Testicular injection of busulfan for recipient preparation in transplantation of spermatogonial stem cells in mice

Intratesticular versus intraperitoneal Busulfan administration: a comparative study on spermatogenesis suppression in quails and chickens

Generation of transgenic birds can be achieved by temporal suppression of endogenous spermatogenesis in males prior to primordial germ cell implantation. One of many established methods to induce male sterility is the intraperitoneal injection of busulfan, an alkylating agent. Nevertheless, the use of busulfan injections, which may also affect hematopoietic stem cells, carries the risk of potential lethality in animals. Given their safety and non-toxic nature, it has been demonstrated that intratesticular busulfan injections in mammals are less effective than intraperitoneal injections. This study aimed to compare, for the first time, the sterility and toxicity effects of intraperitoneal vs. intratesticular busulfan injections in quail and chickens. Our experimental design involved a previously established single intraperitoneal busulfan injection of 40 mg/kg of body weight (BW). In quail, busulfan was then administered intratesticularly at 3 different concentrations (6, 12, and 20 mg/kg BW), while in chickens, the working concentration was 20 mg/kg BW. We found that a single intraperitoneal busulfan injection of 40 mg/kg of BW resulted in 100% mortality in the treated roosters. In quails, however, this concentration only caused a temporary suppression of fertility for a 15-d period. Moreover, we found that a higher dose of intratesticular injection of busulfan is required to suppress spermatogenesis in quail (20 mg/kg BW) compared to mammals (4 mg/kg BW). Following these findings, we further confirmed that intratesticular injection of 20 mg/kg BW busulfan into roosters did not affect their overall viability. However, it induced a temporary state of male sterility, consistent with the effects observed with intraperitoneal injections. Hence, our data demonstrate that quail and chicken respond differently to busulfan administration. Furthermore, the present study provides evidence that direct injection into the rooster testes causes less physiological stress than intraperitoneal injection.

Mechanisms underlying impaired spermatogenic function in orchitis induced by busulfan

Busulfan is an alkylating agent commonly used in cancer chemotherapy. It is also an ideal agent for preparing transplant recipients of spermatogonial stem cells because of its high efficiency in destroying endogenous germ cells in the testis. However, its toxicity mechanism remains unclear, affecting its clinical use and applications. Based on reports of busulfan causing orchitis and a previous study by our team, this article summarizes the relationship between busulfan and orchitis, cytokines, the blood-testis barrier, and the cytoskeleton, unravels the regulatory pathways and mechanism behind busulfan-induced orchitis, and reveals the molecular mechanism underlying impaired spermatogenic function in orchitis, providing new ideas for the clinical application of busulfan while reducing its testicular toxicity.

Peptides from the croceine croaker (Larimichthys crocea) swim bladder attenuate busulfan-induced oligoasthenospermia in mice

CONTEXT

The swim bladder of the croceine croaker is believed to have a therapeutic effect on various diseases. However, there is no research about its effect on mammalian spermatogenesis.

OBJECTIVE

We investigated the swim bladder peptides (SBPs) effect on busulfan-induced oligoasthenospermia in mice.

MATERIALS AND METHODS

We first extracted SBP from protein hydrolysate of the croceine croaker swim bladder, and then five groups of ICR male mice were randomly assigned: control, control + SBP 60 mg/kg, busulfan, busulfan + SBP 30 mg/kg and busulfan + SBP 60 mg/kg. Mice received bilateral intratesticular injections of busulfan to establish oligoasthenospermia model. After treatment with SBP for 4 weeks, testis and epididymis were collected from all mice for further analysis.

RESULTS

After treatment with SBP 30-60 mg/kg for 4 weeks, epididymal sperm concentration and motility increased by 3.9-9.6- and 1.9-2.4-fold than those of oligoasthenospermia mice induced by busulfan. Meanwhile, histology showed that spermatogenic cells decreased, leading to increased lumen diameters and vacuolization in the busulfan group. These features were reversed by SBP treatment. RNA-sequencing analysis revealed that, compared with the busulfan group, Lin28b and Igf2bp1 expression related to germ cell proliferation, increased with a >1.5-fold change after SBP treatment. Additionally, PGK2 and Cfap69 mRNAs associated with sperm motility, also increased with a >1.5-fold change. Furthermore, these findings were validated by quantitative real-time PCR and Western blotting.

