Male infertility is an increasing problem partly due to inherited genetic variations. Mutations in genes involved in formation of the sperm tail cause motility defects and thus male infertility. Therefore, it is crucial to understand the protein networks required for sperm differentiation. Sperm motility is produced through activation of the sperm flagellum, which core structure, the axoneme, resembles motile cilia. In addition to this, cytoskeletal axonemal structure sperm tail motility requires various accessory structures. These structures are important for the integrity of the long tail, sperm capacitation, and generation of energy during sperm passage to fertilize the oocyte. This review discusses the current knowledge of mechanisms required for formation of the sperm tail structures and their effect on fertility. The recent research based on animal models and genetic variants in relation to sperm tail formation and function provides insights into the events leading to fertile sperm production. Here we compile a view of proteins involved in sperm tail development and summarize the current knowledge of factors contributing to reduced sperm motility, asthenozoospermia, underline the mechanisms which require further research, and discuss related clinical aspects on human male infertility.

Summary Sentence

This review studies the known factors contributing to male fertility through production of sperm motility by the sperm tail.

The surge in luteinizing hormone (LH) in preovulatory ovarian follicles triggers the resumption of oocytemeiosis accompanied by expansion of surrounding cumulus cells and ovulation of cumulus–oocyte complexes (COCs) into the oviduct. Over the last 15 years, substantial progress has been made in elucidating the key pathways by which the LH signal spreads within the preovulatory follicle and in identifying the molecules responsible for maintaining oocyte arrest and meiosis resumption. It is now clear that the adenylcyclase-mediated rise in intracellular cyclic adenosine monophosphate leads to activation of the epidermal growth factor receptor (EGFR) network in granulosa and cumulus cells. This signaling network can control the transcription of key genes required for cell metabolism, cumulus expansion, and oocyte meiosis resumption. In addition, EGFR signaling is involved in the regulation of gap junctional communication within follicular somatic cells, and in this way it can control the diffusion of meiosis-arresting molecules as well as energy substrates into the oocyte. Thus, the proper functioning of the follicular EGFR network is a vital precondition for the production of matured and developmentally competent oocytes. However, most current in vitro maturation systems are based on a culture of COCs isolated from growing follicles, in which function of the EGFR network may be insufficient for promoting oocyte meiotic and developmental competence. This review focuses on research identifying the importance of the EGFR signaling in somatic follicular cells for oocyte meiotic and developmental competence, and on special approaches to the culture of COCs isolated from growing follicles to promote oocyte quality.

Summary Sentence

The review summarizes evidence on the crucial role of epidermal growth factor receptor signaling in acquisition of oocyte meiotic and developmental competence and shows that this knowledge may be used for improvement of current culture systems.

Seventeen nonlactating Holstein cows were superovulated in a Latin-square designed experiment to determine the effects of increased propylene glycol (PROP) and luteinizing hormone (LH) during antral follicle development on ovarian function, fertilization, and early embryo quality. PROP was orally drenched every 4 h for 7 days to induce hyperinsulinemia and associated metabolic changes. LH concentrations were altered by increasing LH (3-fold) during last 2 days of superovulation. Treatment groups were as follows: (1) control—oral drenching with water plus low-LH preparation; (2) high LH(HLH)—water plus HLH preparation; (3) PROP—drenching with PROP plus low LH; (4) PROP/HLH—PROP plus HLH. PROP increased glucose (P < 0.05) and insulin (P < 0.02) concentrations at all time points analyzed. Neither PROP nor LH affected numbers of follicles > 9 mm at time of gonadotropin-releasing hormone-induced LH surge, although percentage of these follicles that ovulated was decreased by both PROP (P = 0.002) and LH (P = 0.048). In addition, PROP tended (P = 0.056) to decrease total number of ovulations. PROP reduced (P = 0.028) fertilization rate, while LH tended (P = 0.092) to increase fertilization rate. There was no effect of either PROP or LH on any measure of embryo quality including percentage of embryos that were degenerate, quality 1, or quality 1 and 2 of total structures collected or fertilized structures. These results indicate that acute elevation in insulin during the preovulatory follicular wave can decrease percentage of large follicles that ovulate, particularly when combined with increased LH, and reduce fertilization of ovulated oocytes.

