Sperm preparation for intracytoplasmic injection: methods and relationship to fertilization results

Human sperm handling in intracytoplasmic sperm injection processes: In vitro studies on mouse oocyte activation, embryo development competence and sperm oxidation-reduction potential

Polyvinylpyrrolidone (PVP) and hyaluronic acid (HA) are routinely used in handling spermatozoa for intracytoplasmic sperm injection (ICSI). As there are still concerns about possible adverse effects on the embryo, this study investigated sperm handling in a mouse ICSI model to (i) evaluate oocyte activation after injection of spermatozoa selected for rotational or linear motion in PVP; (ii) assess the effect of sperm selection in PVP, HA and medium on oocyte activation; (iii) examine the effects of PVP and HA on parthenogenetic oocyte activation and embryo development; and (iv) assess the oxidation-reduction potential (ORP) of spermatozoa exposed to PVP, HA or medium. Oocyte activation was higher when spermatozoa exhibited rotational motion rather than linear motion (79% vs. 52%; p = .05). There was no difference in oocyte activation and embryo development after parthenogenetic oocyte activation after sperm injection using PVP, HA or medium-incubated spermatozoa. PVP-selected spermatozoa exhibited lower (p < .0001) ORP levels than using HA. Thus, results indicate that the sperm handling method and the type of medium used impact ICSI outcomes. Overall, sperm incubation in PVP, HA and medium yields similar outcomes with regard to oocyte activation and embryo development. However, PVP provides more antioxidative protection than HA and should therefore be preferred for sperm manipulation.

A short report on current fertility preservation strategies for boys

BACKGROUND

Advances in cancer treatment have led to improved long-term survival after childhood cancer, but often at a price of impaired future fertility. Fertility preservation (FP) in male children and early adolescents poses unique challenges as efficacy is unproven.

OBJECTIVES

To describe characteristics of testicular tissue cryopreservation (TTCP) specimens taken from paediatric and adolescent patients, stratified by age, and prior chemotherapy, if any, and to demonstrate evidence for germ cells.

MATERIALS AND METHODS

Retrospective review of gonadal biopsies and clinical records of patients consented into the Royal Children's Hospital FP programme between 1987 and 2015. Tissue was sliced into blocks, with one section sent for histopathology prior to cryopreservation. In boys ≥12 years where spermatogenesis could be expected, a portion of tissue was disaggregated completely to look for mature sperm and if found, additional tissue was dissected and the resulting suspension frozen.

RESULTS

Testicular tissue cryopreservation specimens in 44 males (0.3-16.8 years) provided an average of 7.8 slices per patient. All the specimens were taken at the same time as another necessary surgical procedure, under one general anaesthesic. There was only one complication of scrotal wound dehiscence. Seven of the forty-four (15.9%) patients had chemotherapy prior to testicular biopsy, while the rest were chemotherapy naïve. Five of these were prepubertal, and two were pubertal patients. Eleven subjects had tissue dissected with mature sperm found in eight. Of these eight patients where sperm were found, all were pubertal with testicular size of more than 10 mL and showing histological evidence of spermatogenesis. No histologic specimen demonstrated any malignant cells.

CONCLUSIONS

Testicular tissue cryopreservation can be performed in young patients without delay, preferably prior to cancer treatment. As testicular tissue contains germ cells from which haploid spermatozoa are ultimately derived, future technologies may allow their utilization for fertility in humans. This may be the only hope for biological offspring in some patients undergoing fertility compromising treatment. Retrieval of mature sperm from some pubertal patients, however, offers realistic hope to these patients of future fertility.

DNA synthesis and epigenetic modification during mouse oocyte fertilization by human or hamster sperm injection

PURPOSE

To evaluate DNA synthesis and epigenetic modification in mouse oocytes during the first cell cycle following the injection of human or hamster sperm.

METHODS

Mouse oocytes following the injection of human and hamster sperm and cultured in M16 medium.

