The cytoplasmic droplet may be indicative of sperm motility and normal spermiogenesis

Although the cytoplasm of spermatids is removed at the end of spermiogenesis, a tiny portion is usually retained in the sperm flagellum, which is termed the cytoplasmic droplet （CD） in mammals. CDs are believed to play a role in sperm volume adaptation. However, we have noticed that epididymal spermatozoa that display initial （flagellation in situ） and progressive motility mostly possess CDs, whereas spermatozoa without CDs are rarely motile, suggesting that CDs have a role in motility development during sperm epididymal maturation. In the present study, we analyzed the relationship between the presence or absence of CDs, motility development and positional changes of CDs during sperm epididymal maturation in mice and monkeys. We also examined CDs on spermatozoa of three knockout mouse lines with late spermiogenic defects. Our data suggest that the CD is a normal organelle transiently present exclusively on epididymal spermatozoa, and normal CD morphology and location are associated with normal motility development during epididymal maturation of spermatozoa. Abnormal CD formation, e.g., a complete lack of CDs or ectopic CDs, is indicative of defective spermiogenesis. If CDs are essential for sperm motility development, then CDs may represent an ideal drug target for the development of non-hormonal male contraceptives.

Localization of AKAP4 and tubulin proteins in sperm with reduced motility

Aim： To perform screening, related to A-kinase anchoring proteins 4 （AKAP4） and tubulin proteins, in spermatozoa with absent or severely reduced motility in order to detect the status of the fibrous sheath and the axonemal structure. Methods： An immunocytochemical study of tubulin, used as a positive control, and AKAP4 was carded out to detect the presence and the distribution of these proteins in different sperm samples. The morphological characteristics of sperm were studied by transmission electron microscope （TEM） and the results were elaborated using a formula reported in previous studies. PCR was carried out on DNA extracted from peripheral blood lymphocytes to analyse partial sequences of the Akap4 and Akap3 genes. Results： Immunolabelling of tubulin and AKAP4 showed different patterns, which led us to divide the patients into groups. In group I, the absence of AKAP4 and tubulin was revealed, although these patients did not show alterations in the Akap4/Akap3 binding site. TEM evaluation highlighted that a high presence of necrosis was associated with total sperm immotility. In group Ⅱ, a regular AKAP4 and tubulin signal was present, although motility was reduced and TEM analysis revealed the presence of immaturity. In group Ⅲ, in which a weak AKAP4 label associated with normal tubulin staining and reduced motility was observed, a severe disorganization of the fibrous sheath was highlighted by TEM. Conclusion： While the role of AKAP4 in sperm motility is unclear, absent or weak AKAP4-1abelling seems to be associated with absent or weak sperm motility.

Sperm motility inhibitory effect of the benzene chromatographic fraction of the chloroform extract of the seeds of Carica papaya in langur monkey, Presbytis entellus entellus

Aim： To assess the contraceptive efficacy of the benzene chromatographic fraction of the chloroform extract of the seeds of Carica papaya in langur monkeys. Methods： The test substance was given p.o. to five monkeys at 50 mg/kg body weight/day for 360 days. Control animals （n = 3） received olive oil as vehicle. Sperm parameters as per World Health Organization standards, sperm functional tests, morphology of testis and epididymis, haematology, clinical biochemistry, serum testosterone and libido were evaluated. Following completion of 360 days treatment the animals were withdrawn from the treatment and the recovery pattern was assessed by semen analysis and sperm functional tests. Results： Total inhibition of sperm motility was observed following 60 days of treatment that continued until 360 days study period. Sperm count, percent viability and percent normal spermatozoa showed a drastic decline following 30 days of treatment. Sperm morphology showed predominant mid piece abnormalities. Sperm functional tests scored in sterile range. Histology and ultrastructure of testis revealed vacuolization in the Sertoli cells and germ cells. Loss of cytoplasmic organelles was evident in spermatocytes and round spermatids. Histology and ultrastructure of epididymis of treated animals were comparable to those of control animals. Hematological and serum clinical parameters and testosterone levels fluctuated within the control range throughout the study period. Recovery was evident following 60--120 days of treatment withdrawal. Conclusion- The results suggest that the benzene chro- matographic fraction of the chloroform extract of the seeds of Carica papaya shows contraceptive efficacy without adverse toxicity, mediated through inhibition of sperm motility. （Asian JAndro12008 Mar; 10： 298-306）

Studies on the Relationship between Urokinase Plasminogen Activator(uPA)and Human Sperm Motility