Summary Sentence

High circulating insulin, due to treatment with propylene glycol every 4 h during final week before ovulation, reduced risk of ovulation of large follicles, reduced fertilization of ovulated oocytes, but had no effect on later embryo development.

Uterine fibroids are a common finding in infertility patients. Impaired implantation and decidualization have been proposed to contribute to compromised fertility. Data are limited on the endometrial transcriptome from subjects with uterine fibroids, as well as endometrial receptivity and decidualization potential of endometrial stromal fibroblasts (eSF) from women with fibroids. Our objective was to investigate the endometrial transcriptome of women with noncavity-distorting intramural fibroids and compare them to control subjects with no uterine pathology throughout the menstrual cycle. We also evaluated endometrial receptivity gene expression and basic endometrial functions such as decidualization, proliferation, and apoptosis in women with fibroid uterus. Results showed that large numbers of transcripts were significantly dysregulated throughout the menstrual cycle in fibroid subjects compared to controls. However, there were essentially no differences in the expression of receptivity markers at the tissue level, as well as decidualization markers in tissue and eSF in subjects with fibroids compared to controls. However, eSF from women with a fibroid uterus exhibited decreased proliferation potential and increased apoptosis upon decidualization. These data indicate preserved implantation and decidualization potential despite observed gene expression changes in endometrium from women with noncavity-distorting fibroids compared to controls. How this phenomenon and altered proliferation/apoptosis may contribute to impairment of endometrial function in subfertile patients warrants further investigation.

Summary Sentence

Decidualization and implantation potentials are not affected in the endometrium of women with noncavity-distorting fibroids compared to controls, despite a large number of differentially regulated genes.

Cellular response to reactive oxygen species (ROS) includes both reversible redox signaling and irreversible nonenzymatic reactions which depend on the nature and concentration of the ROS involved. Changes in thiol/disulfide pairs affect protein conformation, enzymatic activity, ligand binding, and protein–protein interactions. During spermatogenesis and epididymal maturation, there are ROS-dependent modifications of the sperm chromatin and flagellar proteins. The spermatozoon is regulated by redox mechanisms to acquire fertilizing ability. For this purpose, controlled amounts of ROS are necessary to assure sperm activation (motility and capacitation). Modifications of the thiol groups redox status of sperm proteins are needed for spermatozoon to achieve fertilizing ability. However, when ROS are produced at high concentrations, the established oxidative stress promotes pathological changes affecting sperm function and leading to infertility. Sperm proteins are sensitive to high levels of ROS and suffermodifications that impact onmotility, capacitation, and the ability of the spermatozoon to recognize and bind to the zona pellucida and damage of sperm DNA. Thiol oxidation, tyrosine nitration, and S-glutathionylation are highlighted in this review as significant redox-dependent protein modifications associated with impairment of sperm function and alteration of paternal genome leading to infertility. Peroxiredoxins, the primary antioxidant protection in spermatozoa, are affected by most of the protein modifications described in this review. They play a significant role in both physiological and pathological processes in mammalian spermatozoa.

Summary Sentence

Reactive oxygen species promote redox-dependent protein modifications that lead to impairment of sperm function.

NRH: quinone oxidoreductase 2 (NQO2) is a cytosolic and ubiquitously expressed flavoprotein that catalyzes the two-electron reduction of quinone to hydroquinones. Herein, we assessed the protein expression, subcellular localization, and possible functions of NQO2 in mouse oocyte meiotic maturation and embryo development. Western blot analysis detected high and stable protein expression of NQO2 in mouse oocytes during meiotic progression. Immunofluorescence illustrated NQO2 distribution on nuclear membrane, chromosomes, and meiotic spindles. Microtubule poisons treatment (nocodazole and taxol) showed that filamentous assembly of NQO2 and its co-localization with microtubules require microtubule integrity and normal dynamics. Increased levels of NQO2, reactive oxygen species (ROS), malondialdehyde (MDA), and autophagy protein Beclin1 expression were detected in oocytes cultured with ROS stimulator vitamin K3 (VK3), combined with decreased antioxidant glutathione (GSH). These oocytes were arrested at metaphase I with abnormal spindle structure and chromosome configuration. However, this impact was counteracted by melatonin or NQO2 inhibitor S29434, and the spindle configuration and first polar body extrusion were restored. Similarly, morpholino oligo-induced NQO2 knockdown suppressed ROS, MDA, and Beclin1, instead increased GSH in oocytes under VK3. Supplementary S29434 or melatonin limited changes in NQO2, ROS,MDA, Beclin1, and GSH during in vitro aging of ovulated oocytes, thereby maintaining spindle structure, as well as ordered chromosome separation and embryo development potential after parthenogenetic activation with SrCl2. Taken together, NQO2 is involved in ROS generation and subsequent cytotoxicity in oocytes, and its inhibition can restore oocyte maturation and embryo development, suggesting NQO2 as a pharmacological target for infertility cure.

