Regulatory T cells play a crucial role in maintaining sperm tolerance and male fertility.

Regulatory T cells (Tregs) modulate tissue homeostatic processes and immune responses. Understanding tissue-Treg biology will contribute to developing precision-targeting treatment strategies. Here, we show that Tregs maintain the tolerogenic state of the testis and epididymis, where sperm are produced and mature. We found that Treg depletion induces severe autoimmune orchitis and epididymitis, manifested by an exacerbated immune cell infiltration [CD4 T cells, monocytes, and mononuclear phagocytes (MPs)] and the development of antisperm antibodies (ASA). In Treg-depleted mice, MPs increased projections toward the epididymal lumen as well as invading the lumen. ASA-bound sperm enhance sperm agglutination and might facilitate sperm phagocytosis. Tolerance breakdown impaired epididymal epithelial function and altered extracellular vesicle cargo, both of which play crucial roles in the acquisition of sperm fertilizing ability and subsequent embryo development. The affected mice had reduced sperm number and motility and severe fertility defects. Deciphering these immunoregulatory mechanisms may help to design new strategies to treat male infertility, as well as to identify potential targets for immunocontraception.

C2CD6 regulates targeting and organization of the CatSper calcium channel complex in sperm flagella.

The CatSper cation channel is essential for sperm capacitation and male fertility. The multi-subunit CatSper complexes form highly organized calcium signaling nanodomains on flagellar membranes. Here, we report identification of an uncharacterized protein, C2CD6, as a subunit of the mouse CatSper complex. C2CD6 contains a calcium-dependent, membrane-targeting C2 domain. C2CD6 associates with the CatSper calcium-selective, core-forming subunits. Deficiency of C2CD6 depletes the CatSper nanodomains from the flagellum and results in male sterility. C2CD6-deficient sperm are defective in hyperactivation and fail to fertilize oocytes both in vitro and in vivo. CatSper currents are present but at a significantly lower level in C2CD6-deficient sperm. Transient treatments with either Ca2+ ionophore, starvation, or a combination of both restore the fertilization capacity of C2CD6-deficient sperm. C2CD6 interacts with EFCAB9, a pH-dependent calcium sensor in the CatSper complex. We postulate that C2CD6 facilitates incorporation of the CatSper complex into the flagellar plasma membrane and may function as a calcium sensor. The identification of C2CD6 may enable the long-sought reconstitution of the CatSper ion channel complex in a heterologous system for male contraceptive development.

Differential role of bovine serum albumin and HCO3- in the regulation of GSK3 alpha during mouse sperm capacitation.

To become fertile, mammalian sperm are required to undergo capacitation in the female tract or in vitro in defined media containing ions (e.g. HCO3 -, Ca2+, Na+, and Cl-), energy sources (e.g. glucose, pyruvate) and serum albumin (e.g. bovine serum albumin (BSA)). These different molecules initiate sequential and concomitant signaling pathways, leading to capacitation. Physiologically, capacitation induces changes in the sperm motility pattern (e.g. hyperactivation) and prepares sperm for the acrosomal reaction (AR), two events required for fertilization. Molecularly, HCO3 - activates the atypical adenylyl cyclase Adcy10 (aka sAC), increasing cAMP and downstream cAMP-dependent pathways. BSA, on the other hand, induces sperm cholesterol release as well as other signaling pathways. How these signaling events, occurring in different sperm compartments and with different kinetics, coordinate among themselves is not well established. Regarding the AR, recent work has proposed a role for glycogen synthase kinases (GSK3α and GSK3ß). GSK3α and GSK3ß are inactivated by phosphorylation of residues Ser21 and Ser9, respectively, in their N-terminal domain. Here, we present evidence that GSK3α (but not GSK3ß) is present in the anterior head and that it is regulated during capacitation. Interestingly, BSA and HCO3 - regulate GSK3α in opposite directions. While BSA induces a fast GSK3α Ser21 phosphorylation, HCO3 - and cAMP-dependent pathways dephosphorylate this residue. We also show that the HCO3--induced Ser21 dephosphorylation is mediated by hyperpolarization of the sperm plasma membrane potential (Em) and by intracellular pH alkalinization. Previous reports indicate that GSK3 kinases mediate the progesterone-induced AR. Here, we show that GSK3 inhibition also blocks the Ca2+ ionophore ionomycin-induced AR, suggesting a role for GSK3 kinases downstream of the increase in intracellular Ca2+ needed for this exocytotic event. Altogether, our data indicate a temporal and biphasic GSK3α regulation with opposite actions of BSA and HCO3 -. Our results also suggest that this regulation is needed to orchestrate the AR during sperm capacitation.

