Sperm Cytoplasm Research Articles

Sperm development and structure in Bursaphelenchus luxuriosae (Nematoda: Aphelenchoidea: Aphelenchoididae)

Summary Sperm development and structure in the wood-inhabiting fungal and plant-feeding nematode, Bursaphelenchus luxuriosae, were studied using transmission electron microscopy to evaluate interspecific similarities and differences of spermatozoa in nematodes. In general, spermatogenesis in B. luxuriosae fits the ‘rhabditid’ pattern supported by morphological and phylogenetic analysis of the order Rhabditida. Spermatocyte development includes formation of complexes of fibrous bodies (FBs) with membranous organelles (MOs), the complexes dissociate in the spermatids into separate components, and the immature sperm contain MOs but lack FBs, which transform into a dense matrix of sperm cytoplasm. The female spermatheca contains mature spermatozoa as bipolar cells subdivided into a pseudopod devoid of organelles and a main cell body containing a nucleus without a nuclear envelope, numerous mitochondria, and peripheral MOs as pouches opening to the exterior via pores. Data on B. luxuriosae are used for analysis of variable quantitative and morphological characteristics of spermatozoa in Aphelenchoidea. General size of spermatozoa and their MOs have little value for comparative analysis. The MO knobbles look uniform in immature spermatozoa of each aphelenchoidid species studied and may be considered as a taxonomically specific ultrastructural feature. The presence or absence of FBs in immature spermatozoa demonstrates the diagnostic value of the aphelenchoidid sperm structure at the species level. Analysis also shows close similarity of spermatozoa in Bursaphelenchus spp. and Caenorhabditis elegans, the model species with comprehensive data on sperm biology. This may be used to identify new ways for the control and suppression of harmful nematode species such as B. xylophilus.

A CatSper-Uninvolved Mechanism to Induce Forward Sperm Motility in the Internal Fertilization.

Sperm-specific cation channel (CatSper), sperm-specific Na + /H + exchanger (sNHE), and soluble adenylyl cyclase (sAC) are necessary in the signaling pathways to control sperm motility in many animals, whereas some animals have lost some or all of them. In the present study, we examined CatSper-uninvolved signaling for vigorous undulation of the undulating membrane that is attached to the sperm tail and gives thrust for forward motility in the internally fertilizing newt Cynops pyrrhogaster. Reverse-transcription PCR failed to detect sNHE in the newt sperm. However, the pH of sperm cytoplasm was raised under a high extracellular pH equivalent to that of egg jelly, where sperm motility is initiated by sperm motility-initiating substance (SMIS). Carbonic anhydrase XII/ XVI and SLC4A4/8 were suggested to be present in the sperm, and transported bicarbonates raised the intracellular pH. In egg jelly extract that contained SMIS, the anion transporter inhibitor DIDS weakened the undulation of the undulating membrane, while bicarbonates enhanced it. The cyclic AMP concentration was found to increase in sperm cytoplasm in the egg-jelly extract. An inhibitor of sAC (KH7) weakened the undulation of the undulating membrane, and dibutyryl cyclic AMP blocked the inhibitory effect. Inhibitor of transmembrane AC (DDA) limitedly affected the undulation. The undulation was weakened by an inhibitor of protein kinase A (H89), and by an inhibitor of transient receptor potential (TRP) channels (RN1747). Our results support the conclusions that the high pH of the egg jelly triggers a signaling pathway through sAC, PKA, and TRP channels, and coacts with SMIS to induce forward sperm motility.

Deficiency of the Tmem232 Gene Causes Male Infertility with Morphological Abnormalities of the Sperm Flagellum in Mice.

