Spermatid conception: a stage too early, or a time too soon?

Intracytoplasmic sperm injection for male infertility and consequences for offspring

Intracytoplasmic sperm injection (ICSI) has become the most commonly used method of fertilization in assisted reproductive technology. The primary reasons for its popularity stem from its effectiveness, the standardization of the procedure, which means that it can easily be incorporated into the routine practice of fertility centres worldwide, and the fact that it can be used to treat virtually all forms of infertility. ICSI is the clear method of choice for overcoming untreatable severe male factor infertility, but its (over)use in other male and non-male factor infertility scenarios is not evidence-based. Despite all efforts to increase ICSI efficacy and safety through the application of advanced sperm retrieval and cryopreservation techniques, as well as methods for selecting sperm with better chromatin integrity, the overall pregnancy rates from infertile men remain suboptimal. Treating the underlying male infertility factor before ICSI seems to be a promising way to improve ICSI outcomes, but data remain limited. Information regarding the health of ICSI offspring has accumulated over the past 25 years, and there are reasons for concern as risks of congenital malformations, epigenetic disorders, chromosomal abnormalities, subfertility, cancer, delayed psychological and neurological development, and impaired cardiometabolic profile have been observed to be greater in infants born as a result of ICSI than in naturally conceived children. However, as subfertility probably influences the risk estimates, it remains to be determined to what extent the observed adverse outcomes are related to parental factors or associated with ICSI.

Successful fertilization and embryo development after spermatid injection: A hope for nonobstructive azoospermic patients

Spermatids are the earliest male germ cells with haploid set of chromosomes. Spermatid injection was introduced in human assisted reproduction for the treatment of men with non-obstructive azoospermia. Spermatozoa can be recovered in half of patients with nonobstructive azoospermia. The use of spermatids for intracytoplasmic injection (ICSI) has been proposed for cases in which no spermatozoa can be retrieved. However, there are low pregnancy rates following ICSI using round spermatids from men with no elongated spermatids or spermatozoa in their testes. The in vitro culture of immature germ cells has been proposed as a means to improve this poor outcome. Oocyte activation rarely occurs when injected with a spermatid. Therefore, spermatid injection requires use of calcium ionophores for oocyte activation which is otherwise carried out by PLC zeta from mature sperms. This is the only option available for the nonobstructive azoospermic patients to have their own biological child.

Effects of activation on functional aster formation, microtubule assembly, and blastocyst development of goat oocytes injected with round spermatids

A systematic study was conducted on round spermatids (ROS) injection (ROSI) using the goat model. After ROSI, the oocytes were treated or not with ionomycin (ROSI+I and ROSI-I, respectively) and compared with intracytoplasmic sperm injection (ICSI). After ROSI-I, most oocytes were arrested with premature chromatin condensation and few oocytes formed pronuclei. In contrast, most oocytes formed pronuclei after ROSI+I. Some ROS were observed to form asters that organized a dense microtubule network after ROSI+I, but after ROSI-I, no ROS asters were observed. Whereas most of the oocytes showed Ca(2+) rises and a significant decline in maturation-promoting factor (MPF) and mitogen-activated protein kinase (MAPK) activities after ROSI+I, no such changes were observed after ROSI-I. Due to the lack of Ca(2+) oscillations after ROSI-I, oocytes were injected with more ROS. Interestingly, different from the results observed in a single ROS injection, injection with four ROS effectively activated oocytes by inducing typical Ca(2+) oscillations. Whereas ROSI+I oocytes and ICSI oocytes both showed extensive microtubule networks, no such a network was observed in parthenogenetic oocytes. Together, the results suggest that goat ROS is not able to trigger intracellular Ca(2+) rises and thus to inhibit MPF and MAPK activities, but artificial activation improved fertilization and development of ROSI goat oocytes. Goat ROS can organize functional microtubular asters in activated oocytes. A ROS-derived factor(s) may be essential for organization of a functional microtubule network to unite pronuclei. Goat centrosome is of paternal origin because both ROS and sperm asters organized an extensive microtubule network after intra-oocyte injection.

What to do when ICSI fails

The refinement of gamete micromanipulation techniques has made conception possible for couples with male factor infertility who otherwise would remain childless. Moreover, intracytoplasmic sperm injection (ICSI) has ensured that such refractory cases can now generate offspring as successfully as in couples that merely require in vitro insemination. However, despite the now sterling record of ICSI it does not assure a successful outcome for every patient. This can be due, for instance, to the inability of the spermatozoon to activate the oocyte, and applies obviously in cases where spermatozoa are absent from the ejaculate or testicular biopsy. In the present paper we describe in detail the reasons for such failure and review the options that may help overcome it. In particular, we outline the treatment protocol for the situation in which spermatozoa are unable to induce oocyte activation. Further, we report on the clinical outcome achieved with spermatozoa retrieved from the testis, and in cases of extreme oligozoospermia we also explore the option of replicating a single spermatozoon while gaining information on its genomic content. For the most extreme situation in which men have no identifiable germ cells, we will discuss the current status of efforts to accomplish neo-gametogenesis through embryonic stem cell differentiation.