Active surveillance for clinical complete responders after chemoradiotherapy for oesophageal squamous cell carcinoma.

BACKGROUND: Guidelines on the treatment of oesophageal squamous cell carcinoma (SCC) recommend neoadjuvant chemoradiotherapy plus surgery or definitive chemoradiotherapy. The aim of this study was to evaluate the outcome of patients with a cCR after chemoradiotherapy who underwent active surveillance. METHODS: Patients with oesophageal SCC who were treated with chemoradiotherapy between January 2016 and June 2022 were identified from an institutional database. Survival and recurrence of patients with a cCR who underwent active surveillance were compared with those of patients who underwent planned surgery. Survival was calculated according to the Kaplan-Meier method and compared between groups using the log rank test. RESULTS: The 37 patients who underwent active surveillance were older and tumours were more often located in the middle/upper-third of the oesophagus than in the surgery group of 57 patients. Median follow-up was 28.1 (i.q.r. 17.2-47.1) months for the active surveillance group and 20 (12.9-39.1) months for the surgery group. Overall survival was comparable between the two groups, with 3-year survival rates of 50 (95% c.i. 31 to 67) and 59 (40 to 73)% for the active surveillance and surgery groups respectively (P = 0.55). Three-year progression-free survival for patients who underwent active surveillance was better than in the surgery group: 70 (43 to 85) versus 58 (40 to 72)% (P = 0.02). Overall and progression-free survival was comparable between patients in the active surveillance group and 23 patients in the surgery group who had a pCR (ypT0 N0). The overall recurrence rate was comparable between the groups: 7 of 37 (19.4%) in active surveillance group versus 16 of 49 (32.6%) in surgery group (P = 0.26). Locoregional recurrence was noted more often in the active surveillance group and systemic recurrence in the surgery group. CONCLUSION: Active surveillance is feasible and safe for patients with oesophageal SCC who have a cCR after chemoradiotherapy.

Robotic versus open Ivor-Lewis esophagectomy: A more accurate lymph node dissection without burdening the leak rate.

BACKGROUND: Robotic-assisted minimally invasive esophagectomy (RAMIE) combines the beneficial effects of minimally invasive surgery on postoperative complications, especially on pulmonary ones, with the safety of the anastomosis performed in open surgery. Moreover, RAMIE could allow a more accurate lymphadenectomy. METHODS: We reviewed our database to identify all patients with adenocarcinoma of the esophagus treated by Ivor-Lewis esophagectomy in the period January 2014 to June 2022. Patients were divided according to the thoracic approach into RAMIE and open esophagectomy (OE) groups. We compared the groups for early surgical outcomes, 90-day mortality as well as R0 rate, and the number of lymph nodes harvested. RESULTS: We identified 47 patients in RAMIE and 159 patients in the OE group. Baseline characteristics were comparable. Operative time was significantly longer for RAMIE procedures (p < 0.01); however, we did not observe the difference in overall (RAMIE 55.5% vs. OE 61%, p = 0.76) and severe complications rate (RAMIE 17% vs. OE 22.6%, p = 0.4). The anastomotic leak rate was 2.1% after RAMIE and 6.9% after OE (p = 0.56). We did not report the difference in 90-day mortality (RAMIE 2.1% vs. OE 1.9%, p = 0.65). In the RAMIE group, we observed a significantly higher number of thoracic lymph nodes harvested, with a median of 10 lymph nodes in the RAMIE group versus 8 in the OE group (p < 0.01). CONCLUSIONS: In our experience, RAMIE has morbimortality rates comparable to OE. Moreover, it allows a more accurate thoracic lymphadenectomy which results in a higher thoracic lymph nodes retrieval rate.

The "Weekday Effect" on Enhanced Recovery after Surgery Protocol for Gastrectomy.