The axoneme and accessory structures of flagella are critical for sperm motility and male fertilization. Sperm production needs precise and highly ordered gene expression to initiate and sustain the many cellular processes that result in mature spermatozoa. Here, we identified a testis enriched gene transmembrane protein 232 (Tmem232), which is essential for the structural integrity of the spermatozoa flagella axoneme. Tmem232 knockout mice were generated for in vivo analyses of its functions in spermatogenesis. Phenotypic analysis showed that deletion of Tmem232 in mice causes male-specific infertility. Transmission electron microscopy together with scanning electron microscopy were applied to analyze the spermatozoa flagella and it was observed that the lack of TMEM232 caused failure of the cytoplasm removal and the absence of the 7th outer microtubule doublet with its corresponding outer dense fiber (ODF). Co-IP assays further identified that TMEM232 interacts with ODF family protein ODF1, which is essential to maintain sperm motility. In conclusion, our findings indicate that TMEM232 is a critical protein for male fertility and sperm motility by regulating sperm cytoplasm removal and maintaining axoneme integrity.

Calcitriol induces post-thawed bovine sperm capacitation

<b>Background:</b> Capacitation is a set of physiological changes sperms undergo to acquire fertilizing capacity. <i>In vivo</i>, this process is directly associated with high calcium levels in sperm cytoplasm. Calcitriol, the vitamin D hypercalcemic metabolite, is related to human sperm motility, capacitation, and acrosome reaction. This work aimed to study the effect of calcitriol on bull sperm quality parameters and capacitation. <b>Methods:</b> One million freeze-thawed spermatozoa were obtained from different bulls and treated with 20 nM of calcitriol for 30 min. Untreated cells (negative control) and treated ones with calcitriol or heparin (100 µg/mL, positive capacitation control) were evaluated for motility, viability, and functional parameters. Menadione (70 µM, 30 min) treatment was included as a reactive oxygen species (ROS) positive sperm agent. <b>Results:</b> The results elucidated that sperm exposed to 20 nM calcitriol showed higher viability, vigor, and capacitation than their positive and negative controls. The percentage of sperm with intact plasma and acrosome membranes, mitochondrial membrane potential (ΔΨm), and phosphatidylserine externalization was similar in all the conditions evaluated, while ROS production was higher with heparin and menadione-treated groups than the calcitriol group or negative control. <b>Conclusion:</b> Our results indicate that calcitriol induces the capacitation of thawed bull spermatozoa and maintains acceptable values of progressive motility, viability, and vigor without altering key biological parameters such as redox status, ΔΨm, and cell death.

P-031 The extent of late paternal effect: does the blastocyst matter? A retrospective analysis of 703 single, frozen-thawed embryo-transfers

Abstract Study question Do the blastocysts derived from severe male infertility show different ongoing pregnancy rates(OPR) compared to blastocysts of couples requiring assisted reproduction techniques(ART) for other indications? Summary answer First, single, frozen-thawed embryo transfers of blastocysts derived from severe male infertility did not affect OPR in-vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI) cycles. What is known already Several studies reported a negative impact of severe male infertility on fertilization rate, embryo morphology and embryo cleavage speed, due to the so-called early paternal effect, caused by sperm cytoplasm deficiencies. Nuclear sperm defects are responsible for the late paternal effect, causing lower blastocyst formation rates and, theoretically, reducing implantation potential of the obtained blastocysts. However, the effects of male infertility on OPR and live birth rates (LBR) are still debated. Additionally, the heterogeneity in the definition and estimation of male infertility makes the existing data difficult to interpret. Study design, size, duration Retrospective analysis of first IVF/ICSI cycles performed between January 2019 and December 2021 in the Reproductive Sciences Unit of Gynaecology/Obstetrics Department of San Raffaele Hospital in Milan, Italy. Participants/materials, setting, methods First, single, frozen-thawed embryo transfers of infertile couples first IVF/ICSI cycles were included. Embryo transfers obtained by frozen semen were excluded. Couples characteristics, semen parameters and controlled ovarian stimulation (COS) data were collected. Semen quality was assessed using total motile count (TMC) and grouped into quartiles of TMC for the analyses. The effect of severe male factor infertility evaluated through TMC over OPR was the primary outcome of the study. Main results and the role of chance N = 703 transfers were analysed. Performing a logistic regression analysis adjusted for confounding factors (maternal age, COS protocols, number of oocytes retrieved and quality of transferred blastocysts), OPR was not influenced by TMC values [odds ratio (OR) = 0.999; confidence interval (CI) = 0.986-1.013; p = 0.932]. After grouping male infertility population into quartiles of TMC, no significant differences in OPR were found between extreme quartiles (TMC ≤2.55 million and TMC ≥20 million respectively), even when adjusted for confounders [OR = 1.007; CI 0.609-1.663; p = 0.98]. Therefore, the implantation potential of the obtained blastocysts, once formed, seems to be independent from sperm quality. Limitations, reasons for caution The major limitations of the present study are the retrospective design and sample size. Additionally, the estimation of male infertility as well as the routinary use of TMC in clinical practice are not yet standardized. However, having analysed only the first transfers of the included couples makes our results reliable. Wider implications of the findings Further prospective studies with larger sample size are needed to confirm our results and to validate the use TMC as a standard tool to classify male factor and to guide clinical choices. Pregnancy and obstetrical outcomes are also necessary to better understand the role of male infertility in human reproduction. Trial registration number not applicable

