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

Removal of sperm tail using trypsin and pre-activation of oocyte facilitates intracytoplasmic sperm injection in mice and rats

We examined various methods to enhance the accessibility of intracytoplasmic sperm injection (ICSI) technology to more users by making the technique easier, more efficient, and practical. First, the methods for artificially removing the mouse sperm tail were evaluated. Trypsin treatment was found to efficiently remove the sperm tails. The resultant sperm cells had a lower oocyte activation capacity; however, the use of activated oocytes resulted in the same fecundity as that of fresh, untreated sperm. Pre-activated oocytes were more resistant to physical damage, showed higher survival rates, and required less time per injection. Testing this method in rats yielded similar results, although the oocyte activation method was different. Remarkably, this method resulted in higher birth rates of rat progeny than with conventional methods of rat ICSI. Our method thereby streamlines mouse and rat ICSI, making it more accessible to laboratories across many disciplines.

Intracytoplasmic sperm injection in sturgeon species: A promising reproductive technology of selected genitors

Sturgeons are the most endangered species group and their wild populations continue to decrease. In this study, we apply intracytoplasmic sperm injection (ICSI), an assisted reproductive technology, for the first time in endangered and critically endangered sturgeons. Using various egg-sperm species combinations we performed different ICSI experiments with immobilized pre- or non-activated spermatozoa, single or many, fresh or cryopreserved. Then we evaluated the fertilization success as well as the paternity of the resultant embryos and larvae. Surprisingly, all experimental groups exhibited embryonic development. Normal-shaped feeding larvae produced in all egg-sperm species-combination groups after ICSI using single fresh-stripped non-activated spermatozoa, in one group after ICSI using single fresh-stripped pre-activated spermatozoa, and in one group after ICSI using multiple fresh-stripped spermatozoa. ICSI with single cryopreserved non-activated spermatozoa produced neurula stage embryos. Molecular analysis showed genome integration of both egg- and sperm-donor species in most of the ICSI transplants. Overall, ICSI technology could be used as an assisted reproduction technique for producing sturgeons to rescue valuable paternal genomes.

Past, present and future of ICSI in livestock species

During the past 2 decades, intracytoplasmic sperm injection (ICSI) has become a routine technique for clinical applications in humans. The widespread use among domestic species, however, has been limited to horses. In horses, ICSI is used to reproduce elite individuals and, as well as in humans, to mitigate or even circumvent reproductive barriers. Failures in superovulation and conventional in vitro fertilization (IVF) have been the main reason for the use of this technology in horses. In pigs, ICSI has been successfully used to produce transgenic animals. A series of factors have resulted in implementation of ICSI in pigs: need to use zygotes for numerous technologies, complexity of collecting zygotes surgically, and problems of polyspermy when there is utilization of IVF procedures. Nevertheless, there have been very few additional reports confirming positive results with the use of ICSI in pigs. The ICSI procedure could be important for use in cattle of high genetic value by maximizing semen utilization, as well as for utilization of spermatozoa from prepubertal bulls, by providing the opportunity to shorten the generation interval. When attempting to utilize ICSI in ruminants, there are some biological limitations that need to be overcome if this procedure is going to be efficacious for making genetic improvements in livestock in the future. In this review article, there is an overview and projection of the methodologies and applications that are envisioned for ICSI utilization in these species in the future.

Bovine ICSI: limiting factors, strategies to improve its efficiency and alternative approaches

Intracytoplasmic sperm injection (ICSI) is an assisted reproductive technique mainly used to overcome severe infertility problems associated with the male factor, but in cattle its efficiency is far from optimal. Artificial activation treatments combining ionomycin (Io) with 6-dimethylaminopurine after piezo-ICSI or anisomycin after conventional ICSI have recently increased the blastocyst rate obtained. Compounds to capacitate bovine spermatozoa, such as heparin and methyl-β-cyclodextrin and compounds to destabilize sperm membranes such as NaOH, lysolecithin and Triton X-100, have been assessed, although they have failed to substantially improve post-ICSI embryonic development. Disulfide bond reducing agents, such as dithiothreitol (DTT), dithiobutylamine and reduced glutathione, have been assessed to decondense the hypercondensed head of bovine spermatozoa, the two latter being more efficient than DTT and less harmful. Although piezo-directed ICSI without external activation has generated high fertilization rates and modest rates of early embryo development, other studies have required exogenous activation to improve the results. This manuscript thoroughly reviews the different strategies used in bovine ICSI to improve its efficiency and proposes some alternative approaches, such as the use of extracellular vesicles (EVs) as 'biological methods of oocyte activation' or the incorporation of EVs in the in vitro maturation and/or culture medium as antioxidant defence agents to improve the competence of the ooplasm, as well as a preincubation of the spermatozoa in estrous oviductal fluid to induce physiological capacitation and acrosome reaction before ICSI, and the use of hyaluronate in the sperm immobilization medium.

Mysteries and unsolved problems of mammalian fertilization and related topics

Mammalian fertilization is a fascinating process that leads to the formation of a new individual. Eggs and sperm are complex cells that must meet at the appropriate time and position within the female reproductive tract for successful fertilization. I have been studying various aspects of mammalian fertilization over 60 years. In this review, I discuss many different aspects of mammalian fertilization, some of my laboratory's contribution to the field, and discuss enigmas and mysteries that remain to be solved.

CRISPR/Cas9-based genetic screen of SCNT-reprogramming resistant genes identifies critical genes for male germ cell development in mice

Male germ cells undergo complex developmental processes eventually producing spermatozoa through spermatogenesis, although the molecular mechanisms remain largely elusive. We have previously identified somatic cell nuclear transfer-reprogramming resistant genes (SRRGs) that are highly enriched for genes essential for spermatogenesis, although many of them remain uncharacterized in knockout (KO) mice. Here, we performed a CRISPR-based genetic screen using C57BL/6N mice for five uncharacterized SRRGs (Cox8c, Cox7b2, Tuba3a/3b, Faiml, and Gm773), together with meiosis essential gene Majin as a control. RT-qPCR analysis of mouse adult tissues revealed that the five selected SRRGs were exclusively expressed in testis. Analysis of single-cell RNA-seq datasets of adult testis revealed stage-specific expression (pre-, mid-, or post-meiotic expression) in testicular germ cells. Examination of testis morphology, histology, and sperm functions in CRISPR-injected KO adult males revealed that Cox7b2, Gm773, and Tuba3a/3b are required for the production of normal spermatozoa. Specifically, Cox7b2 KO mice produced poorly motile infertile spermatozoa, Gm773 KO mice produced motile spermatozoa with limited zona penetration abilities, and Tuba3a/3b KO mice completely lost germ cells at the early postnatal stages. Our genetic screen focusing on SRRGs efficiently identified critical genes for male germ cell development in mice, which also provides insights into human reproductive medicine.

