GnRH analog, leuprorelin acetate, promotes regeneration of rat spermatogenesis after severe chemical damage

Testicular niche repair after gonadotoxic treatments: Current knowledge and future directions

The testicular niche, which includes the germ cells, somatic cells, and extracellular matrix, plays a crucial role in maintaining the proper functions of the testis. Gonadotoxic treatments, such as chemotherapy and radiation therapy, have significantly improved the survival rates of cancer patients but have also been shown to have adverse effects on the testicular microenvironment. Therefore, repairing the testicular niche after gonadotoxic treatments is essential to restore its function. In recent years, several approaches, such as stem cell transplantation, gene therapy, growth factor therapy, and pharmacological interventions have been proposed as potential therapeutic strategies to repair the testicular niche. This comprehensive review aims to provide an overview of the current understanding of testis damage and repair mechanisms. We will cover a range of topics, including the mechanism of gonadotoxic action, repair mechanisms, and treatment approaches. Overall, this review highlights the importance of repairing the testicular niche after gonadotoxic treatments and identifies potential avenues for future research to improve the outcomes for cancer survivors.

Long-Term Fertility Function Sequelae in Young Male Cancer Survivors

With advances in cancer treatment, such as cytotoxic chemotherapy and radiotherapy, grave new sequelae of treatment have emerged for young cancer survivors. One sequela that cannot be overlooked is male infertility, with reportedly 15% to 30% of cancer survivors losing their fertility potential. Cytotoxic therapy influences spermatogenesis at least temporarily, and in some cases, permanently. The degree of spermatogenesis impairment depends on the combination of drugs used, their cumulative dose, and the level of radiation. The American Society of Clinical Oncology has created an index to classify the risks to fertility based on treatment. Medical professionals currently use this risk classification in fertility preservation (FP) programs. FP programs are currently being promoted to prevent spermatogenesis failure resulting from cancer treatment. For patients who are able to ejaculate and whose semen contains sperm, the semen (sperm) is cryopreserved. Moreover, for patients who lack the ability to ejaculate, those with azoospermia or severe oligozoospermia, and those who have not attained puberty (i.e., spermatogenesis has not begun), testicular biopsy is performed to collect the sperm or germ cells and cryopreserve them. This method of culturing germ cells to differentiate the sperm has been successful in some animal models, but not in humans. FP has recently gained popularity; however, some oncologists and medical professionals involved in cancer treatment still lack adequate knowledge of these procedures. This hinders the dissemination of information to patients and the execution of FP. Information sharing and collaboration between reproductive medicine specialists and oncologists is extremely important for the development of FP. In Japan, the network of clinics and hospitals that support FP is expanding across prefectures.

Pretreatment with gonadotropin-releasing hormone antagonist protects against chemotherapy-induced testicular damage 'in mice

Background

Testicular toxicity following chemotherapy is of increasing importance with the continuous improvement of survival rates. Gonadotropin-releasing hormone (GnRH) was suggested to protect testis against such toxicity; however, its suppressive quality and mechanism of action are still unclear. We examined whether and how pretreatment with GnRH antagonist protects against the testicular damage caused by chemotherapy.

Methods

Mature male mice were injected subcutaneously eight times in 2-day intervals with either saline or GnRH antagonist (Cetrotide; 1 g/mg), followed by an intraperitoneal injection with either saline or cyclophosphamide (CTX;100 mg/kg BW) and sacrificed 2 weeks or 3 months later. Testicular weight, epididymis weight, epididymal sperm count and sperm motility were measured. Serum anti-Müllerian hormone (AMH) was measured by enzyme-linked immunosorbent assay. Immunohistochemistry (Ki-67), immunofluorescence (PCNA, CD34), terminal transferase-mediated deoxyuridine 5-triphosphate nick-end labeling (TUNEL) and computerized analysis were performed to examine testicular proliferation, apoptosis and vascularization. Quantitative real-time PCR was used to assess the amount of spermatogonial reserve (Id4 and Gfra1 mRNAs).

Results

Pretreatment with GnRH antagonist transiently reduced testicular weight, epididymal weight, germinal proliferation and sperm count; it also abolished the permanent long-term effect of CTX on these parameters and prevented cyclophosphamide-induced testicular toxicity characterized by apoptosis and serum AMH increase and irreversible loss of spermatogonial reserve.

Conclusions

Our findings imply that pretreatment with GnRH antagonist temporarily reduces spermatogenesis and may be used as pretreatment for reducing chemotherapeutic testicular toxicity.

