Advances in spermatogonial stem cell transplantation

The Safe Recipient of SSC Transplantation Prepared by Heat Shock With Busulfan Treatment in Mice

Safety is the chief consideration in recipient preparation of spermatogonial stem cell (SSC) transplantation in mammals, especially humans. In this study, we compared the safety of the SSC transplantation recipients that were prepared both by testes heat shock plus testes busulfan injection (heat shock+busulfan(t)) and by busulfan intraperitoneal injection (busulfan i.p.) only. Our results showed that heat shock+busulfan(t) treatment significantly (p < 0.05) reduced mortality in mice and did not produce bone marrow cell toxicity. Furthermore, heat shock+busulfan(t) treatment directly damaged SSCs and exhausted almost all of the germ cells in the testis; the exhaustion of these cells is considered a key factor in the successful preparation of the recipients. Therefore, we used heat shock+busulfan(t) treatment to prepare recipients of SSC transplantation. Two months after SSC transplantation, the number and length of donor SSC-derived colonies in the testis of recipient in heat shock+busulfan(t) group was closed to that in busulfan i.p. group. Therefore, compared with busulfan i.p. treatment, heat shock+busulfan(t) treatment improved the safety of recipient preparation without reducing the efficiency of SSC transplantation. Two GFP-positive offspring were produced from 1 of the 20 recipients that had mated with female mice 72 days after SSC transplantation. In conclusion, heat shock with busulfan treatment is a safe method to prepare the recipient of SSC transplantation in mice.

Alteration of spermatogenesis following spermatogonial stem cells transplantation in testicular torsion-detorsion mice

PURPOSE

Testicular ischemia is the main consequence of testicular torsion, in both clinical and experimental aspects. Preservation and auto-transplantation of spermatogonial stem cells (SSCs) could be a new treatment for infertility in testicular ischemia following testicular torsion.

METHODS

To apply the idea in this study, animals were randomly divided into four groups of control, sham, with torsion, and with torsion followed by transplantation (TT). Isolated SSCs from neonatal mice were cultured and identified by flow cytometry (C-KIT(-), INTEGRIN β1 (+)) and RT-PCR (Reverse transcription polymerase chain reaction) for specific spermatogonial cell markers (Oct4, Gfrα-1, Plzf, Vasa, Itgα 6 , and Itgβ 1 ). SSCs were transplanted upon a 2-h testicular torsion in the TT group. Cultured cells were transplanted into ischemia reperfusion testicle 2 weeks post-testicular torsion. Eight weeks after SSCs transplantation, the SSCs-transplanted testes and epididymis were removed for sperm analysis, weight and histopathological evaluation, and pre- and post-meiotic gene expression assessment by qRT-PCR.

RESULTS

Our findings indicated that all evaluated parameters (epididymal sperm profile, Johnsen score, Plzf, Gfrα-1, Scp-1, Tekt-1 expressions, and histopathological profile) were significantly decreased following testicular torsion (group 3) when compared to the control group (p ≤ 0.05). However, all abovementioned parameters showed a significant increase/improvement in torsion-transplantation group compared to torsion group. However, these parameters in the TT group were significantly lower in the sham and control groups (p ≤ 0.05).

CONCLUSION

SSCs transplantation could up-regulate the expression of pre- and post-meiotic genes in testicular ischemia, which resulted in improvement of both testicular function and structure after testicular torsion.

Developments in techniques for the isolation, enrichment, main culture conditions and identification of spermatogonial stem cells

The in vitro culture system of spermatogonial stem cells (SSCs) provides a basis for studies on spermatogenesis, and also contributes to the development of new methods for the preservation of livestock and animal genetic modification. In vitro culture systems have mainly been established for mouse SSCs, but are lacking for farm animals. We reviewed and analyzed the current progress in SSC techniques such as isolation, purification, cultivation and identification. Based on the published studies, we concluded that two-step enzyme digestion and magnetic-activated cell sorting are fast becoming the main methods for isolation and enrichment of SSCs. With regard to the culture systems, serum and feeders were earlier thought to play an important role in the self-renewal and proliferation of SSCs, but serum- and feeder-free culture systems as a means of overcoming the limitations of SSC differentiation in long-term SSC culture are being explored. However, there is still a need to establish more efficient and ideal culture systems that can also be used for SSC culture in larger mammals. Although the lack of SSC-specific surface markers has seriously affected the efficiency of purification and identification, the transgenic study is helpful for our identification of SSCs. Therefore, future studies on SSC techniques should focus on improving serum- and feeder-free culture techniques, and discovering and identifying specific surface markers of SSCs, which will provide new ideas for the optimization of SSC culture systems for mice and promote related studies in farm animals.