Interspecific ICSI for the Assessment of Sperm DNA Damage: Technology Report

Xenogenic mammalian sperm heads injected into mouse ovulated oocytes decondense and form pronuclei in which sperm DNA parameters can be evaluated. We suggest that this approach can be used for the assessment of sperm DNA damage level and the evaluation of how certain sperm treatments (freezing, lyophilization, etc.) influence the quality of spermatozoa.

Transcriptome and DNA Methylation Profiles of Mouse Fetus and Placenta Generated by Round Spermatid Injection

Low birth efficiency and developmental abnormalities in embryos derived using round spermatid injection (ROSI) limit the clinical application of this method. Further, the underlying molecular mechanisms remain elusive and warrant further in-depth study. In this study, the embryonic day (E) 11.5 mouse fetuses and corresponding placentas derived upon using ROSI, intracytoplasmic sperm injection (ICSI), and natural in vivo fertilized (control) embryos were collected. Transcriptome and DNA methylation profiles were analyzed and compared using RNA-sequencing (RNA-seq) and whole-genome bisulfite sequencing, respectively. RNA-seq results revealed similar gene expression profiles in the ROSI, ICSI, and control fetuses and placentas. Compared with the other two groups, seven differentially expressed genes (DEGs) were identified in ROSI fetuses, and ten DEGs were identified in the corresponding placentas. However, no differences in CpG methylation were observed in fetuses and placentas from the three groups. Imprinting control region methylation and imprinted gene expression were the same between the three fetus and placenta groups. Although 49 repetitive DNA sequences (RS) were abnormally activated in ROSI fetuses, RS DNA methylation did not differ between the three groups. Interestingly, abnormal hypermethylation in promoter regions and low expression of Fggy and Rec8 were correlated with a crown-rump length less than 6 mm in one ROSI fetus. Our study demonstrates that the transcriptome and DNA methylation in ROSI-derived E11.5 mouse fetuses and placentas were comparable with those in the other two groups. However, some abnormally expressed genes in the ROSI fetus and placenta warrant further investigation to elucidate their effect on the development of ROSI-derived embryos.

Spermatogonium-Derived Complete Hydatidiform Mole

A complete hydatidiform mole (CHM) is a conceptus with only sperm-derived chromosomes. Here, we report on a CHM with genomic DNA identical to that of the paternal somatic cells. The CHM developed in a woman who had undergone intrauterine implantation of a blastocyst obtained through in vitro injection of a presumed round spermatid into one of her oocytes. The CHM was genetically identical to peripheral white cells of her husband and contained no maternally derived nuclear DNA. We hypothesize that a spermatogonium, rather than a round spermatid, was inadvertently selected for the procedure. The CHM developed into a gestational trophoblastic neoplasia, which resolved after chemotherapy. (Funded by the Japan Society for the Promotion of Science.).

High mRNA expression of GABA receptors in human sperm with oligoasthenoteratozoospermia and teratozoospermia and its association with sperm parameters and intracytoplasmic sperm injection outcomes

Objective

This study investigated the mRNA expression of gamma-aminobutyric acid (GABA) receptors in the sperm of oligoasthenoteratozoospermic (OAT) and teratozoospermic (TER) men compared to normozoospermic (NOR) men, as well as the relationships between GABA receptor expression and sperm parameters, fertilization rate, and embryo quality.

Methods

The mRNA expression of GABA A-α1 and GABA B-R2 receptors in sperm was examined using reverse transcription–polymerase chain reaction in three groups of patients: NOR (n=32), OAT (n=22), and TER (n=45). The fertilization rate and embryo quality were assessed in 35 patients undergoing intracytoplasmic sperm injection (ICSI; 10 NOR, 10 OAT, and 15 TER men).

Results

OAT men had significantly higher mRNA expression of GABA A-α1 and GABA B-R2 receptors in sperm than NOR men; however, the difference between TER and NOR men was not significant. High levels of these receptors were significantly correlated with low sperm concentration, motility, and morphology, as well as the rate of good-quality embryos (GQEs) at the cleavage stage after ICSI. Patients whose female partners had a >50% GQE rate at the cleavage stage had significantly lower levels of GABA A-α1 receptor expression than those whose partners had a ≤50% GQE rate.

Conclusion

Our findings indicate that mRNA levels of GABA receptors in human sperm are correlated with poor sperm quality and associated with embryo development after ICSI treatment. The GABA A-α1 receptor in sperm has a stronger relationship with embryo quality at the cleavage stage than the GABA B-R2 receptor.

Intracytoplasmic Sperm Injection in Cattle

Intracytoplasmic sperm injection (ICSI) involves the microinjection of sperm into a matured oocyte. Although this reproductive technology is successfully used in humans and many animal species, the efficiency of this procedure is low in the bovine species mainly due to failed oocyte activation following sperm microinjection. This review discusses various reasons for the low efficiency of ICSI in cattle, potential solutions, and future directions for research in this area, emphasizing the contributions of testis-specific isoforms of Na/K-ATPase (ATP1A4) and phospholipase C zeta (PLC ζ). Improving the efficiency of bovine ICSI would benefit the cattle breeding industries by effectively utilizing semen from elite sires at their earliest possible age.

Production of offspring by intracytoplasmic sperm injection using sperm from deceased transgenic mice at different postmortem intervals

Successful fertilization by intracytoplasmic sperm injection (ICSI) is possible as long as the sperm genome is intact, even in the context of defective sperm or sustained adverse treatment. However, there are few reports on rescuing gene-modified mouse lines after accidental death. To investigate whether sperm from a dead transgenic mouse can fertilize an oocyte and enable embryo development into a pup, Nestin-GFP transgenic male mice were sacrificed, and sperm was collected 14 h, 24 h, and 48 h after death. The collected sperm was injected into oocytes from hybrid B6D2F1 or inbred C57BL/6 N mice. The results showed that the sperm in the three groups activated oocytes from B6D2F1 and supported embryo development to the blastocyst stage. For ICSI embryos derived from B6D2F1 mice, the cleavage and blastocyst rates were significantly lower in the three experimental groups than in the control group (0 h) (P < 0.05), and the birth rate in the 24 h and 48 h groups was significantly lower than that in the 14 h and control groups (0 h). For C57BL/6N-derived ICSI embryos, the cleavage rates were significantly lower at 24 h and 48 h than at 14 h and 0 h (control group), and the birth rate in the three experimental groups was significantly lower than that in the control group (0 h). The F0 mice derived from B6D2F1 and C57BL/6 N oocytes had normal reproductive ability, and F1 mice were successfully obtained. The characteristics of the GFP gene were preserved and inherited. The histone H2AX phosphorylation assay showed that the proportion of focus-negative embryos was markedly and significantly lower in the 14 h, 24 h, and 48 h groups than in the control group (0 h). The proportion of focus-negative embryos was significantly lower at 48 h than at 14 h or 24 h. The number of foci was significantly higher in the three experimental groups than in the control group (0 h), indicating that sperm DNA sustained more damage after death and that few sperm had an intact genome. In summary, sperm obtained from mice 14 h, 24 h, and 48 h after death is capable of activating an oocyte and supporting complete embryo development into a pup. This study provides an effective way to rescue accidently died mouse strains.