Germ cell depletion in recipient testis has adverse effects on spermatogenesis in orthotopically transplanted testis pieces via retinoic acid insufficiency

Germ cell depletion in recipient testes is indispensable for successful transplantation of spermatogonial stem cells. However, we found that such treatment had an adverse effect on spermatogenesis of orthotopically transplanted donor testis tissues. In the donor tissue, the frequency of stimulated by retinoic acid (RA) 8 (STRA8) expression was reduced in germ cells, suggesting that RA signalling indispensable for spermatogenesis was attenuated in germ cell-depleted recipient testes. In this context, germ cell depletion diminished expression of testicular Aldh1a2, which is responsible for testicular RA synthesis, while Cyp26b1, which is responsible for testicular RA metabolism, was still expressed even after germ cell depletion, suggesting an alteration of the RA synthesis/metabolism ratio. These observations suggested that RA insufficiency was one of the causes of the defective donor spermatogenesis. Indeed, repetitive RA administrations significantly improved donor spermatogenesis to produce fertile offspring without any side effects. These findings may contribute to improving fertility preservation techniques for males, especially to prevent iatrogenic infertility induced by chemotherapy in prepubertal cancer patients.

Oncofertility: Pharmacological Protection and Immature Testicular Tissue (ITT)-Based Strategies for Prepubertal and Adolescent Male Cancer Patients

While the incidence of cancer in children and adolescents has significantly increased over the last decades, improvements made in the field of cancer therapy have led to an increased life expectancy for childhood cancer survivors. However, the gonadotoxic effect of the treatments may lead to infertility. Although semen cryopreservation represents the most efficient and safe fertility preservation method for males producing sperm, it is not feasible for prepubertal boys. The development of an effective strategy based on the pharmacological protection of the germ cells and testicular function during gonadotoxic exposure is a non-invasive preventive approach that prepubertal boys could benefit from. However, the progress in this field is slow. Currently, cryopreservation of immature testicular tissue (ITT) containing spermatogonial stem cells is offered to prepubertal boys as an experimental fertility preservation strategy by a number of medical centers. Several in vitro and in vivo fertility restoration approaches based on the use of ITT have been developed so far with autotransplantation of ITT appearing more promising. In this review, we discuss the pharmacological approaches for fertility protection in prepubertal and adolescent boys and the fertility restoration approaches developed on the utilization of ITT.

Adverse Effects of Vincristine Chemotherapy on Cell Changes in Seminiferous Tubules and Cetrorelix GnRH Antagonist Inhibitory Effects in Mice

The present study was designed to determine changes in spermatogenesis in adult mice after an intraperitoneal injection of vincristine. The effect of a GnRH antagonist synchronous to chemotherapy, which might protect spermatogenesis by halting cell division in spermatogenic cells, was also investigated.

Increased Sat2 expression is associated with busulfan-induced testicular Sertoli cell injury

Busulfan is a chemotherapeutic agent used to treat chronic myelogenous leukemia and other myeloproliferative disorders. Increasing evidence has demonstrated that busulfan may induce testicular dysfunction by targeting genes that are expressed in the testis. Here, we showed that spermidine/spermine N1-acetyltransferase 2 (Sat2) was present in testicular Sertoli cells, and its expression was significantly increased by busulfan treatment. To investigate the implications of Sat2 upregulation for cell growth and function, a Sat2-overexpressing TM4 Sertoli cell model was established. Increased Sat2 expression led to inhibited cell proliferation and arrested cell cycle. Based on iTRAQ proteomics analysis, we revealed that Sat2 overexpression is detrimental to cell cycle progression and cell communication, and notably, Sat2 may disturb protein metabolic processes by altering translation regulation and protein complex subunit organization. In summary, the present study provides evidence that Sat2 upregulation induces alterations in the growth and function of Sertoli cells. In testis tissue subjected to busulfan, increased expression of Sat2 can cause cellular injury and subsequent organ damage, which could lead to male infertility. Therefore, Sat2 may be a novel molecular target for treating busulfan-induced testicular toxicity.

Leydig cells contribute to the inhibition of spermatogonial differentiation after irradiation of the rat

Irradiation with 6 Gy produces a complete block of spermatogonial differentiation in LBNF1 rats that would be permanent without treatment. Subsequent suppression of gonadotropins and testosterone (T) restores differentiation to the spermatocyte stage; however, this process requires 6 weeks. We evaluated the role of Leydig cells (LCs) in maintenance of the block in spermatogonial differentiation after exposure to radiation by specifically eliminating functional LCs with ethane dimethane sulfonate (EDS). EDS (but not another alkylating agent), given at 10 weeks after irradiation, induced spermatogonial differentiation in 24% of seminiferous tubules 2 weeks later. However, differentiation became blocked again at 4 weeks as LCs recovered. When EDS was followed by treatment with GnRH antagonist and flutamide, sustained spermatogonial differentiation was induced in >70% of tubules within 2 weeks. When EDS was followed by GnRH antagonist plus exogenous T, which also inhibits LC recovery but restores follicle stimulating hormone (FSH) levels, the spermatogonial differentiation was again rapid but transient. These results confirm that the factors that block spermatogonial differentiation are indirectly regulated by T, and probably FSH, and that adult and possibly immature LCs contribute to the production of such inhibitory factors. We tested whether insulin-like 3 (INSL3), a LC-produced protein whose expression correlated with the block in spermatogonial differentiation, was indeed responsible for the block by injecting synthetic INSL3 into the testes and knocking down its expression in vivo with siRNA. Neither treatment had any effect on spermatogonial differentiation. The Leydig cell products that contribute to the inhibition of spermatogonial differentiation in irradiated rats remain to be elucidated.

