Beneficial effects of electrical stimulation before round spermatid nuclei injections into rabbit oocytes on fertilization and subsequent embryonic development

Use of assisted reproductive technologies (ARTs) to shorten the generational interval in ruminants: current status and perspectives

The challenges posed by climate change and increasing world population are stimulating renewed efforts for improving the sustainability of animal production. To meet such challenges, the contribution of genomic selection approaches, in combination with assisted reproductive technologies (ARTs), to spreading and preserving animal genetics is essential. The largest increase in genetic gain can be achieved by shortening the generation interval. This review provides an overview of the current status and progress of advanced ARTs that could be applied to reduce the generation time in both female and male of domestic ruminants. In females, the use of juvenile in vitro embryo transfer (JIVET) enables to generate offspring after the transfer of in vitro produced embryos derived from oocytes of prepubertal genetically superior donors reducing the generational interval and acceleration genetic gain. The current challenge is increasing in vitro embryo production (IVEP) from prepubertal derived oocytes which is still low and variable. The two main factors limiting IVEP success are the intrinsic quality of prepubertal oocytes and the culture systems for in vitro maturation (IVM). In males, advancements in ARTs are providing new strategies to in vitro propagate spermatogonia and differentiate them into mature sperm or even to recapitulate the whole process of spermatogenesis from embryonic stem cells. Moreover, the successful use of immature cells, such as round spermatids, for intracytoplasmic injection (ROSI) and IVEP could allow to complete the entire process in few months. However, these approaches have been successfully applied to human and mouse whereas only a few studies have been published in ruminants and results are still controversial. This is also dependent on the efficiency of ROSI that is limited by the current isolation and selection protocols of round spermatids. In conclusion, the current efforts for improving these reproductive methodologies could lead toward a significant reduction of the generational interval in livestock animals that could have a considerable impact on agriculture sustainability.

Evaluating the Predictive Value of Diagnostic Testicular Biopsy for Sperm Retrieval Outcomes in Men with Non-Obstructive Azoospermia

BACKGROUND

Non-obstructive azoospermia (NOA) presents a challenge in male infertility management. This study aimed to assess the efficacy of diagnostic testicular biopsy (DTB) in predicting sperm retrieval success via therapeutic testicular biopsy (TTB) and to understand the role of systemic inflammation in microdissection testicular sperm extraction (mTESE) outcomes.

METHODS

A retrospective analysis was conducted on 50 NOA males who underwent mTESE at the University of Ioannina's Department of Urology from January 2017 to December 2019. All participants underwent thorough medical evaluations, including semen analyses and endocrinological assessments.

RESULTS

DTB did not detect spermatozoa in half of the patients who later showed positive sperm findings in TTB. Preoperative variables, such as age, plasma levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), total testosterone (TT), prolactin (PRL), estradiol (E2), and inflammation biomarkers (neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), monocyte-eosinophil ratio (MER)), were not consistently predictive of sperm retrieval success. Notably, TTB-negative patients had elevated NLR and PLR values, suggesting a possible link between systemic inflammation and reduced sperm retrieval during mTESE.

CONCLUSIONS

The findings question the necessity of an initial DTB, which might provide misleading results. A negative DTB should not deter further TTB or intracytoplasmic sperm injection (ICSI) attempts. The study emphasizes the need for further research to refine diagnostic approaches and deepen the understanding of factors influencing sperm retrieval in NOA patients, ultimately enhancing their prospects of biological parenthood.

Recent advances in critical nodes of embryo engineering technology

The normal development and maturation of oocytes and sperm, the formation of fertilized ova, the implantation of early embryos, and the growth and development of foetuses are the biological basis of mammalian reproduction. Therefore, research on oocytes has always occupied a very important position in the life sciences and reproductive medicine fields. Various embryo engineering technologies for oocytes, early embryo formation and subsequent developmental stages and different target sites, such as gene editing, intracytoplasmic sperm injection (ICSI), preimplantation genetic diagnosis (PGD), and somatic cell nuclear transfer (SCNT) technologies, have all been established and widely used in industrialization. However, as research continues to deepen and target species become more advanced, embryo engineering technology has also been developing in a more complex and sophisticated direction. At the same time, the success rate also shows a declining trend, resulting in an extension of the research and development cycle and rising costs. By studying the existing embryo engineering technology process, we discovered three critical nodes that have the greatest impact on the development of oocytes and early embryos, namely, oocyte micromanipulation, oocyte electrical activation/reconstructed embryo electrofusion, and the in vitro culture of early embryos. This article mainly demonstrates the efforts made by researchers in the relevant technologies of these three critical nodes from an engineering perspective, analyses the shortcomings of the current technology, and proposes a plan and prospects for the development of embryo engineering technology in the future.

Morphological characterization and conservation of bovine spermatogenic cells by refrigeration at 4°C and freezing using different cryoprotective molecules

The objectives of this study were study a practical method to characterize bovine spermatogenic cells and test the efficiency cells conservation by refrigeration at 4°C and cryopreservation in different solutions using two cooling curves. Cellular identification was performing by analysis of shape, size and morphology, associated with nucleus positioning and nuclear-cytoplasm ratio (NCR). Cellular samples were kept at 4°C for a period of 96 h in refrigeration solution and every 24h plasma membrane and DNA integrity were evaluated. Cryopreservation of cells was carried out using solutions containing 10% Dimethyl sulfoxide, 5% Dimethylformamide, 7% Glycerol and 7% Ethylene glycol, using a controlled and non-controlled cooling curve. Results of cellular characterization demonstrated that spermatocytes II presented a cylindrical shape, NCR of 1:1.5 and diameter ranging from 14.5 to 17.5 μm. Round spermatids presented diameter ranging from 7.6 to 13.4 μm, acrosomal cap and NCR of 1:2. Elongation and elongated spermatids showed to marked divergence in shape. There was a daily significant loss of viability of cooled cells until third day of storage, however they presented 72.77±5.16% viability after 4 days of storage at 4°C. There was no difference among the cryoprotectant solutions and cooling curves. In conclusion we demonstrated that association of microscopes and staining was a practical method to identify bovine spermatogenic cells. Furthermore, refrigeration at 4°C is an important strategy to preserve over 70% of viable cells after 4 days and cryopreservation, regardless of cryoprotectant solution or cooling curve used, can maintain over 50% of cells viable.

