The Death of Sertoli Cells and the Capacity to Phagocytize Elongated Spermatids During Testicular Regression due to Short Photoperiod in Syrian Hamster (Mesocricetus auratus)1

Abstract

In the Syrian hamster (Mesocricetus auratus), an animal that displays testicular regression due to short photoperiod, germ cells are removed by apoptosis during this process and the apoptotic remains are phagocytized by Sertoli cells. The aim of this work was to investigate morphologically whether the testicular regression process due to short photoperiod leads to the apoptosis of Sertoli cells, and whether, during testicular regression, the elongated spermatids are eliminated through phagocytosis by Sertoli cells. To this end, we studied testis sections during testicular regression in Syrian hamster subjected to short photoperiod by means of several morphological techniques using conventional light microscopy (hematoxylin and eosin [H&E], semi-thin section vimentin, immunohistochemistry, SBA lectin, and TUNEL staining), fluorescence microscopy, and transmission electron microscopy (TEM). H&E and semi-thin sections identified Sertoli cells with a degenerated morphology. Greater portion of Sertoli cells that were positive for TUNEL staining were observed especially during the mild regression (MR) and strong regression (SR) phases. In addition, TEM identified the characteristic apoptotic changes in the nucleus and cytoplasm of Sertoli cells. Moreover, during testicular regression and using light microscopy, some elongated spermatids were seen in basal position next to the Sertoli cell nucleus. This Sertoli phagocytic activity was higher in MR and SR phases. TEM confirmed this to be the result of the phagocytic activity of Sertoli cells. In conclusion, during testicular regression in Syrian hamster due to short photoperiod, when germ cells are known to be lost through apoptosis, there is morphological evidences that Sertoli cells are also lost through apoptosis, while some elongated spermatids are phagocytized and eliminated by the Sertoli cells.

Testicular histomorphometry and the proliferative and apoptotic activities of the seminiferous epithelium in Syrian hamster (Mesocricetus auratus) during regression owing to short photoperiod

“…Thus, it was observed that both apoptosis and proliferation play a key role in this phenomenon, as in the MR and SR stages there was a very significant increase in the apoptosis/proliferation ratio owing to increased apoptosis both in general and of each of the germ cell types as well as a decrease in proliferation during the onset of regression. This also correlated with observations made in the period when the apoptotic index in the Sertoli cells was maximum (Seco-Rovira et al, 2014). Later, in the TR group, this ratio is higher than in the controls, mainly at the expense of apoptosis of spermatocytes and spermatids because both the proliferative and apoptotic indexes of spermatogonia are similar to control values.…”

“…The latter phenomenon is essential as it enables a minimal essential pool of spermatogonia to remain available to quickly restore the germinal epithelium during recrudescence. Besides, it should not be forgotten that the depletion of the seminiferous epithelium would be accompanied by the loss of Sertoli cells and the phagocytosis of late spermatids (Seco-Rovira et al, 2014), which would contribute to involution of the epithelium.…”

“…These groups were established not only according to the time of exposure to the short photoperiod (MR: 4 weeks; SR: 6-8 weeks; TR: 12 weeks) but also to the proportion of tubular sections (control: 0%; MR: 3.9%; SR: 42.9%; TR: 81.6%) in spermatid arrest, tubular diameter (control: 285.3 AE 4.3 lm; MR: 234.3 AE 8.6 lm; SR: 163.7 AE 6.4 lm; TR: 128.9 AE 5.6 lm), and the mean tubular seminiferous epithelium area (control: 55039.9 AE 11254. (Seco-Rovira et al, 2013, 2014.…”

“…Such a loss of cells through apoptosis during the epithelium atrophy process seems to affect not only spermatocytes but also other germ cells (Seco-Rovira et al, 2013). Cell loss also includes phagocytosis of round spermatids by Sertoli cells and the death of the latter through apoptosis (Seco-Rovira et al, 2014). Thus, regression of the seminiferous epithelium in the Syrian hamster owing to short photoperiod seems to be caused by a loss of germinal and somatic cells through apoptosis and the phagocytosis of late spermatids, although no detailed study of the apoptosis of germ cells in general or the role of proliferation in epithelial atrophy has been made.…”

Identification of Apoptotic Cells by Means of Lectin Histochemistry: State of the Art Review

“…At the same time, it has been described that other lectins that bind to galactose residues are also positive towards apoptotic Sertoli cells in the spotted ray (Torpedo marmorata)" [55,68]. Therefore, our study, while confirming the usefulness of lectins to identify Sertoli cells undergoing apoptosis in mammals, shows that lectins can also identify their elimination during testicular regression, a fact that has also been observed in our laboratory using TUNEL and transmission electron microscopy [69]. Furthermore, during testicular regression, the Sertoli cell was observed to have a strong phagocytic capacity, which affected whole late spermatids [69].…”