INTRODUCTION: While enhanced recovery after surgery (ERAS) protocol demonstrated to improve outcomes after gastrectomy, some papers evidenced a detrimental effect on postoperative morbidity related to the "weekday effect." We aimed to understand whether the day of gastrectomy could affect postoperative outcomes and compliance with ERAS items. METHODS: We included all patients that underwent gastrectomy for cancer between January 2017 and September 2021. Cohort was divided considering the day of surgery: Early group (Monday-Wednesday) and Late group (Thursday-Friday). Compliance with protocol and postoperative outcomes were compared. RESULTS: Two hundred twenty-seven patients were included in Early group, while 154 were in Late group. The groups were comparable in preoperative characteristics. No significant difference in pre/intraoperative and postoperative ERAS items' compliance was apparent between Early and Late groups, with most items exceeding the 70% threshold. Median length of stay was 6.5 days and 6 days in Early and Late groups (p = 0.616), respectively. Morbidity was 50% in both groups, with severe complications that occurred in 13% of Early patients and 15% of Late patients. Ninety-day mortality was 2%, and it was similar between the two groups. CONCLUSIONS: In a center with a standardized ERAS protocol, the weekday of gastrectomy has no significant impact on the success of each ERAS item and on postoperative surgical and oncological outcomes.

Treatment of EGJ Cancer within or outside Clinical Trials: Does the Setting Matter? A Monocentric Prospective Observational Study.

INTRODUCTION: RCTs support neoadjuvant chemoradiotherapy (nCRT) followed by surgery in locally advanced esophago-gastric junction (LA-EGJ) adenocarcinoma. However, RCTs are performed in highly controlled settings with limited representativeness of real-life patients (RLS). The aim of the study was to compare the outcomes in RLS and clinical trial settings. METHODS: The outcomes of RLS, which comprised 125 patients consequently treated for LA-EGJ adenocarcinoma between 2012 and 2017, were compared with the phase II trial (PIIS), performed on 65 patients from 2003 to 2011. RESULTS: About half of RLS (51.2%) were treated with nCRT according to VR protocol, 20.8% with standard CRT according to CROSS/Al-Sarraf, 20% with chemotherapy (CT) alone. pCR was 36.8%, 28.6%, and 9.1% after VR protocol, standard CRT, and CT, respectively (p = 0.082), while 3-year overall survival (OS) was 58.6% (95% CI 43.2-71.1%), 32.8% (14.6-52.4%), and 44.8% (21.3-65.9%), respectively (p = 0.030). With respect to PIIS, RLS had a higher proportion of cN+ (94% vs. 54%; p < 0.001) and a lower proportion of pCR after CT/CRT (23% vs. 39%; p = 0.041). Three-year OS was slightly higher, although not significantly, in PIIS (58.9%, 45.1-70.2%) than RLS (47.9%, 37.4-57.7%) and nearly identical to 3-year OS in RLS treated with VR protocol. CONCLUSION: Real-life patients with EGJ adenocarcinoma have more advanced cancer at baseline, lower pathologic response to neoadjuvant treatment than patients enrolled in clinical trials, but similar survival.

Intra-amniotic inflammation in the mid-trimester of pregnancy is a risk factor for neuropsychological disorders in childhood.

OBJECTIVES: Intra-amniotic inflammation is a subclinical condition frequently caused by either microbial invasion of the amniotic cavity or sterile inflammatory stimuli, e.g., alarmins. An accumulating body of evidence supports a role for maternal immune activation in the genesis of fetal neuroinflammation and the occurrence of neurodevelopmental disorders such as cerebral palsy, schizophrenia, and autism. The objective of this study was to determine whether fetal exposure to mid-trimester intra-amniotic inflammation is associated with neurodevelopmental disorders in children eight to 12 years of age. METHODS: This is a retrospective case-control study comprising 20 children with evidence of prenatal exposure to intra-amniotic inflammation in the mid-trimester and 20 controls matched for gestational age at amniocentesis and at delivery. Amniotic fluid samples were tested for concentrations of interleukin-6 and C-X-C motif chemokine ligand 10, for bacteria by culture and molecular microbiologic methods as well as by polymerase chain reaction for eight viruses. Neuropsychological testing of children, performed by two experienced psychologists, assessed cognitive and behavioral domains. Neuropsychological dysfunction was defined as the presence of an abnormal score (<2 standard deviations) on at least two cognitive tasks. RESULTS: Neuropsychological dysfunction was present in 45% (9/20) of children exposed to intra-amniotic inflammation but in only 10% (2/20) of those in the control group (p=0.03). The relative risk (RR) of neuropsychological dysfunction conferred by amniotic fluid inflammation remained significant after adjusting for gestational age at delivery [aRR=4.5 (1.07-16.7)]. Of the 11 children diagnosed with neuropsychological dysfunction, nine were delivered at term and eight of them had mothers with intra-amniotic inflammation. Children exposed to intra-amniotic inflammation were found to have abnormalities in neuropsychological tasks evaluating complex skills, e.g., auditory attention, executive functions, and social skills, whereas the domains of reasoning, language, and memory were not affected in the cases and controls. CONCLUSIONS: Asymptomatic sterile intra-amniotic inflammation in the mid-trimester of pregnancy, followed by a term birth, can still confer to the offspring a substantial risk for neurodevelopmental disorders in childhood. Early recognition and treatment of maternal immune activation in pregnancy may be a strategy for the prevention of subsequent neurodevelopmental disorders in offspring.

