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The Sertoli cell (Sc) has been described as a quiescent cell once the animal has reached sexual maturity. Syrian hamster is an animal that displays testicular regression due to short photoperiod, during which process germ cells and Sc are removed through apoptosis. The aim of this work was to investigate histochemically whether the spontaneous testicular recrudescence processes after exposure to a short photoperiod lead to an increase in Sc proliferative activity in order to restore the normal population. Three spontaneous recrudescence groups were established: initial (IR), advanced (AR), and total (TR) recrudescence, which were compared with animal undergoing the regression process (mild: MRg, strong: SRg, and total: TRg) and animals in long photoperiod (Controls). Histological sections were submitted to histochemical techniques for detecting apoptotic and proliferative Sc with bright-field and fluorescence microscopy. For each group, the proliferative Sc index (PScI) and apoptotic Sc index (AScI), and the total number of Sc were obtained. The results revealed the existence of Vimentin+/TUNEL+ as well as Vimentin+/PCNA+ cells. The PScI was significantly higher in TRg and IR than in the other groups. The AScI was only significantly higher in MRg and SRg with respect to the other groups. The total number of Sc increased among TRg, IR, and AR, reaching values similar to those of the Controls. In conclusion, the increase in Sc proliferation from final regression and recrudescence, accompanied by a similar rate of apoptosis to the Control group, is the cause of the restoration of the Sc population during spontaneous recrudescence., (© The Author(s) 2019. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Lectin histochemistry was used to characterise glycoconjugates and cellular apoptosis in the seminiferous epithelium and interstitium of hamster testis during spontaneous recrudescence. An increase in the LTA lectin affinity was observed in spermatids in the Golgi phase. An increase in labelling of PNA and Con-A lectin in acrosome of spermatids (acrosome phase) as well as increased labelling with Con-A in spermatids (cap phase) was observed. Spermatocytes showed decreased affinity with PNA and AAA lectins and an increase in positivity for LTA and GNA lectins. Spermatogonia showed a slight decrease in positivity to WGA and an increase in labelling with Con-A and a decreased affinity for the AAA lectin. At the end of recrudescence, all these germinal cells showed a similar pattern to the control. The Sertoli cells showed a gradual decrease in labelling with the GNA lectin and the Leydig cells an increase in labelling with Con-A and GNA. Particularly unusual was the observation of apoptotic spermatocytes and spermatids positive for PNA, GNA, AAA and Con-A, together with spermatocytes positive to LTA. In conclusion, the normal lectin pattern is recovered during testis recrudescence and germ cell apoptotic activity is low, as is observed by specific lectins for germ cells in apoptosis., (© 2018 Blackwell Verlag GmbH.)

Syrian hamsters are photoperiodic rodents in which reproduction, including testicular function, is stimulated by long photoperiod exposure and curtailed by exposure to a short photoperiod. The objectives of this study were to characterize the testis histomorphometrically and to determine the role of the proliferation and apoptosis phenomena in the recovery of the seminiferous epithelium during spontaneous recrudescence after exposure to short photoperiod. The study was performed using conventional light microscopy, proliferating cell nuclear antigen and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick end labelling staining, image analysis software, and transmission electron microscopy in three recrudescence groups: initial recrudescence (IR), advanced recrudescence (AR) and total recrudescence (TR). The results morphometrically pointed to the gradual recovery of the testicular and tubular volumes, as well as of the seminiferous epithelium. Among the IR and AR groups, the increase in testicular and tubular volumes was accompanied by an increase in tubular diameter and length, with an increase in interstitial volume. From AR to TR, there was an increase in the tubular and total volumes, but, in this case, with a gradual increase in tubular diameter. Recovery of the seminiferous epithelium was accompanied by changes in apoptosis and proliferation activities. The first decreased halfway through the process, and the second remained higher than the control levels throughout the recrudescence stage. Alterations in the spermatozoa were ultrastructurally observed, which indicated that spermiogenesis was not yet completely normal. In conclusion, spontaneous testicular recrudescence in Syrian hamster comprises two histomorphometrical phases: the first related to an increase in tubular length and diameter and interstitial volume and the second depending principally on the gradual increase in tubular diameter. The restoration of the seminiferous epithelium is due to apoptosis reaching normal values in the AR group accompanied by higher proliferative activity than that observed in the Control group., (© 2018 Blackwell Verlag GmbH.)

Lectin histochemistry is commonly used to characterize the pattern of glycoconjugates in cells and tissues. Recent studies show that alterations in these glycoconjugates are associated with the entry of cells into apoptosis. A widely used technique for the detection of apoptotic cell death is TUNEL. In this chapter, we study the sensitivity of both techniques to identify apoptotic cells in the testis of photo-inhibited Syrian hamster.

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., (© 2014 by the Society for the Study of Reproduction, Inc.)