A novel culture system for mouse spermatid maturation which produces elongating spermatids capable of inducing calcium oscillation during fertilization and embryonic development

PURPOSE

To establish an in vitro culture system for mouse round spermatids that models spermiogenesis and enables the assessment of oocyte activation ability.

METHODS

Round spermatids and Sertoli cells were isolated from testicular tissues of B6D2F1 male mice and co-cultured in the presence of testosterone and recombinant FSH. Cultured spermatids were examined for morphology and condensation of nuclei, fertilization and development rate, and Ca²(+) oscillation pattern after ICSI.

RESULTS

The cultured spermatids elongated and resembled normal elongating spermatids in terms of both morphology and nuclear condensation. No significant differences in fertilization and development rates were observed between fresh and cultured elongating spermatids. Moreover, cultured spermatids showed similar Ca²(+) oscillation patterns to fresh elongating spermatids during an initial stage in oocyte activation.

CONCLUSIONS

These data suggest that a co-culture system of spermatids and Sertoli cells, supplemented with testosterone and recombinant FSH, supports normal differentiation of round spermatids into elongating spermatids, as assessed by their morphology, nuclear condensation, and oocyte activation ability.

Differentiation of human round spermatids into motile spermatozoa through in vitro coculture with Vero cells

Purpose

This study was undertaken to examine whether human early round spermatids will differentiate in an in vitro coculture with Vero cells.

Methods

A total of 1450 and 400 isolated early round spermatids mechanically collected from two non-obstructive and three obstructive azoospermic men with a normal karyotype were cocultured on Vero cell monolayers in minimum essential medium plus 10% fetal bovine serum, with or without 50 or 100 IU/L FSH and 1 or 10 μmol/L testosterone, at 32.5°C, in an environment of 5% CO₂ in air. Morphological changes of the spermatids were observed microscopically.

Results

After 7 days of coculture, almost half (40-50%) of the round spermatids from both non-obstructive and obstructive azoospermic men resumed spermiogenesis in vitro. Only cells from the latter patients gave rise to spermatozoa, a few of which had a motile flagellum. Low concentrations of FSH and testosterone increased the percentage of in vitro spermiogenesis.

Conclusions

Isolated round spermatids can resume spermiogenesis in vitro when cocultured on a Vero cell monolayer.

Activation regimens for full-term development of rabbit oocytes injected with round spermatids

The present study was designed to investigate the effect of activation regimens on full-term development of rabbit oocytes after round spermatid injection (ROSI). In the first series, rabbit oocytes were treated with 5 microM ionomycin before ROSI, after ROSI, or before and after ROSI. In addition, non-treated oocytes were subjected to intracytoplasmic sperm injection (ICSI) using ejaculated spermatozoa. Cleavage rate of ROSI oocytes activated before and after ROSI (55%) was comparable with that of ICSI oocytes (60%), and significantly higher than those of ROSI oocytes activated either before or after ROSI (29-39%; P < 0.05). No offspring were produced by transfer of the cleaving ROSI oocytes, while 8% of the cleaving ICSI oocytes transferred gave birth to offspring. In the second series, oocytes were exposed to 5, 10, or 20 microM ionomycin, followed by ROSI, 5 microM ionomycin treatment, and incubation with 5 microg/ml cycloheximide (CHX) + 2 mM 6-dimethylaminopurine (DMAP). Significantly higher cleavage rates were derived from oocytes activated with 10 and 20 microM ionomycin before ROSI (91% and 82%, respectively; P < 0.05) compared to those activated with 5 microM ionomycin before ROSI (53%). Live offspring were obtained when the cleaving ROSI oocytes with the initial ionomycin treatment at 5 and 10 microM were transferred (offspring rate 2% and 4%, respectively). These activation regimens, however, were not valid for the ROSI using cryopreserved round spermatids. In conclusion, rabbit ROSI oocytes were capable of developing into full-term when the oocytes were activated with a combined treatment of ionomycin and CHX/DMAP.

Fertilization and embryonic developmental capacity of epididymal and testicular sperm and immature spermatids and spermatocytes

Spermatogenesis in mammalian species begins after birth. The gonocytes, arrested at G2 of the cell cycle in the foetus, resume mitotic proliferation after birth. As identified in the mouse, the gonocytes migrate towards the periphery of the seminiferous cords at day 4 to day 6 after birth and are located in close contact with the basal lamina. From this stage the gonocytes are referred to as primitive type A spermatogonia. These cells continue mitotic proliferation and differentiate to form type B spermatogonia. By day 10 after birth, many of the type B spermatogonia have formed preleptotene primary spermatocytes which undergo a final phase of DNA synthesis (leptotene) prior to entering meiotic prophase (zygotene).

In vitro spermatogenesis as a method to bypass pre-meiotic or post-meiotic barriers blocking the spermatogenetic process: genetic and epigenetic implications in assisted reproductive technology

Pregnancies achieved by assisted reproduction technologies and particularly by ooplasmic injections of either in vivo or in vitro generated immature male germ cells are susceptible to genetic risks inherent to the male population treated with assisted reproduction and additional risks inherent to these innovative procedures. The documented, as well as the theoretical risks, are discussed in this review. These risks represent mainly the consequences of genetic abnormalities underlying male infertility and may become stimulators for the development of novel approaches and applications in the treatment of infertility. Recent data suggest that techniques employed for in vitro spermatogenesis, male somatic cell haploidization, stem cell differentiation in vitro and assisted reproductive technology may also affect the epigenetic characteristics of the male gamete, the female gamete, or may have an impact on early embryogenesis. They may be also associated with an increased risk for genomic imprinting abnormalities. Production of haploid male gametes in vitro may not allow the male gamete to undergo all the genetic and epigenetic alterations that the male gamete normally undergoes during in vivo spermatogenesis.