Application of iPS in assisted reproductive technology: sperm from somatic cells?

Infertility is an emotionally charged problem, and it is a condition of increasing incidence. In addition, in 40% to 60% of all infertile couples, it was the male who had a problem that led to infertility. Among the male fertility problems, non-obstructive azoospermia (NOA) (caused by testis failure or impaired spermatogenesis) is the most prevalent. Despite enormous clinical and experimental efforts, treatment of this disorder--assistant reproduction technique (ART) with donor spermatozoa remains controversial. We present the hypothesis that induced pluripotent stem (iPS) cell derived spermatozoa can be a potential source for male gametes for patients with NOA; we support this with the following three evidence: the first is the generation of viable, live-born, fertile mature organism from iPS cells; the second is the successful induced differentiation of male gametes from pluripotent cells in vitro; and the last is the wide use of intracytoplasmic sperm injection (ICSI) in human assisted reproduction. If the hiPS derived spermatozoa prove practical in the generation offspring with ICSI, this method might be able to grant a new chance for NOA patients to have their genetic children with fewer emotional, ethical and legislative problems. To ensure the safety of the technology itself and the production of healthy offspring, further investigations are needed. We also suggest several laboratory and clinical approaches for testing our hypothesis.

Efficient and safe recipient preparation for transplantation of mouse spermatogonial stem cells: pretreating testes with heat shock

Recipient preparation is of prime importance for the successful transplantation of spermatogonial stem cells (SSCs). Busulfan destroys endogenous germs cells and is commonly used for recipient preparation. However, busulfan produces significant side effects, including systemic toxicity, and it is lethal in certain species. The side effects associated with busulfan compromise the efficiency of SSC transplantation and threaten the safety of recipients. Here, we show that heat shock treatment of testes can be used as an alternative to busulfan treatment. Fourteen days after heat shock treatment, mice received a testicular injection of donor germ cells expressing enhanced green fluorescent protein (EGFP). Busulfan-treated mice were used as controls. Two months after transplantation, the number (12 ± 1 mm) and length (30.46 ± 5.23 mm) of EGFP-expressing testicular colonies in heat shock-treated recipients were not significantly different from those in busulfan-treated recipients. Furthermore, healthy EGFP-expressing offspring were obtained after intracytoplasmic injection of round spermatids recovered from heat shock-treated recipients. This result indicates that donor SSCs undergo complete spermatogenesis in the heat shock-treated testes of recipients. Our findings demonstrate the feasibility of using heat shock for the preparation of recipients before SSC transplantation in mice. Heat shock may prove to be useful for recipient preparation in mammalian species in which busulfan produces significant toxicity.

Long-term follow-up of porcine male germ cells transplanted into mouse testes

This study investigated the effect of increased phylogenetic distance on the outcome of spermatogonial transplantation, with porcine donors and mice recipients. It was designed to develop a technique for detecting foreign donor cells in recipient animals. Porcine male germ cells were harvested from postnatal male testes and incubated with the lipophilic membrane dye PKH-26. For transplantation, approximately 10(6) PKH-26-labelled porcine male germ cells were injected into the efferent ducts of mouse testes. Animals were sacrificed at post-graft days 1, 10, 30, 45, 60 and 150 (n = 5 each). Serial frozen sections of explanted testes were prepared for detecting labelled cells. Transplanted porcine donor cells were easily detected in the recipient tubules for 8 weeks. After transplantation, we could detect both incorporation into the basement membrane and differentiation of grafted porcine donor cells by our double detection system, using PKH staining and slide PCR. However, our RT-PCR and apoptosis results revealed that most of the grafted porcine male donor cells could not differentiate past early-meiotic spermatocytes. We could induce partial differentiation of xenografted porcine donor cells in mouse testes, but not full induction of spermatogenesis. We have developed a very reliable technique for detecting foreign donor cells in recipient animals using a combination of PKH staining and slide PCR methods. Our results provide a valuable experimental model for applying and evaluating this technology in other species.