To clarify the role of urokinase plasminogen activator(uPA) in the mechanisms of regulating sperm motility and the ability of fertilizing, we investigated the quantities and activities of uPA in human seminal Plasma and on the membrane of spermatozoa.Semens were harvested from 22 infertile patients with asthenospermia and 20 healthy fertile men according to WHO standards. To quantify the membrane-bound uPA in the samples, polyclonal antibodies against human urokinase were employed by means of a sandwich ELISA. The uPA activities in seminal plasma and on the surface of spermatozoa were determined using Agarose-Fibrine-Plate method and the experiment of immunological identification with polyclonal antibodies against urokinase. In lysates of spermatozoa, significantly lower levels of uPA(23. 1±7.35 mu/106 cells ) and uPA activity (5.13±3.85 mu/106 cells) were found in patient group as compared to healthy fertile men exhibiting normospermia (29. 89±9. 40 mu/105 cells and 10. 17±6. 18 mu/106 cells). In seminal plasma, uPA activity in patient group (2134±1581. 3 IU/L)was also found significantly lower than that of normal group (3365±1859. 5 IU/L). Positive correlations were observed between sperm motility and uPA quantities (r=0. 48, P＜0. 005), as well as with uPA activities (r= 0. 45,P＜0. 005).Thus, it is inferred that membrane associated uPA on human spermatozoa may be related directly to sperm motility and fertility.

Optimal analysis conditions for sperm motility parameters with a CASA system in a passerine bird, Passer montanus

Background:Sperm motility parameters,which can be measured objectively and repeatedly by a computer-assisted sperm analysis(CASA)system,are important indicators of sperm quality.However,the sperm motility parameters assessed by a CASA system can be affected by various factors,including instrument components and settings,sperm preparation or analysis procedures.To date,no standardized protocol is available that would permit to assess sperm kinetic characteristics in passerine birds and this lack precludes any comparison of sperm swimming ability and sperm quality across species.Methods:In this study,we chose the Tree Sparrow(Passer montanus)as the object to evaluate sperm motility parameters,including sperm motility,sperm velocity and sperm movement trajectory,at different analysis time,temperatures and pH using the WLJY-9000 CASA system.Results:Sperm motility parameters remained statistically unchanged at 1‒9 min.Progressive motility was similar at 38℃ and 40℃,but a greater percentage of slow progressive sperm was detected at 38℃ compared to 40℃ and 42℃.Additionally,progressive motility was lower and immotility was higher at 42℃than 38℃and/or 40℃(close to the body temperature of the Tree Sparrow).The percentages of rapid progressive sperm,progressive sperm and immotile sperm were statistically similar at pH 7.0,7.5 and 8.0 with the exception of lower percentage of progressive sperm at pH 7.0 compared to pH 7.5.In addition,slower sperm velocity and worse sperm movement trajectory were found at pH 6.0 and 9.0 than those at pH 8.0,7.5 or 7.0.Conclusions:Our study indicates that the ideal conditions for sperm motility parameters assessment in Tree Sparrow are obtained between 1 and 9 min after dilution,an environment at body temperature(40℃)and a pH around 7.5-8.0.The results of this study provide a reference for the evaluation of sperm characteristics and sperm quality using a CASA system in passerine birds.

Influences of dibutyryl cyclic adenosine monophosphate and forskolin on human sperm motility in vitro

Aim: To study the influences of dibutyryl cyclic adenosine monophosphate (dbcAMP) and forskolin on human sperm motility in vitro. Methods: Semen samples, aseptically obtained by masturbation and prepared by swim-up technique from 20 fertile men, were incubated with different concentrations of dbcAMP and forskolin at 37 癈. Measurements were carried out after 10 min, 20 min, 30 min and 60 min incubation. Motility parameters were estimated by using an automatic analyzing system. Results: Treatment with dbcAMP or forskolin resulted in a significant increase in sperm motility and progressive motility. The larger the concentrations of dbcAMP or forskolin, the greater the effect appeared. The straight linear velocity and curvilinear velocity were not affected by both agents. Conclusion: dbcAMP and forskolin increase the motility and progressive motility of human sperm in vitro.