RESULTS

Male and female pronucleus formation, DNA synthesis, histone protein modification, and heterochromatin formation were similar in mouse oocytes injected with human or hamster sperm. However, DNA methylation patterns were altered in mouse oocytes following human sperm injection. Immunocytochemical staining with a histone H3-MeK9 antibody revealed that human and hamster sperm chromatin associated normally with female mouse chromatin, then entered into the metaphase and formed normal, two-cell stage embryos.

CONCLUSIONS

Although differences in epigenetic modification of DNA were observed, fertilization and cleavage occurred in a species non-specific manner in mouse oocytes.

Use of zona pellucida-bound sperm for intracytoplasmic sperm injection produces higher embryo quality and implantation than conventional intracytoplasmic sperm injection

This goal of this study was to compare the outcomes of conventional intracytoplasmic sperm injection (ICSI; control group, n = 53 couples) and a modified ICSI technique using zona pellucida (ZP)-bound sperm for injection of oocytes (test group, n = 53 couples). The proportion of high-quality embryos (grades 1 and 2) and implantation rate were significantly higher in the test group than in the control group, but the difference in fetal heart pregnancy rate was not significant despite seven more pregnancies being obtained in the test group (26 pregnancies) versus the control group (19 pregnancies) following fresh embryo transfers.

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

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

Gamete and embryo isolation and culture with microfluidics

Assisted reproductive technologies (ARTs) encompass some of the most exciting modern scientific developments that tremendously impacts society at many levels. Since the beginning of ARTs, scientists have studied and critically analyzed techniques in order to find ways to improve outcomes; however, little has changed with the actual technology and equipment for embryo in vitro production (IVP). New technologic possibilities exist with the escalating advancements of microfluidic technologies. Microfluidics is based on the behavior of liquids in a microenvironment. Although a young field, substantial research demonstrates the potential of this technology in gamete and embryo isolation and culture. In this review, we briefly discuss physical principles of microfluidics and highlight previous utilization of this technology. We then present designs and outcomes for microfluidic devices utilized thus far for different steps in the IVP process: gamete isolation and processing, fertilization, and embryo culture. Finally, we discuss and speculate on future use of microfluidics for assessing embryo viability and multiparametric analysis of embryo secretions and the integration of ART stage-specific capabilities that will lead to an "IVP-lab-on-a-chip".

Combination of hypoosmotic swelling/eosin Y test for sperm membrane integrity evaluation: correlations with other sperm parameters to predict ICSI cycles

The objective of our study was to evaluate the accuracy of the combination of hypoosmotic swelling (HOS) and eosin Y (Ey) exclusion tests to predict the ICSI cycles' outcome and its correlations with other sperm parameters. The functional and structural integrity of sperm membrane was evaluated with the combined HOS/Ey test in 95 ICSI cycles and the results were correlated with other sperm parameters, including concentration, motility, strict morphology, and total motile sperm count. The combined HOS/Ey test was evaluated for the prediction of the ICSI cycles' outcome parameters including fertilization, cleavage, and pregnancy rates. The HOS/Ey test presented significant relationships with concentration, motility, and strict morphology (p < 0,0001) but it couldn't predict the fertilization, cleavage, and pregnancy outcomes of ICSI cycles. The combined HOS/Ey test has strong correlations with motility and strict morphology parameters of sperm samples but is not sufficiently sensitive to estimate the outcome of ICSI cycles.

Production of a transgenic piglet by a sperm injection technique in which no chemical or physical treatments were used for oocytes or sperm

As a method of producing transgenic animals, spermatozoa have been used to fertilize mammalian oocytes through natural copulation, artificial insemination (AI), and in vitro fertilization (IVF). Our objective was to produce live piglets expressing the enhanced green fluorescent protein (eGFP) by the modified ICSI procedure based on Yong et al. (2003) (Hum. Reprod. 18:2390) where this procedure resulted in an improvement in development in vitro as compared to conventional ICSI and IVF. After injecting frozen-thawed sperm, recovered from the descendant of a transgenic boar derived by oocyte transduction, into in vitro matured oocytes the injected oocytes were surgically transferred into the oviduct of six surrogate gilts. Two gilts (33%) became pregnant. One gave birth to a healthy male piglet. Expression of the eGFP was easily observed in the nose and hooves by direct epifluorescent examination in the newborn piglet. These results show the production of the first viable transgenic piglet by in vitro maturation and our new sperm injection method.