Effects of activation timing on the fertilization rate and early embryo development in porcine ROSI procedure

PURPOSE

This study was undertaken to evaluate the optimal exposure time for nuclear envelope breakdown (NEBD) after injection of a round spermatid and to investigate the effect of oocyte activation timing on the fertilization rate and early embryo development in porcine round spermatid injection procedure.

METHODS

Injected oocytes were fixed at 0.5, 1, 2, 3, and 4 h before activation, and NEBD state was examined. The three groups of oocytes were activated before and after the injection of spermatid using a single direct current pulse (100 V/mm, 50 micros): group 1) at 2 h before the injection (pre), group 2) within 0.5 h after the injection (immediate), and group 3) at 2 h after the injection (post). Activated oocytes were cultured and pronucleus formation and blastocyst development was evaluated at 15-18 h and 7-8 days after the injection, respectively.

RESULTS

The proportion of oocytes with NEBD significantly increased in the groups with over 2 h of exposure time (p < 0.05) and oocyte with premature chromosome condensation began to appear 3 h after the injection. Normal fertilization and development rate to the blastocyst stage were significantly higher in the post group than in those of the pre or immediate group (p < 0.05).

CONCLUSION

The optimal exposure time for NEBD is 2 h after the injection, and activation in 2 h after round spermatid injection improved the normal fertilization and early embryo development rate.

Pre-decondensed sperm head injections into female pronuclei result in chromosomal mingling, zygotic cleavage, and adequate embryonic and fetal development up to delivery of healthy offspring: a novel method of assisted syngamy

Investigation of the developmental potential post-injection of a pre-decondensed or non-pre-decondensed sperm head into the female pronucleus of a pre-activated oocyte. Rat pre-activated oocytes were treated with intrapronuclear pre-decondensed sperm head injections (IPSHI) (n = 133) or intrapronuclear non-pre-decondensed sperm head injections (INPSHI) (n = 138). All injected oocytes were transferred to pseudopregnant female recipients. Rat IPSHI techniques resulted in the delivery of five healthy offspring. Rat INPSHI techniques did not result in any pregnancies. Rat IPSHI techniques can result in delivery of healthy offspring. Successful performance of human IPSHI techniques might serve as a novel method to manage cases of intracytoplasmic sperm injection failure due to lack of development of male pronucleus or due to failure in pronuclei fusion.

Role of testicular tissue telomerase assay for the prediction of the presence of testicular spermatozoa in azoospermic men with varicoceles, pre- and post-varicocelectomy

We evaluated the reproductive potential of frozen/thawed testicular spermatozoa of azoospermic men with left varicocele. The role of testicular tissue telomerase assay (TTA) in the prediction of the presence of testicular spermatozoa pre- and post-varicocelectomy was investigated, as well. Therapeutic testicular biopsy and TTA were performed in 82 nonobstructed azoospermic (NOA) men with varicoceles. Testicular spermatozoa were found in 33 men and processed for cryopreservation. Oocytes were later recovered from the spouses of the latter azoospermic men with varicoceles and injected with frozen/thawed testicular spermatozoa. Among the 49 men who were negative for testicular spermatozoa, 22 men underwent subsequently subinguinal microsurgical varicocelectomy. A total of 198 mature oocytes were successfully injected and 101 were normally fertilized and subsequently cleaved. Transfer of these 101 embryos in 26 women resulted in nine full-term pregnancies. Thirteen healthy babies were delivered. A cut-off value of TTA of 39 TPG U microg(-1) protein had an overall diagnostic accuracy equal to 90.2% to predict the presence of testicular spermatozoa pre-varicocelectomy. Within the group of men who were negative for testicular spermatozoa a cut-off value of TTA equal to 28 TPG U microg(-1) protein (pre-varicocelectomy) had a 84.2 % diagnostic accuracy to recognize the men who would become positive for either ejaculated or testicular spermatozoa post-varicocelectomy. Testicular spermatozoa can be found in 40% of NOA men with left varicocele. Ooplasmic injections with frozen/thawed testicular spermatozoa have a role in the therapeutic management of non-obstructive azoospermia associated with varicocele. Pre-varicocelectomy, a TTA cut-off value equal to 39 TPG U microg(-1) protein has a 90.2% diagnostic accuracy to indicate the men positive/negative for testicular spermatozoa. In addition, pre-varicocelectomy, a cut-off value equal to 28 TPG U microg(-1) protein has a 84.2% diagnostic accuracy to identify those men with varicoceles without testicular spermatozoa, who will become positive/negative for spermatozoa (either ejaculated or testicular) post-varicocelectomy.

Effects of paternal cigarette smoking on testicular function, sperm fertilizing capacity, embryonic development, and blastocyst capacity for implantation in rats

We evaluated the effects of paternal smoking on testicular function, sperm fertilizing capacity, embryonic development, and blastocyst capacity for implantation. Rats of group A were exposed to cigarette smoke for 10 weeks. Rats of group B were exposed to the smoke of incense sticks for 10 weeks. Rats of group C served as a control group. Rats of group D were exposed to cigarette smoke for 7 weeks only. Experimental period was 10 weeks in all groups. At the end of the experimental period serum testosterone responses to human chorionic gonadotropin stimulation, androgen-binding protein activity in testicular cytosols, epididymal sperm motility, and oocyte fertilization rate, oocyte cleavage rate, and blastocyst development rate after in vitro fertilization (IVF) trials were significantly smaller in group A compared with groups B and C. In contrast, fertilization rate, cleavage rate, and blastocyst development rate after intracytoplasmic sperm injection (ICSI) procedures were not significantly different among groups A, B, C, and D. Both after IVF trials and ICSI techniques, the proportion of the alive offspring to the number of transferred oocytes was significantly smaller in group A than in groups B and C. Cigarette smoke-exposure results in a secretory deficiency of Leydig and Sertoli cells leading to an impaired epididymal sperm maturation process and diminished capacity of spermatozoa to penetrate oocytes. In addition paternal cigarette smoke exposure affects the embryonic ability for implantation.