Granulocyte colony-stimulating factor prevents loss of spermatogenesis after sterilizing busulfan chemotherapy

OBJECTIVE

To determine whether granulocyte colony-stimulating factor (G-CSF) could prevent loss of spermatogenesis induced by busulfan chemotherapy via protection of undifferentiated spermatogonia, which might serve as an adjuvant approach to preserving male fertility among cancer patients.

DESIGN

Laboratory animal study.

SETTING

University.

ANIMAL(S)

Laboratory mice.

INTERVENTION(S)

Five-week-old mice were treated with a sterilizing busulfan dose and with 7 days of G-CSF or vehicle treatment and evaluated 10 weeks later (experiment 1) or 24 hours after treatment (experiment 2).

MAIN OUTCOME MEASURE(S)

Experiment 1: testis weights, epididymal sperm counts, testis histology. Experiment 2: PLZF immunofluorescent costaining with apoptotic markers. Molecular analysis of G-CSF receptor expression in undifferentiated spermatogonia.

RESULT(S)

Ten weeks after treatment, busulfan-treated mice that also received treatment with G-CSF exhibited significantly better recovery of spermatogenesis and epididymal sperm counts than animals receiving busulfan alone. G-CSF led to increased numbers of PLZF+ spermatogonia 24 hours after treatment that was not accompanied by changes in apoptosis. To address the cellular target of G-CSF, mRNA for the G-CSF receptor, Csf3r, was found in adult mouse testes and cultured THY1+ (undifferentiated) spermatogonia, and cell-surface localized CSF3R was observed on 3% of cultured THY1+ spermatogonia.

CONCLUSION(S)

These results demonstrate that G-CSF protects spermatogenesis from gonadotoxic insult (busulfan) in rodents, and this may occur via direct action on CSF3R+ undifferentiated spermatogonia. G-CSF treatment might be an effective adjuvant therapy to preserve male fertility in cancer patients receiving sterilizing treatments.

Systemic histopathology of infant rats exposed to busulfan

Busulfan is an antineoplastic bifunctional alkylating agent. We previously reported the busulfan-induced systemic histopathological changes in fetal rats and the sequence of brain lesions in fetal and infant rats. In the present study, in order to clarify the nature and sequence of busulfan-induced systemic histopathological changes in infant rats, 6-day-old male infant rats were subcutaneously administered 20 mg/kg of busulfan and histopathologically examined at 1, 2, 4, 7 and 14 days after treatment (DAT). As a result, histopathological changes characterized by pyknosis of component cells were observed in the heart, lungs, stomach, intestines, liver, kidneys, testes, epididymides, hematopoietic and lymphoid tissues, dorsal skin and femur as well as in the brain and eyes (data not shown in this paper). Such pyknosis transiently appeared until 7 DAT with prominence at 2 and/or 4 DAT in each tissue, except for the thymus, in which pyknosis peaked at 1 DAT. Most of the pyknotic nuclei were immunohistochemically positive for cleaved caspase-3, indicating that pyknotic cells were apoptotic. Different from the reports of fetal and adult rats, apoptosis was also found in cardiomyocytes and osteoblasts in infant rats.

Melatonin and testicular damage in busulfan treated mice

Background:

Advancement in the treatment of various types of cancer has led to greater patient survival. These treatments essentially have toxic effects on different kinds of cells, such as germ cells. Infertility as one of the side effects of cancer treatment has changed the quality of life of young cancer survivors dramatically. Melatonin is an antioxidant with receptors in the reproductive systems.

Objectives:

We supposed that melatonin, as an antioxidant, may protect testis against the toxic effects of the drugs.

Materials and Methods:

In this experimental study, three groups with seven mice each, were allocated. The control group received normal saline for two months, and the busulfan group received a single dose of 40 mg/kg busulfan intra-peritoneally, and the melatonin group received 20 mg/kg melatonin daily for two months, 45 days after a single dose of busulfan. Next, after decapitation and removal of the testis, tissues were fixed in Bouin's solution and stained by H&E and TUNEL. The sections were evaluated, assessing morphology and spermatogenesis.

Results:

In this research, a significant reduction in Johnson’s criteria in the busulfan group (Mean rank = 15.50) was found versus the control group (Mean rank = 45.50), P < 0.001 and in the melatonin group (Mean rank = 45.50) compared to the busulfan group (Mean rank = 15.50), P < 0.001. There was a significant difference between the melatonin and control groups, P < 0.05. In addition, a significant decrease in seminiferous tubule diameter was observed in the busulfan group (763.2 ± 104.41) versus the control group (855.4 ± 52.35), P < 0.01 and melatonin group (834.2 ± 87.26), P < 0.05. Testicular epithelium height was significantly decreased in the busulfan group (Mean rank = 14.60) compared to the control group (Mean rank = 26.40), P < 0.01 and in the busulfan group (Mean rank = 14.95) in comparison with the melatonin group (Mean rank = 26.05), P < 0.01. Also melatonin group (Mean rank = 25.42) showed a significant reduction in epithelium height compared to the control group (Mean rank = 35.58), P < 0.05. Spermatogenesis was impaired in the busulfan group. Although melatonin reduced the rate of apoptosis in the busulfan group, yet it could not remove all apoptotic cells.

