Chromosome analysis of BALB/c mouse spermatozoa with normal and abnormal head morphology

Melphalan induced germ cell toxicity and dose-dependent effects of β-aminoisobutyric acid in experimental rat model: Role of oxidative stress, inflammation and apoptosis

The success of chemotherapy regimens has led to an increase in cancer survival rate over the last decades. Melphalan has been widely used for the treatment of several types of cancers despite its gonadotoxic effects. Due to its ability to cause mutations in the spermatogonial stem cells and spermatids, melphalan can exert a negative impact on male reproductive health in young cancer survivors. β-aminoisobutyric acid (BAIBA), a myokine released by skeletal muscles, has been reported to have beneficial effects in diabetic nephropathy, cardiomyopathy and hepatic toxicity. However, the exact role of BAIBA in chemotherapy-induced germ cell toxicity is still unexplored. The present study aims to determine the dose-dependent (25, 50, and 100 mg/kg) effects of BAIBA on melphalan-induced (1.5 mg/kg) germ cell toxicity in sprague-dawley (SD) rats. The evaluation parameters included quantification of oxidative stress biomarkers, sperm count, sperm motility and head morphology, sperm and testicular DNA damage, sperm mitochondrial membrane potential, ultrastructural changes in sperms, histological and protein expression studies in testes. Melphalan treatment significantly altered all the above-mentioned parameters and the high dose (100 mg/kg) of BAIBA restored melphalan-induced toxicity in a significant manner by exerting antioxidant, anti-inflammatory and antiapoptotic effects. However, the medium dose (50 mg/kg) of BAIBA decreased the toxicity of melphalan and the low dose (25 mg/kg) of BAIBA failed to counteract the melphalan-induced male germ cell toxicity as well as the peripheral blood micronucleus induction. The antioxidant, anti-inflammatory and antiapoptotic role of BAIBA in melphalan-induced gonadal damage is a novel finding in an experimental rat model.

Comparative effects of finasteride and laser-irradiated silver nanoparticles on testicular function and histology in testosterone induced benign prostatic hyperplasia in rats

AIMS

The objective of this study was to compare the effects of finasteride, a medication used to treat benign prostatic hyperplasia (BPH), and laser irradiated silver nanoparticles (AgNPs), a potential candidate for BPH therapy (Sanchez-Salas, 2017; Marghani et al., 2022) [1,2], on the sex hormone profiles, sperm quality, steroidogenesis, testicular oxidative stress, and histomorphology changes in BPH rats.

MATERIALS AND METHODS

BPH was induced in male Sprague-Dawley (SD) rats via intramuscular (i.m.) injection of 5 mg/kg BW testosterone propionate (TP) for 14 days. Once the BPH model was induced, rats were divided into four groups (n = 6) as follows: the control group; the BPH group; the BPH/Fina group, which received 5 mg/kg BW finasteride by oral gavage daily for 14 days; and the BPH/AgNPs group, which received a daily intraperitoneal (i.p.) injection of 50 mg/kg BW AgNPs, followed by 5 min of exposure to a 532 nm NIR laser in the prostatic area for the constitutive 14 days.

KEY FINDINGS

On day 14, the BPH rats had a significant increase in prostate specific antigen (PSA), dihydrotestosterone, and prostate weights, while testicular weights and sperm quality were significantly lower than in the control rats. On day 28, laser irradiated AgNps treated BPH rats showed improved sex hormone balance, testicular weights, sperm quality, steroidogenesis, and an ameliorative effect on testicular histopathology compared to finasteride.

SIGNIFICANCE

Surprisingly, these findings suggest that laser irradiated AgNPs can be used as an alternative therapy to finasteride for the treatment of BPH without causing negative effects on the testes.

Juvenile exposure and adult risk assessment with single versus repeated exposure of melphalan in the germ cells of male SD rat: Deciphering the molecular mechanisms

Melphalan significantly contributes to the increase in childhood cancer survival rate. It acts as a gonadotoxic agent and leads to testes damage, dysbalance in gonadal hormones, and impairment in the germ cell proliferation. Therefore, it might be a potent threat to male fertility in individuals who have undergone melphalan treatment during childhood cancer. However, the molecular mechanisms of melphalan-induced gonadal damage are not yet fully explored and they need to be investigated to determine the benefit-risk profile. In the present study, juvenile male SD rats were subjected to single and intermittent cycles of melphalan exposure in a dose-dependent (0.375, 0.75 and 1.5 mg/kg) manner. Methods of end-points evaluations were quantification of micronuclei formation in peripheral blood, sperm count, sperm motility and head morphology, sperm and testicular DNA damage, histological studies in testes, oxidative/nitrosative stress parameters. A single cycle of exposure at high dose (1.5 mg/kg) produced significant effect on micronuclei formation only after the first week of exposure, whereas failed to produce significant effect at the end of the sixth week. Intermittent cycles of exposure at the dose of 1.5 mg/kg produced significant alterations in all the parameters (micronuclei in peripheral blood, testes and epididymides weight and length, MDA, GSH and nitrite levels, sperm count and motility, sperm head morphology, testicular and sperm DNA damage, protein expression in testes and histological parameters). So, time of exposure as well as the amount of exposure (total dosage administered) is critical in determining the magnitude of the damage in germ cell risk assessment.

In vitro fertilization using sperm activated by ML-2-3 isolated from Morinda lucida Bentham leaves

Purpose

ML-2-3 is a novel tetracyclic iridoid derived from Morinda lucida Bentham leaves. This compound has anti-trypanosomal and anti-leishmanial effects. In this study, the authors investigated effects of ML-2-3 on in vitro fertilization (IVF) rates, motility, and acrosome reaction of the mouse sperm.

Methods

IVF was performed using sperm from BALB/cByJJcl mice treated with ML-2-3. Computer-assisted sperm analysis (CASA) was performed on the sperm of C57BL/6J mice to investigate sperm motility. The effect of ML-2-3 on the acrosome reaction was examined by observing the fluorescence of sperm labeled with the acrosin-EGFP transgene.

Results

ML-2-3 improved IVF in BALB/cByJJcl mice with low fertilization rates. The optimum concentration of ML-2-3 in sperm pre-culture medium was 20 µM, and no significant toxicity of ML-2-3 was observed in developing embryos at this concentration. ML-2-3 affected sperm motility but not the acrosome reaction. ML-2-3 increased the IVF rate of mouse sperm that had been refrigerated for 3 days.

Conclusions

ML-2-3 can improve the outcome of IVF and motility without inducing the acrosome reaction in mice. These effects of ML-2-3 on sperm behaviors are different from those of the similar drugs.

