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01-Mar-2001
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Arch Hellen Med, 17(5), September-October 2000, 477-490
REVIEW
Proliferation and apoptosis of germ cells
R. ANGELOPOULOU, V. KARAYIANNIS
Laboratory of Histology and Embryology, Medical
School, University of Athens, Greece
Cell proliferation and apoptosis are observed at various phases of gametogenesis
and are important for germ cell development and differentiation. Numerous factors
are involved in the control of both processes acting in concert to ensure the
normal evolution of spermatogenesis and oogenesis. Apoptosis is the main cause
of elimination of germ cells during the fetal period in both sexes. In the female,
it follows the phase of intense proliferation and the entry into the meiotic
prophase I. In the male, it occurs later, during the perinatal and the prepubertal
period. The quantitative distribution pattern of Ki-67 protein and the proliferating
cell nuclear antigen (PCNA) are used to investigate mitotic activity in gonadal
biopsies during the reproductive period. Τhe characteristic morphology of the
apoptotic cells detected by the electron microscope and the in situ 3’
end labeling procedure of nuclear DNA fragmentation enables their localisation
on histological sections. The observation of low molecular weight DNA after
gel fractionation and electrophoresis provides biochemical evidence of apoptotic
cell death in the germ cells while quantitative estimation is made by flow cytometry.
Recent advances in the understanding of the mechanism of apoptosis, the regulating
role of the pro-apoptotic and anti-apoptotic genes and the different families
of proteins involved in normal gametogenesis, along with analysis of the factors
implicated in apoptosis of the testis and sperm in association with cell proliferation
under normal conditions, should elucidate the mechanisms ensuring gonadal homeostasis
and reveal the causes of infertility.
Key words: Apoptosis, Cell proliferation, Germ cells, Oogenesis, Spermatogenesis.