Intracytoplasmic spermatid injection can result in the delivery of normal offspring

Almost one-third of all patients with nonobstructive azoospermia undergoing testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI) have cancelled cycles due to failure to find spermatozoa. For these patients, every attempt should be made to rescue the cycles by searching for spermatids. In this retrospective study, we report our experience in using elongating (stage Sb2) and elongated (stage Sc and Sd1) spermatids for ICSI. The study included 488 consecutive ICSI and TESE cycles performed for 452 patients with nonobstructive azoospermia. In 179 (36.7%) cycles, neither spermatozoa nor mature spermatids (stage Sd2) suitable for injection were found. After an extensive search only Sb2, Sc, and Sd1 spermatids were found in 22 of these 179 cycles (12.3%). These spermatids were used for injection of retrieved oocytes. The fertilization rate was 33.2%, and 19 patients (86.4%) reached the embryo transfer stage. In 6 cycles a chemical pregnancy occurred, and 3 clinical pregnancies were established, resulting in the delivery of 3 healthy boys with normal karyotypes. When normal living spermatozoa or mature spermatids (stage Sd2) cannot be found during TESE, late spermatids (stage Sb2, Sc, and Sd1) can be used successfully and result in the delivery of healthy offspring.

Failure of male pronucleus formation is the major cause of lack of fertilization and embryo development in pig oocytes subjected to intracytoplasmic sperm injection

The objectives of this study were 1) to compare the efficiency of intracytoplasmic sperm injection (ICSI) with and without additional artificial stimulation using frozen-thawed sperm and in vitro-matured porcine oocytes and 2) to determine the nuclear anomalies of ICSI oocytes that failed to fertilize or develop. In experiments 1 and 2, we evaluated the effects of additional activation treatments, e.g., electrical stimulus, Ca ionophore (A23187), and/or cycloheximide, on fertilization and development of ICSI porcine oocytes. Significantly higher fertilization, cleavage, and blastocyst rates were obtained for oocytes treated with a combination of ICSI and electrical activation (EA) (P < 0.05) than for those treated with ICSI alone. However, different combinations of electrical and chemical activation treatments did not further improve the rates of fertilization, cleavage, and blastocyst development for ICSI embryos. To elucidate the association between sperm head decondensation and oocyte activation and to investigate the cause of embryonic development failure, in experiment 3 we evaluated the nuclear morphology of oocytes 16-20 h after ICSI. Nearly 100% of oocytes showed female pronucleus formation after ICSI regardless of activation treatment. However, failure of male pronucleus formation with intact or swelling sperm heads was observed in some ICSI embryos, suggesting that these embryos underwent cell division with the female pronucleus only. Artificial activation (EA and A23187) had a beneficial effect on embryonic development, sperm decondensation was independent of the resumption of meiosis, and the failure of formation of a male pronucleus was the major cause for fertilization failure in porcine ICSI embryos.

The role of ultrasonographically guided puncture of the human rete testis in the therapeutic management of nonobstructive azoospermia

We attempted to characterize the cells collected from the rete testis via ultrasonographically guided puncture. Unilateral puncture of the rete testis was performed in nine men with obstructive azoospermia and 51 men with nonobstructive azoospermia. All the aspirated samples from the rete testis were observed via confocal scanning laser microscope and some of them after fluorescent in situ hybridization techniques. Then therapeutic testicular biopsy was performed in the punctured testis of each man. Spermatozoa were found in all rete testis samples and all biopsy samples from obstructed men. Twenty-two nonobstructed men demonstrated absence of spermatozoa in biopsy samples. Twenty-nine nonobstructed men showed spermatozoa in biopsy material and 24 of these men (82%) had demonstrated spermatozoa in rete testis samples. There were no significant differences in fertilization and cleavage rate between intracytoplasmic sperm injection trials using biopsy spermatozoa and rete testis spermatozoa both in obstructed and nonobstructed men. Considering that puncture of the rete testis does not reduce the volume of testicular parenchyma, is less invasive and apparently causes less detrimental effect on testicular vasculature than biopsy, puncture of rete testis is recommended as first line approach for the treatment of azoospermic men. If puncture is negative for spermatozoa in nonobstructed men, biopsy is indicated.

Use of a highly sensitive quantitative telomerase assay in intracytoplasmic sperm injection programmes for the treatment of 47,XXY non-mosaic Klinefelter men

We evaluated the role of the sensitive quantitative telomerase assay (SQTA) in the management of men with non-mosaic Klinefelter's syndrome (KS). Diagnostic testicular biopsy (DTB) was performed in 24 men with KS. A part of the DTB was stained and the remaining fragment was processed for the SQTA. After 3-18 months, a therapeutic testicular biopsy (TTB) was performed in the same testicle and the recovered specimens were processed to identify spermatozoa. Men with a SQTA outcome equal to 0.00 Units microg-1 protein (n = 7) demonstrated therapeutic testicular biopsy material that was negative for spermatogenic cells. In five men with a SQTA outcome of 8.11-38.03 Units microg-1, the most advanced germ cell was the spermatogonium/primary spermatocyte. In the remaining 12 men, the most advanced spermatogenic cell in the TTB was the spermatozoon. In these men, the SQTA outcome was equal to 25.76-92.68 Units microg-1 protein. Using 39.00 Units microg-1 protein as a cut-off value, the accuracy of the SQTA in identifying men positive for spermatozoa was 91.6%. It appears that the SQTA has a role for identifying non-mosaic KS men who have testicular spermatozoa.