Early warming stress on rainbow trout juveniles impairs male reproduction but contrastingly elicits intergenerational thermotolerance

The exposure of adult fish to warm or high temperatures is known to impair reproduction, yet the long-term reproductive impacts for treatments at early life are not well clarified. This study aimed to evaluate the effects of warm temperature (WT) during juvenile stage on gonad maturation, gamete quality, and offspring thermotolerance in rainbow trout. While the comparison of basic reproductive parameters in WT females did not reveal any kind of impairment, many WT males showed an atrophied, undeveloped gonad, or a smaller testis with lower milt volume; sperm quality parameters in WT males and deformity rates in the respective progeny were also highly affected. However, despite of such negative effects, many of the remaining progeny presented better rates of survival and growth when exposed to the same conditions as those of parental fish (WT), suggesting that thermal stress in parr stage males elicited intergenerational thermotolerance after a single generation. The present results support that prolonged warming stress during early life stages can adversely affect key reproductive aspects, but contrastingly increase offspring performance at upper thermal ranges. These findings have implications on the capacity of fish to adapt and to cope with global warming.

Protective effect of vitamin E on sperm parameters, chromatin quality, and DNA fragmentation in mice treated with different doses of ethanol: An experimental study

BACKGROUND

Excessive consumption of alcohol induces an increase in oxidative stress production and can lead to detrimental effects on the male reproductive system.

OBJECTIVE

To evaluate the possible protective effects of coadministration of vitamin (vit) E on the detrimental changes in the sperm quality of mice administered ethanol.

MATERIALS AND METHODS

Fifty-four BALB/c mice were categorized into nine groups (n = 6/each). The control group received a basal diet while the eight experimental groups received ethanol 10%; ethanol 20%; vit. E 100 mg; vit. E 200 mg; ethanol 10% + vit. E 100 mg; ethanol 10% + vit. E 200 mg; ethanol 20% + vit. E 100 mg; ethanol 20% + vit. E 200 mg. After 35 days, the sperm parameters and sperm chromatin were assessed.

RESULTS

The results demonstrated a significant reduction in the motility rate, normal morphology rate, viability rate, increase in abnormal DNA structure and packaging (TB staining), and DNA damage (TUNEL) in ethanol consumer groups. In addition, the findings showed a significant increase in the aforementioned parameters in ethanol- and vit. E-consumer groups compared to the ethanol-only consumer groups. The ethanol group received 20% of the most damage among the groups. The group receiving vit. E 100 mg and those receiving ethanol 10% + vit. E 200 mg gained the highest benefit among the groups.

CONCLUSION

Sperm forward progressive motility, normal morphology rate, and viability decreased in the ethanol groups. Also, the rates of spermatozoa with abnormal DNA structure and DNA fragmentation increased in the ethanol groups. Our findings revealed that the coadministration of vit. E and ethanol can protect destructive changes in DNA structure and damage.

Reproductive toxicity assessment of Olusosun municipal landfill leachate in Mus musculus using abnormal sperm morphology and dominant lethal mutation assays

Mixture of xenobiotics in Olusosun landfill leachates (OSL) induced somatic and germ cell genotoxicity in eukaryotic cells. However, whether the DNA-damaged germ cells can increase reproductive failure, embryotoxicity and/or teratogenicity during fertilization remained unclear. The study herein investigated reproductive toxicity and embryotoxic effects of OSL in mice using abnormal sperm morphology and dominant lethal mutation assays. Six mice per group were exposed to 0.5 mL of 5, 10, 25, and 50% OSL (v/v, leachate/distilled water) for 5 consecutive days. Similar treatment was giving to distilled water and cyclophosphamide (20 mg/kg body weight), as negative and positive control groups, respectively. At 35 day post-treatment, the mice were sacrificed and examined for cauda epididymal abnormal sperm morphology, testicular weight change and histopathological lesions. Male mice were mated to untreated nulliparous females (1 treated male per 2 untreated females) until vaginal plugs were observed. Pregnant females were sacrificed on 14th day post-mating and uterine content examined for number of implants per female, resorptions, and live and dead fetuses. OSL significantly increased teratozoospermia by 31.02% with amorphous sperm head having the highest frequency and sperm with two heads, the least. Histology of the testes revealed congestion of the interstitial blood vessels, spermatid retention and disorganization of the germinal epithelium from the basal compartment. OSL insignificantly increased absolute and relative testes weights but reduced body weight of exposed mice. There was insignificant induction of dominant lethal mutation, although low fertility was observed in the treated mice. The analyzed physico-chemical parameters and heavy metals/metalloids in OSL were higher than permissible limits. The metals, physico-chemical parameters and other unanalyzed substances in OSL induced abnormal sperm morphology, altered testes pathology, but did not significantly induce dominant lethal mutation in mice. Constituents of OSL are toxic to the male reproductive organs in mice and suggests harmful impact on public health. Indiscriminate disposal of solid wastes in the environment should be prevented.

A high-throughput method for unbiased quantitation and categorization of nuclear morphology†

The physical arrangement of chromatin in the nucleus is cell type and species-specific, a fact particularly evident in sperm, in which most of the cytoplasm has been lost. Analysis of the characteristic falciform (“hook shaped”) sperm in mice is important in studies of sperm development, hybrid sterility, infertility, and toxicology. However, quantification of sperm shape differences typically relies on subjective manual assessment, rendering comparisons within and between samples difficult.

We have developed an analysis program for morphometric analysis of asymmetric nuclei and characterized the sperm of mice from a range of inbred, outbred, and wild-derived mouse strains. We find that laboratory strains have elevated sperm shape variability both within and between samples in comparison to wild-derived inbred strains, and that sperm shape in F1 offspring from a cross between CBA and C57Bl6J strains is subtly affected by the direction of the cross. We further show that hierarchical clustering can discriminate distinct sperm shapes with greater efficiency and reproducibility than even experienced manual assessors, and is useful both to distinguish between samples and also to identify different morphological classes within a single sample.

Our approach allows for the analysis of nuclear shape with unprecedented precision and scale and will be widely applicable to different species and different areas of biology.