Evaluation of effects of 1,3-dinitrobenzene on sperm motility of hamster using computer assisted semen analysis (CASA)

Aim: To evaluate the effects of 1,3-dinitrobenznene (mDNB) on sperm motility of hamster and to correlate the re-sults with the fertility. Methods: Adult male hamsters were gavaged with one of the 3 dose regimes of mDNB(1.5 mg daily for 4 weeks ,1.5 mg one day a week for 4 weeks and 1.0 mg 3 days a week for 4 weeks). Computerassisted semen analysis (CASA) was used to analyse the sperm motility parameters, curvilinear velocity (VCL) andstraight line velocity (VSL) of sperm in distal corpus epididymides and distal cauda epididymides. In vitro fertilisationwas carried out only for 1.5 mg mDNB daily group to determine the sperm fertilising capacity. Results: There wasa significant reduction in sperm velocity parameters at weeks 3 and 4 after treatment, which was correlated with a de-cline in sperm fertility. Conclusion; Sperm velocity parameters may be used to determine the effect of a toxic insulton the sperm function.

Inhibition of sperm motility does not affect live-dead separation of bull sperm by glass beads

Aim: This study was designed to explore factors which influence binding of dead versus live sperm to glass filters.Methods: Multiple semen collections from bulls were used to explore selective filtration of bull sperm as influencedby nonlethal inhibition of sperm motility with fluoride, killing of sperm by quick-freezing, alteration of the glass sur-face with silicone, and different intervals of sexual rest between semen collections. Results: A comparison of glassspheres 100, 200 and 390μm in diameter indicated that 200 μm spheres were optimal for selective filtration. Quantita-tive separation of live from dead sperm was demonstrated with a correlation between the percentage of motile sperm andretention of sperm by the filter of r = -0.87 (P < 0.05). Up to 0.02 mol/L NaFl did not alter the proportion ofsperm retained by the filter despite inhibiting sperm motility during filtration, an inhibition which was reversible. Pro-portions of live-dead sperm, based upon eosin staining, were unaffected by fluoride. Coating the glass spheres with sil-icone greatly reduced selective filtration. Dead sperm adherence to glass was reduced and resistance to NaFl inhibitionwas increased by daily ejaculation versus one-week intervals of sexual rest. Conclusion; These studies indicate thatthe adherence of sperm to glass is primarily due to some form of physico-chemical change accompanying death of thesperm cell independent of active sperm motility. This attraction between the sperm plasma membrane and glass is modi-fied by the age of the ejaculated sperm. This information is useful in evaluating different clinical procedures used forsperm separation. (Asian J Androl 2001 Sep; 3: 193-198)

Effects of Environment Factors on Initiation of Sperm Motility in Sea Cucumber Apostichopus japonicus (Selenka)

Sperm of sea cucumber Apostichopus japonicus (Selenka) were quiescent in electrolyte NaCl solution and artificial seawater (ASW) and nonelectrolyte glucose and mannitol solutions when the osmolality was less than 200 mOsm kg-1. The sperm started to be motile as a result of increased osmolality, indicating an osmolality-dependent initiation of sperm motility in sea cucumber. After a brief incubation in hypotonic NaCl and glucose solutions with osmolalities of 200 and 400 mOsm kg-1, sperm lost partial motile ability. Sperm became immobilized when pH was 6.0 in NaCl, glucose and mannitol solutions, suggesting that an H+ release is involved in sperm activation. The decreased pH had no effect on the percentage of motile sperm in ASW, whereas it delayed the time period to reach the maximum motility (motilitymax). Extracellular Ca2+ in electrolyte solutions was not essential for motility stimulation but shortened the time of reaching motilitymax. When Ca2+ was mixed in nonelectrolyte solutions the sperm motility was completely suppressed. The K+ channel blocker, quinine, suppressed the sperm motility in electrolyte solution, showing a possible involvement of K+ transport in the process. High K+ concentration did not affect the sperm motility in NaCl solution, but decreased it in ASW and almost entirely suppressed it in nonelectrolyte solutions. The different effects of pH and K+ in ASW and NaCl solution indicate that external ions may also regulate sperm motility.

Anti-VDAC3 recombinant antibody decreased human sperm motility and membrane integrity: A potential spermicide for contraception

