Increased disruption of sperm plasma membrane at sperm immobilization promotes dissociation of perinuclear theca from sperm chromatin after intracytoplasmic sperm injection in pigs

Aggressive sperm immobilization improves reproductive outcomes in patients with suboptimal semen parameters and previous ICSI fertilization failure

Intracytoplasmic sperm injection (ICSI) is the most effective procedure to resolve male infertility, enhancing overall fertilization and pregnancy outcomes. However, it is important to note that fertilization failure (FF) can still occur in a few cases after ICSI. This study aims to introduce a specialized technique of aggressive sperm immobilization for ICSI and evaluate its impact on reproductive outcomes in cases involving prior fertilization failure. All infertile couples with male partners having suboptimal semen samples and previous ICSI fertilization failure were evaluated using retrospective data from National Taiwan tertiary university hospital (NTUH) between January 2016 and February 2022. Fertilization failure in our study was defined as less than 30% fertilization rate (FR, the number of normally fertilized oocytes divided by the total number of injected mature oocytes). Data involving both standard (routine procedure) and aggressive sperm immobilization (SI) techniques during different ICSI cycles were included in this study. Standard and aggressive SI methods were performed by compressing the distal half tail of the spermatozoa ≦ 5 and 15 times prior to ICSI respectively. Generalized estimating equations analysis were applied to compare the clinical outcomes between two procedures. Overall, data from 23 infertile couples who had undergone 65 ICSI cycles (31 standard SI with low fertilization rate and 34 aggressive SI) were included in the study. The average FR in the ICSI cycles with standard SI and aggressive SI were 23.6 ± 23.1% and 49.5 ± 31.8 respectively (P = 0.0002). The majority of embryos were transferred at the day 3 stage, with an average number transferred of 2.6 ± 0.9 in the aggressive SI group and 1.9 ± 0.9 in the standard group. The number of embryos transferred per transfer cycle was higher in the aggressive SI (P = 0.015), whereas the number of good-quality embryos was similar between the two procedures (P = 0.44). There were one and seven live births from the standard SI cycles and aggressive SI cycles respectively. In conclusion, aggressive SI was associated with a significantly higher FR, resulting in more available embryos for transfer without compromising embryo quality. Therefore, this specialized technique improved pregnancy outcome among infertile couples with a previous ICSI-FF. It can be a safe, economic, and effective method to improve the assisted reproductive technologies outcomes for infertile patients affected by previous ICSI-FF.

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.

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.

Porcine model for the study of sperm capacitation, fertilization and male fertility

Mammalian fertilization remains a poorly understood event with the vast majority of studies done in the mouse model. The purpose of this review is to revise the current knowledge about semen deposition, sperm transport, sperm capacitation, gamete interactions and early embryonic development with a focus on the porcine model as a relevant, alternative model organism to humans. The review provides a thorough overview of post-ejaculation events inside the sow's reproductive tract including comparisons with humans and implications for human fertilization and assisted reproductive therapy (ART). Porcine methodology for sperm handling, preservation, in vitro capacitation, oocyte in vitro maturation, in vitro fertilization and intra-cytoplasmic sperm injection that are routinely used in pig research laboratories can be successfully translated into ART to treat human infertility. Last, but not least, new knowledge about mitochondrial inheritance in the pig can provide an insight into human mitochondrial diseases and new knowledge on polyspermy defense mechanisms could contribute to the development of new male contraceptives.

Lower blastocyst quality after conventional vs. Piezo ICSI in the horse reflects delayed sperm component remodeling and oocyte activation

PURPOSE

The aim of this study was to evaluate the differential effects of conventional and Piezo-driven ICSI on blastocyst development, and on sperm component remodeling and oocyte activation, in an equine model.

METHODS

In vitro-matured equine oocytes underwent conventional (Conv) or Piezo ICSI, the latter utilizing fluorocarbon ballast. Blastocyst development was compared between treatments to validate the model. Then, oocytes were fixed at 0, 6, or 18 h after injection, and stained for the sperm tail, acrosome, oocyte cortical granules, and chromatin. These parameters were compared between injection techniques and between sham-injected and sperm-injected oocytes among time periods.