Are bacteria, fungi, and archaea present in the midtrimester amniotic fluid?

OBJECTIVES: This study was conducted to determine whether bacteria, fungi, or archaea are detected in the amniotic fluid of patients who underwent midtrimester amniocentesis for clinical indications. METHODS: Amniotic fluid samples from 692 pregnancies were tested by using a combination of culture and end-point polymerase chain reaction (PCR) techniques. Intra-amniotic inflammation was defined as an interleukin-6 concentration >2,935 pg/mL. RESULTS: Microorganisms were detected in 0.3% (2/692) of cases based on cultivation, 1.73% (12/692) based on broad-range end-point PCR, and 2% (14/692) based on the combination of both methods. However, most (13/14) of these cases did not have evidence of intra-amniotic inflammation and delivered at term. Therefore, a positive culture or end-point PCR in most patients appears to have no apparent clinical significance. CONCLUSIONS: Amniotic fluid in the midtrimester of pregnancy generally does not contain bacteria, fungi, or archaea. Interpretation of amniotic fluid culture and molecular microbiologic results is aided by the assessment of the inflammatory state of the amniotic cavity. The presence of microorganisms, as determined by culture or a microbial signal in the absence of intra-amniotic inflammation, appears to be a benign condition.

Cdc42 localized in the CatSper signaling complex regulates cAMP-dependent pathways in mouse sperm.

Sperm acquire the ability to fertilize in a process called capacitation and undergo hyperactivation, a change in the motility pattern, which depends on Ca2+ transport by CatSper channels. CatSper is essential for fertilization and it is subjected to a complex regulation that is not fully understood. Here, we report that similar to CatSper, Cdc42 distribution in the principal piece is confined to four linear domains and this localization is disrupted in CatSper1-null sperm. Cdc42 inhibition impaired CatSper activity and other Ca2+ -dependent downstream events resulting in a severe compromise of the sperm fertilizing potential. We also demonstrate that Cdc42 is essential for CatSper function by modulating cAMP production by soluble adenylate cyclase (sAC), providing a new regulatory mechanism for the stimulation of CatSper by the cAMP-dependent pathway. These results reveal a broad mechanistic insight into the regulation of Ca2+ in mammalian sperm, a matter of critical importance in male infertility as well as in contraception.

Sperm Energy Restriction and Recovery (SER) Alters Epigenetic Marks during the First Cell Cycle of Development in Mice.

The sperm energy restriction and recovery (SER) treatment developed in our laboratory was shown to improve fertilization and blastocyst development following in vitro fertilization (IVF) in mice. Here, we investigated the effects of SER on early embryogenesis. Developmental events observed during the first cell cycle indicated that progression through the pronuclear stages of SER-generated embryos is advanced in comparison with control-generated embryos. These findings prompted further analysis of potential effects of SER on pronuclear chromatin dynamics, focusing on the key H3K4me3 and H3K27ac histone modifications. Nearly all the SER-generated embryos displayed H3K4me3 in the male pronuclei at 12 h post-insemination (HPI), while a subset of the control-generated embryos did not. Additionally, SER-generated embryos displayed a more homogenous intensity of H3K27ac at 8 and 12 HPI compared to control embryos. These changes in histone modifications during the first cell cycle were accompanied by differences in gene expression at the two-cell stage; both of these changes in early embryos could potentially play a role in the improved developmental outcomes of these embryos later in development. Our results indicate that sperm incubation conditions have an impact on early embryo development and can be useful for the improvement of assisted reproductive technology outcomes.