Tropical summer induces DNA fragmentation in boar spermatozoa: implications for evaluating seasonal infertility

Summer infertility continues to undermine pig productivity, costing the pig industry millions in annual losses. The boar's inefficient capacity to sweat, non-pendulous scrotum and the extensive use of European breeds in tropical conditions, can make the boar particularly vulnerable to the effects of heat stress; however, the link between summer heat stress and boar sperm DNA damage has not yet been demonstrated. Semen from five Large White boars was collected and evaluated during the early dry, late dry and peak wet seasons to determine the effect of seasonal heat stress on the quality and DNA integrity of boar spermatozoa. DNA damage in spermatozoa during the peak wet was 16-fold greater than during the early dry and nearly 9-fold greater than during the late dry season. Sperm concentration was 1.6-fold lower in the peak wet than early dry whereas no difference was found across several motility parameters as determined by computer-assisted sperm analysis. These results demonstrate that tropical summer (peak wet season) induces DNA damage and reduces concentration without depressing motility in boar spermatozoa, suggesting that traditional methods of evaluating sperm motility may not detect inherently compromised spermatozoa. Boar management strategies (such as antioxidant supplementation) need to be developed to specifically mitigate this problem.

Automated Nuclear Cartography Reveals Conserved Sperm Chromosome Territory Localization across 2 Million Years of Mouse Evolution

Measurements of nuclear organization in asymmetric nuclei in 2D images have traditionally been manual. This is exemplified by attempts to measure chromosome position in sperm samples, typically by dividing the nucleus into zones, and manually scoring which zone a fluorescence in-situ hybridisation (FISH) signal lies in. This is time consuming, limiting the number of nuclei that can be analyzed, and prone to subjectivity. We have developed a new approach for automated mapping of FISH signals in asymmetric nuclei, integrated into an existing image analysis tool for nuclear morphology. Automatic landmark detection defines equivalent structural regions in each nucleus, then dynamic warping of the FISH images to a common shape allows us to generate a composite of the signal within the entire cell population. Using this approach, we mapped the positions of the sex chromosomes and two autosomes in three mouse lineages (Mus musculus domesticus, Mus musculus musculus and Mus spretus). We found that in all three, chromosomes 11 and 19 tend to interact with each other, but are shielded from interactions with the sex chromosomes. This organization is conserved across 2 million years of mouse evolution.

Development of golden hamster embryos effectively produced by injection of sperm heads sonicated in Tris-HCl buffer with EGTA

PURPOSE

To investigate the effects of sperm treatment medium-TCM199 or EGTA in Tris-HCl buffer (TBS + EGTA)-for sonication of frozen-thawed hamster spermatozoa in terms of sperm chromosome integrity and development of hamster oocytes injected with the sperm heads (ICSI).

METHODS

Frozen-thawed hamster spermatozoa were separated into heads and tails by sonication in TCM199 or TBS + EGTA. Sperm heads were injected into mouse oocytes to assess hamster sperm chromosomes. We further compared the development of hamster ICSI embryos produced by injecting sonicated sperm heads in TCM199 vs TBS + EGTA.

RESULTS

Sperm chromosome integrity was greater following sonication of frozen-thawed hamster spermatozoa in TBS + EGTA than in TCM199 (89.7% vs 69.0%). Embryonic development was improved following hamster oocyte injection with sperm heads sonicated in TBS + EGTA compared to in TCM199 (8-cell: 84.1% vs 65.4%; morula: 78.4% vs 43.2%; blastocyst: 42.0% vs 17.3%). Gene expression of zygotic genome activation in 2-cell embryos was significantly higher with TBS + EGTA than with TCM199. We transferred 43 morulae/blastocysts from the TBS + EGTA group to foster mothers, and 4 (9.3%) developed into live offspring.

CONCLUSION

These results showed that the rapid injection of hamster sperm heads separated by sonication in TBS + EGTA effectively produced more ICSI embryos during a short time.

Effect of selenium on testicular damage induced by varicocele in adult male Wistar rats

PROJECT

Varicocele is an abnormal tortuosity and distension of the veins of the pampiniform plexus in the spermatic cord. It is the most common surgically correctable cause of male infertility. Several studies have revealed the effects of increased oxidative stress on serum, semen, and testicular tissues in patients with varicocele or in animal models. The aim of this study was to investigate the effects of sodium selenite on testicular damage induced by experimental left varicocele in male Wistar rats.

PROCEDURE

In the present study, the effects of oral administration of sodium selenite (at doses of 0.05, 0.1, 0.2, and 0.4mg/kg bw) were assessed in normal and varicocelized rats.

RESULTS

The varicocelized control rats showed decrease in sperm quality parameters, decreased activity of testes CAT, GPX and SOD, increased levels of MDA, and damage in testicular architecture. Administration of sodium selenite significantly reduced these changes to nearly normal levels, but did not change these parameters in normal rats. Histopathological studies further confirmed the protective effects of sodium selenite on varicocele-induced testicular damage in rats. Administrations of sodium selenite did not change these parameters in normal rats.

CONCLUSIONS

Taken together, the results of this study suggest that sodium selenite treatment may have beneficial effect on the testes of varicocelized rats.

Headless spermatozoa in infertile men

Spermatozoa morphology, an important parameter in a semen specimen's potential fertility evaluation, is a significant factor for in vitro fertilisation in assisted reproductive technology. Eleven sterile men with headless spermatozoa, a type of human teratozoospermia, are presented. Their ejaculates' headless spermatozoa percentages were high with rare normal spermatozoa forms. Additionally, abnormal morphology (e.g. round-headed or microcephalic spermatozoa) was also found. Spermatozoa motility was somewhat affected, potentially because of the missing mitochondrial sheath at the sperm tail base. Patients who underwent assisted reproductive technology treatment experienced adverse pregnancy outcomes. Work types and corresponding environments seemed irrelevant, but specific family history may have prompted its genetic origin. Computer-assisted semen analysis systems easily mistake headless spermatozoa as oligozoospermia because of nonrecognition of the loose head. However, morphological testing, especially with an electronic microscope, clearly identifies abnormal spermatozoa. Future exploration requires more methods investigating the frequency and percentage of this morphological abnormality in different populations with varied fertility levels. Such research would estimate the probable correlation of the abnormality with other semen parameters and examine the potential developmental or genetic origins. During clinical work, medical staff should detect these cases, avoid misdiagnosis and provide proper consultation about diagnosis and assisted reproductive technology treatment.