A dual-site controlled pH probe revealing the pH of sperm cytoplasm and screening for healthy spermatozoa

A dual-site controlled pH probe, which is composed of gold nanoparticles and modified with rhodamine and fluorescein derivatives, was applied to sensitively monitor intracellular pH changes in sperm. The pH probe revealed the intracellular pH of sperm under different conditions and demonstrated the lower pH in asthenozoospermia patients as compared to healthy individuals. Importantly, the pH probe can help screen for healthy sperm.

Plasmogamic Paternal Contributions to Early Zygotic Development in Flowering Plants.

Flowering plant zygotes possess complete developmental potency, and the mixture of male and female genetic and cytosolic materials in the zygote is a trigger to initiate embryo development. Plasmogamy, the fusion of the gamete cytoplasms, facilitates the cellular dynamics of the zygote. In the last decade, mutant analyses, live cell imaging-based observations, and direct observations of fertilized egg cells by in vitro fusion of isolated gametes have accelerated our understanding of the post-plasmogamic events in flowering plants including cell wall formation, gamete nuclear migration and fusion, and zygotic cell elongation and asymmetric division. Especially, it has become more evident that paternal parent-of-origin effects, via sperm cytoplasm contents, not only control canonical early zygotic development, but also activate a biparental signaling pathway critical for cell fate determination after the first cell division. Here, we summarize the plasmogamic paternal contributions via the entry of sperm contents during/after fertilization in flowering plants.

Genetic peculiarities of free radical oxidation of lipids and proteins in the semen of breeding boars

Complex research into biochemical aspects of the functioning of the antioxidant system for the protection of sperm of the breeding boars has established that the intensity of the flow of peroxide oxidation of lipids in germ cells is much higher than in the extracellular space. Reactions of free radical peroxide oxidation of proteins and lipids in the semen of healthy breeding boars are characterized by a stable level of activity that is necessary for the normal course of implementation of processes of the reproductive function. All components of the antioxidant system stay in mutual compensatory ratios under physiological conditions. As a rule, reducing the concentration or activity of some antioxidant enzymes leads to corresponding changes in others. The main antioxidants of the germ cell genomes are superoxide dismutase and ceruloplasmin. Catalase is a key enzyme that neutralizes H2O2 in the semen fluid of breeding boars. The content of total proteins in the semen of the synthetic line SS23 animals is greater (p &lt; 0.05) than in the breeding boars of the large white breed. The processes of the oxidative modification of proteins in the animals body of the synthetic line runs more intensely, as it is evidenced by the higher content of the aldehyde and ketodinitrophenyl hydrazones of the main and neutral character in the sperm cytoplasm.