Conclusions:

This study indicated that melatonin ameliorates the cytotoxic effects of busulfan on germ cells.

Protective Role of GnRH Antagonist on Chemotherapy-induced Spermatogenesis Disorder: A Morphological Study

PURPOSE

Anti cancer drugs is one of the most important chemotherapeutic factors which can influence spermatogenesis process and germinal epithelium. Since dividing cells are mainly affected by anticancer drugs, the aim of the present study is to investigate the preventive effect of GnRH antagonist on spermatogenic defect produced by anticancer drugs.

METHODS

In the present study thirty adult male mice aging 6-8 weeks were divided into 3 groups as: Control, Experimental 1 and Experimental 2. Experimental 1 group received Cisplatin for 5 days as 2.5 mg/kg intraperitoneally and Experimental 2 group received 0.25 mg/kg cetrorelix (GnRH antagonist) one week before cisplatin treatment and continued for 3 weeks. The mice in all groups were sacrificed 35 days after the last injection and testis specimens were fixed in boueins, formaldehyde fixative and 2.5% Glutaraldehide then prepared for light and electron microscopic examination.

RESULTS

Light microscopy (LM) study showed that the number of spermatogonial cells, thickness of germinal epithelium, was decreased in Experimental 1group. Electron microscopy revealed that in this group several intercellular spaces appeared between spermatogenic cells and secretory granules in interstitial cells was increased. There were several vacuolated mitochondria and destroyed organelles in spermatogonial cells but in Experimental 2 group condition was similar to control group.

CONCLUSION

These results indicate that the cetrorelix administration before cancer treatment may protect germinal epithelium against side effects of cisplatin.

Hormone suppression with GnRH antagonist promotes spermatogenic recovery from transplanted spermatogonial stem cells in irradiated cynomolgus monkeys

Hormone suppression given before or after cytotoxic treatment stimulates the recovery of spermatogenesis from endogenous and transplanted spermatogonial stem cells (SSC) and restores fertility in rodents. To test whether the combination of hormone suppression and transplantation could enhance the recovery of spermatogenesis in primates, we irradiated (7 Gy) the testes of 12 adult cynomolgus monkeys and treated six of them with gonadotropin-releasing hormone antagonist (GnRH-ant) for 8 weeks. At the end of this treatment, we transfected cryopreserved testicular cells with green fluorescent protein-lentivirus and autologously transplanted them back into one of the testes. The only significant effect of GnRH-ant treatment on endogenous spermatogenesis was an increase in the percentage of tubules containing differentiated germ cells (tubule differentiation index; TDI) in the sham-transplanted testes of GnRH-ant-treated monkeys compared with radiation-only monkeys at 24 weeks after irradiation. Although transplantation alone after irradiation did not significantly increase the TDI, detection of lentiviral DNA in the spermatozoa of one radiation-only monkey indicated that some transplanted cells colonized the testis. However, the combination of transplantation and GnRH-ant clearly stimulated spermatogenic recovery as evidenced by several observations in the GnRH-ant-treated monkeys receiving transplantation: (i) significant increases (~20%) in the volume and weight of the testes compared with the contralateral sham-transplanted testes and/or to the transplanted testes of the radiation-only monkeys; (ii) increases in TDI compared to the transplanted testes of radiation-only monkeys at 24 weeks (9.6% vs. 2.9%; p = 0.05) and 44 weeks (16.5% vs. 6.1%, p = 0.055); (iii) detection of lentiviral sequences in the spermatozoa or testes of five of the GnRH-ant-treated monkeys and (iv) significantly higher sperm counts than in the radiation-only monkeys. Thus hormone suppression enhances spermatogenic recovery from transplanted SSC in primates and may be a useful tool in conjunction with spermatogonial transplantation to restore fertility in men after cancer treatment.

Effect of genistein administration on the recovery of spermatogenesis in the busulfan-treated rat testis

Objective

Impairment of spermatogenesis has been identified as an inevitable side effect of cancer treatment. Although estrogen treatment stimulates spermatogenic recovery from the impaired spermatogenesis by suppressing the intra-testicular testosterone (ITT) level, side effects of estrogen are still major impediments to its clinical application in humans. Soybeans are rich in genistein, which is a phytoestrogen that binds to estrogen receptors and has an estrogenic effect. We investigated the effects of genistein administration on ITT levels, testis weight, and recovery of spermatogenesis in rats treated with a chemotherapeutic agent, busulfan.

Methods

Busulfan was administered intraperitoneally to rats, and then a GnRH agonist was injected subcutaneously into the back, or genistein was administered orally.

