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Apoptosis during folliculogenesis in pigs
1Germplasm and Gamete Physiology Laboratory, Agricultural Research Service, US Department of Agriculture, Beltsville, MD 20705, USA. dave@anri.barc.usda.gov
Reproduction (Cambridge, England). Supplement
|May 1, 2002
Summary
Female germ cell numbers decline significantly in pigs due to apoptosis, or programmed cell death. This process, involving caspases, regulates follicle atresia and may prevent ovulation of immature oocytes.
Area of Science:
- Reproductive Biology
- Cell Biology
- Developmental Biology
Background:
- Female germ cell numbers decrease substantially during fetal development and post-birth in pigs.
- Follicular atresia, a major cause of germ cell loss, occurs throughout folliculogenesis, with a notable exception just before oestrus.
- Apoptosis is the established mechanism for germ cell death and follicle atresia.
Purpose of the Study:
- To investigate the role and mechanisms of apoptosis in pig oocyte and follicle development.
- To quantify germ cell loss and follicle atresia during different developmental stages.
- To explore the involvement of caspases and hormonal regulation in apoptosis.
Main Methods:
- DNA fluorescence flow cytometry to measure internucleosomal DNA cleavage.
- Densitometry of fluorescently labeled DNA fragments.
- Immunohistochemical analysis of DNA breaks in frozen tissue sections.
Main Results:
- Apoptosis is confirmed as the mechanism for germ cell death and follicle atresia.
- Follicular atresia is linked to decreased FSH secretion before oestrus.
- Apoptosis in granulosa cells correlates with reduced proliferation and lower oestradiol and inhibin production.
- FSH and IGF-I exhibit anti-apoptotic effects in cultured granulosa cells, and caspase inhibition blocks apoptosis.
Conclusions:
- Apoptosis plays a critical role in regulating female germ cell numbers and follicle development in pigs.
- Caspase activity is central to the apoptotic process in granulosa cells.
- Apoptosis and follicle atresia may serve to prevent the ovulation of oocytes that have not maintained meiotic arrest.