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Despite the advent of ICSI, cases of total fertilization failure (TFF) often lead to cycle cancellation with limited diagnostic and therapeutic strategies currently available. We report on the case of an infertile couple who failed to conceive after repeated IVF and ICSI. Sperm of the husband were morphologically normal and passed a functional test assessing their ability to activate mouse oocytes. Whether oocytes were activated artificially with calcium ionophore after injection of husband's or with donor sperm, all oocytes failed to fertilize. Multiple polar bodies and two disorganized spindle structures were predominantly observed, pointing towards a cytoplasmic defect in the oocytes as the primary cause of the couple's infertility. In fact, injection of husband's sperm into donor oocytes resulted in the delivery of healthy twins. This report describes a course of action that may be applied for couples with TFF after both IVF and ICSI.

Efficient integration of functional genes is an essential prerequisite for successful gene delivery such as cell transfection, animal transgenesis, and gene therapy. Gene delivery strategies based on viral vectors are currently the most efficient. However, limited cargo capacity, host immune response, and the risk of insertional mutagenesis are limiting factors and of concern. Recently, several groups have used transposon-based approaches to deliver genes to a variety of cells. The piggyBac (pB) transposase in particular has been shown to be well suited for cell transfection and gene therapy approaches because of its flexibility for molecular modification, large cargo capacity, and high transposition activity. However, safety considerations regarding transposase gene insertions into host genomes have rarely been addressed. Here we report our results on engineering helper-independent pB plasmids. The single-plasmid gene delivery system carries both the piggyBac transposase (pBt) expression cassette as well as the transposon cargo flanked by terminal repeat element sequences. Improvements to the helper-independent structure were achieved by developing new plasmids in which the pBt gene is rendered inactive after excision of the transposon from the plasmid. As a consequence, potentially negative effects that may develop by the persistence of an active pBt gene posttransposition are eliminated. The results presented herein demonstrate that our helper-independent plasmids represent an important step in the development of safe and efficient gene delivery methods that should prove valuable in gene therapy and transgenic approaches.

We have developed a method that effectively removes all of the perinuclear materials of a mouse sperm head, including the acrosome, plasma membrane, perinuclear theca, and nuclear envelope. By injection of a single purified sperm head into a metaphase II mouse oocyte followed by activation with strontium chloride, 93% of the zygotes developed into two-cell embryos. Although only approximately 17% of the transferred two-cell embryos were born alive, all live pups developed into adults, and they appeared to be normal in reproduction and behavior. We detected RNA species, including mRNAs and miRNAs from the purified sperm heads. Our data demonstrate that pure membrane-free sperm heads are sufficient to produce normal offspring through intracytoplasmic sperm injection and that at least part of the RNA molecules are deeply embedded in the sperm nucleus.

There are cases in which the 1-day-old unfertilized oocytes after IVF, or in vitro matured oocytes obtained from denuded immature oocytes after ICSI, are used clinically. We investigated the morphological change of metaphase II spindle and chromosomal alignment in those oocytes. The spindles and chromosome were stained using an anti-α-tubulin antibody and Hoechst 33258 respectively. One-day-old oocytes displayed significant increases in abnormalities of spindle structure (40.4% vs. 17.6%) and chromosomal alignment (40.4% vs. 29.4%). Oocytes matured in vitro from MI and PI oocytes displayed spindle morphological abnormalities at the rates of 41.7% and 36.0% respectively, and chromosomal alignment abnormality at the rates of 45.8% and 44.0% respectively. These results suggest that 1-day-old oocytes and in vitro matured oocytes obtained from denuded immature oocytes after ICSI might have lowered developmental potential. More than 50% of those oocytes were determined to be unsuitable for use as gametes.

We identified a previously uncharacterized gene, spermatid maturation 1 ( Spem1 ), encoding a protein exclusively expressed in the cytoplasm of steps 14–16 elongated spermatids in the mouse testis. This protein contains no known functional domains and is highly conserved across mammalian species. Male mice deficient in Spem1 were completely infertile because of deformed sperm characterized by a bent head wrapped around by the neck and the middle piece of the tail. We show that lack of Spem1 causes failure of the cytoplasm to become loose and detach from the head and the neck region of the developing spermatozoa. Retained cytoplasmic components mechanically obstruct the straightening of the sperm head and the stretching of the growing tail, leading to the bending of the head in the neck, followed by the wrapping of the head by the neck or the middle piece of the sperm tail. Our study reveals that proper cytoplasm removal is a genetically regulated process requiring the participation of Spem1 and that lack of Spem1 causes sperm deformation and male infertility.