Altered TH1, TH2, TH17 balance in assisted reproductive technology conceived mice

AIM AND PURPOSE

The higher prevalence rate of different diseases may accentuate the possible alteration of the immune system in individuals conceived through the assisted reproductive technologies (ART). The present study was conducted to evaluate the TH1, TH2, TH17 balance in intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF) - conceived mice in comparison to naturally conceived offspring.

METHODS

Mice (6-8 weeks) were divided into three groups (IVF- conceived, ICSI- conceived and naturally conceived). They were subjected to subcutaneous immunization witMycobacterium bovis Bacille Calmette-Guérin (BCG). The blood samples were taken and the sera were separated. Then the spleens were surgically removed at the time the mice were sacrificed. Serum levels of IFN-γ, IL-17A and IL-4 were detected by ELISA. Then the proportion of TCD4 cells possessing the T-bet+, GATA3+, and ROR-γt + were measured using FACS caliber flow cytometer.

RESULTS

In comparison with naturally conceived mice, intracellular expression of T-bet and serum levels of IFN-γ were significantly decreased in ART- conceived mice. Moreover, ART- conceived offspring showed marked increase in IL-4 and IL-17A.

CONCLUSION

It is concluded that compared to naturally conceived male mice, ART- conceived counterparts exhibit less efficient immune responses against BCG through further promotion of humoral and inflammatory related immune response characteristics.

Successful pregnancy after prenatal diagnosis by NGS for a carrier of complex chromosome rearrangements

BACKGROUND

The study is aimed to provide prediction for fertility risk in the setting of assisted reproduction for a woman with complex chromosomal rearrangements (CCRs).

METHODS

We implemented a robust approach, which combined whole-genome low-coverage mate-pair sequencing (WGL-MPS), junction-spanning PCR and preimplantation genetic testing for aneuploidy (PGT-A) method to provide accurate chromosome breakpoint junctional sequences in the embryo selection process in the setting of assisted reproduction for a couple with recurrent abortions due to CCRs.

RESULT

WGL-MPS was applied to a female carrying CCRs which consisted of 9 breakpoints and 1 cryptic deletion related to fertility risks. Sequencing data provided crucial information for designing junction-spanning PCR and PGT-A process, which was performed on the 11 embryos cultivated. One embryo was considered qualified for transplanting, which carried the exact same CCRs as the female carrier, whose phenotype was normal. The amniotic fluid was also investigated by WGL-MPS and karyotyping at 19 weeks' gestation, which verified the results that the baby carried the same CCRs. A healthy baby was born at 39 weeks' gestation by vaginal delivery.

CONCLUSION(S)

Our study illustrates the WGL-MPS approach combining with junction-spanning PCR and PGT-A is a powerful and practical method in the setting of assisted reproduction for couples with recurrent miscarriage due to chromosomal abnormalities, especially CCRs carriers.

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.

The golden (Syrian) hamster as a model for the study of reproductive biology: Past, present, and future

BACKGROUND

The golden (Syrian) hamster (Mesocricetus auratus) is a small rodent that belongs to the Cricetidae family. It has several unique features that are advantageous for the study of reproductive and developmental biology, including a consistent estrous cycle (4 days), high responsiveness to conventional superovulation regimens, and the short gestation period (16 days).

METHODS

Based on the published reports, the development in assisted reproductive technology (ART) in the golden hamsters was summarized.

MAIN FINDINGS

The technical ease of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in this species has contributed to our understanding of the basic mechanisms of mammalian fertilization in the last century. However, a strong developmental block in vitro of hamster embryos and unavailability of gene-modified strains has hampered its broader use in biomedical fields. A recently developed in vivo transfection method has enabled us to generate gene knockout hamsters without any major obstacles. It would be interesting to revisit the genes whose functions could not be identified using mouse models.

CONCLUSION

The authors expect that gene knockout hamsters might be able to substitute for mice-at least in part-for better understanding of gene functions in mammals including humans.

Intra-ooplasmic injection of a multiple number of sperm to induce androgenesis and polyploidy in the dojo loach Misgurnus anguillicaudatus (Teleostei: Cobitidae)

SummaryPolyspermy was initiated by microinjecting a multiple number of sperm into the activated and dechorionated eggs of dojo loach Misgurnus anguillicaudatus (Teleostei: Cobitidae). A 10-nl sperm suspension from an albino (recessive trait) male (105, 106, 107 or 108 sperm ml -1) was microinjected into eggs from a wild-type female. Although the rates of embryos developing into the blastula stage in the injection group at the highest sperm concentration were similar to that of the control group, the hatching rates of the injection group were much lower. A large proportion of embryos that developed from the injected eggs was haploid and were mosaics containing haploid cells. Most of the haploid and mosaic embryos inherited only paternally derived alleles in the microsatellite markers (i.e. androgenesis was initiated by injecting multiple sperm). In contrast, some haploid embryos contained both paternal and maternal alleles despite haploidy, suggesting that they were mosaics consisting of cells with either paternal or maternal inheritance. The injected eggs displayed diploid, hypotriploid and triploid cells, all of which included both maternally and paternally derived alleles. One albino tetraploid with only paternal alleles was also observed from the injected eggs. These results suggested that part of the sperm microinjected into the ooplasm should form a male pronucleus/pronuclei, which could develop by androgenesis or could fuse with the female pronucleus/pronuclei. Therefore, microinjection of multiple sperm should be considered a potential technique to induce androgenesis and polyploidy.

