Spermatogonial apoptosis has three morphologically recognizable phases and shows no circadian rhythm during normal spermatogenesis in the rat

Abstract

In this study we examined the possibility that regular or circadian fluctuations occur in the frequency of spontaneous spermatogonial apoptosis. Apoptosis of A2, A3 and A4 type spermatogonia occurring spontaneously in the normal rat testis was studied by light and electron microscopy. Normal and apoptotic A3 spermatogonia were quantified in 36 animals killed at two-hourly intervals over a 24 h period. Three sequential phases of spermatogonial apoptosis were defined and quantified separately: (i) an early phase in which cells showed margination of nuclear chromatin, (ii) an intermediate phase in which phagocytosed apoptotic bodies were partly degraded and (iii) a late phase in which only debris of degraded apoptotic bodies was evident. Groups of spermatogonia linked by intercellular bridges underwent apoptosis synchronously. Normal and apoptotic A3 spermatogonia occurred at a mean frequency of 33.4 and 9.6 per 10 seminiferous tubule profiles respectively; there was a large variation in these frequencies between animals, but no peaks or circadian periodicity were detected. Progressive degradation of apoptotic bodies was evident, the average ratios of intermediate and late bodies to early bodies being 1.5 and 3.5, respectively. Absence of a circadian rhythm in these data does not exclude the possibility that initiation of apoptosis in susceptible spermatogonial clones is synchronous, and that affected clones undergo lag periods of differing duration before expressing morphological apoptosis.

Clinical aspects of male germ cell apoptosis during testis development and spermatogenesis

“…Germ cell deletion during normal spermatogenesis has been estimated to result in the loss of up to 75% of the potential numbers of mature sperm cells in the adult testis (De Rooij et al, 1987;Huckins, 1978;Oakland, 1956). Detailed analyses of germ cell degeneration have been published (Allan et al, 1992;Clermont, 1962;De Rooij and Lok, 1987;Huckins, 1978;Kerr, 1992;Wing and Christiansen, 1982); morphometric analyses of semithin sections of perfusion-fixed testes have indicated that the loss of germ cells in the rodent testis is greatest during the mitoses of type A2, A3, and A4 spermatogonia and during the first meiotic division ( Figure 4). No degeneration occurs in type A1 spermatogonia, or in intermediate or type B spermatogonia (Johnson et al, 1984;Kerr, 1992) (Figure 4).…”

“…On the basis of morphological evidence, it was first suggested that cell death of spermatogonia during normal spermatogenesis takes place through the apoptotic mechanism, the spermatocytes and spermatids, in contrast undergoing necrosis (Allan et al, 1992). Recently, however, quantification of small molecular weight DNA fragments and in situ DNA 3'end-labeling analyses of apoptosis in the testis have shown that spermatocytes and spermatids can also undergo apoptosis (Billig et al, 1995 Figure 5 Testosterone-mediated inhibition of apoptosis induced in human seminiferous tubules cultured in serum-free conditions.…”

Effects of experimental diabetes on testis proliferations and apoptosis in rats

“…The mechanisms of diabetes-related apoptosis are unclear. However, current studies have indicated that diabetes-mediated oxidative stres can induce apoptosis (Allan et al, 1992;Reiter et al, 2000).…”

Expression of the Fas-ligand gene in ejaculated sperm from adolescents with and without varicocele

“…A large number of germ cells are present in the testes, while Sertoli cell support is finite. Thus, apoptosis is a normal and necessary occurrence during spermatogenesis, in order to select germ cells and regulate the number of germ cells [21][22][23][24][25][26]. In some cases, apoptosis may initiate but abort, in a process known as abortive apoptosis, leading to the ejaculation of mature sperm with apoptotic traits, such as fragmented DNA and membrane-bound Fas [27,28].…”