TSSK3, a novel target for male contraception, is required for spermiogenesis.

We have previously shown that members of the family of testis-specific serine/threonine kinases (TSSKs) are post-meiotically expressed in testicular germ cells and in mature sperm in mammals. The restricted post-meiotic expression of TSSKs as well as the importance of phosphorylation in signaling processes strongly suggest that TSSKs have an important role in germ cell differentiation and/or sperm function. This prediction has been supported by the reported sterile phenotype of the TSSK6 knock-out (KO) mice and of the double TSSK1/TSSK2 KO. The aim of this study was to develop KO mouse models of TSSK3 and to validate this kinase as a target for the development of a male contraceptive. We used CRISPR/Cas9 technology to generate the TSSK3 KO allele on B6D2F1 background mice. Male heterozygous pups were used to establish three independent TSSK3 KO lines. After natural mating of TSSK3 KO males, females that presented a plug (indicative of mating) were monitored for the following 24 days and no pregnancies or pups were found. Sperm numbers were drastically reduced in all three KO lines and, remarkably, round spermatids were detected in the cauda epididymis of KO mice. From the small population of sperm recovered, severe morphology defects were detected. Our results indicate an essential role of TSSK3 in spermiogenesis and support this kinase as a suitable candidate for the development of novel nonhormonal male contraceptives.

Clinical chorioamnionitis at term X: microbiology, clinical signs, placental pathology, and neonatal bacteremia - implications for clinical care.

OBJECTIVES: Clinical chorioamnionitis at term is considered the most common infection-related diagnosis in labor and delivery units worldwide. The syndrome affects 5-12% of all term pregnancies and is a leading cause of maternal morbidity and mortality as well as neonatal death and sepsis. The objectives of this study were to determine the (1) amniotic fluid microbiology using cultivation and molecular microbiologic techniques; (2) diagnostic accuracy of the clinical criteria used to identify patients with intra-amniotic infection; (3) relationship between acute inflammatory lesions of the placenta (maternal and fetal inflammatory responses) and amniotic fluid microbiology and inflammatory markers; and (4) frequency of neonatal bacteremia. METHODS: This retrospective cross-sectional study included 43 women with the diagnosis of clinical chorioamnionitis at term. The presence of microorganisms in the amniotic cavity was determined through the analysis of amniotic fluid samples by cultivation for aerobes, anaerobes, and genital mycoplasmas. A broad-range polymerase chain reaction coupled with electrospray ionization mass spectrometry was also used to detect bacteria, select viruses, and fungi. Intra-amniotic inflammation was defined as an elevated amniotic fluid interleukin-6 (IL-6) concentration ≥2.6 ng/mL. RESULTS: (1) Intra-amniotic infection (defined as the combination of microorganisms detected in amniotic fluid and an elevated IL-6 concentration) was present in 63% (27/43) of cases; (2) the most common microorganisms found in the amniotic fluid samples were Ureaplasma species, followed by Gardnerella vaginalis; (3) sterile intra-amniotic inflammation (elevated IL-6 in amniotic fluid but without detectable microorganisms) was present in 5% (2/43) of cases; (4) 26% of patients with the diagnosis of clinical chorioamnionitis had no evidence of intra-amniotic infection or intra-amniotic inflammation; (5) intra-amniotic infection was more common when the membranes were ruptured than when they were intact (78% [21/27] vs. 38% [6/16]; p=0.01); (6) the traditional criteria for the diagnosis of clinical chorioamnionitis had poor diagnostic performance in identifying proven intra-amniotic infection (overall accuracy, 40-58%); (7) neonatal bacteremia was diagnosed in 4.9% (2/41) of cases; and (8) a fetal inflammatory response defined as the presence of severe acute funisitis was observed in 33% (9/27) of cases. CONCLUSIONS: Clinical chorioamnionitis at term, a syndrome that can result from intra-amniotic infection, was diagnosed in approximately 63% of cases and sterile intra-amniotic inflammation in 5% of cases. However, a substantial number of patients had no evidence of intra-amniotic infection or intra-amniotic inflammation. Evidence of the fetal inflammatory response syndrome was frequently present, but microorganisms were detected in only 4.9% of cases based on cultures of aerobic and anaerobic bacteria in neonatal blood.