Production of inbred offspring by intracytoplasmic sperm injection of oocytes from juvenile female mice

The aim of the present study was to determine whether the use of oocytes from juvenile female mice would improve the efficiency of intracytoplasmic sperm injection (ICSI). In the present study, 15 adult and 14 juvenile C57BL6/J female mice were superovulated, with 17.8 oocytes per mouse harvested from adults, significantly lower than the 40.2 harvested from juveniles (P<0.01). Sixty and 233 oocytes were harvested from C57BL/6J adult and juvenile mice respectively, activated in 10mM SrCl2+5μgmL-1 cytochalasin B for 5-6h and cultured in potassium simplex optimisation medium (KSOM) for 3.5 days, with no differences in morula and blastocyst rates between groups (91.7% vs 96.6%; P>0.05). Twelve hours after injection of human chorionic gonadotrophin, oocytes were harvested from C57BL/6J juvenile mice into KSOM, randomly divided into groups and activated with the same method mentioned above at 0, 2, 4 or 6h and then cultured in KSOM for 3.5 days. There was no significant difference in morula and blastocyst rates among the different groups (P>0.05). Oocytes from juvenile mice activated in 10mM SrCl2 for 2h were subjected to ICSI and the rates of pronuclear formation and Day 1 cleavage were significantly improved compared with the control group (P<0.01). ICSI combined with activation of oocytes from inbred mouse strains (C57BL/6J, C57BL/6N and 129Svev) successfully produced pups. The fertility of some these mice resulting from ICSI was tested, and the animals proved fertile. In conclusion, superovulated juvenile mice can yield more useable oocytes than adult mice, but additional activation is essential for full development of ICSI oocytes harvested from juvenile inbred mice.

Improved expression of green fluorescent protein in cattle embryos produced by ICSI-mediated gene transfer with spermatozoa treated with streptolysin-O

The ICSI-sperm mediated gene transfer (ICSI-SMGT) has been used to produce transgenic mice with high efficiency; however, the efficiency of this technique in farm animals is still less than desirable. Pretreatment of sperm with membrane destabilizing agents can improve the efficiency of ICSI in cattle. The objective of the present study was to evaluate streptolysin-O (SLO) as a novel treatment to permeabilize the bovine sperm membrane and assess its effect on efficiency of generating transgenic embryos by ICSI-SMGT. First, there was evaluation of the plasma membrane integrity (SYBR/PI), acrosome membrane integrity (PNA/FITC), DNA damage (TUNEL) and binding capacity of exogenous DNA (Nick Translation) in bull sperm treated with SLO. Subsequently, there was assessment of embryonic development and the efficiency in generating transgenic embryos with enhanced expression of the gene for green fluorescent protein (EGFP). Results indicate that SLO efficiently permeabilizes the plasma and acrosome membranes of bull spermatozoa and increases binding of exogenous DNA mostly to the post-acrosomal region and tail without greatly affecting the integrity of the DNA. Furthermore, treatment of bull spermatozoa with SLO prior to the injection of oocytes by ICSI-SMGT significantly increased the rate of embryo expression of the EGFP gene. Future experiments are still needed to determine the effect of this treatment on the development and transgene expression in fetuses and animals produced by ICSI-SMGT.

Defective sperm head decondensation undermines the success of ICSI in the bovine

The efficiency of intracytoplasmic sperm injection (ICSI) in the bovine is low compared to other species. It is unknown whether defective oocyte activation and/or sperm head decondensation limit the success of this technique in this species. To elucidate where the main obstacle lies, we used homologous and heterologous ICSI and parthenogenetic activation procedures. We also evaluated whether in vitro maturation negatively impacted the early stages of activation after ICSI. Here we showed that injected bovine sperm are resistant to nuclear decondensation by bovine oocytes and this is only partly overcome by exogenous activation. Remarkably, when we used heterologous ICSI, in vivo-matured mouse eggs were capable of mounting calcium oscillations and displaying normal PN formation following injection of bovine sperm, although in vitro-matured mouse oocytes were unable to do so. Together, our data demonstrate that bovine sperm are especially resistant to nuclear decondensation by in vitro-matured oocytes and this deficiency cannot be simply overcome by exogenous activation protocols, even by inducing physiological calcium oscillations. Therefore, the inability of a suboptimal ooplasmic environment to induce sperm head decondensation limits the success of ICSI in the bovine. Studies aimed to improve the cytoplasmic milieu of in vitro-matured oocytes and to replicate the molecular changes associated with in vivo capacitation and acrosome reaction will deepen our understanding of the mechanism of fertilization and improve the success of ICSI in this species.

Reproductive technologies for the generation and maintenance of valuable animal strains

Many types of mutant and genetically engineered strains have been produced in various animal species. Their numbers have dramatically increased in recent years, with new strains being rapidly produced using genome editing techniques. In the rat, it has been difficult to produce knockout and knock-in strains because the establishment of stem cells has been insufficient. However, a large number of knockout and knock-in strains can currently be produced using genome editing techniques, including zinc-finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), and the clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) system. Microinjection technique has also contributed widely to the production of various kinds of genome edited animal strains. A novel electroporation method, the “Technique for Animal Knockout system by Electroporation (TAKE)” method, is a simple and highly efficient tool that has accelerated the production of new strains. Gamete preservation is extremely useful for maintaining large numbers of these valuable strains as genetic resources in the long term. These reproductive technologies, including microinjection, TAKE method, and gamete preservation, strongly support biomedical research and the bio-resource banking of animal models. In this review, we introduce the latest reproductive technologies used for the production of genetically engineered animals, especially rats, using genome editing techniques and the efficient maintenance of valuable strains as genetic resources. These technologies can also be applied to other laboratory animals, including mice, and domestic and wild animal species.

Sperm selection by thermotaxis improves ICSI outcome in mice

The ejaculate is a heterogeneous pool of spermatozoa containing only a small physiologically adequate subpopulation for fertilization. As there is no method to isolate this subpopulation, its specific characteristics are unknown. This is one of the main reasons why we lack effective tools to identify male infertility and for the low efficiency of assisted reproductive technologies. The aim of this study was to improve ICSI outcome by sperm selection through thermotaxis. Here we show that a specific subpopulation of mouse and human spermatozoa can be selected in vitro by thermotaxis and that this subpopulation is the one that enters the fallopian tube in mice. Further, we confirm that these selected spermatozoa in mice and humans show a much higher DNA integrity and lower chromatin compaction than unselected sperm, and in mice, they give rise to more and better embryos through intracytoplasmic sperm injection, doubling the number of successful pregnancies. Collectively, our results indicate that a high quality sperm subpopulation is selected in vitro by thermotaxis and that this subpopulation is also selected in vivo within the fallopian tube possibly by thermotaxis.