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.

Genetic and epigenetic risks of intracytoplasmic sperm injection method

Pregnancies achieved by assisted reproduction technologies, particularly by intracytoplasmic sperm injection (ICSI) procedures, are susceptible to genetic risks inherent to the male population treated with ICSI and additional risks inherent to this innovative procedure. The documented, as well as the theoretical, risks are discussed in the present review study. These risks mainly represent that consequences of the genetic abnormalities underlying male subfertility (or infertility) and might become stimulators for the development of novel approaches and applications in the treatment of infertility. In addition, risks with a polygenic background appearing at birth as congenital anomalies and other theoretical or stochastic risks are discussed. Recent data suggest that assisted reproductive technology might also affect epigenetic characteristics of the male gamete, the female gamete, or might have an impact on early embryogenesis. It might be also associated with an increased risk for genomic imprinting abnormalities.

Efforts to create an artificial testis: culture systems of male germ cells under biochemical conditions resembling the seminiferous tubular biochemical environment

Induction of meiotic and post-meiotic alterations of male germ cells in vitro has been the target of several research efforts since 1960. However, to date, the establishment of an ideal culture system in which spermatogonial stem cells can be maintained and directed to proliferate and undergo meiosis and complete spermiogenesis does not exist. This is attributed to the difficulties concerning the isolation and purification of defined subpopulations of germ cells and the establishment of male germ cell lines. In addition, there is no adequate knowledge regarding the optimal biochemical conditions that promote the survival and differentiation of germ cells in long-term cultures. This review focuses on the methodologies that have been proved sufficient to achieve differentiation of cultured male germ cells. Furthermore, the factors regulating spermatogenesis and the technical prerequisites to achieve differentiation of cultured male germ cells are described. Finally, the role of in vitro cultures of immature diploid germ cells in the therapeutic management of men negative for haploid cells in their testes and the subsequent potential genetic and epigenetic risks are discussed.

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

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

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.

The first successful pregnancy following injection of testicular round spermatid in Iran

The authors report the healthy delivery of the first successful round spermatid injection in Iran. The male was a 40-year-old with nonobstructive azoospermia whose previous testicular biopsy revealed only round spermatids. The wife was a 29-year-old healthy woman.

Developmental potential of elongating and elongated spermatids obtained after in-vitro maturation of isolated round spermatids

BACKGROUND

Round spermatid injections are associated with disappointing clinical outcomes, and although these cells have been shown to mature into late spermatids in vitro, the developmental potential of such gametes remains to be demonstrated.

METHODS

Round spermatids were isolated from 12 testicle samples of patients with obstructive azoospermia, hypoplasia, complete maturation arrest, and incomplete Sertoli cell-only syndrome. They were cultured for 7 days at 32 degrees C, 5% CO(2)in air, in microdrops of Vero cell-conditioned medium containing 10% synthetic serum substitute.

RESULTS

From the 238 round spermatids cultured, 25.2% attained the elongating and 5.5% the elongated spermatid stage (3-4 days per step). Relatively higher maturation rates were found in cases with obstructive azoospermia, but differences were significant only for elongated spermatids (9.3%). No differences were found in maturation rates between cases with non-obstructive azoospermia (4.3% of elongated spermatids). Experimental microinjections with elongating and elongated spermatids revealed a low fertilization rate (40.9%) but a normal blastocyst formation rate (60%).

CONCLUSIONS

Late spermatids resulting from in-vitro culture of round spermatids in conditioned medium, either in controls in cases with a spermiogenetic block, appeared able to successfully fertilize the human oocyte and elicit normal embryo development.

Relation between different human sperm nuclear maturity tests and in vitro fertilization

PURPOSE

To consider the relationship between different sperm nuclear maturity tests and in vitro fertilization (IVF) rate, in order to select the most sensitive, specific, and independent factor(s) for prediction of in vitro fertilization.