Results

The weight of the testes was significantly reduced by the treatment with busulfan. The testis weight was partially restored after busulfan treatment by additional treatment with either the GnRH agonist or genistein. Busulfan also induced atrophy of a high percentage of the seminiferous tubules, but this percentage was decreased by additional treatment with either the GnRH agonist or genistein. Treatment with genistein was effective at suppressing and maintaining ITT levels comparable to that in the GnRH agonist group.

Conclusion

Genistein effectively suppressed ITT levels and stimulated the recovery of spermatogenesis in rats treated with a chemotherapeutic drug. This suggests that genistein may be a substitute for estrogens, for helping humans to recover fertility after cancer therapy without the risk of side effects.

Suppression of spermatogenesis before grafting increases survival and supports resurgence of spermatogenesis in adult mouse testis

OBJECTIVE

To test whether absence of complete spermatogenesis in mature testicular tissue before grafting will increase graft survival.

DESIGN

Prospective experimental study.

SETTING

Laboratory.

ANIMAL(S)

Donor testes were obtained from adult untreated mice, adult mice rendered cryptorchid, and adult mice treated with a GnRH antagonist (acyline).

INTERVENTION(S)

Donor testes were ectopically grafted to nude mice and recovered at three time points.

MAIN OUTCOME MEASURE(S)

Most advanced germ cell type and presence of spermatogonia were assessed. Donor testes and grafts were analyzed by histology and by immunocytochemistry for ubiquitin C-terminal hydrolase-L1 to mark germ cells.

RESULT(S)

Suppression of spermatogenesis by inducing cryptorchidism or acyline treatment resulted in improved survival of grafted tissue compared with controls and recovery of complete spermatogenesis, whereas control testis grafts mostly degenerated and did not restore complete spermatogenesis.

CONCLUSION(S)

These results indicate that complete spermatogenesis at the time of grafting has a negative effect on graft survival. Grafting of adult testis tissue from donors with suppressed spermatogenesis leads to spermatogenic recovery and may provide a tool to study and preserve fertility and for conservation of genetic resources in individuals that lack complete germ cell differentiation.

Hormonal suppression restores fertility in irradiated mice from both endogenous and donor-derived stem spermatogonia

Irradiation interrupts spermatogenesis and causes prolonged sterility in male mammals. Hormonal suppression treatment with gonadotropin-releasing hormone (GnRH) analogues has restored spermatogenesis in irradiated rats, but similar attempts were unsuccessful in irradiated mice, monkeys, and humans. In this study, we tested a stronger hormonal suppression regimen (the GnRH antagonist, acyline, and plus flutamide) for efficacy both in restoring endogenous spermatogenesis and in enhancing colonization of transplanted stem spermatogonia in mouse testes irradiated with a total doses between 10.5 and 13.5 Gy. A 4-week hormonal suppression treatment, given immediately after irradiation, increased endogenous spermatogenic recovery 1.5-fold, and 11-week hormonal suppression produced twofold increases compared with sham-treated irradiated controls. Furthermore, 10-week hormonal suppression restored fertility from endogenous surviving spermatogonial stem cells in 90% of 10.5-Gy irradiated mice, whereas only 10% were fertile without hormonal suppression. Four- and 11-week hormonal suppression also enhanced spermatogenic development from transplanted stem spermatogonia in irradiated recipient mice, by 3.1- and 4.8-fold, respectively, compared with those not given hormonal treatment. Moreover, the 10-week hormonal suppression regimen, but not a sham treatment, restored fertility of some 13.5-Gy irradiated recipient mice from donor-derived spermatogonial stem cells. This is the first report of hormonal suppression inducing recovery of endogenous spermatogenesis and fertility in a mouse model treated with anticancer agents. The combination of spermatogonial transplantation with hormonal suppression should be investigated as a treatment to restore fertility in young men after cytotoxic cancer therapy.

Preventive role of exogenous testosterone on cisplatin-induced gonadal toxicity: an experimental placebo-controlled prospective trial

OBJECTIVE

To test the preventive role of exogenous T on spermatogenesis after cisplatin chemotherapy.

DESIGN

Placebo-controlled study.

SETTING

The animal laboratory of a medical university.

ANIMAL(S)

Eighty-eight male BALB/c mice were divided into three groups; each group was subdivided into four groups.

INTERVENTION(S)

Subgroups a received two or three cycles of cisplatin (2.5 mg/kg for 5 days + 16 days of recovery), subgroups b received the same chemotherapy regimen with adjuvant high-dose T enanthate (5 mg/100 g body weight) starting 1 week before chemotherapy and repeated every 21 days during chemotherapy, subgroups c received only high-dose T enanthate at the same dosage and intervals; subgroups d received a placebo.

MAIN OUTCOME MEASURE(S)

Testis spermatogenesis function was evaluated after 35 days (short term, group I) or 105 days (long term, groups II and III) of recovery, after the final dose of cisplatin, by histopathology and sperm count.

