Spermatogenesis最新文献

Histopathologic examination of the testis is the most sensitive means to detect effects on spermatogenesis; however, the complexity of testicular histology, interrelatedness of cell types within the testis, and long duration of spermatogenesis can make assessment of a testicular toxicant challenging. A thorough understanding of the histology and morphologic manifestations of response to injury is critical to successfully identify a testicular effect and to begin to understand the underlying mechanism of action. The basic patterns of response to xenobiotic-induced injury to the testis and epididymis are detailed and discussed.

Reduction-oxidation (Redox) reactions are ubiquitous mechanisms for vital activities in all organisms, and they play pivotal roles in the regulation of spermatogenesis as well. Here we focus on 3 redox-involved processes that have drawn much recent attention: the regulation of signal transduction by reactive oxygen species (ROS) such as hydrogen peroxide, oxidative protein folding in the endoplasmic reticulum (ER), and sulfoxidation of protamines during sperm chromatin condensation. The first 2 of these processes are emerging topics in cell biology and are applicable to most living cells, which includes spermatogenic cells. The roles of ROS in signal transduction have been elucidated in the last 2 decades and have received broad attention, most notably from the viewpoint of the proper control of mitotic signals. Redox processes in the ER are important because this is the organelle where secretory and membrane proteins are synthesized and proceed toward their functional structure, so that malfunction of the ER affects not only the involved cells but also the accepting cells of the secreted proteins in multicellular organisms. Sulfoxidation is the third of these processes, and the sulfoxidation of chromatin is a unique process in sperm maturation. During recent sulfoxidase research, GPX4 has emerged as a promising enzyme that plays essential roles in the production of fertile sperm, but the involvement of other redox proteins is also becoming evident. Because the molecules involved in the redox reactions are prone to oxidation, they can be sensitive to oxidative damage, which makes them potential targets for antioxidant therapy.

Current knowledge on avian spermiogenesis, including strengths and weaknesses, has been reviewed. Information on avian spermiogenesis considerably lags behind that in mammals because of the paucity of reports in birds. Spermiogenesis in passerine birds has received even much less attention than in non-passerine birds. Mechanisms underlying morphogenesis of the acrosome and nucleus, and roles of microtubular assemblies are poorly understood. The proximal centriole found in non-passerine birds, but hitherto considered to be absent in passerine birds, has recently been described in spermatids and mature spermatozoa of 2 passeridan species, including the Masked weaver for which new and detailed spermiogenetic information is provided in this review. A great deal more studies on spermiogenesis, and spermatogenesis generally, in various avian species are required to considerably enhance knowledge of this phenomenon, contribute to comparative spermatology, provide a basis for appropriate applied studies, and contribute to understanding of phylogeny in this vast order of vertebrates.

The testis-specific nuclear form of Phospholipid Hydroperoxide Glutathione Peroxidase (nGPx4) is associated with the nuclear matrix during spermiogenesis and is implicated in sperm chromatin condensation. In this study, we have addressed the question whether nGPx4 directly interacts with protamines by transiently sharing a nuclear matrix localization. We first expressed tagged protamine 1-myc and protamine 2-V5 in HeLa and COS-1 cells and showed by both confocal microscopy and immunoblotting analyses that protamines were produced in vitro and colocalized correctly to the nucleus. Co-transfection experiments demonstrated that protamine 1 was physically associated with flag-nGPx4 specifically at the level of nuclear matrix. The peculiar presence of protamines together with nGPx4 in this subnuclear compartment was also confirmed in mouse elongated spermatids by immunofluorescence, suggesting that nGPx4 is a physiological component of a novel protein complex relevant to chromatin assembly in condensing haploid cells. Also, in epididymal sperm, nGPx4 and protamine 1 co-immunoprecipitated, indicating that nGPx4, although localized to a subnuclear compartment different from that of protamines, represents a constant link between nuclear matrix and chromatin in mammalian male gamete.

Azoospermia is classified as obstructive azoospermia (OA) or non-obstructive azoospermia (NOA), each having very different etiologies and treatments. The etiology, diagnosis, and management of azoospermia were reviewed and relevant literature summarized. Differentiation between these two etiologies is of paramount importance and is contingent upon thorough history and physical examination and indicated laboratory/genetic testing. OA occurs secondary to obstruction of the male reproductive tract, and is diagnosed through a combination of history/physical examination, laboratory testing, genetics (CFTR for congenital OA), and imaging studies. NOA (which includes primary testicular failure and secondary testicular failure) is differentiated from OA by clinical assessment (testis consistency/volume), laboratory testing (FSH), and genetic testing (karyotype, Y chromosome microdeletion, or specific genetic testing for hypogonadotropic hypogonadism). For obstructive azoospermia, management includes microsurgical reconstruction when feasible using microsurgical vasovasostomy or vasoepididymostomy. Microsurgical epididymal sperm aspiration with in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) is utilized for those cases not amenable to reconstruction. NOA management includes medical management for congenital hypogonadotropic hypogonadism and microdissection testicular sperm extraction with IVF/ICSI for appropriate candidates based on laboratory/genetic testing. Overall, this important review provides an updated summary of the most recent available literature describing etiology, diagnosis, and management of azoospermia.

The identification of the hormones and other factors regulating Sertoli cell survival, proliferation, and maturation in neonatal, peripubertal, and pubertal life remains one of the most critical questions in testicular biology. The regulation of Sertoli cell proliferation and differentiation is thought to be controlled by cell-cell junctions and a set of circulating and local hormones and growth factors. In this review, we will focus on receptors and intracellular signaling pathways activated by androgen, follicle-stimulating hormone, thyroid hormone, activin, retinoids, insulin, insulin-like growth factor, relaxin, and estrogen, with special emphasis on estrogen receptors. Estrogen receptors activate intracellular signaling pathways that converge on cell cycle and transcription factors and play a role in the regulation of Sertoli cell proliferation and differentiation.

Piwi-interacting RNAs (piRNAs) are a distinct class of small non-coding RNAs specifically expressed in the germline of many species. They are most notably required for transposon silencing. Loss of piRNAs results in defects in germ cell development, and thus, infertility. Most studies of piRNAs have been done in Drosophila, but much progress has also been made on piRNAs in the germline of mammals and other species in the past few years. This review provides a summary of our current knowledge of the biogenesis and functions of piRNAs during mouse spermatogenesis and discusses challenges in the mammalian piRNA field.

The Biology of Spermatozoa (BoS) meetings have run on a biannual basis since the early 1990s. They are dedicated to the fascinating research topic of sperm and their complicated route to fertilization. The BoS meetings focus on sperm, but they also explore additional supporting factors important in fertilization, such as those present in seminal and ovarian fluid, as well as the genomic bases of sperm biology. Here, I present a report of the recent BoS meeting, and showcase some of the highlights of this year's meeting.