Freeze-dried spermatozoa: An alternative biobanking option for endangered species

In addition to the iconic wild species, such as the pandas and Siberian tigers, an ever-increasing number of domestic species are also threatened with extinction. Biobanking of spermatozoa could preserve genetic heritages of extinct species, and maintain biodiversity of existing species. Because lyophilized spermatozoa retain fertilizing capacity, the aim was to assess whether freeze-dried spermatozoa are an alternative option to save endangered sheep breeds. To achieve this objective, semen was collected from an Italian endangered sheep breed (Pagliarola), and a biobank of cryopreserved and freeze-dried spermatozoa was established, and evaluated using IVF (for frozen spermatozoa) and ICSI procedures (for frozen and freeze-dried spermatozoa). As expected, the fertilizing capacity of cryopreserved Pagliarola's spermatozoa was comparable to commercial semen stocks. To evaluate the activating capability of freeze-dried spermatozoa, 108 MII sheep oocytes were subjected to ICSI, and allocated to two groups: 56 oocytes were activated by incubation with ionomycin (ICSI-FDSa) and 52 were not activated (ICSI-FDSna). Pronuclear formation (2PN) was investigated at 14-16 h after ICSI in fixed presumptive zygotes. Only artificially activated oocytes developed into blastocysts after ICSI. In the present study, freeze-dried ram spermatozoa induced blastocyst development following ICSI at a relatively high proportion, providing evidence that sperm lyophilization is an alternative, low cost storage option for biodiversity preservation of domestic species.

[Mg2+]o/[Ca2+]o determines Ca2+ response at fertilization: tuning of adult phenotype?

Alteration of the postnatal phenotype has sparked great concern about the developmental impact of culture media used at fertilization. However, the mechanisms and compounds involved are yet to be determined. Here, we used the Ca²⁺ responses from mouse eggs fertilized by ICSI as a dynamic and quantitative marker to understand the role of compounds in egg functioning and establish possible correlations with adult phenotypes. We computed 134 Ca²⁺ responses from the first to the last oscillation in media with specific formulations. Analyses demonstrate that eggs generated two times as many Ca²⁺ oscillations in KSOM as in M16 media (18.8 ± 7.0 vs 9.2 ± 2.5). Moreover, the time increment of the delay between two consecutive oscillations, named TIbO, is the most sensitive coefficient characterizing the mechanism that paces Ca²⁺ oscillations once the egg has been fertilized. Neither doubling external free Ca²⁺ nor dispermic fertilization increased significantly the total number of Ca²⁺ oscillations. In contrast, removing Mg²⁺ from the M16 boosted Ca²⁺ oscillations to 54.0 ± 35.2. Hence, [Mg²⁺]_o/[Ca²⁺]_o appears to determine the number, duration and frequency of the Ca²⁺ oscillations. These changes were correlated with long-term effects. The rate of female's growth was impacted with the 'KSOM' females having only half the fat deposit of 'M16' females. Moreover, adult animals issued from M16 had significantly smaller brain weight vs 'KSOM' and 'control' animals. TIbO is a new Ca²⁺ coefficient that gauges the very early functional impact of culture media. It offers the possibility of establishing correlations with postnatal consequences according to IVF medium formulation.Free French abstract: A French translation of this abstract is freely available at http://www.reproduction-online.org/content/154/5/675/suppl/DC2.

Sperm capacitation pretreatment positively impacts bovine intracytoplasmic sperm injection

The efficiency of intracytoplasmic sperm injection (ICSI) in bovines is low compared to other species due in part to inadequate egg activation and sperm nucleus decondensation after injection. We hypothesized that this low efficiency is due to the lack of complete sperm capacitation, so we evaluated the effects of isobutylmethylxanthine (IBMX) and methyl-β-cyclodextrin (MβCD) on bovine sperm capacitation and on the preimplantation developmental potential of bovine embryos generated by ICSI. Treatment with IBMX and MβCD decreased sperm viability (between 13-30%); nevertheless, 0.4 mM IBMX and 1 mM MβCD increased (p < 0.05) capacitation metrics-that is, acrosome exocytosis, intracellular calcium level, plasma membrane fluidity, and tyrosine phosphorylation-compared to the control. After ICSI, embryos injected with IBMX- and MβCD-treated sperm showed similar cleavage to the untreated group (range 82-88%). Pronucleus formation rate was higher with MβCD-pretreatment (54%) compared to the control group (25%), and blastocyst rate was significantly improved with MβCD-pretreatment (24%) compared to the IBMX (18%) and control (17%) groups. Importantly, embryo quality-as assessed by the total number of cells, cell allocation, and apoptotic cell index-was not affected by the sperm treatments. In conclusion, MβCD pretreatment of sperm improved the efficiency of blastocyst production in bovine ICSI.

Handling of Gametes for In Vitro Insemination in Birds

A characteristic biological property of avian gamete (e.g., extremely large egg and polyspermic fertilization) does not allow the direct observation of sperm-egg interactions in vitro, but recent research advances make it possible to manipulate the gamete in vitro. Here, we describe the techniques for the handling of gametes required for in vitro fertilization assay. In addition, we also introduce the procedures for sperm-perivitelline membrane assay, intracytoplasmic sperm injection, and ex ovo culture.

Effects of the histone deacetylase inhibitor 'Scriptaid' on the developmental competence of mouse embryos generated through round spermatid injection

STUDY QUESTION

Can the histone deacetylase inhibitor Scriptaid improve the efficiency of the development of round spermatid injection (ROSI)-fertilized embryos in a mouse model?

SUMMARY ANSWER

Treatment of ROSI mouse zygotes with Scriptaid increased the expression levels of several development-related genes at the blastocyst stage, resulting in more efficient in vitro development of the blastocyst and an increased birth rate of ROSI-derived embryos.

WHAT IS KNOWN ALREADY

The full-term development of embryos derived through ROSI is significantly lower than that following ICSI in humans and other species.

STUDY DESIGN, SIZE, DURATION

Oocytes, spermatozoa and round spermatids were collected from BDF1 (C57BL/6 × DBA/2) mice. For in vitro development experiments, mouse ROSI-derived zygotes were treated with Scriptaid at different concentrations (0, 125, 250, 500 and 1000 nM) and for different exposure times (0, 6, 10, 16 or 24 h). Next, blastocysts of the optimal Scriptaid-treated group and the non-treated ROSI group were separately transferred into surrogate ICR mice to compare in vivo development with the ICSI group (control). Each experiment was repeated at least three times.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Metaphase II (MII) oocytes, spermatozoa and round spermatids were obtained from sexually mature BDF1 female or male mice. The developmental potential of embryos among the three groups (the ICSI, ROSI and optimal Scriptaid-treated ROSI groups) was assessed based on the rates of obtaining zygotes, two-cell stage embryos, four-cell stage embryos, blastocysts and full-term offspring. In addition, the expression levels of development-related genes (Oct4, Nanog, Klf4 and Sox2) were analysed using real-time PCR, and the methylation states of imprinted genes (H19 and Snrpn) in these three groups were detected using methylation-specific PCR (MS-PCR) sequencing following bisulfite treatment.