METHODS

Infertile couples (101) were randomly selected from IVF candidates referred to Isfahan Fertility and Infertility center. Semen samples were collected on the day of oocyte recovery. Following routine semen analysis, major portion of the semen was prepared for routine IVF insemination and the remaining was used for following sperm nuclear maturity tests: chromomycin A3 (CMA3), aniline blue, sodium dodecyl sulphate (SDS) test, and acridine orange test with or without heat shock (87 degrees C, 5 min). Sperms (200) were evaluated for each test. The results were recorded and analyzed for their correlation to fertilization rate, using correlation coefficient, logistic regression analysis, student t-test, and receiver operating characteristics (ROC) curve.

RESULTS

Among these tests, aniline blue and CMA3, and semen parameters, sperm morphology, and sperm motility showed a significant correlation with fertilization rate. Using logistic regression analysis, sperm morphology and CMA3 were the only independent factors related to in vitro fertilization. ROC curves showed that among above tests, CMA3 is the most specific and sensitive for sperm nuclear maturity.

CONCLUSION

Among CMA3, aniline blue, SDS test, and acridine orange, CMA3 was the most sensitive and specific test that can be used along with routine semen analysis for more precise prediction of fertilization rate.

Development of blastocyst-stage embryos after round spermatid injection in patients with complete spermiogenesis failure

PURPOSE

Our purpose was to evaluate the progression of embryos derived from round spermatid injection to the blastocyst stage and compare the results with those obtained by the use of testicular or epididymal spermatozoa.

METHODS

Thirty-eight patients with azoospermia enrolled in this study. In 29 patients with obstructive or nonobstructive azoospermia, spermatozoa were recovered from epididymis or testis. In the remaining nine cases with nonobstructive azoospermia, only round spermatids were found in seven, whereas in two of the patients, there were no elongated or round spermatids. Six of these cases underwent round spermatid injection.

RESULTS

Twenty-one of 29 patients with injection of spermatozoa underwent embryo transfer on day 3, and 10 pregnancies (47.6%) were obtained. In eight cycles, embryos were further cultured for delayed transfer. In six cases undergoing round spermatid injection, no transfer was performed on day 3 and extended culture with delayed embryo transfer was applied. The mean number of fertilized oocytes and mean number of embryos on day 3 and also the fertilization rate and mean number of good-quality embryos on day 3, mainly grade 1 or 2, were statistically significantly higher in the spermatozoa group than the round spermatid injection group. Compared to the spermatozoa group, the number of arrested embryos was significantly higher and the number of blastocyst-stage embryos and number of good-quality blastocysts were significantly lower in the spermatid injection group. No blastocysts developed in two spermatid cycles and embryo transfer was not possible, and in the remaining four cycles, after at least one blastocyst transfer, no pregnancies were achieved. However, in eight cycles with extended culture in the spermatozoa group, embryo transfers were achieved in all and three pregnancies, for a pregnancy rate of 37.5%, were obtained after blastocyst transfer.

CONCLUSIONS

Our preliminary results showed that round spermatid injection was associated with a significantly lower fertilization and embryo development rate and a significantly higher developmental arrest rate compared with the injection of spermatozoa. Extended culture and delayed embryo transfer did not improve the clinical outcome after round spermatid injection, and these results suggested a developmental failure in embryos preventing successful implantation after round spermatid injection.

Comparison of oocyte activation and Ca2+ oscillation-inducing abilities of round/elongated spermatids of mouse, hamster, rat, rabbit and human assessed by mouse oocyte activation assay

Oocyte activation and Ca2+ oscillation-inducing abilities of round spermatid (ROS) and elongated spermatid (ELS) of some rodents and human were assessed by their injection into mouse (B6D2F1) oocytes (mouse test). With mice (B6D2F1, ICR) and rat, ROS displayed no oocyte activation or Ca2+ oscillation-inducing abilities. Although ELS could induce activation at 87, 86 and 31% of injected oocytes respectively, most of the intracellular calcium concentration ([Ca2+]i) responses of ELS-injected oocytes did not show oscillation patterns; only several transient [Ca2+]i rises (transient pattern) were seen. Similarly, with hamster, rabbit and human, while ROS could induce oocyte activation efficiently (70, 71 and 52% respectively), most of the [Ca2+]i patterns of injected oocytes were transient patterns, and not oscillation patterns. When ROS nuclei only from these latter species were injected into mouse oocytes, most of the oocytes could not be activated. [Ca2+]i patterns of oocytes injected with immature sperm cells changed from transient pattern to oscillation pattern while the cells were maturing into spermatozoa. With hamster ROS, oocyte-activating factor was found to be distributed mainly in the cytoplasm. It was interesting that there is a dissociation between the timings of appearance of oocyte activation and that of Ca2+ oscillation of oocytes injected with developing immature sperm cells.