DISCUSSION AND CONCLUSIONS

This is the first reported evidence for the therapeutic effect of SBP on oligoasthenospermia. SBP may be a promising drug for oligoasthenospermia in humans.

The Therapeutic Potential of Amniotic Fluid-Derived Stem Cells on Busulfan-Induced Azoospermia in Adult Rats

BACKGROUND

Busulfan is an alkylating chemotherapeutic agent that is routinely prescribed for leukemic patients to induce myelo-ablation. However, it also results in azoospermia and infertility in cancer survivors. This research was constructed to explore the possible therapeutic role of amniotic fluid-derived stem cells (AFSCs) in improving busulfan-induced azoospermia in adult rats.

METHODS

Forty two adult male albino rats were randomized into: (1) control group, (2) azoospermia group, (3) spontaneous recovery group, and (4) AFSCs-treated group, in which AFSCs were transplanted through their injection into the testicular efferent ducts. The assessment included a histo-pathological examination of the seminiferous tubules by the light and transmission electron microscopes. Additionally, the confocal laser scanning microscope was used for confirmation of homing of the implanted cells. Moreover, we conducted an immuno-fluorescence study for detection of the proliferating cell nuclear antigen (PCNA) in the spermatogenic cells, epididymal sperm count, and a histo-morphometric study.

RESULTS

AFSCs successfully homed over the basement membrane of the injured seminiferous tubules. They greatly attenuated busulfan-induced degenerative and oxidative changes. They also caused a re-expression of PCNA in the germ cells, leading to resumption of spermatogenesis and re-appearance of spermatozoa.

CONCLUSION

AFSCs could be a promising treatment modality for male infertility induced by chemotherapy, as they possess prominent regenerative, anti-apoptotic, and anti-inflammatory potentials.

Establishing a nonlethal and efficient mouse model of male gonadotoxicity by intraperitoneal busulfan injection

An ideal animal model of azoospermia would be a powerful tool for the evaluation of spermatogonial stem cell (SSC) transplantation. Busulfan has been commonly used to develop such a model, but 30%–87% of mice die when administered an intraperitoneal injection of 40 mg kg⁻¹. In the present study, hematoxylin and eosin staining, Western blot, immunofluorescence, and quantitative real-time polymerase chain reaction were used to test the effects of busulfan exposure in a mouse model that received two intraperitoneal injections of busulfan at a 3-h interval at different doses (20, 30, and 40 mg kg⁻¹) on day 36 or a dose of 40 mg kg⁻¹ at different time points (0, 9, 18, 27, 36, and 63 days). The survival rate of the mice was 100%. When the mice were treated with 40 mg kg⁻¹ busulfan, dramatic SSC depletion occurred 18 days later and all of the germ cells were cleared by day 36. In addition, the gene expressions of glial cell line-derived neurotrophic factor (GDNF), fibroblast growth factor 2 (FGF2), chemokine (C-X-C Motif) ligand 12 (CXCL12), and colony-stimulating factor 1 (CSF1) were moderately increased by day 36. A 63-day, long-term observation showed the rare restoration of endogenous germ cells in the testes, suggesting that the potential period for SSC transplantation was between day 36 and day 63. Our results demonstrate that the administration of two intraperitoneal injections of busulfan (40 mg kg⁻¹ in total) at a 3-h interval to mice provided a nonlethal and efficient method for recipient preparation in SSC transplantation and could improve treatments for infertility and the understanding of chemotherapy-induced gonadotoxicity.

Review of injection techniques for spermatogonial stem cell transplantation

BACKGROUND

Although the prognosis of childhood cancer survivors has increased dramatically during recent years, chemotherapy and radiation treatments for cancer and other conditions may lead to permanent infertility in prepubertal boys. Recent developments have shown that spermatogonial stem cell (SSC) transplantation may be a hope for restoring fertility in adult survivors of childhood cancers. For this reason, several centres around the world are collecting and cryopreserving testicular tissue or cells anticipating that, in the near future, some patients will return for SSC transplantation. This review summarizes the current knowledge and utility of SSC transplantation techniques.