Predictive value of testicular histology in secretory azoospermic subgroups and clinical outcome after microinjection of fresh and frozen-thawed sperm and spermatids

BACKGROUND

A retrospective study was carried out on 159 treatment cycles in 148 secretory azoospermic patients to determine whether histopathological secretory azoospermic subgroups were predictive for gamete retrieval, and to evaluate outcome of microinjection using fresh or frozen-thawed testicular sperm and spermatids.

METHODS

Sperm and spermatids were recovered by open testicular biopsy and microinjected into oocytes. Fertilization and pregnancy rates were assessed.

RESULTS

In hypoplasia, 97.7% of the 44 patients had late spermatids/sperm recovered. In maturation-arrest (MA; 47 patients), 31.9% had complete MA, and 68.1% incomplete MA due to a focus of early (36.2%) or late (31.9%) spermiogenesis. Gamete retrieval was achieved in 53.3, 41.2 and 93.3% of the cases respectively. In Sertoli cell-only syndrome (SCOS; 57 patients), 61.4% were complete SCOS, whereas incomplete SCOS cases showed one focus of MA (5.3%), or of early (29.8%) and late (3.5%) spermiogenesis. Only 29.8% of the patients had a successful gamete retrieval, 2.9% in complete and 77.3% in incomplete SCOS cases. In total, there were 87 ICSI, 39 elongated spermatid injection (ELSI) and 33 round spermatid injection (ROSI) treatment cycles, with mean values of fertilization rate of 71.4, 53.6 and 17%, and clinical pregnancy rates of 31.7, 26.3 and 0% respectively.

CONCLUSIONS

Histopathological subgroups were positively correlated with successful gamete retrieval. No major outcome differences were observed between testicular sperm and elongated spermatids, either fresh or frozen-thawed. However, injection of intact round-spermatids showed very low rates of fertilization and no pregnancies.

Rhesus offspring produced by intracytoplasmic injection of testicular sperm and elongated spermatids

OBJECTIVE

To establish pregnancies in rhesus monkeys using testicular sperm and elongated spermatids injected into oocytes.

DESIGN

Comparative animal study.

SETTING

Regional Primate Research Center.

ANIMAL(S)

Prime, fertile rhesus monkeys.

INTERVENTION(S)

Oocytes collected by laparoscopy from gonadotropin-stimulated female rhesus monkeys were injected with testicular sperm or elongated spermatids obtained from the testis of males. Cleavage stage embryos were transferred to surrogate females.

MAIN OUTCOME MEASURE(S)

Fertilization, embryo cleavage, and the establishment of pregnancies. Fertilization failures were fixed and processed for the detection of microtubules and chromatin configurations.

RESULT(S)

Fertilization, assessed by the presence of two pronuclei within 15 hours after injection, was 60% for intracytoplasmic sperm injection with testicular sperm and 47% for elongated spermatid injection. Fertilized zygotes co-cultured in Connaughts Medical Research Labs (CMRL) medium on a Buffalo Rat Liver cell monolayer resulted in hatched blastocysts after testicular sperm extraction-intracytoplasmic sperm injection and elongated spermatids. Embryos transferred at the 4- to 8-cell stage gave rise to three pregnancies: 2/3 from testicular sperm and 1/1 from an elongated spermatid. Three healthy infants were delivered by cesarean. Oocytes that failed to fertilize typically remained arrested in metaphase of meiosis.

CONCLUSION(S)

Testicular sperm and elongated spermatids can be used for fertilization in the rhesus monkey resulting in live births.

Immature germ cell conception-in vitro germ cell manipulation

Experimental studies in laboratory animals have shown that successful conception can be achieved by fertilizing oocytes with immature male germ cells. This gave rise to the concept that immature germ cells recovered from the testes of azoospermic men with maturation arrest may be used for assisted reproduction. However, in contrast to using germ cells recovered from healthy animals, clinical application to the treatment of male sterility is burdened by inherent defects in germ cells attributable to underlying testicular pathology. The recent introduction of in vitro germ cell culture/manipulation techniques makes it possible, in some cases, to overcome the in vivo maturation arrest by allowing an additional meiotic and post-meiotic differentiation and the selective harvesting of cells devoid of apoptosis-related nuclear and cytoplasmic damage. These techniques enabled the first births of normal infants fathered by azoospermic men with maturation arrest at the primary spermatocyte stage and improved the efficacy of assisted reproduction in men with maturation arrest at the round spermatid stage.

Paternal contributions to the mammalian zygote: fertilization after sperm-egg fusion

Mammalian fertilization has traditionally been regarded as a simple blending of two gametes, during which the haploid genome of the fertilizing spermatozoon constitutes the primary paternal contribution to the resulting embryo. In contrast to this view, new research provides evidence of important cytoplasmic contributions made by the fertilizing spermatozoon to the zygotic makeup, to the organization of preimplantation development, and even reproductive success of new forms of assisted fertilization. The central role of the sperm-contributed centriole in the reconstitution of zygotic centrosome has been established in most mammalian species and is put in contrast with strictly maternal centrosomal inheritance in rodents. The complementary reduction or multiplication of sperm and oocyte organelles during gametogenesis, exemplified by the differences in the biogenesis of centrosome in sperm and oocytes, represents an intriguing mechanism for avoiding their redundancy during early embryogenesis. New studies on perinuclear theca of sperm revealed its importance for both spermatogenesis and fertilization. Remodeling of the sperm chromatin into a male pronucleus is guided by oocyte-produced, reducing peptide glutathione and a number of molecules required for the reconstitution of the functional nuclear envelope and nuclear skeleton. Although some of the sperm structures are transformed into zygotic components, the elimination of others is vital to early stages of embryonic development. Sperm mitochondria, carrying potentially harmful paternal mtDNA, appear to be eliminated by a ubiquitin-dependent mechanism. Other accessory structures of the sperm axoneme, including fibrous sheath, microtubule doublets, outer dense fibers, and the striated columns of connecting piece, are discarded in an orderly fashion. The new methods of assisted fertilization, represented by intracytoplasmic sperm injection and round spermatid injection, bypass multiple steps of natural fertilization by introducing an intact spermatozoon or spermatogenic cell into oocyte cytoplasm. Consequently, the carryover of sperm accessory structures that would normally be eliminated before or during the entry of sperm into oocyte cytoplasm persist therein and may interfere with early embryonic development, thus decreasing the success rate of assisted fertilization and possibly causing severe embryonic anomalies. Similarly, foreign organelles, proteins, messenger RNAs, and mitochondrial DNAs, which may have a profound impact on the embryonic development, are propagated by the nuclear transfer of embryonic blastomeres and somatic cell nuclei. This aspect of assisted fertilization is yet to be explored by a focused effort.

