Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2000
Publication Date: N/A
Interpretive Summary: The conservation of germ cells is poor in mammalian species. Germ cell survival is a function of several proto-oncogene Bcl-2 gene family members that form homo- and heterodimers which represent a cell death switch that determines whether cells live or die. The expression of Bcl-2, a cell survival factor was measured immunohistochemically on paraffin sections of ovaries and related to folliculogenesis and expression of 3-beta hydroxysteroid dehydrogenase (3BHSD), a marker for steroidogenesis. Ovarian expression of Bcl-2 was localized to stromal cells in the developing ovary. 3BHSD was expressed in stromal cells and in granulosa cells of early, but not late formed follicles. These results are important to other scientists because Bcl-2 may act directly on germ cells as a cell survival factor or may act indirectly by promoting production of stromal cell survival factors. Differential cell localization of 3BHSD expression supports the dual source hypothesis of granulosa cells, namely the ovarian rete, and germinal epithelium.
Technical Abstract: The protooncogene Bcl-2 was measured immunohistochemically on paraffin sections of pig ovaries to determine its relationship with folliculogenesis and expression of 3beta-hydroxysteroid dehydrogenase (3BHSD) on days 50 and 80 post coitum (p.c.) and on days 1, 21, and 56 post partum (p.p.). Immunohistochemical determination of the cell proliferation-associated nuclear antigen Ki-67 showed that many oogonia were in a proliferative stage of the cell cycle on days 50 and 80 p.c. Granulosa cells were more proliferative on day 56 p.p. than at any other stage; Ki-67 was expressed in 70 % of growing follicles and granulosa cells had a 3 % mean staining index per section. Less than 4 % of germ cells and follicles had morphological signs of degeneration. Bcl-2 was most abundant on days 21 p.p. and 56 p.p.; staining was localized to stromal cells among follicles and in small clusters in the cortical-medullary-junction (CMJ). 3BHSD staining on day 50 p.c. was seen in cords of stromal cells within the medulla of the ovary, and in the stromal cells investing the oogonial nests. On days 80 p.c., 1 p.p., 21 p.p., and 56 p.p., 3BHSD was expressed in the granulosa cells of primary or primordial follicles at the CMJ. Production of Bcl-2 by somatic cells may support germ cell and preantral follicle survival.