Use of a laser to detect viable but immotile spermatozoa

A prerequisite for the success of intracytoplasmic sperm injection (ICSI) is the use of viable sperm that will support oocyte activation and embryo development. Usually, spermatozoa are selected according to motility, which is a clear indication for viability. However, in cases with complete asthenozoospermia, it is impossible to select viable sperm by morphological means. Here we report for the first time on the use of a laser to discriminate between viable and dead immotile spermatozoa. The application of a single laser shot to the far end of the sperm tail causes a curling of the sperm tail only in viable sperm, similar to the reaction observed in the hypo-osmotic swelling test. Using this method for sperm selection prior to ICSI we achieved high fertilization and cleavage rates in cases with immotile sperm in fresh testicular biopsy material as well in cases with ejaculated immotile sperm. It is concluded that laser sperm interaction allows for the identification of viable but immotile spermatozoa.

Intra-cytoplasmic sperm injection in a marsupial

Here we report the first use of intra-cytoplasmic sperm injection (ICSI) in a marsupial, the tammar wallaby (Macropus eugenii), to achieve in vitro fertilization and cleavage. A single epididymal spermatozoon was injected into the cytoplasm of each mature oocyte collected from Graafian follicles or from the oviduct within hours of ovulation. The day after sperm injection, oocytes were assessed for the presence of pronuclei and polar body extrusion and in vitro development was monitored for up to 4 days. After ICSI, three of four (75%) follicular and four of eight (50%) tubal oocytes underwent cleavage. The cleavage pattern was similar to that previously reported for in vivo fertilized oocytes placed in culture, where development also halted at the 4- to 8-cell stage. One-third of injected oocytes completed the second cleavage division, but only a single embryo reached the 8-cell stage. The success of ICSI in the tammar wallaby provided an opportunity to examine the influence of the mucoid coat that is deposited around oocytes passing through the oviduct after fertilization. The presence of a mucoid coat in tubal oocytes did not prevent fertilization by ICSI and the oocytes cleaved in vitro to a similar stage as follicular oocytes lacking a mucoid coat. Cell-zona and cell-cell adhesion occurred in embryos from follicular oocytes, suggesting that the mucoid coat is not essential for these processes. However, blastomeres were more closely apposed in embryos from tubal oocytes and cell-cell adhesion was more pronounced, indicating that the mucoid coat may be involved in maintaining the integrity of the conceptus during cleavage.

Development of rat oocytes following intracytoplasmic injection of sperm heads isolated from testicular and epididymal spermatozoa

The possibility of obtaining normal development of rat oocytes following intracytoplasmic injection of rat sperm heads, obtained by sonicating spermatozoa from testes and epididymides, was evaluated. Irrespective of the source of spermatozoa, sperm heads were successfully injected into approximately 45% of oocytes used; after 9-12h of culture, approximately 55% of injected oocytes still had normal morphology. Of the oocytes injected with testicular sperm heads 45% were activated, with a female pronucleus and a second polar body, but significantly more oocytes (approximately 68%) injected with caput and cauda epididymal sperm heads were activated. Male pronuclear formation was observed in 67-84% of the activated oocytes, with no difference in the proportions among the different sources of sperm heads. When zygotes showing two pronuclei and a second polar body at 10h after injection were cultured in conditions that support development of 1-cell embryos produced in vivo, no embryos derived from testicular sperm heads developed to blastocysts after 120 h of culture. Development of embryos derived from cauda sperm heads was significantly higher at all points of assessment, while embryos from caput sperm showed an intermediate degree of development, compared with embryos from testicular spermatozoa. However, similar proportions (2-4%) of 1-cell embryos derived from all three groups of sperm heads developed into normal offspring after transfer to foster mothers; of the limited number of offspring tested, all were fertile. These results demonstrate that sperm heads from all sources tested are similar in their ability to contribute to full development of normal, fertile offspring.