The first thrombotic event in purely obstetric antiphospholipid syndrome patients and in antiphospholipid antibody carriers: comparison of incidence and characteristics.

PURPOSE: The long-term risk of thrombosis after pregnancy in women with purely obstetric antiphospholipid syndrome (OAPS) is not well defined. The current study's primary outcome was to evaluate the incidence and characteristics of the first thrombotic event in OAPS, identifying the risk factors for thrombosis in OAPS was its secondary one. METHODS: Patients with purely OAPS were consecutively enrolled between September 1999 and September 2019. Subjects without a history of pregnancy morbidity or thrombosis but with persistent positivity for one or more antiphospholipid antibodies (aPL carriers) made up the control group. The study groups included 94 OAPS patients and 124 aPL carriers who were matched for clinical and laboratory parameters. RESULTS: An event rate of 0.49/100 patient years was registered in OAPS patients during a mean follow-up of 8.7 years ± 5.5 SD. Kaplan-Meier survival analysis revealed that the cumulative incidence of thromboembolic events was not significantly different in OAPS patients vs aPL carriers. Arterial thrombosis and cerebrovascular events were the more frequent types of vascular involvement in the two groups. As far as risk factors for thrombosis were concerned, the presence of lupus anticoagulant significantly prevailed in both thrombotic OAPS patients and thrombotic aPL carriers with respect to purely OAPS patients and aPL carriers who did not develop thrombosis (p = 0.01 and p = 0.00, respectively). CONCLUSION: Just as for aPL carriers, closer monitoring and possibly, a pharmacological prophylaxis should be reserved for OAPS patients at highest risk of developing the first thrombotic event.

Caput Ligation Renders Immature Mouse Sperm Motile and Capable to Undergo cAMP-Dependent Phosphorylation.

Mammalian sperm must undergo two post-testicular processes to become fertilization-competent: maturation in the male epididymis and capacitation in the female reproductive tract. While caput epididymal sperm are unable to move and have not yet acquired fertilization potential, sperm in the cauda epididymis have completed their maturation, can move actively, and have gained the ability to undergo capacitation in the female tract or in vitro. Due to the impossibility of mimicking sperm maturation in vitro, the molecular pathways underlying this process remain largely unknown. We aimed to investigate the use of caput epididymal ligation as a tool for the study of sperm maturation in mice. Our results indicate that after seven days of ligation, caput sperm gained motility and underwent molecular changes comparable with those observed for cauda mature sperm. Moreover, ligated caput sperm were able to activate pathways related to sperm capacitation. Despite these changes, ligated caput sperm were unable to fertilize in vitro. Our results suggest that transit through the epididymis is not required for the acquisition of motility and some capacitation-associated signaling but is essential for full epididymal maturation. Caput epididymal ligation is a useful tool for the study of the molecular pathways involved in the acquisition of sperm motility during maturation.

The actin cytoskeleton of the mouse sperm flagellum is organized in a helical structure.

Conception in mammals is determined by the fusion of a sperm cell with an oocyte during fertilization. Motility is one of the features of sperm that allows them to succeed in fertilization, and their flagellum is essential for this function. Longitudinally, the flagellum can be divided into the midpiece, the principal piece and the end piece. A precise cytoskeletal architecture of the sperm tail is key for the acquisition of fertilization competence. It has been proposed that the actin cytoskeleton plays essential roles in the regulation of sperm motility; however, the actin organization in sperm remains elusive. In the present work, we show that there are different types of actin structures in the sperm tail by using three-dimensional stochastic optical reconstruction microscopy (STORM). In the principal piece, actin is radially distributed between the axoneme and the plasma membrane. The actin-associated proteins spectrin and adducin are also found in these structures. Strikingly, polymerized actin in the midpiece forms a double-helix that accompanies mitochondria. Our findings illustrate a novel specialized structure of actin filaments in a mammalian cell.

Super-resolution imaging of live sperm reveals dynamic changes of the actin cytoskeleton during acrosomal exocytosis.