Objective:To express recombinant protein that comprises an important fragment of human sperm specific voltage dependent anion channel 3 (VDAC3) protein as a potential molecule for generation of antibody, which can affect sperm function, aiming at spermicide development. Methods: The produce of VDAC3 recombinant protein encoded by cDNA sequence of human VDAC3 exon 5-8, based on experimental design of VDAC3 knock-out mice study. And after the purification of various human sperm VDAC3 recombinant proteins, epitope has been predicted in our recombinant protein determined by ElliPro program. Polyclonal antibody was produced for 14 wk. Then anti-VDAC3-exon 5-8 recombinant antiserum was inoculated to human sperm. After the process, antibody VDAC3 protein in human sperm was incubation with anti-VDAC3 recombinant antibody. Finally evaluation the effect of VDAC3 antiserum to human sperm motility and plasma membrane integrity was proceeded.Results: Human VDAC3 recombinant protein was successfully over-expressed in Escherichia coli and purified by affinity chromatography method. Purified human sperm VDAC3 recombinant protein could stimulate immune response in rabbit producing an antibody against VDAC3. Anti-VDAC3 recombinant antibody recognized VDAC3 antigen in human sperm could decrease human sperm motility and membrane integrity significantly.Conclusions:Anti-VDAC3 recombinant polyclonal antibody that we produced in rabbit by ourselves could decrease sperm motility and sperm membrane integrity. The authors suggest this polyclonal antibody could be used as a candidate agent for male contraception in the future. Furthermore, the authors intend to explore the effect of this antibody into sperm function aiming at male contraceptive vaccine development.

B超监测梅花鹿性控精液腹腔镜输精试验

梅花鹿常规冻精与性控冻精解冻后进行品质鉴定,结合B超监测卵泡有选择的对60只同期发情处理的梅花鹿进行腹腔镜精准输精。数据分析显示,同期发情处理后梅花鹿卵巢B超监测结果与腹腔镜输精受胎率存在明显的正相关;X和Y型冻精产仔率为83.33%,而常规冻精产仔率为65.31%,X、Y型冻精与常规冻精组间差异显著(P<0.05);常规冻精组、X冻精组与Y冻精组所产后代性别比(公/母)分别为9:8、0:10和16:1,X、Y型冻精与常规冻精组间差异显著(P<0.05),X、Y型冻精与常规冻精所产后代出生及60 d时的体重差异不显著(P <0.05)。结果表明,结合B超监测有选择的进行梅花鹿性控精液腹腔镜人工输精,可显著提高受胎率,降低成本,技术可行。

Influence of several uropathogenic microorganisms on human sperm motility parameters in vitro

Aim: The effects of certain uropathogenic microorganisms (Neisseria gonorrhoeae, Staphylococcus aureus, Staphylococcus epidermidis and Mycobacterium tuberculosis) on human sperm motility characteristics were studied in vitro. Methods: In 10 healthy fertile men, ejaculates were aseptically obtained by masturbation and With a swim-up technique, a sperm suspension of high motility and purity was obtained. Several uropathogenic bacteria were obtained from outpatients with genitourinary tract infections. The sperm suspension was incubated with the pathogens at a bacteria: sperm ratio of 50:1 at 37℃. The sperm mobility parameters were estimated with a computerassisted sperm analyzer (CASA) provided with a multiple-exposure photography system (Madi Corp., Zhejiang, China). Measurements were carried out at 0, 2 and 4 hours of incubation. Results: Staphylococcus aureus significantly decreased the sperm motility and viability, but Staphylococcus epidermidis, Mycobacterium tuberculosis and Neisseria gonorrhoeae did not. Conclusion: Staphylococcus aureus has an inhibitory effect on human sperm motility in vitro.

Protein phosphatase PP1γ2 in sperm morphogenesis and epididymal initiation of sperm motility

The serine/threonine phosphatase （PP1） isoform PP1γ2, predominantly expressed in the testis, is a key enzyme in spermatozoa. High PP1γ2 catalytic activity holds motility in check in immature spermatozoa. Inhibition of PP1γ2 causes motility initiation in immature spermatozoa and motility stimulation and changes in flagellar beat parameters in mature spermatozoa. The PP1γ2 isoform is present in all mammalian spermatozoa studied： mouse, rat, hamster, bovine, non-human primate and man. We have now identified at least four of its regulatory proteins that regulate distinct pools of PP1γ2 within spermatozoa. Our studies provide new insights into biochemical mechanisms underlying development and regulation of sperm motility. We hypothesize that changes in sperm PP1γ2 activity as a result of phosphorylation and reversible binding of the regulatory proteins to the catalytic subunit are critical in the development and regulation of motility and the ability of sperm to fertilize eggs. Targeted disruption of the Ppplcc gene, which encodes the PP1γ1 or PP1γ2 isoforms, causes male infertility in mice as a result of impaired spermiogenesis. Our observations suggest that, in addition to motility, the protein phosphatase PP1γ2 might play an isoform-specific function in the development of specialized flagellar structures of mammalian spermatozoa. （Asian J Androl 2007 July; 9： 445--452）