Biological aspects of testicular sperm extraction

Since the first reports of successful pregnancies after treatment with intra cytoplasmic sperm injection (ICSI) in humans, intensive investigations focused on the use of testicular spermatozoa and immature sperm cells in the treatment of azoopsermic patients. Several studies explore the technical development of the preparation, isolation and cryo storage of testicular germ cells. Other studies focus on ICSI itself and try to identify the biochemical and biophysical processes involved in fertilisation after injection of a testicular sperm cell into a human oocyte. Indications for azoospermic patients to whom this first line treatment can be offered are becoming more defined. But one of the major concerns is of course the safety of the technique, especially, for the health and reproductive life of the babies born after application of ICSI with testicular germ cells. An evaluation of ICSI with testicular germ cells is presented in this manuscript.

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.

Prognostic factors for successful testicle spermatid recover

Men with non-obstructive azoospermia exhibit different histopathologic syndromes in the testicle biopsy, varying from aplasia, Sertoli cell only syndrome, maturation arrest and hypoplasia. The genetic basis of these syndromes is discussed. We present the diagnostic testicle biopsies performed on 160 consecutive non-obstructive azoospermic patients, and these results were correlated with the findings after multiple bilateral treatment testicle biopsy. Each syndrome had to be reevaluated as for the presence of at least one focus of spermatogenesis up to the primary spermatocyte, round spermatid, elongating spermatid, elongated spermatid, or spermatozoa stages. The clinical outcome using donor sperm-IVF, spermatid or sperm intracytoplasmic injection is thereafter presented. A new prognosis based on the findings of this large clinical series coupled to results obtained with Y chromosome molecular screening is offered. Alternative treatments to donor sperm for men without spermatids are discussed.

Progression to the blastocyst stage of embryos derived from testicular round spermatids

Progression to the blastocyst stage of embryos derived from testicular round spermatids in men with non-obstructive azoospermia was studied. A total of 56 men were studied in whom partial spermatogenesis failure had occurred where only very few spermatozoa (fewer than the number of oocytes retrieved) were extracted from multiple testicular biopsy specimens. Oocytes remaining after intracytoplasmic injection of testicular spermatozoa (group 1) were injected with round spermatids (ROSI, group 2). Only embryos derived from group 1 were transferred. Remaining embryos were observed under culture for 8 days and their progression to the blastocyst stage was recorded. Of the 546 oocytes injected with testicular spermatozoa, 404 (73.9%) showed evidence of 2-pronuclear (2PN) fertilization. Injection of testicular round spermatids resulted in 2PN fertilization rate of 50% (P < 0.05). Using a four-point grading system, 53% of the good quality embryos (grade 1 or 2) in group 1 reached the blastocyst stage compared with 25% in group 2 (P < 0.05). The rate of progression to the blastocyst stage of grade 3 and grade 4 embryos was 46 and 8.5% in the two groups respectively (P < 0.05). Using a different three-point grading system for the blastocysts, 75.3% of the blastocysts in group 1 were either grade 1 or grade 2 and 24.7% were grade 3. However, in group 2 all blastocysts were grade 3. All embryos observed in group 1 reached the blastocyst stage by day 5 or 6 compared with 25% of the embryos reaching the blastocyst stage by this time in group 2. While 31.2% of the blastocysts in group 1 showed evidence of spontaneous hatching in vitro, none of the blastocysts in group 2 hatched. In conclusion, progression to the blastocyst stage occurred at a much lower and slower rate in embryos derived from testicular round spermatids. Furthermore, all blastocysts resulting from ROSI were of poor quality and none showed spontaneous hatching. These results may explain the dismal outcome associated with ROSI.

In-vitro spermatogenesis resumption in men with maturation arrest: relationship with in-vivo blocking stage and serum FSH

We have shown previously that germ cells recovered from some men with maturation arrest can resume spermatogenesis in vitro and give rise to late elongated spermatids. This study relates the ability of germ cells to differentiate in vitro to the stage at which spermatogenesis is blocked in vivo and to the patient's serum FSH concentration. The presence of germ cells at different stages of spermatogenesis was assessed, before and after culture, by classical cytology, by fluorescence in-situ hybridization and by immunocytochemistry with a germline-specific marker. The proportion of cases of maturation arrest at the primary spermatocyte, secondary spermatocyte and spermatid stage in which in-vitro resumption of meiosis was achieved was 24.3% (9/37), 100% (3/3) and 51.1% (23/45) respectively. Serum FSH concentrations were higher than normal in most cases. However, lower values were measured in patients in whom in-vitro spermatogenesis was achieved compared with those in whom no progression was detected. These data show that, under the conditions of this study, germ cells from men with very high serum FSH concentrations (>20 IU/l) are less likely to resume spermatogenesis in vitro than those coming from men with only moderate increase (10-20 IU/l).