OBJECTIVE AND RATIONALE

The aim of this narrative review is to provide an overview of the currently used experimental injection techniques for SSC transplantation in animal and human testes. This is crucial in understanding and determining the role of the different techniques necessary for successful transplantation.

SEARCH METHODS

A comprehensive review of peer-reviewed publications on this topic was performed using the PubMed and Google Scholar databases. The search was limited to English language work and studies between 1994 (from the first study on SSC transplantation) and April 2019. Key search terms included mouse, rat, boar, ram, dog, sheep, goat, cattle, monkey, human, cadaver, testes, SSC transplantation, injection and technique.

OUTCOMES

This review provides an extensive clinical overview of the current research in the field of human SSC transplantation. Rete testis injection with ultrasonography guidance currently seems the most promising injection technique thus far; however, the ability to draw clear conclusions is limited due to long ischemia time of cadaver testis, the relatively decreased volume of the testis, the diminishing size of seminiferous tubules, a lack of intratesticular pressure and leakage into the interstitium during the injection on human cadaver testis. Current evidence does not support improved outcomes from multiple infusions through the rete testes. Overall, further optimization is required to increase the efficiency and safety of the infusion method.

WIDER IMPLICATIONS

Identifying a favourable injection method for SSC transplantation will provide insight into the mechanisms of successful assisted human reproduction. Future research could focus on reducing leakage and establishing the optimal infusion cell concentrations and pressure.

Spermatogonial stem cell survival in ram lambs following busulfan treatment

To clarify the effect of busulfan on the depletion of spermatogonial stem cells (SSCs) from shal rams testis, in the first experiment, lambs were treated by intraperitoneal injection with 4 mg/kg busulfan. In the second experiment, different concentrations of busulfan (1, 2 and 4 mg/kg) were injected directly into both sides of the left testis. The testes of 8 lambs were collected by standard castration procedure for histological analysis five weeks after the treatments and the left testis of remaining lambs were collected after eight weeks and a two-time enzymatic digestion process was used to isolate SSCs. The results showed that all rams that had received intraperitoneal injections of busulfan died. But by testicular injecting of same dose of the drug, 40% of the animals died. The testicular injection of rams with 1, 2 and 4 mg/kg of busulfan resulted in a dose dependent decrease in testis size and also spermatocytes population after 5 weeks of treatments. From the results of colony formation 8 weeks after treatment with busulfan, it can be concluded that only in 1 and 2 mg/kg of busulfan, recovery of endogenous germ cells was performed. In conclusion, the results demonstrated that intra-testicular injections of busulfan (2 mg/kg) reduced spermatocytes population in ram testis within 5 weeks of treatments, and this effect was reversible within 8 weeks of injection. However, it was not recommended to inject 4 mg/kg busulfan into the peritoneal cavity or testis of lambs based on its side effects.

The testicular soma of Tsc22d3 knockout mice supports spermatogenesis and germline transmission from spermatogonial stem cell lines upon transplantation

Spermatogonial stem cells (SSCs) are adult stem cells that are slowly cycling and self-renewing. The pool of SSCs generates very large numbers of male gametes throughout the life of the individual. SSCs can be cultured in vitro for long periods of time, and established SSC lines can be manipulated genetically. Upon transplantation into the testes of infertile mice, long-term cultured mouse SSCs can differentiate into fertile spermatozoa, which can give rise to live offspring. Here, we show that the testicular soma of mice with a conditional knockout (conKO) in the X-linked gene Tsc22d3 supports spermatogenesis and germline transmission from cultured mouse SSCs upon transplantation. Infertile males were produced by crossing homozygous Tsc22d3 floxed females with homozygous ROSA26-Cre males. We obtained 96 live offspring from six long-term cultured SSC lines with the aid of intracytoplasmic sperm injection. We advocate the further optimization of Tsc22d3-conKO males as recipients for testis transplantation of SSC lines.