RESULTS

Blastocyst rates were 39 and 40%. The nucleus number was lower, and the nuclear fragmentation rate was higher, in blastocysts produced by Conv. Cortical granule loss started at 0H after both sperm and sham injection. The acrosome was present at 0H in both ICSI treatments, and persisted to 18H in significantly more Conv than Piezo oocytes (72 vs. 21%). Sperm head area was unchanged at 6H in Conv but significantly increased at this time in Piezo; correspondingly, at 6H significantly more Conv than Piezo oocytes remained at MII (80 vs. 9.5%). Sham injection did not induce significant meiotic resumption.

CONCLUSIONS

These data show that Piezo ICSI is associated with more rapid sperm component remodeling and oocyte meiotic resumption after sperm injection than is conventional ICSI, and with higher embryo quality at the blastocyst stage. This suggests that there is value in exploring the Piezo technique, utilized with a non-toxic fluorocarbon ballast, for use in clinical human ICSI.

Pretreating porcine sperm with lipase enhances developmental competence of embryos produced by intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) has been widely applied in humans, mice, and some domestic animals to cure human infertility, or produce genetically superior or genetically engineered animals. However, the production efficiency of ICSI in pigs remains quite low. In this study, we developed a new sperm pretreatment method to improve production efficiency of ICSI in pigs. Experiment 1 revealed that pretreating porcine sperm with 2.5 mg/ml lipase before ICSI operation, not only can reduce the adhesion between sperm and the injection pipette without adding polyvinylpyrrolidone (PVP) in the operating medium, but also significantly improve male pronuclei (MPN) formation rate (55.56% vs. 40.00% (0 mg/ml), 42.59% (5.0 mg/ml), 40.00% (10.0 mg/ml), P < 0.05) and enhance developmental competence of ICSI embryos (26.03% vs. 10.87% (0 mg/ml), 10.00% (5.0 mg/ml), 10.13% (10.0 mg/ml), P < 0.05). Experiment 2 showed that this method has a higher MPN formation rate (50.47% vs. 30.78%, P < 0.05) and blastocyst rate (18.81% vs. 7.41%, P < 0.05) than the PVP method, and was better than the Triton X-100 treatment method (50.47% vs. 46.23%, 18.81% vs. 12.75%). Therefore, pretreating porcine sperm with 2.5 mg/ml lipase before ICSI operation is highly recommended, instead of adding PVP in the operating medium.

Understanding the spermatozoon

The former perception of the spermatozoon as a delivery device of the male genome has been expanded to include a new understanding of the cell's complex role in fertilization. Once the spermatozoon reaches the oocyte, it triggers egg activation and orchestrates the stages of pre- and post-fertilization in a preprogrammed pattern while tapping the oocyte's resources in an effort to generate a new life.

Sperm capacitation combined with removal of the sperm acrosome and plasma membrane enhances paternal nucleus remodelling and early development of bovine androgenetic embryos

The androgenetic embryo is a useful model for functional analysis of the paternal genome during embryogenesis. However, few studies have focused on the factors involved in the suppressed developmental competence of such embryos or why sperm cloning-derived androgenetic embryos fail to develop beyond the morula stage in large domestic animals. To overcome this developmental failure, we tried to improve sperm decondensation, as well as to enhance embryonic development by sperm capacitation and removal of the acrosome and plasma membrane before injection of the spermatozoa. Before injection of the spermatozoa, we quantified the effects of sperm capacitation combined with sperm pretreatment on the acrosome and plasma membrane status. We also evaluated sperm decondensation potential, sperm viability and chromatin integrity. Immunostaining data showed that the sperm acrosome and plasma membrane could be more efficiently removed after capacitation. Dithiothreitol-induced sperm decondensation potential was improved with capacitation and removal of the acrosome and plasma membrane. Although most spermatozoa lost viability after pretreatment, their chromatin remained integrated. The patterns of paternal chromatin remodelling within uncleaved androgenetic embryos and the nucleus morphology of cleaved embryos indicated that capacitation combined with membrane disruption could make injected spermatozoa decondense synchronously not only with each other, but also with the developmental pace of the ooplasm. We successfully produced androgenetic blastocysts, and efficiency increased with sperm pretreatment. In conclusion, sperm decondensation and the early development of androgenetic embryos were enhanced with sperm capacitation and removal of the acrosome and plasma membrane prior to sperm injection.