Veratridine-sensitive Na+ channels regulate human sperm fertilization capacity

AimsThe sperm plasma membrane contains specific ion channels and transporters that initiate changes in Ca2+, Na+, K+ and H+ ions in the sperm cytoplasm. Ion channels are key regulators of the sperm membrane potential, cytoplasmic Ca2+ and intracellular pH (pHi), which leads to regulate motility, capacitation, acrosome reaction and other physiological processes crucial for successful fertilization. Expression of epithelial sodium channels (ENaC) and voltage-gated sodium channels (Nav) in human spermatozoa has been reported, but the role of Na+ fluxes sodium channels in the regulation of sperm cell function remains poorly understood. In this context, we aimed to analyze the physiological role of Nav channels in human sperm. Main methodsMotility and hyperactivation analysis was conducted by CASA analysis. Flow cytometry and spectrophotometry approaches were carried out to measure Capacitation, Acrosome reaction, immunohistochemistry for Tyr-residues phosporylation, [Ca2+]i levels and membrane potential. Key findingsFunctional studies showed that veratridine, a voltage-gated sodium channel activator, increased sperm progressive motility without producing hyperactivation while the Nav antagonist lidocaine did induce hyperactivated motility. Veratridine increased protein tyrosine phosphorylation, an event occurring during capacitation, and its effects were inhibited in the presence of lidocaine and tetrodotoxin. Veratridine had no effect on the acrosome reaction by itself, but was able to block the progesterone-induced acrosome reaction. Moreover, veratridine caused a membrane depolarization and modified the effect of progesterone on [Ca2+]i and sperm membrane potential. SignificanceOur results suggest that veratridine-sensitive Nav channels are involved on human sperm fertility acquisition regulating motility, capacitation and the progesterone-induced acrosome reaction in human sperm.

Dilution degree influence of Holstein sires' depreserved sperm on its quality

The article investigates the impact of dilution depressive semen sires, frozen in ASIL TҮLІK and French technology, its quality indicators. It was established that the increase in the degree of dilution increases the permeability depressive sperm cytoplasm sperm membranes, significantly reducing their mobility, and absolute figure, regardless of the cryopreservation technology, diluents and formulation components used anti-shock.

Molecular and structural changes related to hepatitis E virus antigen and its expression in testis inducing apoptosis in Mongolian gerbil model.

Hepatitis E virus (HEV) infection has been associated with a wide range of extrahepatic manifestations, so this study was designed to examine the effect and role of HEV on structural and molecular changes in the testicular tissues of Mongolian gerbils experimentally infected with swine HEV. HEV RNA was first detected in testis at 14days post-inoculation and reached a peak between 28 and 42days later with viral load between 3.12 and 6.23 logs/g by PCR assays. Changes including vacuolation, sloughing of germ cells, formation of multinuclear giant cells, degeneration, necrosis of tubules and damaged blood-testis barrier were observed through transmission electron microscopy. HEV ORF2 antigen was detected in the sperm cell cytoplasm along with decrease in relative protein of zonula occludens-1 through immunohistochemistry. HEV ORF3 antigen and ZO-1 protein were detectable by Western blotting. Lower (P<.05) serum testosterone and higher (P<.05) blood urea nitrogen level was observed in inoculated Mongolian gerbils. Likewise, increased (P<.05) germ cell apoptosis rate was detected with significant increased expression of Fas-L and Fas in HEV-inoculated groups at each time points. Up-regulation (P<.05 or P<.01) in mRNA level of Fas-L, Fas, Bax, Bcl-2 and caspase-3 was observed in HEV RNA-positive testes. Our study demonstrated that after experimental inoculation, HEV can be detected in testis tissues and viral proteins produce structural and molecular changes that in turn disrupt the blood-testis barrier and induce germ cell apoptosis.

MATRILINEAL, a sperm-specific phospholipase, triggers maize haploid induction.