Progress on the study of the mechanism of busulfan cytotoxicity

The preparation of spermatogonial stem cell (SSC) transplant recipients laid the technical foundation for SSC transplant technology and the understanding of spermatogenesis mechanisms. Busulfan is commonly used to prepare recipients for mouse SSC transplantation; however, its safety and efficiency have been questioned. This review summarizes the relationship between SSCs and Sertoli cells (SCs), and the mechanism of busulfan toxicity against sperm cells. We concluded that the proliferation, differentiation, and apoptosis of SSCs are regulated by SCs. The endogenous spermatogenic cells are depleted by busulfan treatment via alkylation of DNA, destruction of vimentin filament distribution, disruption of SSC differentiation, promotion of SSC dormancy, and generation of oxidative stress. However, the mechanisms require further exploration. The recent establishment of a model in vitro culture system has provided a good technical foundation to further explore these mechanisms, which will help us to find more efficient methods of recipient preparation and optimal transplantation times.

The antineoplastic busulphan impairs peritubular and Leydig cells, and vitamin B12 stimulates spermatogonia proliferation and prevents busulphan-induced germ cell death

Busulphan (Bu), an alkylating agent used for bone marrow and spermatogonial stem cell transplantation (SSCT), impairs Sertoli (SC) cells, which are necessary for the spermatogonial stem cell (SSC) homing during transplantation. As Leydig (LC) and peritubular myoid (PMC) cells are essential for SC support and maintenance of spermatogonial niche, we evaluated the impact of Bu on the LC and PMC structural integrity. Vitamin B₁₂ (B₁₂) has demonstrated beneficial effects against drug-induced testicular changes; thus, we also examined whether this vitamin is able to stimulate spermatogonia mitotic activity and prevent Bu-induced germ cell death. Rats received 10mg/kg of Bu in the 1st and 4th days, and daily B₁₂ supplementation during Bu treatment and for 6days after the last injection of Bu (Bu-6d), totaling 10days of treatment. Other animals received the same treatment as Bu-6d, and B₁₂ supplementation (Bu+7dB₁₂) or saline (Bu+7dS) for 7 more days, totaling 17days of treatment. Serum testosterone levels were measured. In the historesin-embedded testis sections, the seminiferous tubule and epithelial areas were measured, and the number of spermatogonia and PMC was quantified. Actin and 17β-HSD6 immunofluorescence was detected, and the number of TUNEL-positive LC and germ cells was computed. In Bu-6d, PMC number reduced, and a weak actin immunoexpression and death in these cells was observed. The testosterone levels reduced, and the interstitial tissue showed a weak 17β-HSD6 immunoexpression and increased number of TUNEL-positive LC. In Bu+7dB₁₂, the number of spermatogonia was higher than in Bu-6d and Bu+7dS, and the number of TUNEL-positive germ cells was significantly lower than in Bu+7dS. Bu exerts a harmful impact on PMC and LC, reducing the testosterone levels. Vitamin B₁₂ prevents significantly Bu-induced germ cell death and stimulates spermatogonia proliferation, being a useful strategy for the enrichment of SSC in vitro and an adjuvant therapy for spermatogenesis recovery in oncologic patients.

An efficient method for generating a germ cell depleted animal model for studies related to spermatogonial stem cell transplantation

BACKGROUND

Spermatogonial stem cell (SSC) transplantation (SSCT) has become important for conservation of endangered species, transgenesis and for rejuvenating testes which have lost germ cells (Gc) due to gonadotoxic chemotherapy or radiotherapy during the prepubertal phase of life. Creating a germ cell-depleted animal model for transplantation of normal or gene-transfected SSC is a prerequisite for such experimental studies. Traditionally used intraperitoneal injections of busulfan to achieve this are associated with painful hematopoietic toxicity and affects the wellbeing of the animals. Use of testicular busulfan has been reported recently to avoid this but with a very low success rate of SSCT. Therefore, it is necessary to establish a more efficient method to achieve higher SSCT without any suffering or mortality of the animals.

METHODS

A solution of busulfan, ranging from 25 μg/20 μl to 100 μg/20 μl in 50 % DMSO was used for this study. Each testis received two diagonally opposite injections of 10 μl each. Only DMSO was used as control. Germ cell depletion was checked every 15 days. GFP-expressing SSC from transgenic donor mice C57BL/6-Tg (UBC-GFP) 30Scha/J were transplanted into busulfan-treated testis. Two months after SSCT, mice were analyzed for presence of colonies of donor-derived SSC and their ability to generate offspring.