Highly sensitive quantitative telomerase assay of diagnostic testicular biopsy material predicts the presence of haploid spermatogenic cells in therapeutic testicular biopsy in men with Sertoli cell-only syndrome

The role of a telomerase assay in the recognition of Sertoli cell-only syndrome with testicular foci of haploid cells was evaluated. Men with Sertoli cell-only syndrome (n = 23) were given a new diagnostic testicular biopsy. Part of the biopsy was stained and the remainder was processed for the quantitative telomerase assay. After 3-13 months, a therapeutic testicular biopsy was performed. This material was minced and then examined using confocal laser scanning microscopy and fluorescent in-situ hybridization. Histology of diagnostic testicular biopsy material confirmed the diagnosis of Sertoli cell-only syndrome in all the participants. All seven men with a telomerase assay value in their diagnostic testicular biopsy of >42 total product generated (TPG) U/microg protein had haploid cells (i.e. spermatozoa and/or spermatids) in their therapeutic testicular biopsy. Among participants with telomerase assay values <42 TPG U/microg protein, only one man had haploid cells in his therapeutic testicular biopsy. Thus, telomerase assay values >42 TPG U/microg protein in the diagnostic biopsy identified 87.5% of the Sertoli cell-only syndrome men with haploid cells in their therapeutic testicular biopsy. Significantly higher values of the telomerase assay were found in men with testicular foci of haploid cells than in men without these foci. The use of a quantitative telomerase assay biopsy appears to be important for identifying those men with Sertoli cell-only syndrome who have foci of haploid cells and can be candidates for assisted reproduction techniques.

Oocyte insemination with spermatozoa precursors

Since the use of testicular spermatozoa in programs of assisted fertilization proved very successful, attention was focussed on the use of spermatids also carrying 23 chromosomes. Several difficulties became obvious; the first one concerned the recognition of round spermatids. This is a problem which does not concern elongating and elongated cells. The intra-cytoplasmic injection of elongated spermatids resulted in several pregnancies but this is not so for the round ones. Although, in the group of patients in whom only round spermatids are found at the time of the attempt, is to be divided into two categories; patients in whom previous research allowed to find spermatozoa, however few, and patients who never produced spermatozoa at all. This last group is no longer an indication for intracytoplasmic sperm injection procedure unless in the future new culture media allow a maturation into elongated forms.

A comparative morphological study of human germ cells in vitro or in situ within seminiferous tubules

For many infertile couples, intracytoplasmic germ cell/spermatozoon injection into unfertilized eggs may be their only hope for producing their own biological children. Thus far, success with injection of pre-spermatozoan germ cells such as round spermatids has not been as great as that of spermatozoon injection. This could be due in part to the difficulty of identifying younger (less mature) male germ cells in testicular biopsy dispersions. To improve the identification of various types of live, dispersed, human testicular cells in vitro, a comparative study of the morphological characteristics of human spermatogenic germ cells in vitro or in situ within seminiferous tubules was conducted. Live human testicular tissue was obtained from an organ-donating, brain-dead person with a high density of various germ cells. A cell suspension was obtained by enzymatic digestion, and cells were cultured for 3 days in an excessive volume (100-fold medium:cells; v:v) of HEPES-TC 199 medium at 5 degrees C and observed live with Nomarski optics (interference-contrast microscopy). For comparative purposes, testes from ten men obtained at autopsy were fixed, embedded in epoxy resin, sectioned at 20 microm, and observed unstained by Nomarski optics. This approach allowed comparison of morphological characteristics of individual germ cells seen in vitro or in situ in the human testis. In both live and fixed preparations from control men with varied daily sperm production rates, Sertoli cells have oval to pear-shaped nuclei with indented nuclear envelopes and large nucleoli, which makes their appearance distinctly different from germ cells. The size, shape, and chromatin pattern of nuclei, and the presence of meiotic metaphase figures, acrosomic vesicles/structures, tails, and/or mitochondria in the middle piece of germ cells are characteristically seen in live cells in vitro and in those cells observed in the fixed seminiferous tubules. Hence, this comparative approach allows verification of the identity of individual germ cells seen in vitro and provides a checklist of distinguishing characteristics of live human germ cells, to be used by scientists and technical staff in infertility clinics when selecting specific germ cells from a testicular aspirate or enzymatically digested biopsy.

On-stage selection of single round spermatids using a vital, mitochondrion-specific fluorescent probe MitoTracker(TM) and high resolution differential interference contrast microscopy

The selection of individual round spermatids for round spermatid injection (ROSI), a prerequisite for the successful application of this infertility treatment, has been hampered by the ambiguous definition of a round spermatid and the lack of specific vital and non-vital markers. Using cells from rhesus monkey and bull, we describe a non-invasive method for the on-stage selection of individual round spermatids for ROSI, based on the polarized patterns of mitochondria, visualized in live round spermatid cells by epifluorescence microscopy after incubation with MitoTracker(TM), a vital, mitochondrion-specific fluorescent probe. The correct identification of live round spermatid was confirmed by the presence of the acrosomal granule or acrosomal cap in parallel observations by Nomarski differential interference contrast microscopy. The existence of mitochondrial polarization was first established by the labelling of MitoTracker-tagged round spermatids with spermatid-specific antibodies against proteins of nascent sperm accessory structures combined with antibodies against a nuclear pore complex component, known to disappear at the round spermatid stage. Using an inverted microscope equipped with epifluorescence, the round spermatids can be individually selected from a heterogeneous population of testicular cells labelled with MitoTracker dyes. A major advantage of this approach is that the dyes are incorporated into the paternal mitochondria, destined for rapid elimination after fertilization. In addition, the relatively high excitation and emission wavelengths of MitoTracker dyes are less harmful to DNA after their photon excitation. Before the appropriate clinical testing is conducted, the MitoTracker-based round spermatid selection may be instrumental in the training of clinical staff.