RESULT(S)

Testis tissue destruction and a significant dose-dependent decrease in spermatogenesis were identified in subgroups a. Both recovered partially during long-term recovery. Exogenous high-dose T caused damage to spermatogenesis, which was reversible (subgroups c). Adjuvant treatment with T had no additive long-term effect in animals treated with low-dose cisplatin (two cycles). However, a significant long-term preventive effect of T was seen in animals receiving high-dose cisplatin (three cycles).

CONCLUSION(S)

Hormonal intervention with exogenous T during chemotherapy had promising effects on spermatogenesis in mice receiving high-dose chemotherapy (regimens frequently used clinically). It had no additive long-term effects in animals receiving low-dose regimens.

Amifostine protective effect on cisplatin-treated rat testis

Cisplatin is a potent drug used in clinical oncology but causes spermatogenesis damage. Amifostine is a drug used against toxicity caused by ionizing irradiation and chemotherapeutic drugs. Since cisplatin provokes fertility and induces germ cell apoptosis and necrosis, we proposed to evaluate the amifostine cytoprotective action on testes of cisplatin-treated rats. Thirty-day-old prepubertal Wistar rats received a single cisplatin dose of 5 mg/kg and were killed after 3, 6, and 12 hr. The hematoxylin-eosin stained testicular sections were submitted to histological, morphometric, and stereological analysis. The terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick end-labeling (TUNEL) method was used to label apoptotic cells. TUNEL-positive and TUNEL-negative germ cells with abnormal nuclear morphology (ANM) were scored. Significant alterations of greater part of the parameters occurred in the cisplatin-treated group (CE) compared to the group that received amifostine before the cisplatin-treatment (ACE); however, testicular weight and volume did not vary between these groups. Tubular diameter was reduced in CE in comparison to ACE rats, while interstitial tissue and lymphatic space volume and volume density were significantly higher in CE rats; interstitial testicular edema probably occurred in cisplatin-treated rats. CE rats showed important histological alterations, which were more accentuated than in ACE rats. The numerical densities of apoptotic germ cells and TUNEL-negative cells with ANM were lower in ACE than in CE rats. In conclusion, the amifostine previously administered to prepubertal rats reduced the testicular damage caused by cisplatin. We conclude that amifostine partially protected the rat seminiferous epithelium against cisplatin toxicity.

Hormonal suppression for fertility preservation in males and females

Methods to restore fertility of men and women sterilized by medical treatments and environmental toxicant exposures are under investigation. Rendering spermatogenesis and ovarian follicular development kinetically quiescent by suppression of gonadotropins has been proposed to protect them from damage by cytotoxic therapy. Although the method fails to protect the fertility of male mice and monkeys, gonadotropin and testosterone suppression in rats before or after cytotoxic therapy do enhance the recovery of spermatogenesis. However, the mechanism involves not the induction of quiescence but rather the reversal, by suppression of testosterone, of a block in differentiation of surviving spermatogonia caused by damage to the somatic environment. In men, only one of eight clinical trials was successful in protecting or restoring spermatogenesis after cytotoxic therapy. In women, protection of primordial follicles in several species from damage by cytotoxic agents using GnRH analogs has been claimed; however, only two studies in mice appear convincing. The protection cannot involve the induction of quiescence in the already dormant primordial follicle but may involve direct effects of GnRH analogs or indirect effects of gonadotropin suppression on the whole ovary. Although numerous studies in female patients undergoing chemotherapy indicate that GnRH analogs might be protective of ovarian function, none of the studies showing protection were prospective randomized clinical trials and thus they are inconclusive. Considering interspecies differences and similarities in the gonadal sensitivity to cytotoxic agents and hormones, mechanistic studies are needed to identify the specific beneficial effects of hormonal suppression in select animal models that may be applicable to humans.

Strontium fructose 1,6-diphosphate rescues adenine-induced male hypogonadism and upregulates the testicular endothelin-1 system

1. Male hypogonadism is a major problem that starts to affect middle-aged men and has adversely effects on human sexual life. The aim of the present study was to investigate the effect of strontium fructose 1,6-diphosphate (FDP-Sr) on male hypogonadism in rats. 2. The pharmacological model of testis dysfunction was created by administration of adenine (200 mg/kg per day, i.g.) for 30 days. Three doses of FDP-Srs (200, 100 and 50 mg/kg per day, i.g.) were administered in parallel with adenine. Finally, mating behaviour index (the mounting latency and the number of mounting events), the total number of spermatozoa and sperm motility, related enzyme function and gene regulation and the mRNA levels of steroidogenic acute regulatory protein (StAR), cytochrome P450 side-chain cleavage enzyme (P450scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), prepro-endothelin (ET)-1, endothelin-converting enzyme (ECE) and endothelin receptor A (ET(A)) were analysed. 3. The results showed that adenine significantly prolonged the mounting latency and decreased the number of mounting events, markedly reduced the total number of spermatozoa, slowed sperm motility and decreased testicular enzyme activity in the testes. At the mRNA level, adenine significantly downregulated serum testosterone, StAR, P450sc and 3beta-HSD. In parallel, adenine also targeted the ET-1 system, significantly downregulating mRNA levels of prepro-ET-1, ECE and ET(A). Administration of FDP-Sr dose-dependently reversed these effects. 4. In conclusion, adenine-induced testis dysfunction appears to be manifested as loss of sexual function in association with decreased spermatogenesis and reduced mRNA levels of steroidogenesis and the testicular ET-1 system. These abnormalities were significantly restored by FDP-Sr in a dose-dependent manner. These data indicate the possibility of using FDP-Sr to treat male hypogonadism.