Sexual reproduction in flowering plants involves double fertilization, the union of two sperm from pollen with two sex cells in the female embryo sac. Modern plant breeders increasingly seek to circumvent this process to produce doubled haploid individuals, which derive from the chromosome-doubled cells of the haploid gametophyte. Doubled haploid production fixes recombinant haploid genomes in inbred lines, shaving years off the breeding process. Costly, genotype-dependent tissue culture methods are used in many crops, while seed-based in vivo doubled haploid systems are rare in nature and difficult to manage in breeding programmes. The multi-billion-dollar maize hybrid seed business, however, is supported by industrial doubled haploid pipelines using intraspecific crosses to in vivo haploid inducer males derived from Stock 6, first reported in 1959 (ref. 5), followed by colchicine treatment. Despite decades of use, the mode of action remains controversial. Here we establish, through fine mapping, genome sequencing, genetic complementation, and gene editing, that haploid induction in maize (Zea mays) is triggered by a frame-shift mutation in MATRILINEAL (MTL), a pollen-specific phospholipase, and that novel edits in MTL lead to a 6.7% haploid induction rate (the percentage of haploid progeny versus total progeny). Wild-type MTL protein localizes exclusively to sperm cytoplasm, and pollen RNA-sequence profiling identifies a suite of pollen-specific genes overexpressed during haploid induction, some of which may mediate the formation of haploid seed. These findings highlight the importance of male gamete cytoplasmic components to reproductive success and male genome transmittance. Given the conservation of MTL in the cereals, this discovery may enable development of in vivo haploid induction systems to accelerate breeding in crop plants.

Effects of the IGF-1/PTEN/Akt/FoxO signaling pathway on male reproduction in rats subjected to water immersion and restraint stress.

The aim of the present study was to determine the effects of the insulin-like growth factor 1 (IGF-1)/phosphatase and tensin homologue deleted on chromosome 10 (PTEN)/Akt/forkhead box (FoxO) signaling pathway on male reproduction in rats subjected to water immersion and restraint stress (WRS). Sperm morphology, sperm malformation rate, and serum testosterone concentration were analyzed following WRS. In addition, the expression levels and immunolocalization of IGF-1, PTEN, Akt and FoxO proteins, as well as the rate of cell apoptosis in rat testes, were investigated. The results indicated that sperm malformation rate, serum testosterone concentration, and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were increased in the testes after WRS. Furthermore, IGF-1 and FoxO1 proteins were predominantly localized in the sperm cytoplasm during the late stages of spermatogenesis. FoxO1 protein was also localized in Leydig cell cytoplasm. PTEN and total Akt proteins were predominantly expressed in the cytoplasm of Leydig cells and spermatogonia. PTEN protein was also detected in vascular endothelial cells. In addition, IGF-1, PTEN, Akt1, Akt2, FoxO3 and FoxO4 gene expression levels were upregulated following WRS, and peaked after 7 h of WRS. During the recovery period, the expression levels of these genes gradually returned to normal levels. The present study demonstrated that WRS induced sperm damage in the testes. In addition, the results indicated that the IGF-1/PTEN/Akt/FoxO signaling pathway may serve an anti-stress role in the testes of rats subjected to WRS.

Molecular characterization and expression profile of the estrogen receptor α gene during different reproductive phases in Monopterus albus.

To understand the molecular mechanism of estrogen and to evaluate the role of the estrogen receptor in mediating estrogen action, the full-length cDNA of estrogen receptor α (ERα) was cloned from Monopterus albus, and its expression pattern and distribution were investigated. The ERα cDNA of M. albus includes an open reading frame of 1863 bp, a 140-bp 5’-untranslated region and a 797-bp 3’-untranslated region. Amino acid sequence homology analysis showed that the Monopterus albus ERα has a moderate degree of similarity with Sebastes schlegelii, Zoarces viviparus and Haplochromis burtoni (81.1%, 80.7% and 80.4%, respectively). Quantitative PCR results showed that the highest level of ERα expression was in the liver; the next highest level of expression was observed in the gonads, where it was expressed at high levels particularly in the ovary in developmental stages IV and V and in the testis in developmental stage II/III. Immunohistochemistry analysis showed that ERα was present as slender particles distributed mainly in the membranes of spermatocytes and oocytes in the testis and ovary, whereas no positive signal was observed in the cytoplasm of sperm cells. This report describes the first molecular characterization of full-length ERα and its tissue-specific distribution in M. albus.

