Adverse temporal trends in human semen quality and cryptorchidism in infants have been associated with exposure to environmental chemicals (ECs) during development. Here we report that a population of breeding dogs exhibit a 26 year (1988-2014) decline in sperm quality and a concurrent increased incidence of cryptorchidism in male offspring (1995-2014). A decline in the number of males born relative to the number of females was also observed. ECs, including diethylhexyl phthalate (DEHP) and polychlorinated bisphenol 153 (PCB153), were detected in adult dog testes and commercial dog foods at concentrations reported to perturb reproductive function in other species. Testicular concentrations of DEHP and PCB153 perturbed sperm viability, motility and DNA integrity in vitro but did not affect LH stimulated testosterone secretion from adult testis explants. The direct effects of chemicals on sperm may therefore contribute to the decline in canine semen quality that parallels that reported in the human.
Healthy offspring from freeze-dried mouse spermatozoa held on the International Space Station for 9 months
- Proceedings of the National Academy of Sciences of the United States of America
- Published almost 4 years ago
If humans ever start to live permanently in space, assisted reproductive technology using preserved spermatozoa will be important for producing offspring; however, radiation on the International Space Station (ISS) is more than 100 times stronger than that on Earth, and irradiation causes DNA damage in cells and gametes. Here we examined the effect of space radiation on freeze-dried mouse spermatozoa held on the ISS for 9 mo at -95 °C, with launch and recovery at room temperature. DNA damage to the spermatozoa and male pronuclei was slightly increased, but the fertilization and birth rates were similar to those of controls. Next-generation sequencing showed only minor genomic differences between offspring derived from space-preserved spermatozoa and controls, and all offspring grew to adulthood and had normal fertility. Thus, we demonstrate that although space radiation can damage sperm DNA, it does not affect the production of viable offspring after at least 9 mo of storage on the ISS.
- Proceedings of the National Academy of Sciences of the United States of America
- Published almost 4 years ago
The calcium channel of sperm (CatSper) is essential for sperm hyperactivated motility and fertility. The steroid hormone progesterone activates CatSper of human sperm via binding to the serine hydrolase ABHD2. However, steroid specificity of ABHD2 has not been evaluated. Here, we explored whether steroid hormones to which human spermatozoa are exposed in the male and female genital tract influence CatSper activation via modulation of ABHD2. The results show that testosterone, estrogen, and hydrocortisone did not alter basal CatSper currents, whereas the neurosteroid pregnenolone sulfate exerted similar effects as progesterone, likely binding to the same site. However, physiological concentrations of testosterone and hydrocortisone inhibited CatSper activation by progesterone. Additionally, testosterone antagonized the effect of pregnenolone sulfate. We have also explored whether steroid-like molecules, such as the plant triterpenoids pristimerin and lupeol, affect sperm fertility. Interestingly, both compounds competed with progesterone and pregnenolone sulfate and significantly reduced CatSper activation by either steroid. Furthermore, pristimerin and lupeol considerably diminished hyperactivation of capacitated spermatozoa. These results indicate that (i) pregnenolone sulfate together with progesterone are the main steroids that activate CatSper and (ii) pristimerin and lupeol can act as contraceptive compounds by averting sperm hyperactivation, thus preventing fertilization.
In humans, the most common chromosomal abnormality is aneuploidy. Because the majority of aneuploid conceptuses die during the early stages of embryonic development, an accurate estimate of the frequency of aneuploidy at conception can only be assessed by directly studying the gametes. The vast majority of aneuploidies arise de novo as a result of sporadic chromosome missegregation in paternal or maternal meiosis. In this review, we present the basic current knowledge about the incidence of aneuploidy in human spermatozoa in the general population and in patient populations where elevated levels of sperm aneuploidy are observed. These include infertile patients, patients with abnormal somatic karyotypes, and individuals exposed to certain environmental/ lifestyle hazards. The clinical impact of increased levels of aneuploidy is discussed. We then focus on the nondisjunction mechanisms that cause aneuploidy during spermatogenesis and the factors that predispose to nondisjunction in male germ cells followed by an analysis of the sex differences in the incidence of gamete aneuploidy. Recent meiotic studies using multiplex-FISH on three fertile men have revealed that the frequency of conservative aneuploidy of metaphase II spermatocytes is similar to that observed in non-inseminated oocytes of young women. These findings suggest that the differences in the incidence of aneuploidy between spermatozoa and oocytes are not due to differences in chromosome segregation errors but rather to more effective checkpoint mechanisms in spermatogenesis than in oogenesis.