The radiation-induced block in spermatogonial differentiation is due to damage to the somatic environment, not the germ cells

Radiation and chemotherapeutic drugs cause permanent sterility in male rats, not by killing most of the spermatogonial stem cells, but by blocking their differentiation in a testosterone-dependent manner. However, it is not known whether radiation induces this block by altering the germ or the somatic cells. To address this question, we transplanted populations of rat testicular cells containing stem spermatogonia and expressing the green fluorescent protein (GFP) transgene into various hosts. Transplantation of the stem spermatogonia from irradiated adult rats into the testes of irradiated nude mice, which do not show the differentiation block of their own spermatogonia, permitted differentiation of the rat spermatogonia into spermatozoa. Conversely transplantation of spermatogonial stem cells from untreated prepubertal rats into irradiated rat testes showed that the donor spermatogonia were able to colonize along the basement membrane of the seminiferous tubules but could not differentiate. Finally, suppression of testosterone in the recipient irradiated rats allowed the differentiation of the transplanted spermatogonia. These results conclusively show that the defect caused by radiation in the rat testes that results in the block of spermatogonial differentiation is due to injury to the somatic compartment. We also observed colonization of tubules by transplanted Sertoli cells from immature rats. The present results suggest that transplantation of spermatogonia, harvested from prepubertal testes to adult testes that have been exposed to cytotoxic therapy might be limited by the somatic damage and may require hormonal treatments or transplantation of somatic elements to restore the ability of the tissue to support spermatogenesis.

Testosterone administration promotes regeneration of chemically impaired spermatogenesis in rats

AIM

It has been proposed that gonadotropin-releasing hormone (GnRH) analog administered after testicular damage stimulates the recovery of spermatogenesis. However, GnRH analogs suppress the function of sex accessory organs. In this study, we investigated whether testosterone also stimulates the regeneration of rat spermatogenesis after exposure to busulfan.

METHODS

Male Fisher rats were divided into three groups of five each and all rats were treated with busulfan, 25 mg/kg, intraperitoneally at week 0. Group A served as the control. The other two groups received testosterone enanthate, 8 mg/kg, subcutaneous injections at 3 week intervals two times before (group B) or three times after (group C) busulfan. States of spermatogenesis were evaluated by histology and by the number of spermatid nuclei per testis at week 25.

RESULTS

The mean percentage of 'recovered' seminiferous tubules plus or minus standard deviation was 10.3 +/- 7.8% in group A and 2.1 +/- 1.2% in group B. In both groups, more than 80% of the tubules remained degenerated. However, testes of group C rats showed an improvement of up to 37.1 +/- 20.5% (P < 0.05). The significant recovery of spermatogenesis was also demonstrated in group C by counting the number of spermatid nuclei per testis ([78.8 +/- 57.5] x 106). However, the count was only (7.6 +/- 13.5) x 106 and (0.52 +/- 1.0) x 106 in group A and B, respectively.

CONCLUSIONS

Testosterone administration after severe testicular damage enhanced the regeneration of spermatogenesis in rats. We assumed that supplementary doses of testosterone would be more practical for clinical application than GnRH analogs, because exogenous testosterone maintains androgenicity.

Testicular edema is associated with spermatogonial arrest in irradiated rats

Irradiation of LBNF1 rat testes induces arrest of spermatogonial differentiation, which can be reversed by suppression of testosterone with GnRH antagonist treatment. The cause of the arrest is unknown. We investigated the time course and hormonal effects on radiation-induced arrest and changes in interstitial fluid volume. We postulated that the edema evident in irradiated testes caused the differentiation blockade. Rat testes were irradiated with 3.5 or 6 Gy. Interstitial fluid testosterone (IFT) increased between 2 and 6 wk after irradiation, followed by increased interstitial fluid volume at 6 wk and spermatogonial blockade at 8 wk. Additional rats irradiated with 6 Gy were given GnRH antagonist, alone or with exogenous testosterone, for 8 wk starting at 15 wk after irradiation. In rats treated with GnRH antagonist, IFT started falling within 1 wk of treatment, followed by interstitial fluid volume decreases at wk 2 and 3, with recovery of spermatogenesis starting at wk 4. Addition of exogenous testosterone largely blocked the effects of GnRH antagonist on IFT, interstitial fluid volume, and spermatogenesis. Thus the testicular edema was largely modulated by intratesticular testosterone levels. The time course of changes in the spermatogonial blockade more closely followed that of the testicular edema than of IFT, indicating that testosterone may block spermatogonial differentiation indirectly by producing edema. This conclusion was further supported by an experiment in which irradiated rats were treated with GnRH antagonist plus estrogen; the treatment further reduced IFT and interstitial fluid volume and reduced the time to initiation of recovery of spermatogonial differentiation. These results suggest that studies of the edematous process or composition of the fluid would help elucidate the mechanism of spermatogonial arrest in toxicant-treated rats.