Influence of the male reproductive tract on the reproductive potential of round spermatids abnormally released from the seminiferous epithelium

Round spermatids can be collected from testicular biopsy material or occasionally from semen samples. We evaluated the influence of the passage of round spermatids through the male reproductive tract on their reproductive potential. A model of abnormal release of round spermatids from the seminiferous epithelium was created in mature male rats (group A). Additional sham-treated rats of the same age served as a control group (group B). Round spermatids were collected from the testicles of rats of both groups, the epididymides of rats of group A, and the vaginae of mature female rats mated with rats of group A. Isolated round spermatids were processed for ooplasmic injections. Injected oocytes were cultured. At 96 h post-injection, the blastocyst development rate was significantly higher in the groups of oocytes injected with testicular spermatids than the groups of oocytes injected with spermatids recovered from the vaginae, or the head, body, or tail of the epididymides. It appears that round spermatids recovered from testicular biopsy material have larger reproductive capacity than ejaculated round spermatids, due to mechanical or chemical detrimental influences of storage/passage through the male reproductive tract (outside the testicle) on the capacity of round spermatids to induce optimal early embryonic development.

Effects of hypercholesterolaemia on Leydig and Sertoli cell secretory function and the overall sperm fertilizing capacity in the rabbit

The effects of hypercholesterolaemia on testicular endocrine and exocrine function were evaluated. The influence of hypercholesterolaemia on sperm quality, quantity, and fertilizing potential was also determined. Ten mature rabbits (group A) were fed chow containing 3% cholesterol for 12 weeks. Ten control rabbits (group B) were fed normal chow for the same period. At the end of the experimental period testosterone profiles and sperm parameters were evaluated and the sperm reproductive potential was assessed by in vitro fertilization (IVF) techniques. Peripheral serum testosterone responses to testicular stimulation with human chorionic gonadotrophin, androgen-binding protein activity in testicular cytosols, sperm concentration, sperm motility, length of sperm midpiece, and IVF outcome were all significantly lower in group A than in group B. In contrast, serum cholesterol concentrations were significantly higher in group A. There were no significant differences in either testicular versus intra-abdominal temperature differences or cholesterol concentrations in seminal plasma or testicular tissue between groups A and B. The results suggest that hypercholesterolaemia has a detrimental effect on Leydig and Sertoli cell secretory function, spermatogenesis, epididymal sperm maturation process, and the overall sperm fertilizing capacity.

Ooplasmic injections of rabbit round spermatid nuclei or intact round spermatids from fresh, cryopreserved and cryostored samples

We compared the outcome of ooplasmic round spermatid nuclear injections (ROSNI) versus intact round spermatid injections (ROSI). Rabbit round spermatid nuclei and intact round spermatids were recovered and injected into rabbit oocytes (groups A and B, respectively). Fertilization, cleavage and embryonic development rates were compared. In additional studies, five protocols for cryopreservation of round spermatids and two protocols for cryostorage of round spermatids were applied. The outcome of ROSNI techniques using frozen-thawed or cryostored-warmed round spermatids was evaluated. The cleavage rate and the overall morula plus blastocyst development rate were significantly larger in group A than group B. ROSNI procedures are superior to ROSI techniques in the rabbit. The largest fertilization, cleavage and embryonic development rates after ROSNI techniques using cryopreserved or cryostored round spermatids were demonstrated in groups of round spermatids in which a mixture of seminal plasma plus test yolk buffer was employed as an extender, and dimethyl sulphoxide plus a high concentration of glycerol served as cryoprotectants. It appears that the seminal plasma contains factors protecting round spermatids during cryopreservation or cryostorage, and/or the employment of two cryoprotectants has a beneficial role in the maintenance of round spermatid reproductive capacity.

Fertilization and in vitro development of porcine oocytes following intracytoplasmic injection of round spermatid or round spermatid nuclei

The objective of this study was to determine fertilization rates and developmental ability of porcine oocytes following injection of round spermatid and round spermatid nucleus with artificial activation either 2 h before or immediately after injection. Electrical stimulation at 2 h before spermatid injection significantly increased the incidence of normal fertilization compared with that following injection without stimulation or with stimulation immediately after injection. Incidences of formation of 2 pronuclei and of apposition were not different in oocytes following intracytoplasmic spermatid and spermatid nucleus injection. Chromosome analysis revealed that most oocytes were diploid either following round spermatid or round spermatid nucleus injection. There was no diploid set of chromatin in oocytes at 20 h following sham injection. At 6 d following injection blastocoele formation was seen in the oocytes following round spermatid (25%) and round spermatid nucleus injection (27%). However, none of the oocytes developed to the blastocyst stage 6 d following sham injection. The average cell numbers of blastocysts 8 d after injection of spermatid and spermatid nucleus were 99 and 87, respectively. These results suggest that electrical stimulation before injection enhances the incidence of fertilization following round spermatid injection in the pig. Our study also indicates that either the round spermatid or it's nucleus can be used to produce viable embryos by injection into unfertilized porcine oocytes.