MAIN RESULTS AND THE ROLE OF CHANCE

The in vitro experiments revealed that treating ROSI-derived zygotes with 250 nM Scriptaid for 10 h significantly improved the blastocyst formation rate (59%) compared with the non-treated group (38%) and further increased the birth rates of ROSI-derived embryos from 21% to 40% in vivo. Moreover, in ROSI-derived embryos, the expression of the Oct4, Nanog and Sox2 genes at the blastocyst stage was decreased, but the optimal Scriptaid treatment restored expression to a level similar to their ICSI counterparts. In addition, Scriptaid treatment moderately repaired the abnormal DNA methylation pattern in the imprinting control regions (ICRs) of H19 and Snrpn.

LARGE SCALE DATA

N/A LIMITATIONS, REASONS FOR CAUTION: Because of the ethics regarding the use of human gametes for ROSI studies, the mouse model was used as an approach to explore the effects of Scriptaid on the developmental potential of ROSI-derived embryos. However, to determine whether these findings can be applied to humans, further investigation will be required.

WIDER IMPLICATIONS OF THE FINDINGS

Scriptaid treatment provides a new means of improving the efficiency and safety of clinical human ROSI.

STUDY FUNDING/COMPETING INTERESTS

The study was financially supported through grants from the National Key Research Program of China (No. 2016YFC1304800); the National Natural Science Foundation of China (Nos: 81170756, 81571486); the Natural Science Foundation of Shanghai (Nos: 15140901700, 15ZR1424900) and the Programme for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning. There are no conflicts of interest to declare.

Sperm freeze-drying and micro-insemination for biobanking and maintenance of genetic diversity in mammals

Breeding by natural mating is ideal for maintaining animal populations. However, the lack of breeding space resulting from an increased number of strains and the decline in fertility caused by inbreeding inhibits the reproduction of subsequent generations. Reproductive technologies, such as gamete preservation and artificial fertilisation, have been developed to overcome these problems. These approaches efficiently produce offspring of laboratory, domestic and wild animals, and can also be used to treat human infertility. Gamete preservation using sperm contributes to improvements in reproductive systems and enables the use of smaller breeding spaces. Although cryopreservation with liquid nitrogen has been used to preserve spermatozoa, freeze-drying without liquid nitrogen, a novel method, facilitates long-term storage of spermatozoa. This method has recently been applied to maintain animal strains. Micro-insemination techniques, such as intracytoplasmic sperm injection (ICSI), are exceptional for improving assisted reproduction. ICSI can be used to fertilise oocytes, even with immotile and immature spermatozoa that are unsuitable for AI and IVF. Reproductive technologies provide a substantial advantage for biobanking and maintaining the genetic diversity of laboratory, domestic and wild animals. This review covers the latest method of sperm freeze-drying and micro-insemination, and future possibilities for maintaining animal strains and populations.

Fertilisation of cryopreserved sperm and unfertilised quail ovum by intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) is an important technique in animal biotechnology for animal cloning and conservation of genetic resources, but has been a challenge for avian species. In the present study, we investigated the ability of cryopreserved quail spermatozoa to achieve fertilisation and embryo development. Female quail were killed 70–120 min after previous oviposition to collect unfertilised oocytes from the oviduct. Fresh or cryopreserved–thawed spermatozoa were injected into the cytoplasm of unfertilised oocytes, and the manipulated oocytes were incubated in quail surrogate eggshells. Injection of fresh spermatozoa supplemented with inositol 1,4,5-trisphosphate (IP3) resulted in a significantly increased rate of embryo development compared with injection of fresh spermatozoa alone (90% vs 13%, respectively). Although >80% of embryos stopped cell division and development before Hamburger and Hamilton (HH) Stage 3, approximately 15% of embryos from the fresh sperm injection developed to past HH Stage 4, and one embryo survived up to HH Stage 39 (11 days of incubation). In the case of cryopreserved spermatozoa, the embryo development rate was 30% after ICSI, and this increased significantly to 74% with IP3 supplementation. In conclusion, cryopreserved spermatozoa combined with ICSI followed by surrogate eggshell culture can develop quail embryos.

Identification of small segmental translocations in patients with repeated implantation failure and recurrent miscarriage using next generation sequencing after in vitro fertilization/intracytoplasmic sperm injection

BACKGROUND

To develop a novel preimplantation genetic screening (PGS) test using next generation sequencing(NGS) as a alternative to current array comparative genomic hybridization (array CGH) method for detection of small segmental translocations in two patients with repeated implantation failure (RIF) and recurrent miscarriage (RM). Inconsistent results were resolved by validation with fluorescence in situ hybridization (FISH).

CASE PRESENTATION

One couple with normal cytogenetic and array CGH result suffered from implantation failure. Later NGS analysis showed 46,XY.ngs[GRCh37/hg19] 9p24.3-9p24.1(10,291-8,680,890×1),13q33.1-13q34(103,046,327-114,785,444×3). The other couple with normal cytogenetic and array CGH result also received NGS analysis. Due to the detected abnormal finding, which was 46,XY.ngs 4q34.3-4q35.2(179,673,982-191,016,503×3),6p25.3-6p22.3 (146,672-17,829,693×1), the couple decided against the corresponding embryo transfer.

CONCLUSIONS

The NGS approach is a reliable alternative to array CGH for the discovery of small segmental translocations in patients with RIF and RM.

Transgenic mouse offspring generated by ROSI

The production of transgenic animals is an important tool for experimental and applied biology. Over the years, many approaches for the production of transgenic animals have been tried, including pronuclear microinjection, sperm-mediated gene transfer, transfection of male germ cells, somatic cell nuclear transfer and the use of lentiviral vectors. In the present study, we developed a new transgene delivery approach, and we report for the first time the production of transgenic animals by co-injection of DNA and round spermatid nuclei into non-fertilized mouse oocytes (ROSI). The transgene used was a construct containing the human CMV immediate early promoter and the enhanced GFP gene. With this procedure, 12% of the live offspring we obtained carried the transgene. This efficiency of transgenic production by ROSI was similar to the efficiency by pronuclear injection or intracytoplasmic injection of male gamete nuclei (ICSI). However, ICSI required fewer embryos to produce the same number of transgenic animals. The expression of Egfp mRNA and fluorescence of EGFP were found in the majority of the organs examined in 4 transgenic lines generated by ROSI. Tissue morphology and transgene expression were not distinguishable between transgenic animals produced by ROSI or pronuclear injection. Furthermore, our results are of particular interest because they indicate that the transgene incorporation mediated by intracytoplasmic injection of male gamete nuclei is not an exclusive property of mature sperm cell nuclei with compact chromatin but it can be accomplished with immature sperm cell nuclei with decondensed chromatin as well. The present study also provides alternative procedures for transgene delivery into embryos or reconstituted oocytes.