Fertility issues in survivors from adolescent cancers

Infertility is a common and distressing late-effect of cancer treatment. Whist sperm banking for post-pubertal males and embryo freezing for women (who are in a stable relationship at the time of treatment) are highly successful fertility preservation strategies, for females without a partner (including young and pre-pubescent girls) and pre-pubescent boys (or azoospermic men), there remain no effective approaches. Whilst the biological effects of cancer treatments on the reproductive system are well described, there are few data on the relative incidence of infertility (failure to conceive after one year of trying) in cancer survivors. This makes it difficult to advise survivors about their future fertility prospects. Whilst some will undoubtedly conceive naturally with their partner, others will require assisted conception treatment of which in vitro fertilisation (IVF) and intra-cytoplasmic sperm injection (ICSI) are the most common. Pregnancy outcomes of cancer survivors are generally good, although there is increased risk of pre-term birth and low birth-weight in the offspring of women who have received pelvic irradiation. There is no increased incidence of genetic disease or cancer incidence in the offspring of cancer survivors. Current research directions are focussing on alternative fertility preservation strategies including in vitro maturation techniques, xenotransplantation and the development of technology to create artificial gametes in the laboratory. Finally, although the reproductive techniques discussed are highly effective, country specific differences in the legal framework means that cancer survivors may be denied access to certain treatments (e.g. embryo cryopreservation) because they are forbidden by specific national legislation.

In vitro effects of epidermal growth factor, follicle stimulating hormone and testosterone on mouse spermatogonial cell colony formation

The complex process of spermatogenesis is regulated by various factors. In the present study, the in vitro effects of epidermal growth factor (EGF), follicle stimulating hormone (FSH) and testosterone on spermatogonial cell colony formation were investigated, and the best colonising factor was chosen for treating cells before transplantation. Sertoli and spermatogonial cells were isolated from neonatal mouse testes. The identity of the cells was confirmed through analysis of morphology, alkaline phosphatase activity, immunoreactivity and transplantation. Co-cultured Sertoli and spermatogonial cells were treated with EGF, FSH and testosterone before colony assay. Results indicated that EGF is the best factor for in vitro colonisation of spermatogonial cells, but transplantation of the EGF-treated group did not show any significant change compared with the control groups. In conclusion, EGF increased in vitro colonisation of spermatogonial cells, but, as a result of differential effects, did not influence transplantation efficiency.

A review of in vitro gamete maturation and embryo culture and potential impact on future animal biotechnology

This review considers the relationship of in vitro gamete maturation and embryo culture to the future development of animal biotechnology. The areas reviewed are oocyte maturation in vitro and embryo culture and their importance for successful in vitro embryo production. The rapidly developing area of spermatogonial cell transplantation and culture is also reviewed. The scientific milestones leading to the development of each area, the problems and prospects for future development and the possible significance of major advances in each area are discussed.

Transplantation of germ cells from glial cell line-derived neurotrophic factor-overexpressing mice to host testes depleted of endogenous spermatogenesis by fractionated irradiation

With a novel method of eliminating spermatogenesis in host animals, male germ cells isolated from mice with targeted overexpression of glial cell line-derived neurotrophic factor (GDNF) were transplanted to evaluate their ability to reproduce the phenotype previously found in the transgenic animals. Successful depletion of endogenous spermatogenesis was achieved using fractionated ionizing irradiation. A dose of 1.5 Gy followed by a dose of 12 Gy after 24 h reduced the percentage of tubule cross-sections displaying endogenous spermatogenesis to approximately 3% and 10% as evidenced by histologic evaluation of testes at 12 and 21 wk, respectively, after irradiation. At this dose, no apparent harmful side effects were noted in the animals. Upon transplantation, GDNF-overexpressing germ cells were found to be able to repopulate the irradiated testes and to form clusters of spermatogonia-like cells resembling those found in the overexpressing donor mice. The cluster cells in transplanted host testes expressed human GDNF, as had been shown previously for clusters in donor animals, and both were strongly positive for the tyrosine kinase receptor Ret. Thus, we devised an efficient method for depleting the seminiferous epithelium of host mice without appreciable adverse effects. In these host mice, GDNF-overexpressing cells reproduced the aberrant phenotype found in the donor transgenic mice.