Three-dimensional reconstruction of black tiger prawn (Penaeus monodon) spermatozoa using serial block-face scanning electron microscopy.

Serial Block-Face Scanning Electron Microscopy (SBF-SEM) was used in this study to examine the ultrastructural morphology of Penaeus monodon spermatozoa. SBF-SEM provided a large dataset of sequential electron-microscopic-level images that facilitated comprehensive ultrastructural observations and three-dimensional reconstructions of the sperm cell. Reconstruction divulged a nuclear region of the spermatophoral spermatozoon filled with decondensed chromatin but with two apparent levels of packaging density. In addition, the nuclear region contained, not only numerous filamentous chromatin elements with dense microregions, but also large centrally gathered granular masses. Analysis of the sperm cytoplasm revealed the presence of degenerated mitochondria and membrane-less dense granules. A large electron-lucent vesicle and "arch-like" structures were apparent in the subacrosomal area, and an acrosomal core was found in the acrosomal vesicle. The spermatozoal spike arose from the inner membrane of the acrosomal vesicle, which was slightly bulbous in the middle region of the acrosomal vesicle, but then extended distally into a broad dense plate and to a sharp point proximally. This study has demonstrated that SBF-SEM is a powerful technique for the 3D ultrastructural reconstruction of prawn spermatozoa, that will no doubt be informative for further studies of sperm assessment, reproductive pathology and the spermiocladistics of penaeid prawns, and other decapod crustaceans.

Sperm storage in the uterium of the insect-parasitic nematode Sphaerularia vespae (Nematoda: Sphaerulariidae)

The spermatheca found in the ‘uterium’ (highly transformed part of parasitic female) of the sphaerularioidid nematode Sphaerularia vespae, an endoparasite of a common Japanese hornet, Vespa simillima, was studied with TEM. The uterium consists of a thick trophic epithelium exposed to the insect haemocoel and a protective cavity which contains the female genital tube and storage cells (fat body). The uterium cavity contains the female reproductive system composed of the usual parts: uterus, oviduct and ovary. The genital pore of the young uterium is an opening of the short narrow uterine tube which joins to the voluminous spermatheca. The spermatheca is a dilated distal part of the uterus, storing numerous tiny spermatozoa. The spermatheca is blocked distally by the oviduct. The spermatozoa are uniform amoeboid cells only 1.4-1.6 μm in size with a highly condensed nucleus about 0.8 μm in size. The transparent sperm cytoplasm contains several mitochondria, small membranous organelles (specific organelles characteristic of nematode spermatozoa), occasional bundles of fibres and centriole-like bodies. The S. vespae spermatozoa are very similar to the spermatozoa stored in the uterus of infective females of another sphaerularioidid nematode, Deladenus sp., and have the main features of sperm found in many other rhabditid nematodes.

Effect of Wuziyanzong Pill on sperm quality and calcium ion content in oligoasthenospermia rats