In vitro matured oocytes are more susceptible than in vivo matured oocytes to mock ICSI induced functional and genetic changes

Background

Concerns regarding the safety of ICSI have been intensified recently due to increased risk of birth defects in ICSI born children. Although fertilization rate is significantly higher in ICSI cycles, studies have failed to demonstrate the benefits of ICSI in improving the pregnancy rate. Poor technical skill, and suboptimal in vitro conditions may account for the ICSI results however, there is no report on the effects of oocyte manipulations on the ICSI outcome.

Objective

The present study elucidates the influence of mock ICSI on the functional and genetic integrity of the mouse oocytes.

Methods

Reactive Oxygen Species (ROS) level, mitochondrial status, and phosphorylation of H2AX were assessed in the in vivo matured and IVM oocytes subjected to mock ICSI.

Results

A significant increase in ROS level was observed in both in vivo matured and IVM oocytes subjected to mock ICSI (P<0.05-0.001) whereas unique mitochondrial distribution pattern was found only in IVM oocytes (P<0.01-0.001). Importantly, differential H2AX phosphorylation was observed in both in vivo matured and IVM oocytes subjected to mock ICSI (P <0.001).

Conclusion

The data from this study suggests that mock ICSI can alter genetic and functional integrity in oocytes and IVM oocytes are more vulnerable to mock ICSI induced changes.

mir-34b/c and mir-449a/b/c are required for spermatogenesis, but not for the first cleavage division in mice

Mammalian sperm are carriers of not only the paternal genome, but also the paternal epigenome in the forms of DNA methylation, retained histones and noncoding RNAs. Although paternal DNA methylation and histone retention sites have been correlated with protein-coding genes that are critical for preimplantation embryonic development, physiological evidence of an essential role of these epigenetic marks in fertilization and early development remains lacking. Two miRNA clusters consisting of five miRNAs (miR-34b/c and miR-449a/b/c) are present in sperm, but absent in oocytes, and miR-34c has been reported to be essential for the first cleavage division in vitro. Here, we show that both miR-34b/c- and miR-449-null male mice displayed normal fertility, and that intracytoplasmic injection of either miR-34b/c- or miR-449-null sperm led to normal fertilization, normal preimplantation development and normal birth rate. However, miR-34b/c and miR-449 double knockout (miR-dKO) males were infertile due to severe spermatogenic disruptions and oligo-astheno-teratozoospermia. Injection of miR-dKO sperm into wild-type oocytes led to a block at the two-pronucleus to zygote transition, whereas normal preimplantation development and healthy pups were obtained through injection of miR-dKO round spermatids. Our data demonstrate that miR-34b/c and miR-449a/b/c are essential for normal spermatogenesis and male fertility, but their presence in sperm is dispensable for fertilization and preimplantation development.

Simple gamete preservation and artificial reproduction of mammals using micro-insemination techniques

Assisted reproductive technology (ART) has been applied in various procedures as an effective breeding method in experimental, domestic, and wild animals, and for the treatment of human infertility. Micro-insemination techniques such as intracytoplasmic injection of spermatozoa and spermatids are now routinely used ART tools. With these techniques, even immotile and immature sperm cells can be employed as donors for producing the next generation. Gamete preservation, another ART tool, has contributed to reproductive regulation, worldwide transportation, and disease protection of animal strains, and the preserved gametes have been effectively used for the production of offspring. ART is now an indispensable tool in mammalian reproduction. This review covers the latest ART tools, with a particular emphasis on micro-insemination and gamete preservation, and discusses the future direction of mammalian artificial reproductive technology.

Potential roles of noncoding RNAs in environmental epigenetic transgenerational inheritance

"Epigenetic transgenerational inheritance" (ETI) has been defined as germline (sperm or egg) transmission of epigenetic information between generations in the absence of direct exposures or genetic manipulations. Among reported cases of ETI in mammals, the majority are induced by environmental factors, including environmental toxicants [e.g. agricultural fungicide vinclozolin, plastic additive bisphenol A, pesticide methoxychlor, dioxin, di-(2-ethylhexyl) phthalate, dichlorodiphenyltrichloroethane, and hydrocarbons] and poor nutritional conditions. Although the ETI phenomenon is well established, the underlying mechanism remains elusive. Putative epimutations, including changes in DNA methylation and histone modification patterns, have been reported, but it remains unclear how these epimutations are formed in the first place, and how they are memorized in the germline and then get transmitted to subsequent generations. Based on recent advances in our understanding of regulatory noncoding RNAs (ncRNAs), I propose that ncRNAs are involved in ETI, during both the initial epimutation formation and the subsequent germline transmission of epimutations. ncRNAs can function at epigenetic levels by affecting DNA methylation and histone modifications, thereby changing gene transcriptional activities, which can lead to an altered mRNA transcriptome associated with a disease phenotype. Alternatively, novel or altered ncRNA expression can cause dysregulated post-transcriptional regulation, thus directly affecting the mRNA transcriptome and inducing a disease phenotype. Sperm-borne ncRNAs are potential mediators for epigenetic memory across generations, but they alone may not be sufficient for stable transmission of epimutations across generations. Overall, research on ncRNAs in the context of ETI is urgently needed to shed light on the underlying mechanism of ETI.

Intracytoplasmic sperm injection affects embryo developmental potential and gene expression in cattle

Some reports have linked intracytoplasmic sperm injection (ICSI) with chromosomal abnormalities, low developmental potential and altered gene expression in embryos. ICSI has also been linked with obesity, early aging and increased incidence of tumors in offspring. Other reports have demonstrated that some of these complications disappeared within a few weeks of life or even showed a lack of such associations. The aim of this study was to evaluate and compare embryo development, quality and gene expression in bovine embryos generated by ICSI and by conventional in vitro fertilization (IVF) insemination. The results showed differences in cleavage (88.5% in IVF and 64.1% in ICSI) and blastocyst formation rates (36.1% in IVF and 22.3% in ICSI). The proportion of ICM cells to total cell count was higher in ICSI (39.2%) than in IVF embryos (29.5%). However, no differences were observed in the total embryonic cell numbers (159.3±28.5 and 161.2±56.2 for IVF and ICSI, respectively) or in the proportion of apoptotic nuclei to the total embryonic cell numbers (2.12 and 2.64% for IVF and ICSI, respectively). Gene expression analysis showed a down-regulation of insulin-like growth factor 2 (IGF2) and overexpression of bcl-2-like protein 4 (BAX), octamer-binding transcription factor four (OCT4), interferon-tau (IFNt), Mn-superoxide dismutase in the mitochondria (SOD2), and catalase (CAT) in embryos generated by ICSI. In conclusion, our study demonstrated differences in the morphological development of bovine embryos as well as in the expression of genes involved in early development between ICSI and IVF embryos. The results may indicate lower developmental potential of ICSI embryos compared with that of IVF.