L-carnitine protects against testicular dysfunction caused by gamma irradiation in mice

This study was conducted on mice to evaluate the radioprotective role of L-carnitine against γ-ray irradiation-induced testicular damage. Adult male mice were exposed to whole body irradiation at a total dose of 1 Gy. Radiation exposure was continued 24 h a day (0.1 Gy/day) throughout the 10 days exposure period either in the absence and/or presence of L-carnitine at an i.p. dose of 10 mg/kg body weight/day. Results revealed that γ-rays irradiation suppressed the expression of ABP and CYP450SCC mRNA, whereas treatment with L-carnitine prior and throughout γ-rays irradiation exposure inhibited this suppression. Treatment with γ-ray irradiation or L-carnitine down-regulated expression of aromatase mRNA. With combined treatment, L-carnitine significantly normalized aromatase expression. γ-Ray irradiation up-regulated expression of FasL and Cyclin D2 mRNA, while L-carnitine inhibited these up-regulations. Results also showed that γ-ray-irradiation up-regulated TNF-α, IL1-β and IFN-γ mRNA expressions compared to either controls or the L-carnitine treated group. Moreover, γ-irradiation greatly reduced serum testosterone levels, while L-carnitine, either alone or in combination with irradiation, significantly increased serum testosterone levels compared to controls. In addition, γ-irradiation induced high levels of sperm abnormalities (43%) which were decreased to 12% in the presence of L-carnitine. In parallel with these findings, histological examination showed that γ-irradiation induced severe tubular degenerative changes, which were reduced by L-carnitine pre-treatment. These results clarified the immunostimulatory effects of L-carnitine and its radioprotective role against testicular injury.

Protective role of atorvastatin against doxorubicin-induced cardiotoxicity and testicular toxicity in mice

Doxorubicin (DOX), a potent chemotherapeutic agent, is widely used for the treatment of various malignancies. However, its clinical uses are limited due to its dose-dependent adverse effects particularly cardiac and testicular toxicities. DOX-induced toxicity is mainly due to the induction of oxidative stress. Atorvastatin (ATV), a 3-hydroxy 3-methyl glutaryl coenzyme A reductase inhibitor, with lipid-lowering activity, acts as an antioxidant at lower doses. It possesses pleiotropic effects independent of cholesterol-lowering property usually shown at lower doses, which include antioxidant and anti-inflammatory activities. The present study was aimed to investigate the possible protection exerted by atorvastatin against oxidative stress and DNA damage induced by DOX in the heart and testes of mice. The protective role of ATV in the heart and testes of DOX-treated mice was evident from the amelioration of oxidative stress, DNA and cellular damage. The present study clearly indicates that ATV offers a significant protection against DOX-induced oxidative stress and DNA damage in the heart and testes of mice.

Modification of the testicular function in laboratory male mice during social interactions: effect of female presence

The count of spermatozoa in both caudal epididymides, percentage of abnormal spermatozoon heads and of mobile spermatozoa, body weight, weights of the testes and caudal epididymides were evaluated in adult inbred males (PT and CBA/Lac) kept with females for 5 days. Male mice of the same genotypes and age separated from females served as controls. In males kept with females, the weights of the testes increased in PT male mice, the percentage of rapidly mobile spermatozoa increased in CBA/Lac mice, and body weights decreased in males of both genotypes. The morphometric and spermatogenic parameters in laboratory mice were modulated by the presence of a female, but the effect was determined by the male genotype.

Superovulation, in vitro fertilization (IVF) and in vitro development (IVD) protocols for inbred BALB/cJ mice in comparison with outbred NMRI mice

Purpose

To study assisted reproductive technology (ART) protocols including superovulation, in vitro fertilization (IVF) and in vitro development (IVD) for BALB/cJ mice in comparison with a common ART protocol for NMRI mice.

Methods

Adult NMRI and BALB/cJ mice were superovulated using a 48 h G-interval. In order to find a more suitable G-interval for the BALB/cJ strain, G-intervals including 44, 46 and 50 h were also examined. Superovulation rates were recorded in all groups. IVF rate of BALB/c oocytes in T6 and mHTF media were compared. IVD rates of BALB/cJ zygotes in mHTF, T6 and G1V₅/G2V₅ media were compared. In addition, IVF and IVD rates of BALB/cJ and NMRI oocytes were compared in T6 medium during IVF-IVD procedures.

Results

In BALB/cJ mice the highest superovulation rates were observed with 44-46 h G-intervals. However, with a 48 h G-interval, superovulation rates were significantly lower in BALB/cJ compared to NMRI mice (p < 0.05). mHTF medium significantly increased in vitro fertilization of BALB/cJ oocytes compared to T6 medium (p < 0.05). Fertilization rate of NMRI oocytes was significantly higher than BALB/cJ oocytes in T6 medium (p < 0.05). The BALB/cJ embryo IVD was significantly higher in G1/G2 medium compared to mHTF and T6 media (p < 0.01).

Conclusions

Superovulation with 48 h G-interval and using T6 during all in vitro procedures produces embryos more efficiently for NMRI mice than for BALB/cJ mice. For BALB/cJ mice, a protocol including superovulation with a 44-46 h G-interval, using mHTF during IVF and G1V₅/G2V₅ medium during IVD, may improve in vitro embryo production.

Treatment of sperm with extracellular adenosine 5'-triphosphate improves the in vitro fertility rate of inbred and genetically modified mice with low fertility

In vitro fertilization (IVF) is one of the most important techniques used for assisted reproduction in mouse colony management. As with natural mating, where mice have varying fertility indices, fertility rates of genetically modified (GM) [transgenic (Tg), knock out (KO) and congenic (Cg)] mice are influenced by their genetic background. Lines of GM mice that have poor fertility have a concomitant poor IVF outcome. Treatment of mouse sperm with extracellular adenosine 5'-triphosphate (ATPe) enhanced in vitro fertilization rates in outbred and hybrid mice. The objective of this study was to analyze the effects of using extracellular adenosine 5'-triphosphate-treated sperm for IVF of inbred wild type, and genetically modified mouse lines, for which standard IVF did not work well. The IVF was performed using the GM mice on C57BL/10SnJ, C57BL/6J, BALB/cJ and NFS/N background strains and wild type (WT) mice such as C57BL/6N, BALB/cAnN, and B6129SF1 strains. Oocytes from superovulated females were fertilized in vitro with sperm from the same background strain, and either treated or not treated with ATPe. The ATPe treatment enhanced IVF outcome in most of the GM and some WT strains, as indicated by the percentage of embryos that progressed to the two-cell stage. There was no marked difference between ATPe treated and control groups for the development rate of two-cell embryos to blastocysts in culture, or in the number of pups born after transfer of two-cell embryos into recipient females. The observed improvement of the IVF results following ATPe treatment of transgenic and KO mouse sperm were a potential solution for improving the outcome of assisted reproduction techniques used for rederivation or for gamete banking.