Nucleoli from two-cell embryos support the development of enucleolated germinal vesicle oocytes in the pig

Recent research has shown that nucleoli of oocytes at the germinal vesicle (GV) stage (GV nucleoli) are not necessary for oocyte maturation but are essential for early embryonic development. Nucleoli of 2-cell embryos (2-cell nucleoli) have morphology similar to that of nucleoli in oocytes at the GV stage. In this study, we examined the ability of 2-cell nucleoli to substitute for GV nucleoli in terms of supporting early embryonic development by nucleolus aspiration (enucleolation) and transfer into metaphase II (MII) oocytes or 2-cell embryos that were derived from enucleolated oocytes at the GV stage in the pig. When 2-cell embryos were centrifuged to move the lipid droplets to one side of the blastomere, multiple nucleoli in the nucleus fused into a single nucleolus. The nucleoli were then aspirated from the 2-cell embryos by micromanipulation. The injection of 2-cell nucleoli to GV enucleolated oocytes at the MII stage rescued the embryos from the early embryonic arrest, and the resulting oocytes developed to blastocysts. However, the injection of 2-cell and GV nucleoli to 2-cell embryos derived from GV enucleolated oocytes rarely restored the development to blastocysts. These results indicate that 2-cell nucleoli support early embryonic development as GV nucleoli and that the presence of nucleoli is essential for pig embryos before the 2-cell stage.

Pre-treatment of sperm reduces success of ICSI in the pig

In pigs, although ICSI is a feasible fertilization technique, its efficiency is low. In general, injected pig sperm are insufficient to induce oocyte activation and embryonic development. Pretreatments for disrupting sperm membranes have been applied to improve the fertility of ICSI oocytes; however, we hypothesize that such pretreatment(s) may reduce the ability of the sperm to induce oocyte activation. We first evaluated the effects of sperm pretreatments (sonication (SO) to isolate the sperm heads from the tails, Triton X-100 (TX), and three cycles of repeated freezing/thawing (3×-FT) for disrupting sperm membranes) on the rate of pronucleus (PN) formation after ICSI. We found that oocytes injected with control (whole) sperm had higher rates of PN formation than those obtained after subjecting the sperm to SO, TX, and 3×-FT. The amounts of phospholipase Cζ (PLCζ), which is thought to be the oocyte-activating factor in mammalian sperm, in sperm treated by each method was significantly lower than that in whole untreated sperm. Furthermore, using immunofluorescence, it was found that in pig sperm, PLCζ was localized to both the post-acrosomal region and the tail area. Thus we demonstrated for the first time that sperm pretreatment leads to a reduction of oocyte-activating capacity. Our data also show that in addition to its expected localization to the sperm head, PLCζ is also localized in the tail of pig sperm, thus raising the possibility that injection of whole sperm may be required to attain successful activation in pigs.