The birth of quail chicks after intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) has been successfully used to produce offspring in several mammalian species including humans. However, ICSI has not been successful in birds because of the size of the egg and difficulty in mimicking the physiological polyspermy that takes place during normal fertilization. Microsurgical injection of 20 or more spermatozoa into an egg is detrimental to its survival. Here, we report that injection of a single spermatozoon with a small volume of sperm extract (SE) or its components led to the development and birth of healthy quail chicks. SE contains three factors – phospholipase Cζ (PLCZ), aconitate hydratase (AH) and citrate synthase (CS) – all of which are essential for full egg activation and subsequent embryonic development. PLCZ induces an immediate, transient Ca2+ rise required for the resumption of meiosis. AH and CS are required for long-lasting, spiral-like Ca2+ oscillations within the activated egg, which are essential for cell cycle progression in early embryos. We also found that co-injection of cRNAs encoding PLCZ, AH and CS support the full development of ICSI-generated zygotes without the use of SE. These findings will aid our understanding of the mechanism of avian fertilization and embryo development, as well as assisting in the manipulation of the avian genome and the production of transgenic and cloned birds.

The latest improvements in the mouse sperm preservation

Sperm preservation is an important technique for maintaining valuable genetic resources in biomedical research and wildlife. In the mouse, the sperm cryopreservation method has been established and adopted by large-scale sperm preservation projects in cryobanks. Recently, a new sperm preservation method using freeze-drying has been studied in various mammals. Freeze-drying is the ultimate method by which sperm can be preserved long term in a refrigerator (4 °C). And it is possible to realize easy and safe transportation of sperm at an ambient temperature that requires neither liquid nitrogen nor dry ice. Furthermore, it has been demonstrated that the fertilizing ability of sperm cryopreserved or freeze-dried by the methods described in this chapter is well maintained during long-term preservation. This chapter introduces the latest protocols for cryopreservation and freeze-drying of mouse sperm, and the anticipated results of the fertilizing ability of these sperm preserved long-term.

Treatment of male infertility

Major difficulties exist in the accurate and meaningful diagnosis of male reproductive dysfunction, and our understanding of the epidemiology and etiology of male infertility has proven quite complex.The numerous spermatozoa produced in mammals and other species provides some degree of protection against adverse environmental conditions represented by physical and chemical factors that can reduce reproductive function and increase gonadal damage even resulting in testicular cancer or congenital malformations. The wide fluctuations of sperm production in men, both geographical and temporal, may reflect disparate environmental exposures, occurring on differing genetic backgrounds, in varying psychosocial conditions, and leading to the diversified observed outcomes.Sperm analysis is still the cornerstone in diagnosis of male factor infertility, indeed, individually compromised semen paramaters while adequately address therapeutic practices is progressively flanked by additional tests. Administration of drugs, IUI, correction of varicocele, and, to a certain extent, IVF although they may not be capable of restoring fertility itself often result in childbearing.

Effect of sperm pretreatment with sodium hydroxide and dithiothreitol on the efficiency of bovine intracytoplasmic sperm injection

The efficiency of intracytoplasmic sperm injection (ICSI) in bovines is lower than in other species due, in part, to a lack of optimal conditions for its implementation; this has hindered the achievement of high rates of embryonic development and the birth of live offspring. The aim of the present study was to evaluate the effects of pretreatment of bovine spermatozoa with NaOH and dithiothreitol (DTT) on the viability, plasma membrane integrity, DNA fragmentation and in vitro developmental potential of embryos generated by ICSI. Following pretreatment of spermatozoa with 5 mM DTT for 20 min and a low concentration of NaOH (1 mM for 60 min), there were fewer live and acrosome reacted spermatozoa (44% and 34%, respectively) than in the control group without treatment (82%). Spermatozoa subjected to higher alkali concentrations (10–50 mM) were mostly dead and reacted. However, pronuclear formation, cleavage, blastocyst rate and embryo quality did not differ between these pretreatment groups and the untreated control group. In conclusion, we have described, for the first time, the effects of NaOH treatment on bovine spermatozoa and subsequent in vitro embryonic development after ICSI, and have demonstrated that pretreatment of bovine spermatozoa with NaOH or DTT is not necessary for an appropriate in vitro embryo development in this species.

Embryo manipulation via assisted reproductive technology and epigenetic asymmetry in mammalian early development

The early stage of mammalian development from fertilization to implantation is a period when global and differential changes in the epigenetic landscape occur in paternally and maternally derived genomes, respectively. The sperm and egg DNA methylation profiles are very different from each other, and just after fertilization, only the paternally derived genome is subjected to genome-wide hydroxylation of 5-methylcytosine, resulting in an epigenetic asymmetry in parentally derived genomes. Although most of these differences are not present by the blastocyst stage, presumably due to passive demethylation, the maintenance of genomic imprinting memory and X chromosome inactivation in this stage are of critical importance for post-implantation development. Zygotic gene activation from paternally or maternally derived genomes also starts around the two-cell stage, presumably in a different manner in each of them. It is during this period that embryo manipulation, including assisted reproductive technology, is normally performed; so it is critically important to determine whether embryo manipulation procedures increase developmental risks by disturbing subsequent gene expression during the embryonic and/or neonatal development stages. In this review, we discuss the effects of various embryo manipulation procedures applied at the fertilization stage in relation to the epigenetic asymmetry in pre-implantation development. In particular, we focus on the effects of intracytoplasmic sperm injection that can result in long-lasting transcriptome disturbances, at least in mice.

Safety, efficacy and efficiency of laser-assisted IVF in subfertile mutant mouse strains

In the present report we studied the safety, efficacy and efficiency of using an infrared laser to facilitate IVF by assessing fertilization, development and birth rates after laser-zona drilling (LZD) in 30 subfertile genetically modified (GM) mouse lines. We determined that LZD increased the fertilization rate four to ten times that of regular IVF, thus facilitating the derivation of 26 of 30 (86.7%) GM mouse lines. Cryopreserved two-cell stage embryos derived by LZD-assisted IVF were recovered and developed to blastocysts in vitro at the same rate as frozen-thawed embryos derived by regular IVF. Surprisingly after surgical transfer to pseudopregnant recipients the birth rate of embryos derived by LZD-assisted IVF was significantly lower than that of embryos derived by regular IVF. However this result could be completely mitigated by the addition of 0.25 M sucrose to the culture medium during LZD which caused the oocyte to shrink in volume relative to the perivitelline space. By increasing the distance from the laser target site on the zona pellucida, we hypothesize that the hyperosmotic effect of sucrose reduced the potential for laser-induced cytotoxic thermal damage to the underlying oocytes. With appropriate preparation and cautious application, our results indicate that LZD-assisted IVF is a safe, efficacious and efficient assisted reproductive technology for deriving mutant mouse lines with male factor infertility and subfertility caused by sperm-zona penetration defects.