Genetic variability of spermatozoon production and morphology in laboratory mice

Strain-specific differences in the production of spermatozoa and incidence of atypical spermatogenesis were studied in males of 7 inbred strains: BALB/cLac, PT, CBA/Lac, DD, A/He, C57Bl/6J, and YT. The results attest to significant genetic variability of the counts of epididymal spermatozoa (differing by more than 1.5-2 times) and incidence of abnormal spermatozoon heads (differing by more than 4 times). However, the strain-specific variability of both signs was not coordinated. The selected set of inbred mouse strains can become a prospective genetic model for studies of physiological and hereditary nature of spermatogenesis variability.

Characterization of chromosomal damage accumulated in freeze-dried mouse spermatozoa preserved under ambient and heat stress conditions

Structural chromosome aberrations and DNA damage generated in freeze-dried mouse spermatozoa were investigated. Freeze-dried sperm samples were preserved at 4, 25 and 50°C for short duration (1 day to 2 months) and at 25°C for long duration (2 years). The spermatozoa were injected into mouse oocytes to analyse the chromosomes of the zygotes at the first cleavage metaphase. Chromosome break of the chromosome-type aberrations was the most common type of structural chromosome aberrations observed in all freeze-dried samples. The frequency of chromatid exchanges rapidly increased in freeze-dried spermatozoa preserved at 50°C for 1-5 days. The frequency of chromatid-type aberrations (break and exchange) gradually increased in freeze-dried spermatozoa preserved at 25°C for up to 2 months. Alkaline comet assay revealed significant migration of damaged DNA accumulated in freeze-dried spermatozoa preserved at 50°C for 3 days and 25°C for 2 years. However, no DNA damage was detected using the same sperm samples by neutral comet assay, which can detect mostly DNA double-strand breaks in cellular DNA. These results suggest that DNA single-strand breaks were accumulated in freeze-dried spermatozoa preserved under ambient or heat conditions, and then chromatid-type aberrations, especially the chromatid exchanges, were formed via post-replication repair system in zygotes.

Possible causal factors of structural chromosome aberrations in intracytoplasmic sperm injection of the mouse

Incidence of structural chromosome aberrations in mouse one-cell embryos produced by intracytoplasmic sperm injection (ICSI) with mature epididymal spermatozoa were influenced by sperm incubation medium and time. When spermatozoa were incubated in bicarbonate-buffered TYH for ≤0.5 h, the embryo aberration rates were significantly higher than in vitro fertilization (IVF) embryos. However, after the incubation of spermatozoa in the same medium for ≥2 h, the aberration rates were close to the IVF embryo level. When spermatozoa were incubated in bicarbonate-buffered mCZB, hepes-buffered H-TYH and H-mCZB, and phosphate-buffered PB1, the increased incidences of aberrations were observed at any incubation time. In the case of sperm incubation in H-TYH, H-mCZB and PB1, the aberration rates increased in a time-dependent manner. Chromosome aberrations generated by ICSI were transmissible to offspring. On the other hand, the aberration rate in embryos derived from testicular spermatozoa was independent of the medium type and incubation time. Thus, the incubation media appears to have no effect on sperm chromatin. TYH can effectively induce capacitation and acrosome reaction, while H-TYH, H-mCZB and PB1 never induce these spermatozoal events. It is probable that the cholesterol-rich plasma membrane and intact acrosome injected into the ooplasm affect sperm chromatin remodeling, thus resulting in the generation of chromosome damage in ICSI embryos.

Methotrexate-induced cytotoxicity and genotoxicity in germ cells of mice: intervention of folic and folinic acid

Methotrexate (MTX) is an anti-metabolite widely used in the treatment of neoplastic disorders, rheumatoid arthritis and psoriasis. The basis for its therapeutic efficacy is the inhibition of dihydrofolate reductase (DHFR), a key enzyme in the folic acid (FA) metabolism. FA is a water-soluble vitamin which is involved in the synthesis of purines and pyrimidines, the essential precursors of DNA. Folinic acid (FNA) is the reduced form of FA that circumvents the inhibition of DHFR. Folate supplementation during MTX therapy for psoriasis and inflammatory arthritis reduces both toxicity and side effects without compromising the efficacy. Further, FNA supplementation reduces the common side effects of MTX in the treatment of juvenile idiopathic arthritis. FA and FNA are reported to have protective effects on MTX-induced genotoxicity in the somatic cells; however their protective effects on the germ cells have not been much explored. Previously, we evaluated the cytotoxic and genotoxic effects of MTX in the germ cells of mice. In the present study, we have intervened FA and FNA for the protection of germ cell toxicity induced by MTX in male swiss mice. The animals were pre-treated with FA at the doses of 50, 100 and 200 microg/kg for 4 consecutive days per week and on day five; MTX was administered at the dose of 20mg/kg once. FNA was administered at the doses of 2.5, 5 and 10 mg/kg, 6 h (h) after single administration of MTX at the dose of 20 mg/kg. The dosing regimen was continued up to 10 weeks. The germ cell toxicity was evaluated using testes weight (wt), sperm count, sperm head morphology, sperm comet assay, histology, TUNEL and halo assay in testis. The results clearly demonstrate that prior administration of FA and post-treatment with FNA reduces the germ cell toxicity induced by MTX as evident from the decreased sperm head abnormalities, seminiferous tubule damage, sperm DNA damage, TUNEL positive cells and increased sperm counts. In the present study, we report that FA and FNA ameliorate the germ cell toxicity of MTX in mice.

Differential sensitivity of mouse strains to an N-alkylated imino sugar: glycosphingolipid metabolism and acrosome formation

This review deals with the pharmacological properties of an alkylated monosaccharide mimetic, N-butyldeoxynojirimycin (NB-DNJ). This compound is of pharmacogenetic interest because one of its biological effects in mice - impairment of spermatogenesis, leading to male infertility - depends greatly on the genetic background of the animal. In susceptible mice, administration of NB-DNJ perturbs the formation of an organelle, the acrosome, in early post-meiotic male germ cells. In all recipient mice, irrespective of reproductive phenotype, NB-DNJ has a similar biochemical effect: inhibition of the glucosylceramidase beta-glucosidase 2 and subsequent elevation of glucosylceramide, a glycosphingolipid. The questions that we now need to address are: how can glucosylceramide specifically affect early acrosome formation, and why is this contingent on genetic factors? Here we discuss relevant aspects of reproductive biology, the metabolism and cell biology of sphingolipids, and complex trait analysis; we also present a speculative model that takes our observations into account.

