Further observations on the early events that contribute to establishing the morphological pattern shown by the oestradiol suppressed testis

Oestrogens as apoptosis regulators in mammalian testis: angels or devils?

In the mammalian testis, spermatogenesis is a highly coordinated process of germ cell development, which ends with the release of ‘mature’ spermatozoa. The fine regulation of spermatogenesis is strictly dependent on sex steroid hormones, which orchestrate the cellular and molecular events underlying normal development of germ cells. Sex steroids actions also rely on the control of germ cell survival, and the programmed cell death by apoptosis has been indicated as a critical process in regulating the size and quality of the germ line. Recently, oestrogens have emerged as important regulators of germ cell fate. However, the beneficial or detrimental effects of oestrogens in spermatogenesis are controversial, with independent reports arguing for their role as cell survival factors or as apoptosis-inducers. The dual behaviour of oestrogens, shifting from ‘angels to devils’ is supported by the clinical findings of increased oestrogens levels in serum and intratesticular milieu of idiopathic infertile men. This review aims to discuss the available information concerning the role of oestrogens in the control of germ cell death and summarises the signalling mechanisms driven oestrogen-induced apoptosis. The present data represent a valuable basis for the clinical management of hyperoestrogenism-related infertility and provide a rationale for the use of oestrogen-target therapies in male infertility.

Effects of neonatal administration of 17beta-estradiol, beta-estradiol 3-benzoate, or bisphenol A on mouse and rat spermatogenesis

Bisphenol A (BPA) is a global environmental contaminant that has been implicated as a potential endocrine disruptor. In the present study, newborn rats and mice were injected subcutaneously with BPA to determine the potential developmental effects on the testis. Testes were examined by light and electron microscopy at 15 weeks of age. Other groups of newborn mice and rats were injected with 17beta-estradiol (E2) or beta-estradiol 3-benzoate (E2B) in a similar manner. BPA, E2, and E2B had similar effects on testes. When treated animals reached puberty and spermiogenesis began, the first sign of the effects was detected in the steps 2-3 spermatids: the acrosomal granule and nucleus were deformed. Henceforth, abnormalities in the acrosome and nucleus were observed in older spermatids and spermatozoa. Ectoplasmic specialization between the Sertoli cell and spermatids was also affected: some specializations were partially or totally deleted. When animals fully matured, the effects of the agents were not found in the testes, and the animals were found to be fertile. The results of the present study show that BPA acts as an estrogen, and causes changes which appear to revert in adults.

Adverse effects of bisphenol A to spermiogenesis in mice and rats

Either a 20 or 200 microg/kg body weight/injection of bisphenol A (BPA) was subcutaneously administered to adult mice and rats for 6 days, and the effects on the testes were investigated by electron and light microscopy. Abnormalities were observed in the spermatids: acrosomal vesicles, acrosomal caps, acrosomes and nuclei of the spermatids were severely deformed. The ectoplasmic specialization between the Sertoli cell and spermatids were also affected: incomplete specialization, redundant ectopic specialization and aplasia were observed. Rats and mice responded similarly to BPA. There were no dose dependencies between the 20- and 200 microg/kg body weight/injection groups. The ectoplasmic specialization between adjoining Sertoli cells, or blood-testis barrier, was not affected. Since similar adverse effects were observed when adult mice were treated with beta-estradiol 3-benzoate, the effects of BPA reported here seem to reflect the estrogenic effects on the testes. Animals kept for an additional two months after cessation of the administration were shown to be fertile and the testes showed normal histology, indicating that the adverse effects were transitory.

Ectoplasmic specializations in the Sertoli cell: new vistas based on genetic defects and testicular toxicology

Abstract The ectoplasmic specialization is a unique junctional complex formed in two cortical areas of the Sertoli cell in the mammalian testis: one near the base of the seminiferous epithelium forming the blood-testis barrier, and the other near the lumen of the seminiferous tubule embracing the acrosome region of the developing spermatids. The specialization consists of the Sertoli cell plasma membrane, a subsurface cistern of the endoplasmic reticulum and a layer of closely packed actin filaments that is sandwiched between the plasma membrane and the subsurface cistern. No functions of the specializations other than the blood-testis barrier have been established. However, over the past decade, knowledge about the ectoplasmic specialization has been steadily accumulating and, in particular, there has been a tremendous increase in knowledge based on molecular biological approaches to specialization-associated proteins, including tight junction-associated proteins, based on phenotype analyses of gene-knockout mice and mutant animals, and based on analyses of the effects of exogenous estrogens, so-called endocrine disruptors. Progress in studies on the ectoplasmic specialization will facilitate the elucidation of numerous important questions regarding spermatogenesis, including the pathogenesis of azoospermia and the mechanisms of action of endocrine disruptors.