OBJECTIVE: To determine the diagnostic value of the following sperm function tests in predicting the fertilizing ability of spermatozoa in conventional in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI): hyaluronan-binding assay (HBA), DNA fragmentation (Halosperm), and hyperactivity. DESIGN: Prospective study. SETTING: University medical center. PATIENT(S): 133 couples undergoing infertility treatment with IVF/ICSI. INTERVENTION(S): Analysis of sperm DNA fragmentation, hyaluronan-binding ability, and hyperactivation on washed semen samples used for the insemination of oocytes. MAIN OUTCOME MEASURE(S): Correlation between the results of sperm function tests and the fertilization rate (FR) or embryo quality (EQ) after IVF and ICSI. Comparison of the sperm DNA fragmentation, hyperactivation, and hyaluronan binding ability between cycles with less than 50% (group 1) and more than 50% (group 2) of oocytes fertilized after IVF. RESULT(S): Both FR and EQ in IVF cycles negatively correlated with sperm DNA fragmentation. Furthermore, a positive correlation was observed between FR and hyaluronan-binding ability or induced hyperactivity. The semen samples from the IVF cycles with low FR (group 1) were characterized by statistically significantly higher sperm DNA fragmentation and lower hyaluronan-binding ability in comparison with semen samples from the group with high levels of fertilization (group 2). In ICSI cycles, no relationship was found between sperm function tests and FR or EQ. CONCLUSION(S): The Halosperm test, the HBA test, and induced hyperactivity are useful in predicting the ability of spermatozoa to fertilize oocytes in IVF and are helpful in distinguishing semen samples suitable for IVF or ICSI.
In order to be able to fertilize oocytes, human sperm must undergo a series of morphological and structural alterations, known as capacitation. It has been shown that the production of endogenous sperm reactive oxygen species (ROS) plays a key role in causing cells to undergo a massive acrosome reaction (AR). Astaxanthin (Asta), a photo-protective red pigment belonging to the carotenoid family, is recognized as having anti-oxidant, anti-cancer, anti-diabetic and anti-inflammatory properties and is present in many dietary supplements. This study evaluates the effect of Asta in a capacitating buffer which induces low ROS production and low percentages of acrosome-reacted cells (ARC). Sperm cells were incubated in the presence or absence of increasing concentrations of Asta or diamide (Diam) and analyzed for their ROS production, Tyr-phosphorylation (Tyr-P) pattern and percentages of ARC and non-viable cells (NVC). Results show that Asta ameliorated both sperm head Tyr-P and ARC values without affecting the ROS generation curve, whereas Diam succeeded in enhancing the Tyr-P level but only of the flagellum without increasing ARC values. It is suggested that Asta can be inserted in the membrane and therefore create capacitation-like membrane alteration which allow Tyr-P of the head. Once this has occurred, AR can take place and involves a higher numbers of cells.
Understanding and sustaining biodiversity is a multi-disciplinary science that benefits highly from the creation of organized and accessible collections of biomaterials (Genome Resource Banks). Large cryo-collections are invaluable tools for understanding, cataloging, and protecting the genetic diversity of the world’s unique animals and plants. Specifically, the systematic collection and preservation of semen from rare species has been developed significantly in recent decades with some biobanks now being actively used for endangered species management and propagation (including the introduction of species such as the black-footed ferret and the giant panda). Innovations emerging from the growing field of male fertility preservation for humans, livestock species, and laboratory animals are also becoming relevant to the protection and the propagation of valuable domestic and wild species. These new approaches extend beyond the “classical” methods associated with sperm freezing to include testicular tissue preservation combined with xenografting or in vitro culture, all of which have potential for rescuing vast amounts of unused germplasm. There also are other options under development that are predicted to have a high impact within the next decade (stem cell technologies, bio-stabilization of sperm cells at ambient temperatures, and the use of genomics tools). However, biobanking efforts and new fertility preservation strategies have to expand the way beyond mammalian species, which will offer knowledge and tools to better manage species that serve as valuable biomedical models or require assistance to reverse endangerment.