ObjectiveTo study the effect of Wuziyanzong treatment on the sperm quality and content of calcium ions (Ca2+) in oligoasthenospermia rats. MethodsA model of oligoasthenospermia was induced in 50 Sprague Dawley rats by treatment with tripterygium glycosides at 30 mg/kg per day for 8 weeks. They were divided randomly into a model group, a positive group (Huangjingzanyu capsule, 3.01 g/kg), and low, medium and high dose Wuziyanzong treatment groups (2.30, 4.60, 9.20 g/kg crude drug respectively) with 10 in each group. Another 10 rats were used as a control group. The rats in the control and model groups were administered distilled water, while the rats in the remaining groups were administered Wuziyanzong for 30 d. The epididymides were removed, spermatozoa recovered and the sperm density and viability were measured. The spermatozoa were purified and the contents of Ca2+ in the cytoplasm and mitochondria were detected by flow cytometry and atomic absorption spectrometry, respectively. ResultsAfter 8 weeks of treatment with tripterygium glycosides, the sperm density, sperm activity and the Ca2+ content of spermatozoa in the model rats were all significantly decreased compared with the control group (all P<0.05). After 30 d treatment, the sperm density and activity improved and the Ca2+ content of sperm were increased significantly in the medium and high dose Wuziyanzong treatment groups in comparison with the model group (all P<0.05). ConclusionsThe Wuziyanzong treatment increased sperm density, improved sperm viability and enhanced the content of Ca2+ in the sperm cytoplasm and mitochondria in this rat model of oligoasthenospermia.

Perfringolysin O as a useful tool to study human sperm physiology

To evaluate perfringolysin O, a cholesterol-dependent pore-forming cytolysin, as a tool to study several aspects of human sperm physiology. Prospective study. Basic research laboratory. Human semen samples with normal parameters obtained from healthy donors. Interaction of recombinant perfringolysin O with human spermatozoa. Assessment of perfringolysin O binding to spermatozoa, tests for acrosome and plasma membrane integrity, and acrosomal exocytosis assays. Perfringolysin O associated with human spermatozoa at 4°C. The binding was sensitive to changes in cholesterol concentrations and distribution occurring in the plasma membrane of these cells during capacitation. When perfringolysin O-treated sperm were incubated at 37°C, the plasma membrane became permeable, whereas the acrosome membrane remained intact. Permeabilized spermatozoa were able to respond to exocytic stimuli. The process was inhibited by proteins that interfere with membrane fusion, indicating that large molecules, including antibodies, were able to permeate into the spermatozoa. PFO is a useful probe to assess changes in the amount and distribution of the active sterol fraction present in the sperm plasma membrane. The toxin can be used for the efficient and selective permeabilization of this membrane, rendering a flexible experimental model suitable for studying molecular processes occurring in the sperm cytoplasm.

The Simmet Lecture: New Horizons on an Old Landscape – Oxidative Stress, DNA Damage and Apoptosis in the Male Germ Line

Our ability to diagnose and treat male infertility is gradually improving in concert with advances in our understanding of the molecular mechanisms underpinning defective sperm function. In this context, one of the factors to emerge as a major causative agent in male infertility is oxidative stress. Spermatozoa are particularly susceptible to such stress because they are exceptionally rich in vulnerable substrates such as polyunsaturated fatty acids, proteins and DNA. The lack of sperm cytoplasm also provides these cells with little capacity to protect themselves from oxidative attack or to effect any repair, should damage occur. Similarly, sperm chromatin is in a quasi-crystalline state and has very little capacity to respond to any DNA damage induced by oxidative attack. When the latter does occur, it appears to be initiated by reactive oxygen species (ROS) generated by the sperm mitochondria. These free radicals attack the lipids present in the sperm mitochondria generating electrophilic aldehydes, which bind to components of the mitochondrial electron transport chain stimulating yet more ROS production. The oxidative stress created via this self-propagating mechanism initiates an apoptotic cascade as a result of which the spermatozoa loose their capacity for fertilization and suffer damage to their DNA. Phosphatidylserine externalization is a late event in sperm apoptosis and may facilitate the silent phagocytosis of moribund cells in the female reproductive tract, that is, the phagocytosis of senescent spermatozoa without the accompanying generation of an inflammatory response. Encouragingly, the involvement of oxidative stress in the aetiology of male infertility has opened up new opportunities for therapeutic interventions involving the judicious administration of nucleophiles and other forms of antioxidants.

Disentangling the spermatozoon’s transcriptome

Disentangling the spermatozoon’s transcriptome