The developing human ovary: immunohistochemical analysis of germ-cell-specific VASA protein, BCL-2/BAX expression balance and apoptosis.
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 (<or=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.
Departamento de Estudios Biomédicos y Biotecnológicos, Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y Diagnóstico, CEBBAD, Universidad Maimónides, Hidalgo 775, C1405BCK Buenos Aires, Argentina.
Mirta S
MS
Albamonte
Miguel A
MA
Willis
María I
MI
Albamonte
Federico
F
Jensen
María B
MB
Espinosa
Alfredo D
AD
Vitullo
D000022:Abortion, Spontaneous; D017209:Apoptosis / Q000502:physiology*; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D053938:DNA Fragmentation; D005260:Female; D005854:Germ Cells / Q000737:chemistry*; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D010053:Ovary / Q000166:cytology / Q000196:embryology*; D011247:Pregnancy; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C498288:DDX4 protein, human; D053487:DEAD-box RNA Helicases