Nucleoli from growing oocytes inhibit the maturation of enucleolated, full-grown oocytes in the pig

In mammals, the nucleolus of full-grown oocyte is essential for embryonic development but not for oocyte maturation. In our study, the role of the growing oocyte nucleolus in oocyte maturation was examined by nucleolus removal and/or transfer into previously enucleolated, growing (around 100 µm in diameter) or full-grown (120 µm) pig oocytes. In the first experiment, the nucleoli were aspirated from growing oocytes whose nucleoli had been compacted by actinomycin D treatment, and the enucleolated oocytes were matured in vitro. Most of non-treated or actinomycin D-treated oocytes did not undergo germinal vesicle breakdown (GVBD; 13% and 12%, respectively). However, the GVBD rate of enucleolated, growing oocytes significantly increased to 46%. The low GVBD rate of enucleolated, growing oocytes was restored again by the re-injection of nucleoli from growing oocytes (23%), but not when nucleoli from full-grown oocytes were re-injected into enucleolated, growing oocytes (49%). When enucleolated, full-grown oocytes were injected with nucleoli from growing or full-grown oocytes, the nucleolus in the germinal vesicle was reassembled (73% and 60%, respectively). After maturation, the enucleolated, full-grown oocytes injected with nucleoli from full-grown oocytes matured to metaphase II (56%), whereas injection with growing-oocyte nucleoli reduced this maturation to 21%. These results suggest that the growing-oocyte nucleolus is involved in the oocyte's meiotic arrest, and that the full-grown oocyte nucleolus has lost the ability.

Nucleoli from growing oocytes support the development of enucleolated full-grown oocytes in the pig

Recent research has shown that the maternal nucleolus is essential for embryonic development. The morphology of the nucleolus in growing oocytes differs from that in full-grown oocytes. We determined the ability of nucleoli from growing oocytes to substitute for nucleoli of full-grown oocytes in terms of supporting embryonic development in this study. Growing (around 100 microm in diameter) and full-grown porcine oocytes (120 microm) were collected from small (0.6-1.0 mm) and large antral follicles (4-5 mm), respectively. The nucleolus was aspirated from full-grown oocytes by micromanipulation, and the resulting enucleolated oocytes were matured to metaphase II; the nucleoli originating from full-grown and growing oocytes were then injected into the oocytes. The Chromatin of growing oocytes was aspirated with the nucleolus during the enucleolation process. Growing oocytes were thus treated with actinomycin D to release the chromatin from their nucleoli, and the nucleoli were collected and transferred to the enucleolated and matured full-grown oocytes. After activation by electro-stimulation, nucleoli were formed in pronuclei of sham-operated oocytes. Enucleolated oocytes that had been injected with nucleoli from either full-grown or growing, however, did not form any nucleoli in the pronuclei. No enucleolated oocytes developed to blastocysts, whereas enucleolated oocytes injected with nucleoli from full-grown oocytes (15%) or growing oocytes (18%) developed to blastocysts. These results indicate that the nucleoli from growing oocytes can substitute for nucleoli from full-grown oocytes during early embryonic development.

Effect of PVP on sperm capacitation status and embryonic development in cattle

The objective of this study was to investigate the effects of polyvinylpyrrolidone (PVP) on sperm capacitation status and embryonic development in cattle (Bos taurus). Acrosome-reacted sperm (chlortetracycline stain) and the fertilization rate after intracytoplasmic sperm injection (ICSI) were enhanced (P<0.05) when sperm were cultured in a medium containing 10% PVP. However, injection of bovine in vitro-produced (IVP) embryos with medium containing 10% PVP suppressed development of these embryos to the 2-cell, morula, and blastocyst stages and cell number at the blastocyst stage (P<0.01) but did not affect chromosomal integrity (P>0.05). Embryo developmental capacity differed (P<0.01) among PVP from three suppliers, but there were no significant differences among three solvent media. The PVP remained localized in 40.9% of PVP-injected IVP embryos. In conclusion, PVP affected the acrosome reaction and enhanced the fertilization rate after ICSI. However, PVP remained detectable in IVP embryos and suppressed their developmental capacity.