beta-estradiol 3-benzoate affects spermatogenesis in the adult mouse

beta-estradiol 3-benzoate (E(2)B) (10, 16, 20, 40, 80 and 160 microg/kg body weight) was administered daily to experimental groups of adult mice for the following periods; 2, 3 days, 1, 2, 4, and 8 weeks. Morphological changes in the testes were observed by both light and electron microscopy. Exfoliation of the germ cells was observed in the lumen of the seminiferous tubule. The spermatogenic cycle, especially stage XII, was disordered. Spermatids older than step 6 were severely affected. Detected abnormalities in the spermatids were deformation of the nucleus and acrosome. Partial deletion in the Sertoli-spermatid ectoplasmic specialization was also observed. Germ cells younger than step 7 spermatids were not affected morphologically. These abnormalities were not detected in the mice treated with the chemical at less than 16 microg/kg body weight. It is concluded that the chemical seems to affect round spermatids metabolically, but the morphological effect can be detected only from the spermatids older than step 6. The effects of the chemical on adult mice were reversible.

Apoptosis precedes detachment of germ cells from the seminiferous epithelium after hormone suppression by short-term oestradiol treatment of rats

Spermatogenesis is a highly synchronized process in which FSH and testosterone are considered the major regulators. Nevertheless, the mechanism by which these hormones act on germ cells is unclear. Cell adhesion has been proved to play an essential role in the regulation of programmed cell death in epithelial cells and it is now known that FSH and testosterone withdrawal results in the triggering of apoptosis as well as germ cell detachment from the seminiferous epithelium. Therefore, it seemed important to investigate whether the triggering of apoptosis in germ cells by experimental hormone suppression occurred as a result of their previous detachment from the epithelium. To achieve this goal, adult male rats were injected with 50 micrograms oestradiol benzoate for 1, 2, 3, 4, 5 or 10 days to suppress gonadotrophin secretion and thus intratesticular levels of testosterone. Germ cell apoptosis was assessed in testes from these animals by in situ 3' end-labelling of DNA fragments and quantified in seminiferous tubule sections at stages VII-VIII. Serial sections throughout the epididymides from these animals were analysed to search for immature germ cells detached from the epithelium. These cells were scored and quantified in non-consecutive randomly selected epididymal sections. Our data indicate that the triggering of apoptosis in germ cells precedes germ cell detachment, suggesting that detachment of germ cells from the epithelium, occurring after hormone suppression, is not necessary for germ cell apoptosis.

Induction of apoptotic cell death in the seminiferous tubule of the adult rat testis: assessment of the germ cell types that exhibit the ability to enter apoptosis after hormone suppression by oestradiol treatment

The involvement of apoptosis in germ cell degeneration in the adult rat testis after gonadotrophin suppression has recently been shown in several studies, which have focused on the localization of apoptotic cells to the stages of the spermatogenic cycle. However, the precise germ cell types and maturing steps at which apoptosis is elicited remain controversial. The present study used oestradiol treatment to produce hormone suppression and to study induced germ cell degeneration. Adult male rats were administered a daily injection of 50 micrograms oestradiol benzoate for 5, 10 or 15 days. Characterization of the ultrastructural features of the dying cells and in-situ 3'-end labelling of DNA showed clearly that the deaths of all the germ cell types occurred by apoptosis. High-resolution light microscopy, although time-consuming, resulted in a precise method for analysis of the localization of the cells involved. Stages IV-X of the seminiferous epithelium were found to be the most sensitive to degeneration in response to oestradiol treatment. Our results are discussed in the light of current knowledge about the hormonal control of the spermatogenic cycle. Oestradiol treatment has proved to provide a suitable in-vivo model to study germ cell death.