Significance of Apoptosis in the Temporal and Stage-Specific Loss of Germ Cells in the Adult Rat after Gonadotropin Deprivation1

Abstract

The major objectives of the present study were to document the temporal and stage-specific acceleration of germ cell apoptosis in adult rats after selective suppression of pituitary gonadotropins by GnRH antagonist (GnRH-A) treatment, and to examine the possibility that apoptosis is the sole mechanism of germ cell death in response to hormonal deprivation. Groups of adult male rats were given a daily injection of a vehicle for 14 days or GnRH-A (1.25 mg/kg BW) for 2, 5, 7, and 14 days. Analysis of testicular apoptotic DNA fragmentation revealed a detectable increase at Day 5 and a maximal increase at 14 days after treatment. In situ analysis of germ cell apoptosis fully corroborated the observed increase in the degree of DNA fragmentation with time and also revealed a stage-related activation of apoptosis of specific germ cells. A low incidence (0.06-0.09) of germ cell apoptosis (expressed as numbers per Sertoli cell) was detectable at stages I, IX-XI, and XII-XIV in control rats. Mean incidence of apoptotic germ cells specifically at stages VII-VIII increased significantly (0.40 +/- 0.06) by Day 5 and increased another 2.2-fold (over the 5-day treatment values) on Day 7 after GnRH-A treatment as compared to values in controls, where no apoptosis was detected. Significantly increased incidence of apoptosis at stages IX-XI (0.37 +/- 0.05) over control values (0.07 +/- 0.01) was noted by Day 7. Within the study paradigm, the highest number of dying cells occurred by Day 14, at which time a modest but significant (p < 0.05) increase in the incidence of apoptosis was also noted at stages I, II-IV, V-VI, and XII-XIV in comparison with control values. Stages VII-VIII and IX-XI still exhibited the higher number of cells undergoing apoptosis (0.97 +/- 0.22, and 1.03 +/- 0.22, respectively). Comparison between rates of apoptosis and cell degeneration measured at stages VII-VIII demonstrated an intimate association (r = 0.94; p < 0.001) between apoptosis and germ cell loss, strongly supporting the concept that germ cell death (at these stages) after removal of hormonal support in the adult rat occurs almost exclusively via apoptosis.

Histological Changes of the Ovary of Adult Mice Exposed Prenatally to Flunitrazepam

“…In consequence, this increase possibly causes theca and granulosa cells hypertrophy, changing the follicular morphology and physiology, resulting in probable apoptosis (Wyllie et al, 1980). Sinha-Hikim et al (1997), confirmed the effects of absent hyphophyseal hormones in the ovary of adult rats, which raised the apoptotic cell proportion.…”

Lower sperm DNA fragmentation after r-FSH administration in functional hypogonadotropic hypogonadism

“…Normally, breaks are physiologically reassembled before spermatozoa are released from germinal epithelium [27], but, as a consequence of testicular injuries, including heat, exposure to toxicant [26,31,34] radiation [37], withdrawal of hormonal support [22,55,61], other testicular pathologies [18] or life habits (smoke, drug use), the repair process could be impaired, so that spermatozoa show high levels of DNA damage [8,49].…”

A sequential methodology that allows apoptotic cell sorting and FISH analysis in human testicular cells

“…In the immature testicle of prepubertal individuals, a massive wave of apoptosis of spermatogonium and primary spermatocytes has been described, due to the absence of adequate levels of gonadotropin (reviewed by [Shaha et al 2010]). During adult life, the apoptotic process responds to hormonal changes [Sinha Hikim et al 1997], to maintain the ratio between Sertoli cells and germ cells (reviewed by [Shaha et al 2010]) and to activate checkpoints monitoring the correct development of spermatogenesis (reviewed by [Morelli and Cohen 2005]). The pachytene checkpoint prevents the progression beyond prophase until DSB repair and homolog synapsis are completed [Li et al 2009].…”