Evaluation on Sensitivity of the Human Sperm Motility Assay for Detecting Endotoxin in Culture Medium

Objective To investigate the sensitivity of the human sperm motility assay for detecting endotoxin in culture mediumMaterials &. Methods Motile sperm were separated and exposed to different concentrations of endotoxin (0.5 ng/mL, 1ng/mL, 10ng/mL, 1000ng/mL, 10 000ng/ mL, and 50 000ng/mL), and sperm motility was determined after incubation. Effects of endotoxin on sperm motility in media without albumin were also examined. In addition, at the same concentrations of endotoxin (0. 5ng/mL, 1 ng/mL, and 10 ng/ mL ) , the sensitivity of the human sperm motility assay was compared to those of 1-cell and 2-cell mouse embryo bioassays.Results At levels of 0. 5ng/mL-1000ng/mL endotoxin in media with 2mg/mL albumin, sperm did not show significant change in motility during 24 h of incubation when compared with the control (P>0. 05). However, the sperm motility was significantly inhibited at endotoxin dosages of 10 000 and 50 000 ng/mL. In the absence of albumin supplementation, at endotoxin levels of 50 000ng/mL, and 1 000ng/mL, there was a marked decrease in sperm motility compared with the control after 2 h or 8 h of incubation, respectively (P<0. 01). In media containing 0. 5 ng/mL and 1 ng/ mL endotoxin, 1-cell and 2-cell mouse embryos had significantly reduced developmental rates in all developmental stages, and at the level of 10ng/mL, the development of the embryos was arrested. Conclusion The human sperm motility assay could detect high levels of endotoxin in culture medium but its sensitivity to endotoxin would be inferior to that of the 1-cell or 2-cell mouse embryo bioassay. In the absence of albumin supplementation, the sensitivity of the sperm motility assay could be improved.

Effect of vitamin E on human sperm motility and lipid peroxidation in vitro

Aim: To assess the protective efficacy of vitamin E to counteract the reactive oxygen species (ROS) mediated damage onsperm motility, viability and lipid peroxidation. Methods: Human semen samples were obtained from the local hospi-tal. The split seminal fractions freed of seminal plasma were reconstituted in Ringer-Tyrode and subjected to varied vita-min E concentrations (0.1 - 2 mmol/L). Results: Dose-dependent improvement in both motility and viability accom-panied by concomitant decrease in malondialdehyde (MDA--an end product of lipid peroxidation) following vitamin Esupplementation was noticed. Conclusion: Vitamin E protects against the ROS mediated damage on spermatozoa.Vitamin E supplementation could be of clinical importance for prolonged spermatozoal storage whenever needed. (AsianJ Androl 1999 Sep; 1: 151 - 154 )

Estimate of oxygen consumption and intracellular zinc concentration of human spermatozoa in relation to motility

<abstract>Aim: To investigate the human sperm oxygen/energy consumption and zinc content in relation to motility. Methods: In washed spermatozoa from 67 ejaculates, the oxygen consumption was determined. Following calculation of the total oxygen consumed by the Ideal Gas Law, the energy consumption of spermatozoa was calculated. In addition, the zinc content of the sperm was determined using an atomic absorption spectrometer. The resulting data were correlated to the vitality and motility. Results: The oxygen consumption averaged 0.24μmol/106 sperm×24 h, 0.28μmol/106 live sperm×24 h and 0.85μmol/106 live & motile sperm×24 h. Further calculations revealed that sperm motility was the most energy consuming process (164.31 mJ/106 motile spermatozoa×24 h), while the oxygen consumption of the total spermatozoa was 46.06 mJ/106 spermatozoa×24 h. The correlation of the oxygen/ energy consumption and zinc content with motility showed significant negative correlations (r= -0.759; P<0.0001 and r=-0.441; P<0.0001, respectively). However, when correlating sperm energy consumption with the zinc content, a significant positive relation (r=0.323; P=0.01) was observed. Conclusion: Poorly motile sperm are actually wasting the available energy. Moreover, our data clearly support the 'Geometric Clutch Model' of the axoneme function and demonstrate the importance of the outer dense fibers for the generation of sperm motility, especially progressive motility.

