The developing human ovary: immunohistochemical analysis of germ-cell-specific VASA protein, BCL-2/BAX expression balance and apoptosis

• Published in: Human reproduction (Oxford) Vol. 23; no. 8; pp. 1895 - 1901
• Main Authors: Albamonte, Mirta S., Willis, Miguel A., Albamonte, María I., Jensen, Federico, Espinosa, María B., Vitullo, Alfredo D.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.08.2008; Oxford Publishing Limited (England)
• Subjects: Abortion, Spontaneous; apoptosis; Apoptosis - physiology; bcl-2-Associated X Protein - metabolism; BCL-2/BAX; Biological and medical sciences; DEAD-box RNA Helicases - metabolism; DNA Fragmentation; Female; female germ cells; Germ Cells - chemistry; Gynecology. Andrology. Obstetrics; human fetal ovary; Humans; Immunohistochemistry; In Situ Nick-End Labeling; Medical sciences; Ovary - cytology; Ovary - embryology; Pregnancy; Proto-Oncogene Proteins c-bcl-2 - metabolism; VASA; apoptosis; female germ cells; human fetal ovary; /; Human; Immunohistochemistry; Germinal cell; Gene expression; Pregnancy; Ovary; VASA; Vertebrata; Mammalia; Female genital system; BCL-2/BAX; Development; Female; Fetus; Balance; Apoptosis
• ISSN: 0268-1161; 1460-2350
• DOI: 10.1093/humrep/den197

BACKGROUND Germ cell number during ovarian organogenesis is regulated through programmed cell death. We investigated the expression of germ-cell-specific VASA protein, apoptosis-related proteins BAX and BCL-2 and DNA fragmentation in developing human ovaries from gestation week 12 to term. METHODS Human fetal ovaries from 13 women undergoing spontaneous abortion were fixed, paraffin-embedded and processed for immunohistochemistry to analyse temporal and cellular localization of VASA, BCL-2 and BAX, and to detect apoptosis by TUNEL assay. RESULTS VASA showed a differential pattern of expression throughout the differentiation and proliferative phase and prophase I to finally associate with Balbiani's body in primordial and primary follicles. BCL-2 was detected from week 12 to 17 and became undetectable thereafter. Strong BAX signal was detected in oogonia and oocytes from week 12 to term. Low levels (≤10%) of TUNEL positive germ cells were detectable throughout gestation with a higher incidence (around 20%) at 18–20 weeks. CONCLUSIONS VASA was specifically expressed in germ cells and displayed a stage-specific intracellular localization enabling one to follow oogenesis throughout gestation. Apoptosis-inhibiting BCL-2 was associated with the germ cell proliferative phase and prophase I, whereas BAX remained positive throughout gestation. The highest incidence of apoptotic germ cells was coincident with the lack of detectable BCL-2 protein, and when primordial follicle formation became widespread.