Astaxanthin inhibits cytotoxic and genotoxic effects of cyclophosphamide in mice germ cells

Cyclophosphamide (CP), an alkylating agent used in the treatment of several cancers as well as an immunosuppressant in rheumatoid arthritis. It is used against several cancers due to its broad spectrum efficacy, but at the same time possesses unwanted risks for occupational exposure as well as therapy related toxicities to patients. The present study was aimed to investigate the protective effect of astaxanthin (AST) a red carotenoid pigment on CP induced germ cell toxicity in male mice. CP was administered intraperitoneally (i.p.) at the dose of 50, 100 and 200mg/kg body weight to mice (20-25 g) once in a week for a period of five weeks. AST was given at the dose of 25mg/kg per oral (p.o.) for five consecutive days in a week for five weeks. The animals were sacrificed one week after the last injection of CP. The protective effect of AST against CP induced male germ cell toxicity was evaluated using body weight, testes and epididymis weight, sperm count, sperm head morphology, sperm comet assay, histology of testes and TUNEL assay. AST treatment significantly improved the testes weight, sperm count and sperm head morphology as compared to only CP treated animals. The result of comet assay showed that AST treatment significantly restored the sperm DNA damage induced by CP. Further, AST treatment showed protection against CP induced testicular toxicity as evident from testes histology and TUNEL assay. The present results indicate the chemoprotective potential of AST against CP induced germ cell toxicity in mice.

Cryoprotective effects of various saccharides on cryopreserved mouse sperm from various strains

Aim:  Cryopreservation of mouse sperm commonly uses raffinose, which is a trisaccharide, plus 3% skim milk. Because of the present lack of knowledge of the effectiveness of any other saccharides, we examined the cryoprotective effects of various saccharides on the viability of mouse sperm from various strains to determine which saccharides are the best cryoprotectants for mouse sperm. Methods:  Sperm from the caudae epididymides of mature C57BL/6J mice were frozen with monosaccharides (fructose, glucose, rhamnose, xylose), disaccharides (lactose, maltose, sucrose, trehalose) or trisaccharides (melezitose, raffinose) in a range of concentrations (4-33%). After thawing, the optimal concentration was determined to be the concentration in which there was the highest proportion of motile sperm. In addition, sperm of inbred and hybrid mice were frozen with the saccharides at the optimal concentrations and used for in vitro fertilization. Results:  The optimal concentration was 12% for the disaccharides and 18% for the trisaccharides. The fertility of all strains, except C57BL/6J, showed the best cryoprotective effects with maltose, melezitose and raffinose when compared with fresh sperm. Conclusion:  Maltose, melezitose and raffinose have the best effects when used as a protectant for cryopreservation of mouse sperm. (Reprod Med Biol 2007; 6: 229-233).

Evaluation of Chromosomal Risk Following Intracytoplasmic Sperm Injection in the Mouse

To investigate whether cytogenetic risks occur using the mouse intracytoplasmic sperm injection (ICSI) technique, the incidence of chromosome aberrations was compared in one-cell embryos produced by ICSI technique and those by conventional in vitro fertilization (IVF) technique. Spermatozoa were incubated in TYH medium for 1.5-2 h before IVF insemination. For the ICSI technique, spermatozoa were incubated in five different media: TYH, Hepes-buffered TYH (H-TYH), modified CZB (mCZB), Hepes-buffered mCZB (H-mCZB), and PB1 for 0.5 h, 2-2.5 h, and 6 h before injection into metaphase II oocytes. The incidence of IVF embryos with structural chromosome aberrations was 2%, whereas the occurrence of structural chromosome aberrations in ICSI embryos was dependent on the kind of medium and sperm incubation time. When spermatozoa were incubated in TYH medium for 2 h or more, the aberration rates in the resultant ICSI embryos (4%) were not significantly different from that of IVF embryos. However, there was a significant increase in aberration rates in ICSI embryos derived from spermatozoa that were incubated in other culture conditions (6%-28%). In addition, a time-dependent increase in aberration rates was found in ICSI embryos when H-TYH, H-mCZB, and PB1 were used for sperm incubation. There was no significant difference in incidence of aneuploidy between IVF and ICSI embryos. The chromosome analysis results of one-cell embryos were reflected by the performance of postimplantation embryo development. The causal mechanism of chromosome damage in ICSI embryos was discussed in relation to the plasma membrane cholesterol, the acrosome, and in vitro aging of spermatozoa.

Influence of the male on embryo quality

Early pregnancy failure or loss (EPL) represents a major source of wastage and inefficiency in livestock production systems. Although successful embryo development is dependent upon genetic and epigenetic contributions from both the male and female, potential adverse male affects on embryo quality and development are probably often underestimated. Of adverse male effects which have been identified, those associated with sperm and semen "quality" have been best characterized. In turn, although many factors can adversely impact semen quality, the mechanisms involved are relatively few. This presents opportunities for identifying biological markers for spermatogenic damage, as well as protective measures.

Metronidazole-induced alterations in murine spermatozoa morphology

The aim of this work was to assess the effect of metronidazole (MTZ) on the stages of the seminiferous epithelial cycle and spermatozoa morphology when the drug is administered in human therapeutic doses to 60-day-old CFW male mice. The frequency of the stages was established by counting spermatocytes in pachytene and spermatids. Abnormalities in the flagellum or the head, lack of maturity and multiple malformations, were considered in the morphological analysis. Murine control strain was compared with MTZ treated group (v.ip 130 mg/kg/bw) both kept in standard captivity conditions. Cellular composition or number of stages in the seminiferous tubules were not altered in MTZ exposed animals, though the number of cells in stages I, V and XII was increased. The sperm cell morphology was severely affected by the treatment with potentially serious consequences on the normal fertilization process. Thus, the MTZ has to be considered as a conceivable thread regarding male fertility.

The relationship between sperm morphology and in vitro fertilization ability in mice

In vitro fertilization (IVF) is widely used in reproduction research, but the sperm of some inbred strains of mice yield low fertilization rates in IVF. To determine the cause of this problem, we examined the effect of epididymal sperm morphology, in particular, tail bending and the presence and type of cytoplasmic droplet (CD), on fertilizability in vitro. Sperm suspensions were obtained from the following five strains: C57BL/6J, BALB/cA, C3H/HeN, DBA/2J, and 129 x 1/SvJ. The sperm were fixed in 10% formalin and three parts of the sperm, namely the head, tail, and CD, were examined. We recorded the proportion of abnormal sperm heads and hairpins at the neck; tails were categorized as straight, proximal bent, or distal bent; and the CDs were categorized as none, light-type, and heavy-type. Based on these parameters, we determined the correlations between sperm morphology and fertilizability in vitro, as judged by IVF using ICR oocytes. The proportion of sperm with a hairpin neck was higher in strain C57BL/6J, while abnormal head morphology occurred significantly more often in strain BALB/cA. The percentage of sperm with a proximal bent tail was highest in strain DBA/2J and lowest in strain 129 x 1/SvJ. A heavy-type CD was observed more frequently in the 129 x 1/SvJ and C57BL/6J strains than in the other three strains in which a light-type CD predominated. The rank order of the fertilization rates was 129 x 1/SvJ < C57BL/6J < C3H/HeN < BALB/cA < DBA/2J. In addition, fertilization rate was positively correlated with a proximal bent tail, but negatively correlated with a heavy-type CD and distal bent tail. This new classification system establishes that the morphological characteristics of epididymal sperm differ among inbred strains of mice and that tail and CD morphology are closely related to fertilization ability in IVF. Thus, our results provide a novel method for assessing the quality of mouse sperm used for IVF.