Viability, acrosome morphology and fertilizing capacity of boar spermatozoa treated with strontium chloride

The positive effect of strontium ions (Sr2+) on sperm motility, capacitation and acrosome reaction has been demonstrated in the mouse, human, guinea pig and hamster. In the present study, we have evaluated the effect of Sr2+ on the viability and acrosome morphology of boar spermatozoa, and on the fertilization and development after the microinjection of Sr2+-treated spermatozoa into porcine oocytes. Before incubation, 79% of spermatozoa were classified as propidium iodide (PI)-negative (live) using the LIVE/DEAD Sperm Viability Kit. After incubation with strontium chloride (SrCl2), 39% (0 mM; no divalent cations), 25% (1.9 mM) and 24% (7.5 mM) of them were classified as PI-negative. The proportion of spermatozoa that had initiated the acrosome reaction was higher in Sr2+-containing medium than in Sr2+-free medium, when assessed by electron microscopy. There was no significant difference in percentage of spermatozoa initiating the acrosome reaction between Sr2+-treated groups (1.9 mM: 22%, 7.5 mM: 33%, p > 0.05). After the microinjection of spermatozoa incubated with SrCl2, 67% (1.9 mM) and 61% (7.5 mM) of injected oocytes were successfully fertilized, and then 43% (1.9 mM) and 41% (7.5 mM) contained a fully decondensed sperm head. Sham-injected oocytes were significantly activated at a lower rate than Sr2+-treated groups (27%, p < 0.05). Next, after microinjection of spermatozoa incubated with 1.9 mM SrCl2 (n = 51), 45% of injected oocytes cleaved on day 2, and 18% developed to blastocysts on day 7 (sham-injection, n = 48: 15% to cleavage and 0% to blastocyst). These results demonstrate that Sr2+ is likely to positively affect the fertilizing capacity of spermatozoa in the pig.

Effects of sperm pretreatment on efficiency of ICSI-mediated gene transfer in pigs

Intracytoplasmic sperm injection (ICSI)-mediated gene transfer has recently been shown to be an effective technique for producing transgenic pigs; however, the types of sperm pretreatment having the most beneficial effects on post-ICSI embryogenesis or transgenic efficiency have not been clarified. In the present study, we performed ICSI-mediated gene transfer using pig sperm subjected to various pretreatments and determined the developmental potential of sperm-injected oocytes and introduction efficiency of exogenous DNA. Embryos were then transferred to recipient pigs to confirm gene transfer efficiency during the fetal period. When ICSI was performed using unfrozen sperm heads with tails removed by piezo-pulse, the rates of blastocyst formation (14.2%, 17/120) and transgene (EGFP) expression (11.8%, 2/17) were both low. When unfrozen sperm heads were used that were removed by sonication, EGFP expression efficiency (11/21, 52.4%) improved significantly (P<0.05). Pretreatment of unfrozen sperm with a surfactant or acrosomal reaction did not further improve the rates of blastocyst formation and EGFP expression. However, use of the heads of sperm frozen-thawed with or without a cryoprotective agent resulted in rates of blastocyst formation and EGFP expression that tended to be generally high (23.0%, 14/61-33.8%, 26/77 and 42.9%, 6/14-66.7%, 10/15). A total of 219 in vitro matured oocytes were fertilized by ICSI-mediated gene transfer using the heads of frozen-thawed sperm and then transferred into two recipient pigs. Seven fetuses were obtained, and EGFP expression and integration of the transgene (10-30 copies) were confirmed in two of the seven fetuses. Use of unfrozen sperm thus confers no advantages on ICSI-mediated gene transfer, and although further investigations are needed, frozen-thawed sperm heads appear to be useful in ICSI-mediated gene transfer.

Ubiquitin C-terminal hydrolase-activity is involved in sperm acrosomal function and anti-polyspermy defense during porcine fertilization

