The heparin-glutathione test: an alternative to the hypo-osmotic swelling test to select viable sperm for intracytoplasmic sperm injection

Glutathione treatment of Japanese Black bull sperm prior to intracytoplasmic sperm injection promotes embryo development

Intracytoplasmic sperm injection (ICSI) was expected to enable more efficient use of sperm from sires with preferable genetic traits and result in a generation containing a larger number of offspring with superior genetic characteristics in livestock. However, the efficiency of the early development of embryos produced by ICSI is still far from satisfactory in cattle. The present study aimed to investigate the effects of the treatment of cryopreserved sperm with glutathione (GSH) on the early development of embryos produced by ICSI in Japanese Black cattle. Moreover, the disulfide bond state and mitochondrial function were investigated in the sperm treated with GSH to confirm the effectiveness of the abovementioned treatment. We also investigated the effect of 7% ethanol activation treatment on the developmental ability of ICSI embryos using GSH-treated sperm. There was no effect on the blastocyst rate from the activation treatment. When sperm-injected oocytes were cultured in vitro, the treatment with GSH significantly improved the early development of embryos. Specifically, the rates of embryos reaching the 4-8-cell stage and blastocyst stage were significantly higher in ICSI with GSH-treated sperm (71.4% and 31.0%, respectively) than that with the control sperm (36.6% and 7.0%, respectively). Moreover, the GSH-treated sperm treatment significantly decreased the number of disulfide bonds in the sperm head (as shown by monobromobimane staining) and enhanced the mitochondrial function in the sperm middle piece (as shown by Rhodamine 123 staining and the adenosine triphosphate-dependent bioluminescence assay). Based on these results, we suggest that the treatment of cryopreserved sperm with GSH might contribute to the improvement of ICSI techniques for the production of blastocysts in Japanese Black cattle.

Effects of disulfide bond reducing agents on sperm chromatin structural integrity and developmental competence of in vitro matured oocytes after intracytoplasmic sperm injection in pigs

We recently reported that electrical activation followed by secondary chemical activation greatly enhanced the developmental competence of in vitro matured porcine oocytes fertilized by intracytoplasmic sperm injection (ICSI). We hypothesized that sperm treatment with disulfide bond reducing agents will enhance the development competence of porcine embryos produced by this ICSI procedure. We examined the effects of glutathione (GSH), dithiothreitol (DTT), GSH or DTT in combination with heparin on sperm DNA structure, paternal chromosomal integrity, pronuclear formation, and developmental competence of in vitro matured porcine oocytes after ICSI. Acridine orange staining and flow cytometry based sperm chromatin structure assay were used to determine sperm DNA integrity by calculating the cells outside the main population (COMP alphaT). No differences were observed in COMP alphaT values among GSH-treated and control groups. COMP alphaT values in GSH-treated groups were significantly lower than that in DTT-treated groups. Following ICSI, GSH treatments did not significantly alter paternal chromosomal integrity. Paternal chromosomal integrity in sperm treated with DTT plus or minus heparin was also the lowest among all groups. GSH-treated sperm yielded the highest rates of normal fertilization and blastocyst formation, which were significantly higher than that of control and DTT-treated groups. The majority of blastocysts derived from control and GSH-treated spermatozoa were diploid, whereas blastocysts derived from DTT-treated spermatozoa were haploid. In conclusion, sperm treatment with GSH enhanced the developmental capacity of porcine embryos produced by our optimized ICSI procedure.

Nucleons II: cryopreservation and metabolic activity

The establishment of intracytoplasmatic sperm injection (ICSI) as a routine procedure in assisted fertilization has been used in the treatment of male infertility. The major technical problem that has arisen with the use of immotile sperm for ICSI has been differentiating between live and dead cells. Nucleons from human, pig, hamster, mouse, rat, and bull have been able to induce their chromatin decondensation by the action of heparin/GSH. Cryopreservation is deleterious to sperm function, killing more than 50% of the spermatozoa during the process. Nucleon cryostorage was performed at 5 and -5 degrees C and analyzed for total area (mu2), perimeter (mu), width (mu), and length (mu), using Metamorph Imaging System software. On the other hand, fluorescein diacetate (FDA) is hydrolyzed by intracellular estereases to produce fluorescein, which exhibits green fluorescence when excited by blue light. This fact is a striking result since the presence of this metabolic activity opens the possibility to select the nucleons for ICSI. In the present study, the authors decided to search for a suitable metabolic test, which might reflect the metabolism and viability of these chromatin structures. This is a simple cryostorage technique that after months of cryopreservation, allow the use of nucleons for ICSI with suitable fertilization and pregnancies rates.

Pentoxifylline initiates motility in spontaneously immotile epididymal and testicular spermatozoa and allows normal fertilization, pregnancy, and birth after intracytoplasmic sperm injection

PURPOSE

Pentoxifylline (PF) has been used to enhance sperm motility in many in vitro fertilization programs. The twofold purpose of this study was to determine whether PF stimulates fresh or frozen epididymal and testicular totally immotile spermatozoa and whether it can be used to select viable spermatozoa for intracytoplasmic sperm injection (ICSI).

METHODS

To test the effect of PF on motility, 10 samples of totally immotile spermatozoa were incubated for 10 min with 3.6 mM PF. Motility was initiated in all cases (14.8% mean motility after PF treatment of five samples of fresh or frozen epididymal spermatozoa and 13.6% mean motility of five samples of fresh or frozen testicular spermatozoa). To assess PF for selection of viable spermatozoa before ICSI, we compared the outcome of ICSI in 20 cycles using fresh or frozen epididymal or testicular PF-treated immotile spermatozoa and 139 control ICSI using fresh or frozen epididymal or testicular spontaneously motile spermatozoa.

RESULTS

Fertilization rates were similar in the PF and control groups (45.2% vs. 51.0%). Embryo quality and division stages at the time of transfer were comparable. Six pregnancies occurred in PF-ICSI group (30.0% per cycle vs. 26.6% in control group) including two deliveries of healthy children and four ongoing pregnancies.