Filamentous actin (F-actin) is a key factor in exocytosis in many cell types. In mammalian sperm, acrosomal exocytosis (denoted the acrosome reaction or AR), a special type of controlled secretion, is regulated by multiple signaling pathways and the actin cytoskeleton. However, the dynamic changes of the actin cytoskeleton in live sperm are largely not understood. Here, we used the powerful properties of SiR-actin to examine actin dynamics in live mouse sperm at the onset of the AR. By using a combination of super-resolution microscopy techniques to image sperm loaded with SiR-actin or sperm from transgenic mice containing Lifeact-EGFP, six regions containing F-actin within the sperm head were revealed. The proportion of sperm possessing these structures changed upon capacitation. By performing live-cell imaging experiments, we report that dynamic changes of F-actin during the AR occur in specific regions of the sperm head. While certain F-actin regions undergo depolymerization prior to the initiation of the AR, others remain unaltered or are lost after exocytosis occurs. Our work emphasizes the utility of live-cell nanoscopy, which will undoubtedly impact the search for mechanisms that underlie basic sperm functions.This article has an associated First Person interview with the first author of the paper.

Metabolic changes in mouse sperm during capacitation†.

Mammalian sperm are stored in the epididymis in a dormant state. Upon ejaculation, they must immediately start producing sufficient energy to maintain motility and support capacitation. While this increased energy demand during capacitation is well established, it remains unclear how mouse sperm modify their metabolism to meet this need. We now show that capacitating mouse sperm enhance glucose uptake, identifying glucose uptake as a functional marker of capacitation. Using an extracellular flux analyzer, we show that glycolysis and oxidative phosphorylation increase during capacitation. Furthermore, this increase in oxidative phosphorylation is dependent on glycolysis, providing experimental evidence for a link between glycolysis and oxidative phosphorylation in mouse sperm.

Testis-specific serine kinase protein family in male fertility and as targets for non-hormonal male contraception†.

Male contraception is a very active area of research. Several hormonal agents have entered clinical trials, while potential non-hormonal targets have been brought to light more recently and are at earlier stages of development. The general strategy is to target genes along the molecular pathways of sperm production, maturation, or function, and it is predicted that these novel approaches will hopefully lead to more selective male contraceptive compounds with a decreased side effect burden. Protein kinases are known to play a major role in signaling events associated with sperm differentiation and function. In this review, we focus our analysis on the testis-specific serine kinase (TSSK) protein family. We have previously shown that members of the family of TSSKs are postmeiotically expressed in male germ cells and in mature mammalian sperm. The restricted postmeiotic expression of TSSKs as well as the importance of phosphorylation in signaling processes strongly suggests that TSSKs have an important role in germ cell differentiation and/or sperm function. This prediction has been supported by the reported sterile phenotype of the Tssk6 knockout (KO) mice and of the double Tssk1 and Tssk2 KO mice and by the male subfertile phenotype observed in a Tssk4 KO mouse model.

Capacitation increases glucose consumption in murine sperm.

Mammalian sperm acquire fertilization capacity in the female reproductive tract in a process known as capacitation. During capacitation, sperm change their motility pattern (i.e., hyperactivation) and become competent to undergo the acrosome reaction. We have recently shown that, in the mouse, sperm capacitation is associated with increased uptake of fluorescently labeled deoxyglucose and with extracellular acidification suggesting enhanced glycolysis. Consistently, in the present work we showed that glucose consumption is enhanced in media that support mouse sperm capacitation suggesting upregulation of glucose metabolic pathways. The increase in glucose consumption was modulated by bicarbonate and blocked by protein kinase A and soluble adenylyl cyclase inhibitors. Moreover, permeable cyclic adenosine monophosphate (cAMP) agonists increase glucose consumption in sperm incubated in conditions that do not support capacitation. Also, the increase in glucose consumption was reduced when sperm were incubated in low calcium conditions. Interestingly, this reduction was not overcome with cAMP agonists. Despite these findings, glucose consumption of sperm from Catsper1 knockout mice was similar to the one from wild type suggesting that other sources of calcium are also relevant. Altogether, these results suggest that cAMP and calcium pathways are involved in the regulation of glycolytic energy pathways during murine sperm capacitation.