Comparison of the ICSI outcome of ejaculated sperm with normal, abnormal parameters and testicular sperm

OBJECTIVE(S)

To compare fertilization rates, quality of embryos, pregnancy rates (PRs) and outcome of pregnancies in intracytoplasmic sperm injection (ICSI) using sperm from ejaculates of normal and abnormal semen and testicular sperm of non-obstructive azoospermia.

STUDY DESIGN

Four hundred fifty-four patients who underwent 454 ICSI cycles were evaluated retrospectively. Patients were divided into three groups according to the quality and source of sperm. Patients in group 1 underwent 133 cycles of ICSI using ejaculated normal semen, group 2 underwent 235 cycles using ejaculated abnormal semen, and group 3 underwent 86 cycles using testicular sperm.

RESULTS

The parameters were compared among the groups with respect to cycles induced by long (n = 160) and short (n = 294) protocol. In group 3, the fertilization and PRs were significantly lower than in all other groups (51.3 and 10.6% in the long protocol cycles, 53.3 and 5.1% in the short protocol cycles, respectively). There was no significant difference in the outcome of pregnancies in respect to abortion rates between different groups.

CONCLUSION(S)

The fertilizing ability of sperm in ICSI is highest with ejaculated sperm and lowest with sperm extracted by testicular biopsy. Also, the clinical PRs are significantly lower in ICSI with sperm from testicular biopsy. However, the outcomes of pregnancies are not affected by using surgically retrieved sperm from ejaculated semen.

Intracytoplasmic injection of porcine, bovine, mouse, or human spermatozoon into porcine oocytes

We determined the incidence of activation, male pronuclear formation, and apposition of pronuclei in porcine oocytes following intracytoplasmic injection of various porcine sperm components and foreign species spermatozoa, such as that of cattle, mouse or human. The porcine oocytes were activated by injection of a spermatozoon or an isolated sperm head. In contrast, injection of either sperm tail or a trypsin- or NaOH-treated sperm head failed to induce oocyte activation. Because injection of mouse, bovine, or human spermatozoon activated porcine oocytes, the sperm-borne activation factor(s) is not strictly species-specific. Male pronuclear formation and pronuclear apposition were observed in porcine oocytes following injection of porcine, bovine, mouse or human spermatozoa. Electrical stimulation following sperm cell injection did not enhance the incidence of male pronuclear formation or pronuclear apposition compared with sperm cell injection alone (P > 0.1). Following porcine sperm injection, the microtubular aster was organized from the neck of the spermatozoon, and filled the whole cytoplasm. In contrast, following injection of bovine, mouse, or human spermatozoon, the maternal-derived microtubules were organized from the cortex to the center of the oocytes, which seems to move both pronuclei to the center of oocytes. Cleavage to the two-cell stage was observed at 19-21 hr after injection of porcine spermatozoon. However, none of the oocytes following injection of mouse, bovine, or human spermatozoa developed to the mitotic metaphase or the two-cell stage. These results suggested that the oocyte activating factor(s) is present in the perinuclear material and that it is not species-specific for the porcine oocyte. Self-organized microtubules seemed to move the pronuclei into center of oocytes when foreign species spermatozoa were injected into porcine oocytes.