Summary Sentence

NQO2 is involved in ROS generation and cytotoxicity in oocytes; its inhibition can restore oocyte maturation and embryo development.

The perinuclear theca (PT) is a condensed, nonionic detergent resistant cytosolic protein layer encapsulating the sperm head nucleus. It can be divided into two regions: the subacrosomal layer, whose proteins are involved in acrosomal assembly during spermiogenesis, and the postacrosomal sheath (PAS), whose proteins are implicated in sperm–oocyte interactions during fertilization. In continuation of our proteomic analysis of the PT, we have isolated two prominent PT-derived proteins of 28 and 31 kDa from demembranated bovine sperm head fractions. These proteins were identified by mass spectrometry as isoforms of glutathione-s-transferase omega 2 (GSTO2). Immunoblots probed with anti-GSTO2 antibodies confirmed the presence of the GSTO2 isoforms in these fractions while fluorescent immunocytochemistry localized the isoforms to the PAS region of the bull, boar, and murid PT. In addition to the PAS labeling of GSTO2, the performatorium of murid spermatozoa was also labeled. Immunohistochemistry of rat testes revealed that GSTO2 was expressed in the third phase of spermatogenesis (i.e., spermiogenesis) and assembled in the PAS and perforatorial regions of late elongating spermatids. Fluorescent immunocytochemistry performed on murine testis cells co-localized GSTO2 and tubulin on the transient microtubularmanchette of elongating spermatids. These findings imply that GSTO2 is transported and deposited in the PAS region by the manchette, conforming to the pattern of assembly found with other PAS proteins. The late assembly of GSTO2 and its localization in the PAS suggests a role in regulating the oxidative and reductive state of covalently linked spermatid/sperm proteins, especially during the disassembly of the sperm accessory structures after fertilization.

Summary Sentence

GSTO2 isoforms are prominent constituents of the perinuclear theca and are deposited in this sperm head region by the microtubular-manchette late in spermiogenesis.

Pituitary gonadotropes synthesize and secrete follicle-stimulating hormone (FSH). FSH is a heterodimer that consists of an α- and β-subunit. The α-subunit is common to other pituitary and placental glycoprotein hormones, and the β-subunit is the hormone/receptor-specific subunit. Although the pituitary is the main tissue that accounts for circulating hormone, previous and recent reports indicate extra-pituitary sources of FSH production including mouse gonads, human stomach, prostate, umbilical cord vein endothelial cells, uterine myometrium, placenta, and chicken abdominal adipose tissue. Whether extra-pituitary derived FSH exerts any physiologically significant actions is not known. In this review, we have comprehensively analyzed the expression of mRNAs that encode mouse and human FSH subunits and also their corresponding expressed sequence tags in normal tissues, cancer cell lines, and primary tumors by public database mining. We propose criteria to assess the significance of individual FSH subunit or FSH dimer expression as well as genetic approaches to unambiguously define the physiological relevance of extra-pituitary FSH expression.

Summary Sentence

Extra-pituitary FSH expression was analyzed and several criteria proposed.