Effect of peroxiredoxin 6 on total and progressive motility of human spermatozoa after cryopreservation

Sperm cryopreservation is useful in assisted reproductive technology and male fertility preservation.However,freezing and thawing significantly reduces the total and progressive motility of human spermatozoa.In the present study,we explored the effects of peroxiredoxin 6(PRDX6)on total and progressive motility of human spermatozoa after cryopreservation.Semen samples of 20 males with normal parameters were collected and frozen in media supplemented with different concentrations of PRDX6(0 mM,10−5 mM,10−7 mM,and 10−9 mM,respectively).Postthaw total and progressive motility of sperms were measured.The results showed that in comparison with 0 mM,the concentrations of 10−5 mM,10−7 mM,and 10−9 mM of PRDX6 all significantly improved total motility and progressive motility of sperms(p<0.05).The 10−7 mM of PRDX6 showed the best performance.In conclusion,the supplementation of PRDX6 helps to maintain the total and progressive motility of human spermatozoa.

Addition of peroxiredoxin 6 (PRDX6) to IVF fertilization medium maintains motility and longevity of human spermatozoa

This study aims to investigate the protective effects of peroxiredoxin 6 on the total motility and progressive motility of human spermatozoa.Semen samples with normal parameters were collected from 23 males and supplemented with different concentrations of peroxiredoxin 6.All the semen samples were measured according to the WHO 5th manual,and the motile spermatozoa were extracted using IVF fertilization medium supplemented with different peroxiredoxin 6 concentrations.Total motility and progressive motility were observed at different time-points of culture at room temperature.After peroxiredoxin 6 supplementation,all groups had a significant increase in total motility and progressive motility compared to the control group.The difference in total motility and progressive motility between the 0 and 10−7 mM groups was observed at 24 and 48 h of culture at room temperature.At 24 h,the total motility increased by 30%in the control group(16.03±11.91 vs.11.51±7.84),and progressive motility increased by 21%(10.53±9.4 vs.8.31±6.04).A similar trend was observed in the 48 h group.In addition,we also found that peroxiredoxin 6 had a well protective effect on sperm kinetic parameters at 10−7 mM.The findings of this study suggest that peroxiredoxin 6 can enhance sperm total motility and progressive motility in IVF fertilization medium.Peroxiredoxin 6 may have potential benefits for sperm preparation in assisted reproductive technology.

Sperm function, mitochondrial activity and in vivo fertility are associated to their mitochondrial DNA content in pigs

Background Despite their low abundance in sperm, mitochondria have diverse functions in this cell type, includ-ing energy production, signalling and calcium regulation. In humans, sperm mitochondrial DNA content(mtDNAc) has been reported to be negatively linked to sperm function and fertility. Yet, the association between mtDNAc and sperm function in livestock remains unexplored. For this reason, this study aimed to shed some light on the link between mtDNAc and sperm function and fertilising potential in pigs. A qPCR method for mtDNAc quantification was optimised for pig sperm, and the association of this parameter with sperm motility, kinematics, mitochondrial activity, and fertility was subsequently interrogated.Results First, the q PCR method was found to be sensitive and efficient for mtDNAc quantification in pig sperm. By using this technique, mtDNAc was observed to be associated to sperm motility, mitochondrial activity and in vivo, but not in vitro, fertility outcomes. Specifically, sperm with low mtDNAc were seen to exhibit greater motility but decreased mitochondrial activity and intracellular reactive oxygen species. Interestingly, samples with lower mtD-NAc showed higher conception and farrowing rates, but similar in vitro fertilisation rates and embryo development, when compared to those with greater mtDNAc.Conclusions These findings enrich our comprehension of the association of mtDNAc with sperm biology, and lay the foundation for future research into employing this parameter as a molecular predictor for sperm function and fer-tility in livestock.

Pyruvate kinase M in germ cells is essential for sperm motility and male fertility but not spermatogenesis

Male germ cells employ specific metabolic pathways throughout their developmental stages.In a previous study,we discovered heightened expression of pyruvate kinase M(PKM),a pivotal glycolytic enzyme,in spermatogonia and spermatids.To gain deeper insights into PKM's roles in spermatogenesis,sperm function,and male fertility,we engineered a conditional-knockout mouse model(Pkm-vkO mice)to selectively disrupt the Pkm gene within germ cells.Despite maintaining regular testicular histology and sperm morphology,the male Pkm-vko mice were infertility,characterized by significant impairments in sperm motility and adenosine triphosphate(ATP)generation.In addition,Pkm-null spermatozoa exhibited similar deficits in protein tyrosine phosphorylation linked to capacitation,as well as compromised performance in in vitro fertilization experiments.To conclude,PKM's presence is not obligatory for the entirety of spermatogenesis in male germ cells;however,it emerges as a critical factor influencing sperm motility and overall male fertility.