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.

Electrical activation and in vitro development of human oocytes that fail to fertilize after intracytoplasmic sperm injection

OBJECTIVE

To determine whether electrically stimulated Ca2+ influx can "rescue" fertilization and early embryogenesis in human oocytes that fail to fertilize after intracytoplasmic sperm injection (ICSI).

DESIGN

Prospective, randomized trial of a laboratory procedure.

SETTING

A research laboratory at a university medical center.

PATIENT(S)

Discarded oocytes from ICSI-IVF cycles.

INTERVENTION(S)

Oocytes (n = 104) that showed no evidence of fertilization 16-24 hours after ICSI were assigned to three treatment groups: group 1 (one direct current electrical pulse at 1.36-1.50 kV/cm for 40-60 micros), group 2 (three pulses every 15-20 minutes), or group 3 (treated the same as group 2 but with no electrical stimulation).

MAIN OUTCOME MEASURE(S)

After stimulation, the oocytes were cultured in vitro for 3-5 days. Oocytes that displayed two pronuclei and a second polar body within 16 hours were considered to have fertilized normally. Fertilization and embryo cleavage rates were compared between groups.

RESULT(S)

Fertilization occurred in 26 (70%) of 37 and 38 (78%) of 49 group 1 and 2 oocytes, respectively, but in only 5 (27%) of 18 group 3 oocytes. Within 3 days, group 2 embryos routinely developed beyond the two-cell to four-cell stage (61% versus 13% in group 1); 11% of these oocytes developed to the morula or early blastocyst stage. Sex chromosome analyses indicated 10 male and 8 female embryos.

CONCLUSION(S)

Oocytes that fail to fertilize by 24 hours after ICSI can resume apparently normal fertilization and early embryonic development in response to electrical stimulation. Moreover, the degree of cytoplasmic activation as determined by the number of pulses applied affects fertilization efficiency and early embryonic development.

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.

Type and frequency of chromosome aberrations in 781 couples undergoing intracytoplasmic sperm injection

Cytogenetic investigations were performed in 781 couples prior to intracytoplasmic sperm injection (ICSI) because of severe male infertility or fertilization failures in previous in-vitro fertilization attempts. Out of these 1562 patients, 1012 had a normal karyotype without any aberrations (64.8%), 204 patients had an abnormal karyotypes (13.1%). These chromosome aberrations included constitutional aberrations (4.4%), fragile sites of autosomes (3.0%), low level mosaicism of sex chromosomes (4.0%) and secondary structural chromosome aberrations (4.2%). Combinations of different types of abnormalities were stated. Another 346 patients (22.1%) showed single cell aberrations; the significance of these is unclear at the moment. Constitutional chromosome aberrations were detected in 69 patients. The following chromosome aberrations were observed: 35 sex chromosomal aberrations (comprising hyperploidies of X or Y chromosomes, mosaicisms and derivative X and Y chromosomes), 34 autosomal aberrations including 14 reciprocal translocations, five Robertsonian translocations, six inversions, one marker chromosome, one trisomy 18 mosaicism and seven other structural aberrations. Three autosomal regions showed fragile sites: 6q13 in 2.9% of the patients, 17p12 and 10q24 in 0.05% each. In conclusion, our data show that a high number of infertile couples in an ICSI programme are affected by chromosome aberrations which occur in both sexes. It is suggested that a chromosomal analysis should be performed on both partners before ICSI treatment is initiated.

Evaluation of the fertilization potential of freshly isolated, in-vitro cultured and cryopreserved human spermatids by injection into hamster oocytes

The clinical potential for fertilization was examined by using the human sperm-hamster oocyte assay system after microinjection of round (RS), elongating (ES) or elongated (EtedS) spermatids retrieved from obstructive and non-obstructive azoospermic patients. Freshly isolated, in-vitro cultured and cryopreserved spermatids were utilized. For each category of microinjected spermatids, we demonstrated that the more mature the injected spermatid, the higher the incidence of fertilization (for freshly isolated spermatids, P < 0.006 and P < 0.008, for in-vitro cultured spermatids, P < 0.007 and P < 0.007 and for cryopreserved spermatids, P < 0.006 and P < 0.007 for obstructive and non-obstructive azoospermic patients respectively). Short term in-vitro culture of the spermatogenic cells did not improve the incidence of fertilization. However, cryopreservation significantly decreased (P < 0.001) the incidence of fertilization when each corresponding spermatogenic cell stage was compared. The incidence of fertilization was not statistically different when corresponding stages of spermatogenic cells were compared from obstructive and non-obstructive patients.

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.