Assessment of pronuclear formation following in vitro fertilization with bovine spermatozoa obtained after thermal insulation of the testis

This study was conducted to follow the chronology of pronuclear formation in bovine zygotes after in vitro insemination with a population of spermatozoa having abnormal morphology. Semen samples were obtained and cryopreserved from four Holstein bulls before and after a scrotal insulation period of 48 h (Day 0). A pre-insult (Day 5) and a Day 20 post-insult semen sample were evaluated for morphology and used for IVF after standard swim-up sperm separation protocols. Pronuclear formation was scored on subpopulations of presumptive zygotes after they were fixed and stained at 3-h time intervals from 6 to 18 h post in vitro insemination (hpi). Post-thaw morphological evaluation of semen samples revealed a decrease in the percentages of normal spermatozoa in the post-insult samples compared with the pre-insult samples for Bull I (74-22%) and Bull III (68-1%). The sperm penetration rate decreased (P<0.05) between the pre- and post-insult samples for Bulls I (90-76%) and III (92-70%), but was not different for Bulls II (92-90%) and IV (78-85%). The pronuclear formation rates for post-insult zygotes for Bulls II and IV had comparable increases in development over time, whereas there was no increase in the pronuclear development for the zygotes from the post-insult samples for Bulls I and III, and generally a condensed sperm head was observed in the oolemma. At 18 hpi the fertilization rate between the pre- and post-insult samples for Bulls I (51-4%), II (88-75%) and III (94-2%) decreased (P<0.01), but there was no change for Bull IV (66%). In conclusion, we inferred that the failure in normal pronuclear formation was associated with an absence of normal decondensation of the penetrating spermatozoon; this suggested that the effect of morphologically abnormal spermatozoa occurred prior to cleavage, thus limiting early development.

Is there a relationship between sperm chromosome abnormalities and sperm morphology?

This review explores the relationship between sperm chromosomal constitution and morphology. With the advent of techniques for obtaining information on the chromosome complements of spermatozoa, this relationship has been studied in fertile men and in men with a high frequency of chromosomal abnormalities. Using human sperm karyotype analysis, no relationship between sperm chromosome abnormalities and morphology was found in fertile men, translocation carriers or post-radiotherapy cancer patients. Fluorescence in situ hybridization (FISH) analysis has not generally revealed a specific association between morphologically abnormal sperm and sperm chromosome abnormalities, but has indicated that teratozoospermia, like other forms of abnormal semen profiles (aesthenozoospermia, oligozoospermia) is associated with a modest increase in the frequency of sperm chromosome abnormalities. However, FISH studies on some infertile men and mouse strains have suggested that certain types of morphologically abnormal spermatozoa, such as macrocephalic multitailed spermatozoa, are associated with a very significantly increased frequency of aneuploidy. Thus, there may be an association between sperm morphology and aneuploidy in infertile men with specific abnormalities.

Male Gamete Contributions to the Embryo

During normal fertilization, plasma membranes of a spermatozoon and an oocyte mingle to form a mosaic plasma membrane of a zygote. This may contribute to the polyspermy block of the zygote. Sperm tail components (mitochondria, axonema, and accessory fibers) that enter the oocyte are "digested" without playing major roles in embryo development. The proximal centrosome adjacent to the sperm nucleus may become the center of the sperm aster that brings the male and female pronuclei to the center of the zygote, but it may not be essential for embryonic development per se. Whether sperm RNAs contribute to embryonic development is the subject of controversy. The nucleus is the most important sperm component that enters the oocyte. It is known that 7-15% of the spermatozoa of fertile men are chromosomally abnormal. The proportion of the spermatozoa with subchromosomal abnormalities (including damage at the DNA level) is expected to be even higher. The majority of embryos and fetuses with genomic abnormalities are aborted before reaching term. Structurally abnormal spermatozoa are not necessarily genomically abnormal, even though the incidence of genomically abnormal spermatozoa is higher among structurally abnormal than normal spermatozoa. In mammals, certain genes (estimated to be about 100) in the spermatozoon and oocyte must be "imprinted" in a gender-specific manner to warrant normal embryonic development.

Decline in fertility of mouse sperm with abnormal chromatin during epididymal passage as revealed by ICSI

BACKGROUND

Recent studies showed that ICSI with cauda epididymal or ejaculated sperm of infertile mice or men, respectively, was less effective in fertilization and normal embryo development than ICSI using sperm from the testes. These studies suggested that sperm nuclear quality declined after release from the testis, but the site where this loss of fertility occurs has not been localized.

METHODS

We performed ICSI with testicular, caput, and cauda epididymal sperm from infertile Tnp1-/-Tnp2+/- mutant mice, which have a minimal level of transition nuclear proteins and are sterile by natural mating.

RESULTS

When the heads of motile sperm from the testis or caput epididymis of Tnp1-/-Tnp2+/- males were injected into enucleated mouse oocytes, sperm chromosomes showed no difference from those of wild-type mice, but the chromosomes from sperm taken from the cauda epididymis of mutant males showed increased abnormalities. Injection of testicular or caput epididymal sperm from Tnp1-/-Tnp2+/- males into intact oocytes resulted in normal embryonic and fetal development and yields of liveborn equivalent to wild-type, but cauda sperm from Tnp1-/-Tnp2-/- mice produced lower implantation rates and yields of liveborn than did those from wild-type mice.

CONCLUSIONS

These results demonstrate that in mice with sperm chromatin abnormalities, the decline in fertility of sperm with ICSI occurs after the caput epididymis. The advantage of using caput epididymal sperm for ICSI in certain situations may be considered as an approach to be tested in human assisted reproduction.

