less than 4% of germ cellsand follicles had morphological signs of degeneration during the period of thestudy. Bcl-2 was most abundant on Days 21 p.p. and 56 p.p.; staining waslocalized to stromal cells among follicles and in small clusters in thecortical-medullary junction (CMJ). 3βHSD staining on Day 50 p.c. wasseen in cords of stromal cells within the medulla of the ovary, and in thestromal cells investing the oogonial nests. On Days 80 p.c., 1 p.p., 21 p.p.,and 56 p.p., 3βHSD was expressed in the granulosa cells of primary orprimordial follicles at the CMJ. Production of Bcl-2 by somatic cells maysupport germ cell and preantral follicle survival.