In non-azoospermic patients with low semen volume (LSV), looking for partial retrograde ejaculation (PRE) by searching sperm in the postejaculatory urine (PEU) is required. The use of a retro-ejaculatory index (R-ratio) was suggested to define PRE, but none of the studies indicated a specific threshold above which PRE must be considered. Our objective was to propose a threshold value for the R-ratio as indicative of PRE in patients with LSV selected to be devoid of any known causes or risk factors for retrograde ejaculation or LSV. Among our data base (2000-2009) including 632 patients with PEU, 245 male patients from infertile couples who had had a first semen analysis with LSV (< 2mL) and a second semen analysis associated with PEU, were selected on the previous criteria. A prospective control group was randomly constituted (2007-2008) of 162 first consulting male patients from infertile couples, with a normal semen volume (≥ 2mL) on a first semen analysis and who accepted to collect PEU with their usual second semen analysis, selected on the previous criteria. To define an R-ratio threshold indicative of PRE, we used a ROC curve analysis and a regression tree based on a classification and regression tree (CART) algorithm. Of the 245 LSV patients, 146 still presented low semen volume (< 2 mL) on the second semen analysis. From the use of the CART algorithm, two low (1.5% and 2.8%) and two high R-values (7.1% and 8.3%) were defined, according to the lower reference limit for semen volume of 2.0 mL (WHO 1999) or 1.5 mL (WHO 2010) respectively. As only one or no patient with normal semen volume was observed above the two high R-values, we suggest an R-value higher than the range of [7.1-8.3]% as indicative of PRE until confirmation by a prospective multicenter study.
Anurans show the highest diversity in reproductive modes of all vertebrate taxa, with a variety of associated breeding behaviours. One striking feature of anuran reproduction is amplexus. During this process, in which the male clasps the female, both individuals' cloacae are juxtaposed to ensure successful external fertilization. Several types of amplexus have evolved with the diversification of anurans, and secondary loss of amplexus has been reported in a few distantly related taxa. Within Nyctibatrachus, a genus endemic to the Western Ghats of India, normal axillary amplexus, a complete loss of amplexus, and intermediate forms of amplexus have all been suggested to occur, but many species remain unstudied. Here, we describe the reproductive behaviour of N. humayuni, including a new type of amplexus. The dorsal straddle, here defined as a loose form of contact in which the male sits on the dorsum of the female prior to oviposition but without clasping her, is previously unreported for anurans. When compared to known amplexus types, it most closely resembles the form of amplexus observed in Mantellinae. Furthermore, we prove that, opposed to the situation in most anurans, male semen release happens before egg deposition. We hypothesize that the male ejaculates on the female’s dorsum and that sperm subsequently runs from her back and hind legs before fertilizing the eggs. A second feature characterizing anuran breeding is the advertisement call, mostly produced solely by males. Despite recent descriptions of several new Nyctibatrachus species, few studies have explored their vocal repertoire. We describe both the male advertisement call and a female call for N. humayuni. The presence of a female call has not been reported within Nyctibatrachidae, and has been reported in less than 0.5% of anuran species. Altogether, our results highlight a striking diversity and several unique aspects of Nyctibatrachus breeding behaviour.
Na,K-ATPase α4 is a testis specific plasma membrane Na+ and K+ transporter expressed in the sperm flagellum. Deletion of Na,K-ATPase α4 in male mice results in complete infertility, making it an attractive target for male contraception. Na,K-ATPase α4 is characterized by high affinity for the cardiac glycoside ouabain. With the goal of discovering selective inhibitors of the Na,K-ATPase α4 and of sperm function, ouabain derivatives were modified at the glycone (C3) and the lactone (C17) domains. Ouabagenin analog 25, carrying a benzyltriazole moiety at C17, is a picomolar inhibitor of Na,K-ATPase α4, with an outstanding α4 isoform selectivity profile. Moreover, compound 25 decreased sperm motility in vitro and in vivo, and affected sperm membrane potential, intracellular Ca2+, pH and hypermotility. These results proved that the new ouabagenin triazole analog is an effective and selective inhibitor of Na,K- ATPase α4 and sperm function.