RESULTS

A dose of 75 μg of busulfan resulted in reduction of testis size and depletion of the majority of Gc of testis in all mice within 15 days post injection without causing mortality or a cytotoxic effect in other organs. Two months after SSCT, colonies of donor-derived Gc-expressing GFP were observed in recipient testes. When cohabitated with females, donor-derived offspring were obtained. By our method, 71 % of transplanted males sired transgenic progeny as opposed to 5.5 % by previously described procedures. About 56 % of progeny born were transgenic by our method as opposed to 1.2 % by the previously reported methods.

CONCLUSIONS

We have established an efficient method of generating a germ cell-depleted animal model by using a lower dose of busulfan, injected through two diagonally opposite sites in the testis, which allows efficient colonization of transplanted SSC resulting in a remarkably higher proportion of donor-derived offspring generation.

Seminiferous epithelium damage after short period of busulphan treatment in adult rats and vitamin B12 efficacy in the recovery of spermatogonial germ cells

Several different strategies have been adopted in attempt to recover from chemotherapy-damaged spermatogenesis that is often seen in oncologic patients. In this study, we have evaluated the impact of short period of exposure to busulphan on the haemogram and seminiferous epithelium of adult rats, focusing on spermatogonial depletion and Sertoli cell (SC) integrity. We then examined whether vitamin B₁₂ supplementation improves the haematological parameters and spermatogonia number. The animals received 10 mg/kg of busulphan (BuG) or busulfan+vitamin B₁₂ (Bu/B₁₂ G) on the first and fourth days of treatment. In H.E.-stained testicular sections, the areas of the seminiferous tubule (ST) and seminiferous epithelium were measured. The number of spermatogonia in H.E-stained and PCNA-immunolabelled testicular sections was quantified. The frequency of tubules with abnormal SC nuclei or TUNEL-positive SC was evaluated. Vimentin immunofluorescence in ST was also evaluated. In BuG and Bu/B₁₂ G, the animals showed leukopenia and thrombocytopenia, but the body weight reduced only in BuG. The areas of ST and seminiferous epithelium decreased in Bu/B₁₂ G and BuG. In BuG, the number of H.E.-stained and PCNA-immunolabelled spermatogonia reduced significantly. The frequency of tubules containing abnormal SC nuclei and TUNEL-positive SC increased and the vimentin immunoexpression pattern changed. In Bu/B₁₂ G, the number of H.E.-stained or PCNA-immunolabelled spermatogonia increased fourfold in comparison with BuG. The structural changes in ST after 6 days of busulphan exposure may be associated with the potential effect of this anti-neoplastic agent on SC. The increased number of spermatogonia in the busulphan-treated animals receiving vitamin B₁₂ indicates that this vitamin can be an adjuvant therapy to improve the fertility in male cancer patients.

Testicular Busulfan Injection in Mice to Prepare Recipients for Spermatogonial Stem Cell Transplantation Is Safe and Non-Toxic

Current methods of administering busulfan to remove the endogenous germ cells cause hematopoietic toxicity, require special instruments and a narrow transplantation time. We use a direct testicular injection of busulfan method for preparing recipients for SSC transplantation. Male ICR mice (recipients) were divided into four groups, and two experimental groups were treated with a bilateral testicular injection of 4 or 6 mg/kg/side busulfan (n = 60 per concentration group). Mice received an intraperitoneal injection (i.p.) of 40 mg/kg busulfan (n = 60, positive control) and bilateral testicular injections of 50% DMSO (n = 60, negative control). Donor SSCs from RFP-transgenic C57BL/6J mice were introduced into the seminiferous tubules of each recipient testis via efferent duct injection on day 16–17 after busulfan treatment. Recipient mice mated with mature female ICR mice and the number of progeny was recorded. The index detected at day 14, 21, 28, 35 and 70 after busulfan treatment. Blood analysis shows that the toxicity of busulfan treated groups was much lower than i.p. injection groups. Fertility was restored in mice treated with busulfan and donor-derived offspring were obtained after SSC transplantation. Our study indicated that intratesticular injection busulfan for the preparation of recipients in mice is safe and feasible.