The Developing Human Ovary: ImmunoHistochemical Analysis of Germ Cell-Specific VASA Protein BCL2/BAX Expression Balance and Apoptosis (Pages: 0-0)


Vitullo A.D *, Albamonte M.S , Willis M.A , Albamonte M.I , Jensen C.F , Espinosa M.B ,

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Objective: 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 BCL2 and DNA fragmentation in human developing ovaries from gestation week 12 to term Materials and Methods: Human foetal ovaries from 13 women undergoing spontaneous abortion were fixed paraffin-embedded and processed for immunohistochemistry to analyse temporal and cellular localisation of VASA BCL-2 and BAX and to detect apoptosis by TUNEL assay. Results: VASA showed a differential pattern of expression throughout differentiation and proliferative phase prophase I to finally associate to 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. Conclusion: VASA was specifically expressed in germ cells and displayed a stage-specific intracellular localisation enabling to follow oogenesis throughout gestation. Apoptosis-inhibiting BCL-2 was associated to germ cell proliferative phase and prophase I while 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.