Fertilization of porcine oocytes following intracytoplasmic spermatozoon or isolated sperm head injection

We demonstrated normal fertilization processes (as determined by pronuclear formation, pronuclear apposition and syngamy) in porcine oocytes either following intracytoplasmic spermatozoon (ICSI) or isolated sperm head injection. Microtubule organization and chromatin configuration were investigated in these oocytes during the first cell cycle. Following ICSI, the microtubular aster was organized from the neck of the spermatozoon and filled the whole cytoplasm. These male-derived microtubules appear to move both pronuclei to the center of oocytes. These cytoskeletal changes are analogous to those seen following conventional fertilization. In contrast, following isolated sperm head injection, the sperm aster was not seen. Instead, the microtubule matrix was organized from the cortex and then filled the whole cytoplasm in all cases in normally fertilized oocytes following injection (n=35). This organization is similar to what has been shown in the parthenogenetically activated oocytes. Chromosome analysis revealed that the oocytes injected with isolated sperm heads were fertilized normally. At 7 days following injection, the incidence of blastocoele formation following ICSI (38%) and isolated sperm head injection (22%) was higher than that following sham injection (2%). These results suggested that successful fertilization and preimplantation development occurred in porcine oocytes following either ICSI or isolated sperm head injection. Our results also indicated that fertilization processes can occur by self-assembled microtubules within cytoplasm in the absence of a sperm centrosome.

Pregnancy following intracytoplasmic sperm injection of immotile spermatozoa selected by the hypo-osmotic swelling-test: a case report

The success of intracytoplasmic sperm injection (ICSI) is poor when only immotile spermatozoa can be retrieved. In a couple with complete male asthenozoospermia the possible use of the hypo-osmotic swelling test to select spermatozoa for microinjection was examined. Following incubation in hypo-osmotic medium (Hypo 10, IVF Science, Göteborg, Sweden), 26% of immotile spermatozoa showed signs of sperm swelling (HOS-positive). After injection of HOS-positive spermatozoa, 5 out of 12 oocytes fertilized (41%) and after transfer of three embryos a healthy singleton pregnancy was achieved. In a previous ICSI cycle of this couple without preselection of spermatozoa by the HOS test, only 1 out of 10 oocytes fertilized. It is concluded that selection of spermatozoa by hypo-osmotic swelling-test prior to sperm microinjection seems to be a valuable tool to increase the fertilization rate in cases with complete asthenozoospermia.

Pregnancy rates after intracytoplasmic sperm injection in relation to sperm recovery techniques

PURPOSE/METHODS

Clinical outcome after intracytoplasmic sperm injection (ICSI) was evaluated in relation to three techniques of sperm recovery, mini-Percoll, simple concentration, and centrifugation and washing.

RESULTS

Whereas fertilization and embryonic cleavage rates were similar in the three groups, the rates of implantation and clinical pregnancy were statistically significantly higher following sperm recovery by the techniques of mini-Percoll and centrifugation and washing.

Testicular and epididymal sperm in a microinjection program: methods of retrieval and results

OBJECTIVE

To describe the methods of collection and laboratory preparation of epididymal and testicular sperm; to compare the fertilization and pregnancy rates; and to establish prognostic factors.

DESIGN

Retrospective analysis.

SETTING

Academic reproductive medicine clinic.

PATIENT(S)

One hundred twelve consecutive microinjection cycles in 80 patients using either epididymal or testicular sperm.

INTERVENTION(S)

Sperm were collected by microepididymal sperm aspiration, open testicular biopsy, or fine needle tissue aspiration testicular biopsy.

MAIN OUTCOME MEASURE(S)

Fertilization rate, implantation, and clinical pregnancy rates.

RESULT(S)

The fertilization rate was higher with epididymal sperm (67%) than with testicular sperm (50%). Implantation rates (fetal hearts per embryo, testicular: 11%, epididymal: 8%) and pregnancy rates (clinical pregnancy per oocyte collection procedure, testicular: 25%, epididymal: 29%) were not significantly different with epididymal and testicular sperm. Multiple regression analysis showed that normal fertilization rates were significantly lower with testicular sperm, immotile sperm, and severe spermatogenic disorders.

CONCLUSION(S)

Although fertilization rates are significantly lower with testicular sperm, higher implantation rates resulted in equivalent pregnancy rates. Thus, testicular aspiration of sperm for intracytoplasmic sperm injection is a simple, inexpensive method of sperm retrieval in cases of azoospermia resulting from genital tract obstruction or severe spermatogenic disorder.