A novel method for chromosome analysis of human sperm using enucleated mouse oocytes

BACKGROUND

Mouse oocytes can be used in conjunction with intracytoplasmic sperm injection (ICSI) as a technique to permit chromosomal analysis of human sperm. However, chromosomes derived both from the human sperm and the mouse oocyte appear simultaneously following ICSI. The present study focused on evaluating whether or not previously enucleated mouse oocytes are usable for the analysis of human sperm chromosomes.

METHODS

The metaphase chromosome-spindle complex was removed from a mouse oocyte. Human sperm from a donor with proven fertility were injected into mouse enucleated oocytes or intact oocytes. The presence of pronuclei in the oocytes was confirmed approximately 7-11 h after ICSI, and the oocytes were then fixed so that the nuclei could be observed as chromosome samples at 15-16 h after ICSI.

RESULTS

The formation rate of one pronucleus in enucleated oocytes after ICSI was 93.9% (186/198) while that of two pronuclei in intact oocytes after ICSI was 85.4% (88/103). The appearance rate of metaphase chromosomes of human sperm in the enucleated oocytes, 89.4% (160/179), was significantly higher than that in intact oocytes, 78.7% (74/94) (P = 0.017).

CONCLUSIONS

An efficient ICSI method using enucleated mouse oocytes was established to allow the visualization of the human sperm chromosome complement without the risk of confusion with mouse oocyte chromosomes.

Alkylated Imino Sugars, Reversible Male Infertility-Inducing Agents, Do Not Affect the Genetic Integrity of Male Mouse Germ Cells During Short-Term Treatment Despite Induction of Sperm Deformities1

Reversible infertility can be induced in male mice by oral administration of the alkylated imino sugars N-butyldeoxynojirimycin (NB-DNJ) and N-butyldeoxygalactonojirimycin (NB-DGJ). Spermatozoa of these mice have grossly misshapen heads and reduced motility. Because NB-DNJ and related compounds may hold promise as nonhormonal male contraceptives, a comprehensive examination of their effects on male reproduction is necessary. To this end, we further examined reproductive properties of the dysmorphic spermatozoa that are produced after short-term imino sugar administration at the minimal dose that completely abolishes the ability of male C57BL/6 mice to produce offspring by natural mating. Here, we report that, in vitro, the abnormal spermatozoa from the NB-DNJ- and NB-DGJ-treated mice were unable to fertilize oocytes. In addition, we investigated whether the imino sugars damage the genetic integrity of spermatozoa. To test this, we microsurgically injected deformed spermatozoa from imino sugar-treated males into oocytes. The deformed spermatozoa from the testis were able to activate oocytes very efficiently, but those from the cauda epididymis often failed to do so. This problem was overcome when the sperm-injected oocytes were treated with a parthenogenetic agent, Sr(2+). Oocytes injected with the misshapen spermatozoa from NB-DNJ- and NB-DGJ-treated mice developed (with or without Sr(2+) treatment) into live offspring that grew normally and were normally fertile. This indicates that during short-term administration, alkylated imino sugars alter sperm morphology and physiology but do not diminish the genetic potential of spermatozoa.

Intracytoplasmic injection of spermatozoa and spermatogenic cells: its biology and applications in humans and animals

Intracytoplasmic sperm injection (ICSI) has become the method of choice to overcome male infertility when all other forms of assisted fertilization have failed. Animals in which ICSI has produced normal offspring include many species. Success rate with normal spermatozoa is well above 50% in the mouse but ICSI success rates in other animals have been low, ranging from 0.3 to 16.5%. Mouse ICSI revealed that spermatozoa that cannot participate in normal fertilization can produce normal offspring by ICSI, provided their nuclei are genomically intact. Human ICSI using infertile spermatozoa has been highly successful perhaps because of the intrinsic instability of human sperm plasma membrane. The health of children born after ICSI and other assisted fertilization techniques is of major concern. Careful analyses suggest that higher incidences of congenital malformations and/or low birth weights after assisted fertilization are largely attributable to parental genetic background and increased incidence of multiple births, rather than to the techniques of assisted fertilization. Since the physiological and nutritional environments of developing embryos may cause persisting alteration in DNA methylation, extreme caution must be exercised in handling gametes and embryos in vitro. In the mouse, round spermatid injection (ROSI) has been routinely successful but its use in humans is controversial. Whether human ROSI and assisted fertilization involving younger spermatogenic cells are medically safe must be the subject of further investigations.

Microinsemination and Nuclear Transfer Using Male Germ Cells

Microinsemination has been widely used in basic reproductive research and in human-assisted reproductive technology for treating infertility. Historically, microinsemination in mammals started with research on the golden hamster; since then, it has provided invaluable information on the mechanisms of mammalian fertilization. Thanks to advances in animal genetic engineering and germ-cell technologies, microinsemination techniques are now used extensively to identify the biological significance of genes of interest or to confirm the genetic normality of gametes produced by experimental manipulations in vitro. Fortunately, in mice, high rates of embryo development to offspring can be obtained so long as postmeiotic spermatogenic cells are used as male gametes-that is, round spermatids, elongated spermatids, and spermatozoa. For some other mammalian species, using immature spermatogenic cells significantly decreases the efficiency of microinsemination. Physically unstable chromatin and low oocyte-activating capacity are the major causes of fertilization failure. The youngest male germ cells, including primordial germ cells and gonocytes, can be used in the construction of diploid embryos by nuclear-transfer cloning. The cloned embryos obtained in this way provide invaluable information on the erasure and reestablishment of genomic imprinting in germ cells.

Chromosome analysis of mouse zygotes after injecting oocytes with spermatozoa treated in vitro with green tea catechin, (−)-epigallocatechin gallate (EGCG)

The cytogenetic effects of (-)-epigallocatechin gallate (EGCG) on mouse spermatozoa were studied in vitro using an intracytoplasmic sperm injection (ICSI) technique. Spermatozoa were collected by the swim-up method and treated with EGCG at 1 microM and 10 microM. When motile, EGCG-treated spermatozoa were injected into oocytes, structural chromosome aberrations (SCAs) at the first cleavage metaphase did not increase significantly. However, a majority of immotile spermatozoa treated with 10 microM EGCG had the following abnormalities: pronuclear arrest (11% of activated oocytes), degenerated sperm chromatin (chromosome) mass (30% of activated oocytes) and occurrence of structural chromosome aberrations (57% of analyzed metaphases). The incidence of these abnormalities suggests that immotile spermatozoa were susceptible to EGCG, and that the damage of sperm chromatin was accelerated in immotile spermatozoa by 10 microM EGCG treatment.