Low protein (LP) diet during pregnancy leads to reduced plasma insulin levels in rodents, but the underlying mechanisms remain unclear. Glucose is the primary insulin secretagogue, and enhanced glucose-stimulated insulin secretion (GSIS) in beta cells contributes to compensation for insulin resistance and maintenance of glucose homeostasis during pregnancy. In this study, we hypothesized that plasma insulin levels in pregnant rats fed LP diet are reduced due to disrupted GSIS of pancreatic islets. We first confirmed reduced plasma insulin levels, then investigated in vivo insulin secretion by glucose tolerance test and ex vivo GSIS of pancreatic islets in the presence of glucose at different doses, and KCl, glibenclamide, and L-arginine. Main findings include (1) plasma insulin levels were unaltered on day 10, but significantly reduced on days 14–22 of pregnancy in rats fed LP diet compared to those of control (CT) rats; (2) insulin sensitivity was unchanged, but glucose intolerance was more severe in pregnant rats fed LP diet; (3) GSIS in pancreatic islets was lower in LP rats compared to CT rats in the presence of glucose, KCl, and glibenclamide, and the response to L-arginine was abolished in LP rats; and (4) the total insulin content in pancreatic islets and expression of Ins2 were reduced in LP rats, but expression of Gcg was unaltered. These studies demonstrate that decreased GSIS in beta cells of LP rats contributes to reduced plasma insulin levels, which may lead to placental and fetal growth restriction and programs hypertension and other metabolic diseases in offspring.

Summary Sentence

Decreased glucose-stimulated insulin secretion of pancreatic islets in pregnant rats fed a low diet is responsible for the reduced plasma insulin levels and consequently enhanced glucose intolerance.

Hypertension can originate from early-life insults, whereas maternal melatonin therapy can be protective in a variety of models of programmed hypertension. We hypothesize that melatonin or melatonin receptor agonist agomelatine can prevent programmed hypertension in adult offspring induced by maternal exposure to continuous light. Female Sprague-Dawley pregnant rats randomly divided into four groups: controls, rats exposed to continuous light, exposed to continuous light plus treated with agomelatine (50 mg/day i.p.), and exposed to continuous light plus treated with 0.01% melatonin in drinking water throughout pregnancy and lactation period. Male offspring (n = 10/group) from three litters were examined at 12 weeks of age. Maternal continuous light exposure-induced hypertension in male offspring, which was prevented by melatonin or agomelatine therapy. Continuous light exposure did not affect melatonin pathway in adult offspring kidney. Genes that belong to the renin-angiotensin system (RAS), sodium transporters, AMP-activated protein kinase pathway, and circadian rhythm were potentially involved in the maternal exposure to continuous light-induced programmed hypertension. Maternal agomelatine therapy decreased Ace expression but increased Agtr2 and Mas1. Maternal melatonin therapy prevented the increases of Slc9a3, Slc12a3, and Atp1a1 expression induced by maternal continuous light exposure. In conclusion, maternal melatonin or agomelatine therapy prevents programmed hypertension induced by maternal exposure to continuous light. Agomelatine and melatonin reprogram the RAS and sodium transporters differentially, to prevent negative programming of continuous light. Our data highlight candidate genes and pathways in renal programming as targets for therapeutic approaches to prevent programmed hypertension caused by early-life disturbance of the circadian rhythm.

Summary Sentence

Exposure of the mother to continuous light-induced programmed hypertension in adult offspring, which was prevented by maternal agomelatine or melatonin therapy via regulating reninangiotensin system, sodium transporters, AMP-activated protein kinase pathway, and circadian rhythm.

Follicular fluid within ovarian antral follicles contains numerous factors, which influence the development of a healthy oocyte including nucleic acids, steroids, proteins, and extracellular vesicles (EVs). Current evidence indicates that follicular EVs promote changes in cellular gene expression and support cumulus–oocyte complex expansion in vitro. In this study, we found EVs from different sized follicles differentially stimulate granulosa cell proliferation and this could be explained by both the differential contents associated, on or within the vesicles and by the preferential uptake of EVs dependent on follicle size from which they were isolated. Antibody array and inhibitor studies indicated that the Src, PI3K/Akt, and MAPK signaling pathways mediate the stimulatory effects of EVs on granulosa cell proliferation. This study demonstrates for the first time that EVs isolated from follicular fluid are capable of stimulating granulosa cell proliferation and that this stimulatory response is associated with the size of antral follicle from which the EVs originated. The study further also provides the first evidence that vesicles released by small antral follicles are preferentially taken up when compared to those isolated from large follicles, suggesting that vesicular surface proteins change during follicular maturation.

Summary Sentence

Follicular fluid derived extracellular vesicles exhibit differential ability to stimulate granulosa cell proliferation and uptake that is dependent upon the stage of follicle development.