Simple Summary: Exposure to pesticides poses a significant threat to male fertility by compromising crucial cells involved in spermatogenesis. Although aminocarb is a widely used carbamate insecticide, little is known about its impact on male fertility and, consequently, on sustentacular Sertoli cells. In this study, we investigated the effects of increasing concentrations of aminocarb on a mouse Sertoli cell line, TM4. Assessments included analyses of cellular proliferation and viability, membrane integrity, mitochondrial biogenesis and membrane potential and expression and the activity of apoptotic proteins, as well as oxidative stress. Our findings revealed a dose-dependent reduction in the proliferation and viability of TM4 cells following exposure to aminocarb. Moreover, exposure to 5 μM of aminocarb induced depolarization of mitochondria membrane potential, and a decrease in the ratio of phosphorylated eIF2α to total eIF2α, suggesting heightened endoplasmic reticulum stress via the activation of the eIF2α pathway. An elevation in both caspase-3 protein levels and activity was also observed for the cells under this same aminocarb concentration, thus indicating an apoptotic induction. Altogether, our results demonstrate that aminocarb serves as an apoptotic inducer for mouse sustentacular Sertoli cells in vitro, suggesting its potential to modulate independent pathways of the apoptotic cascade. Exposure to pesticides, poses a significant threat to male fertility by compromising crucial cells involved in spermatogenesis. Aminocarb, is a widely used carbamate insecticide, although its detrimental effects on the male reproductive system, especially on sustentacular Sertoli cells, pivotal for spermatogenesis, remains poorly understood. In this study, we investigated the effects of escalating concentrations of aminocarb on a mouse Sertoli cell line, TM4. Assessments included cytotoxic analysis, mitochondrial biogenesis and membrane potential, expression of apoptotic proteins, caspase-3 activity, and oxidative stress evaluation. Our findings revealed a dose-dependent reduction in the proliferation and viability of TM4 cells following exposure to increasing concentrations of aminocarb. Notably, exposure to 5 μM of aminocarb induced depolarization of mitochondria membrane potential, and a significant decrease in the ratio of phosphorylated eIF2α to total eIF2α, suggesting heightened endoplasmic reticulum stress via the activation of the eIF2α pathway. Moreover, the same aminocarb concentration was demonstrated to increase both caspase-3 protein levels and activity, indicating an apoptotic induction. Collectively, our results demonstrate that aminocarb serves as an apoptotic inducer for mouse sustentacular Sertoli cells in vitro, suggesting its potential to modulate independent pathways of the apoptotic cascade. These findings underscore the deleterious impact of aminocarb on spermatogenic performance and male fertility, highlighting the urgent need for further investigation into its mechanisms of action and mitigation strategies to safeguard male fertility. [ABSTRACT FROM AUTHOR]

Simple Summary: The most common form of reproduction in mammals is seasonal reproduction. This ensures that offspring are born at the most suitable time for survival, due to the abundance of food and the optimal temperatures for early postnatal development. In males, one way to achieve this is to decrease or lose fertility over a given period. This loss is associated with a greater or lesser degree of spermatogenesis modification that affects both germ and Sertoli cells. This paper reviews the different cellular mechanisms that have been postulated in recent years to explain how the activity of the seminiferous epithelium decreases during the non-reproductive period. Testicular regression occurs during the non-breeding season in many mammals. This affects spermatogenesis, resulting in decreased or arrested activity. Both lead to a decrease or cessation in sperm production. In recent years, the cellular mechanisms that lead to infertility in males in non-reproductive periods have been studied in very different species of mammals. At the start of the present century, the main mechanism involved was considered as an increase in the apoptotic activity of germ cells during the regression period. The loss of spermatogonia and spermatocytes causes not only a decrease in spermatogenesis, but an arrest of the seminiferous epithelium activity at the end of regression. Recently, in some mammal species, it was found that apoptosis is the usual mechanism involved in epithelium activity arrest, although it is firstly atrophied by massive desquamation of the germ cells that are released from their binding with the Sertoli cells, and which are shed into the lumen of the seminiferous tubule. In other species, it has been shown that not only germ cell apoptosis, but also Sertoli cell apoptosis, including decreased proliferative activity, spermatophagy or autophagy, are involved in testicular regression. Furthermore, the most recent studies indicate that there are multiple patterns of seminiferous epithelium regression in seasonally breeding animals, which may not only be used by different species, but also by the same ones to reproduce in the best conditions, ensuring their survival. In conclusion, at this time, it is not possible to consider the existence of a paradigmatic cellular mechanism in the involution of the seminiferous epithelium applicable to all male mammals with seasonal reproduction, rather the existence of several mechanisms which participate to a greater or lesser extent in each of the species that have been studied to date. [ABSTRACT FROM AUTHOR]

Lectin histochemistry was used to characterise glycoconjugates and cellular apoptosis in the seminiferous epithelium and interstitium of hamster testis during spontaneous recrudescence. An increase in the LTA lectin affinity was observed in spermatids in the Golgi phase. An increase in labelling of PNA and Con‐A lectin in acrosome of spermatids (acrosome phase) as well as increased labelling with Con‐A in spermatids (cap phase) was observed. Spermatocytes showed decreased affinity with PNA and AAA lectins and an increase in positivity for LTA and GNA lectins. Spermatogonia showed a slight decrease in positivity to WGA and an increase in labelling with Con‐A and a decreased affinity for the AAA lectin. At the end of recrudescence, all these germinal cells showed a similar pattern to the control. The Sertoli cells showed a gradual decrease in labelling with the GNA lectin and the Leydig cells an increase in labelling with Con‐A and GNA. Particularly unusual was the observation of apoptotic spermatocytes and spermatids positive for PNA, GNA, AAA and Con‐A, together with spermatocytes positive to LTA. In conclusion, the normal lectin pattern is recovered during testis recrudescence and germ cell apoptotic activity is low, as is observed by specific lectins for germ cells in apoptosis. [ABSTRACT FROM AUTHOR]