Flow cytometry isolation and reverse transcriptase-polymerase chain reaction characterization of human round spermatids in infertile patients

Flow cytometry coupled to cell sorting is proposed as a method to isolate round spermatids from testicular biopsies in obstructive azoospermic patients. The cells were separated on the basis of their size and density only. We obtained homogenous populations of alive round spermatids free of lymphocytes and diploid germ cells. The detection of protamine 1 gene (PRM1) and PRM2 expression in the sorted cells proves that these cells are round spermatids. On the contrary, neither the expression of CD3-delta, which is specific to lymphoid cells, nor that of MAGE1, which has been demonstrated in diploid germ cells, could be observed in the round spermatid population even after using a nested polymerase chain reaction (PCR) assay. The flow cytometry procedure failed to isolate round spermatids from ejaculates in non-obstructive azoospermic patients. In > 39 ejaculates tested by reverse transcriptase-PCR, only nine revealed the presence of some round spermatids, as demonstrated by the expression of PRM1. However, these round spermatids did not express PRM2.

Pregnancy and birth after transfer of embryos that developed from single-nucleated zygotes obtained by injection of round spermatids into oocytes

OBJECTIVE

To use injection of spermatids into oocytes as a mode of infertility treatment in cases in which spermatozoa are not available.

DESIGN

Prospective clinical evaluation and case report.

SETTING

In Vitro Fertilization Unit, Herzliya Medical Centers, Herzliya-on-Sea, Israel.

PATIENT(S)

Thirteen couples with male factor infertility in which the male partner lacked spermatozoa in the ejaculate or testicular biopsy samples.

INTERVENTION(S)

Round spermatid injection and elongated spermatid injection into oocytes.

MAIN OUTCOME MEASURE(S)

Evaluation of the rate of two-pronucleated and single-nucleated zygote development.

RESULT(S)

The rate of two-pronucleated zygote development after round spermatid injection and elongated spermatid injection was relatively low (27% and 36%, respectively). Single-nucleated zygotes develop more frequently after round spermatid injection and elongated spermatid injection (35% and 17%, respectively) than after intracytoplasmic sperm injection with mature spermatozoa. A normal pregnancy and childbirth resulted from the transfer of 4 cleaving embryos, each of which developed from a single-nucleated zygote in a round spermatid injection treatment cycle with ejaculated spermatids.

CONCLUSION(S)

Embryos derived from single-nucleated zygotes after spermatid conception can be viable and give rise to an ongoing clinical pregnancy and childbirth.

Microtubule and chromatin organization during the first cell-cycle following intracytoplasmic injection of round spermatid into porcine oocytes

The objective of this study was to determine microtubule assembly and chromatin configuration in porcine oocytes during the first cell cycle following round spermatid injection into matured porcine oocytes in the presence or absence of electrical stimulation. The oocytes with two large pronuclei and two polar bodies were classified as normal fertilization at 6 to 8 h following injection. The incidence of normal fertilization following round spermatid injection with electrical stimulation was significantly higher (21/45, 47%) than that following injection alone (6/39, 15%). Although a small microtubular aster was organized near the decondensed spermatid chromatin in some oocytes (2/6, 33%, spermatid injection alone; 9/21, 29%, spermatid injection and electrical stimulation), it did not enlarge nor fill the cytoplasm. Instead, a dense network of microtubules in the cytoplasm was organized from cortex. At 12 to 15 h after injection, we classified the oocytes with closely apposed pronuclei as normal fertilization. The electrical stimulation following spermatid injection enhanced (P < 0.05) the incidence of normal fertilization (18/54, 33%) compared with spermatid injection alone (7/52, 13%). During pronuclear movement, the maternally derived microtubules filled the whole cytoplasm, which appeared to move male and female chromatin. Mitosis and two-cell division were observed at 20 to 24 h after spermatid injection with electrical stimulation (12/41, 29%). At mitotic metaphase, the microtubular spindle had focused astral poles, and chromosomes were aligned on the spindle equator. During mitosis, asters were assembled at each spindle pole, and they filled the cytoplasm. These results suggested that round spermatid nuclei of the pig can develop into a morphologically normal pronucleus in matured porcine oocytes and are competent to participate in syngamy with the ootid chromatin. In addition, functional microtubules for complete fertilization with spermatid were not associated with male-derived centrosome but were organized solely from maternal stores.

Use of immature germ cells for the treatment of male infertility

Both animal experimentation data and preliminary clinical experience converge to suggest that normal progeny can be obtained by fertilizing oocytes with spermatids, the youngest male germ cells to have a set of haploid chromosomes. Spermatids can be obtained from the ejaculate of many patients with non-obstructive azoospermia. The use of ejaculated spermatids in the treatment of non-obstructive azoospermia is thus to be considered as an alternative to that of testicular spermatozoa. Fertilization with ejaculated spermatids makes it possible to avoid the potential adverse consequences of extensive testicular biopsy and may thus become the treatment of first choice. The recourse to testicular spermatids represents a treatment of last chance if no spermatids can be recovered either from the ejaculate and no spermatozoa from the testis.

Ooplasmic round spermatid nuclear injection procedures as an experimental treatment for nonobstructive azoospermia

PURPOSE

Our objective was to apply ooplasmic round spermatid nuclear injections for the treatment of nonobstructive azoospermia.

MATERIALS

Participants were nine azoospermic men who had previously undergone diagnostic testicular biopsy. Spermatogenetic arrest was diagnosed at the round spermatid stage (n = 6) or primary spermatocyte stage (n = 3). A second (therapeutic) testicular biopsy was performed and round spermatid nuclei were recovered from all the participants.

RESULTS

Forty-nine mature oocytes were successfully injected with nuclei and then cultured for 72 hr. Twenty-four embryos were transferred to nine women. No pregnancy was achieved.

CONCLUSIONS

Round spermatids can be recovered from therapeutic testicular biopsy material of men negative for round spermatids in previous routine diagnostic testicular biopsy specimens. Round spermatid nuclear injections may play a role in the treatment of nonobstructive azoospermia.