Cryopreservation of male germ cells is a strategy to conserve animal species and strains of animals valuable to biomedical research. We tested whether mouse male germ cells could be cryopreserved without cryoprotection by simply freezing epididymides, testes, or whole bodies. The reproductive organs were isolated from killed mice and frozen for 1 week to 1 year at −80°C before spermatozoa and spermatids were collected and injected into mature oocytes. Normal pups were born irrespective of strains tested (ICR and C57BL/6). Epididymides and testes frozen and transported internationally to another laboratory by air could produce pups of inbred C57BL/6 mice. Testicular spermatozoa retrieved from the bodies of male mice (BALB/c nude and C3H/He strains) that had been kept frozen (−20°C) for 15 years could also produce normal offspring by microinsemination. Thus, freezing of either male reproductive organs or whole bodies is the simplest way to preserve male germ cells. Restoration of extinct species could be possible if male individuals are found in permafrost.

In mice and humans, a normal offspring can be obtained by injecting a single spermatozoon into an oocyte, the process called intracytoplasmic sperm injection (ICSI). When three or more mouse spermatozoa with intact acrosomes were injected into individual mouse oocytes, an increasing proportion of oocytes became deformed and lysed. Oocytes did not deform and lyse when acrosome-less spermatozoa were injected, regardless of the number of spermatozoa injected. Injection of more than four human spermatozoa into a mouse oocyte produced vacuole-like structures in each oocyte. This vacuolation did not happen when spermatozoa were freed from acrosomes before injection. Hamsters, cattle, and pigs have much larger acrosomes than the mouse or human. Injection of a single acrosome-intact hamster, bovine, and porcine spermatozoon deformed and lysed many or all mouse oocytes. This deformation did not happen when these spermatozoa were freed from acrosomes before ICSI, regardless of the number of spermatozoa injected. Because trypsin and hyaluronidase mimicked the action of acrosome-intact spermatozoa, it is likely that the acrosomal enzymes deform and lyse the oocytes. Injection of small amounts of trypsin and hyaluronidase into normally fertilized mouse eggs disturbed their pre- and postimplantation development. In view of potentially harmful effects of acrosomal enzymes on embryo development, the removal of acrosomes before ICSI is recommended for animals with large sperm acrosomes. The removal of acrosomes may increase the efficiency of ICSI in these animals. Although human and mouse spermatozoa do not need to be freed from acrosomes, the removal of acrosomes before ICSI is theoretically preferable.

Human immunodeficiency virus (HIV) can be inactivated by heating at 56 °C for 30 min, treating with 50% ethanol at room temperature for 10 min, or treating with 2% sodium hypochlorite solution (NaClO) at room temperature for 60 min. Using a mouse model, we evaluated the risk of generating chromosome damage in spermatozoa following these treatments. The spermatozoa were all dead after the treatments. Although 41.3% of oocytes injected with ethanol-treated spermatozoa successfully activated, none of the oocytes injected with heated or NaClO-treated spermatozoa activated. When artificial stimulation with strontium was used, the fertilization of oocytes with heated or ethanol-treated spermatozoa was completely rescued. Sperm nuclei treated with NaClO neither decondensed nor developed to a male pronucleus. The incidences of structural chromosome aberrations in 1-cell zygotes derived from the heated spermatozoa (45.6%) and ethanol-treated spermatozoa (91.2%) were significantly higher than those in the matched controls (5.5% and 10.5%, respectively). Further study is needed to develop a methodology for the protection of spermatozoa against chromosome damage or the separation of damaged spermatozoa before intracytoplasmic sperm injection.

Cryopreservation of male germ cells is a strategy to conserve animal species and strains of animals valuable to biomedical research. However, to minimize damage that may occur during freezing and thawing, complex cryopreservation protocols that have been optimized for the stage and species of male germ cells are usually employed. Recently, we have found that mouse male germ cells can be cryopreserved at -80�C by freezing the whole epididymides and testes without cryoprotectant for at least one year (Ogonuki et al. 2006 Reprod. Fertil. Dev. 18, 286 abst). This study was undertaken to determine whether mouse male germ cells retrieved from the bodies of mice frozen at -20�C for 15 years could produce normal offspring by microinsemination. Mature males of BALB/c-nude and C3H/He (8 weeks of age) were euthanized by overdose of pentobarbital on February 20 and March 8, 1991, respectively, and kept in a -20�C freezer. The frozen body was thawed about 15 years after freezing (February 2006) by putting it in a water bath until the outer surface of the body was softened. The body was then removed from the water, and the testes were isolated through an abdominal incision. Testicular spermatozoa were collected from the testes and microinseminated into B6D2F1 oocytes. Within 24 h after sperm injection, over 80% of oocytes developed into 2-cell embryos. Apparently normal pups were born after embryo transfer in both strains of mice at rates of 21% (17/81) and 12% (12/97) per transfer, respectively. Two pups from the BALB/c-nude group died shortly after Caesarian section due to respiratory failure, but others grew normally and were proven to be fertile when they matured (at least 19 mice out of 20 mice tested). We further mated these F1 offspring and confirmed that the nude gene was safely propagated. The present study demonstrates that spermatozoa can retain their fertilizing ability in frozen whole bodies for longer than we anticipated. If spermatozoa of extinct mammalian species (e.g. woolly mammoth) can be retrieved from animal bodies that were kept frozen in permanent frost, live animals might be restored by injecting them into oocytes from females of closely related species.