Suppression of testosterone stimulates recovery of spermatogenesis after cancer treatment

It is important to develop methods to prevent or reverse the infertility caused by chemotherapy or radiation therapy for cancer in men. Radiation and some chemotherapeutic agents kill spermatogonial stem cells, but we have shown that these cells survive in rats, although they are unable to differentiate. There is evidence that this phenomenon also occurs in men. The block to spermatogonial differentiation in rats is caused by some unknown change, either in the spermatogonia or the somatic elements of the testis, such that testosterone inhibits spermatogonial differentiation. In the rat, the spermatogenesis and fertility lost following treatment with radiation or some chemotherapeutic agents can be restored by suppressing testosterone with gonadotropin releasing hormone (GnRH) agonists or antagonists, either before or after the cytotoxic insult. The applicability of this procedure to humans is still unknown. Some anticancer regimens may kill all the stem cells, in which case the only option would be spermatogonial transplantation. However, in some cases stem cells survive and there is one report of stimulation of recovery of spermatogenesis with hormonal treatment. Clinical trials should focus on treating patients with hormones during or soon after anticancer treatment. The hormone regimen should involve suppression of testosterone production with minimum androgen supplementation used to improve the diminished libido.

Increment of murine spermatogonial cell number by gonadotropin-releasing hormone analogue is independent of stem cell factor c-kit signal

Recent studies have demonstrated that GnRH-analogues can stimulate regeneration of spermatogenesis of rats when administered after testicular damages. Although the mechanism of this phenomenon has not been elucidated yet, stem cell factor (SCF) produced by Sertoli cells was proposed to mediate the effects of GnRH-analogues on spermatogonial proliferation and/or survival. In the present study, we quantitatively evaluated the proliferation of spermatogonia and addressed whether SCF mediates the effect of GnRH-analogue on spermatogonial proliferation, using a novel approach combining spermatogonial transplantation and laser confocal microscopic observation. In the first experiment, using wild-type mice as recipients for spermatogonial transplantation, the number of donor spermatogonia per 100 Sertoli cells in each spermatogenic colony was significantly higher in the experimental group of mice treated with leuprorelin, a GnRH-agonist, than that of the control group at 4 and 5 wk after transplantation. In the second experiment, Steel/Steeldickie (Sl/Sld) mutant mice, which lack expression of membrane bound form SCF, were used as recipients. As seen in the first experiment, the number of undifferentiated spermatogonia was significantly higher in leuprorelin-treated than in the control group. Since undifferentiated spermatogonia do not express the receptor of SCF, the present study clearly demonstrates that neither membrane-bound nor secreted forms of SCF are involved in the mechanism of GnRH-analogue's effect on spermatogonial proliferation and/or survival.

Recovery of spermatogenesis by high dose gonadotropin-releasing hormone analogue treatment in rat cryptorchid testis after orchiopexy

PURPOSE

Cryptorchidism is an adverse condition of spermatogenesis in many mammals. Surgical cryptorchidism in rats lasting more than a few weeks is so detrimental that spermatogenesis cannot be completely recovered even after orchiopexy. We evaluated the efficacy of the high dose gonadotropin-releasing hormone (Gn-RH) agonist leuprorelin acetate on damaged spermatogenesis in rat cryptorchid testes.

MATERIALS AND METHODS

Male Fisher rats were divided into 2 groups of 6 each and bilateral cryptorchidism was artificially produced. Five weeks later all rats underwent bilateral orchiopexy. One group served as the control, while the other received Gn-RH agonist injections at orchiopexy and 4 weeks later. The animals were sacrificed 15 weeks after orchiopexy. The weight of the body, testis and epididymis was measured and the histology of spermatogenesis was examined. For statistical analysis the Student t test was applied.

RESULTS

Testes in the Gn-RH group rats showed significant recovery of spermatogenesis up to complete spermatozoa formation, while those in control rats remained almost degenerated. The mean incidence of seminiferous tubules with recovered spermatogenesis plus or minus standard deviation was significantly higher in the Gn-RH than in the control group (87.8% +/- 6.0% versus 12.5% +/- 7.7%, p <0.001).

CONCLUSIONS

Administering the high dose Gn-RH agonist leuprorelin acetate after orchiopexy greatly enhanced the recovery of spermatogenesis in rats. This finding is in accordance with other recent reports that treatment with Gn-RH analogues promotes the regeneration of once damaged spermatogenesis. On the other hand, these findings may cause one to question supplementation therapy now used in regular practice to boys with cryptorchidism.