The 26S proteasome, which is a multi-subunit protease with specificity for substrate proteins that are postranslationally modified by ubiquitination, has been implicated in acrosomal function and sperm-zona pellucida (ZP) penetration during mammalian fertilization. Ubiquitin C-terminal hydrolases (UCHs) are responsible for the removal of polyubiquitin chains during substrate priming for proteasomal proteolysis. The inhibition of deubiquitination increases the rate of proteasomal proteolysis. Consequently, we have hypothesized that inhibition of sperm acrosome-borne UCHs increases the rate of sperm-ZP penetration and polyspermy during porcine in vitro fertilization (IVF). Ubiquitin aldehyde (UA), which is a specific nonpermeating UCH inhibitor, significantly (P < 0.05) increased polyspermy during porcine IVF and reduced (P < 0.05) UCH enzymatic activity measured in motile boar spermatozoa using a specific fluorometric UCH substrate, ubiquitin-AMC. Antibodies against two closely related UCHs, UCHL1 and UCHL3, detected these UCHs in the oocyte cortex and on the sperm acrosome, respectively, and increased the rate of polyspermy during IVF, consistent with the UA-induced polyspermy surge. In the oocyte, UCHL3 was primarily associated with the meiotic spindle. Sperm-borne UCHL3 was localized to the acrosomal surface and coimmunoprecipitated with a peripheral acrosomal membrane protein, spermadhesin AQN1. Recombinant UCHs, UCHL3, and isopeptidase T reduced polyspermy when added to the fertilization medium. UCHL1 was detected in the oocyte cortex but not on the sperm surface, and was partially degraded 6-8 h after fertilization. Enucleated oocyte-somatic cell electrofusion caused polarized redistribution of cortical UCHL1. We conclude that sperm-acrosomal UCHs are involved in sperm-ZP interactions and antipolyspermy defense. Modulation of UCH activity could facilitate the management of polyspermy during IVF and provide insights into male infertility.

Improved fertilization and embryo development resulting in birth of live piglets after intracytoplasmic sperm injection and in vitro culture in a cysteine-supplemented medium

The effects of cysteine treatment on fertilization rate, intracellular concentration of glutathione, and embryo development in vitro and after embryo transfer were examined following intracytoplasmic sperm injection (ICSI) of in vitro-matured porcine oocytes using a piezo drive unit. Culture of presumed zygotes after ICSI with 1.71-3.71 mM cysteine for 3-12h improved (P<0.05) fertilization rates as compared to treatment with 0.57 mM cysteine or to controls (0mM) (56 to 68%, 48%, 35%, respectively). Extension of treatment time with cysteine beyond 3h did not further increase fertilization rates, suggesting that cysteine promoted early developmental events after ICSI (e.g. decondensation of sperm chromatin). There was no effect of cysteine supplementation on oocyte glutathione levels after ICSI. Pretreatment of spermatozoa for 3h with 1.71 mM cysteine did not improve fertilization rates. The incidence of blastocysts formation when cultured in 1.71 mM cysteine for 3h after ICSI was 31%, which was higher (P<0.05) than controls (18%). Transfer of 20-38 embryos cultured with 1.71 mM cysteine for 3h after ICSI to each of seven recipients yielded three deliveries with an average litter size of 4.0. We concluded that cysteine supplementation for the first 3h after ICSI improved fertilization and embryo development rates, with no influence on glutathione levels in oocytes, and that the cysteine-treated ICSI embryos developed to full term. The study also showed that porcine oocytes matured in a chemically defined medium had the ability for full-term development after piezo-ICSI without additional treatments for oocyte activation.

Simultaneous removal of sperm plasma membrane and acrosome before intracytoplasmic sperm injection improves oocyte activation/embryonic development

Direct injection of a single spermatozoon into an oocyte (ICSI) can produce apparently normal offspring. Although the production of normal offspring by ICSI has been successful in mice and humans, it has been less successful in many other species. The reason for this is not clear, but could be, in part, due to inconsistent activation of oocytes because of delayed disintegration of sperm plasma membrane within oocytes and incorporation of the acrosome containing a spectrum of hydrolyzing enzymes. In the mouse, the removal of sperm plasma membrane and acrosome was not a prerequisite to produce offspring by ICSI, but it resulted in earlier onset of oocyte activation and better embryonic development. The best result was obtained when spermatozoa were demembranated individually immediately before ICSI by using lysolecithin, a hydrolysis product of membrane phospholipids.