Effect of Previous Alkylating Agent Exposure on Follicle Numbers in Cryopreserved Prepubertal and Young Adult Ovarian Tissue after Long-Term Xenografting.

PURPOSE AND METHODS: To elucidate whether previous cancer treatment affects graft recovery and follicle numbers, morphology, and development in grafts, cryopreserved ovarian biopsies obtained from 18 cancer patients aged 1-24 years with and without exposure to chemotherapy were xenografted as 1 mm3 fragments to immunodeficient mice for 22 weeks with exogenous stimulation. RESULTS: Graft recovery showed no association with chemotherapy exposure, pubertal stage, or leukemia contamination. Total follicle number per recovered graft varied between 0 and 1031 in the chemotherapy-exposed and between 0 and 502 in the non-chemotherapy-exposed group. Atretic follicles formed the largest proportion of the follicle pool in chemotherapy-exposed grafts. Increased atresia correlated with exposure to alkylating agents (mean ± SD 8866.2 ± 9316.3 mg/m2) but not with anthracyclines, pubertal stage, or leukemia contamination. CONCLUSION: The observation confirms the harmful effects of alkylating agents on ovarian tissue. Therapy at the median cumulative dose of 8866 mg/m2 leads to the decreased quality of cryopreserved ovarian follicles in children and young adults.

The effects of perfluorooctanoic acid (PFOA) on fetal and adult rat testis.

Perfluorooctanoic acid (PFOA) is a widely dispersed synthetic chemical, which accumulates in living organisms and has been connected with male reproductive disorders. To monitor the effects of PFOA, fetal rat testes or seminiferous tubule segments (stage VII-VIII) of adult rats were cultured in 0-100 µg/ml PFOA for 24 h. Afterwards, cAMP, progesterone, testosterone and StAR protein levels were measured from the fetal testes culture. Measurements were combined with immunohistochemistry, immunofluorescence, TUNEL and flow cytometric analysis to monitor cell death in somatic and germ cells. This study shows that the levels of cAMP, progesterone, testosterone and expression of StAR decreased significantly in PFOA 50 and 100 µg/ml. PFOA affected cell populations significantly by decreasing the amount of diploid, proliferating, meiotic I and G2/M-phase cells in adult rat testis. However, PFOA did not affect fetal, proliferating or adult rat Sertoli cells but an increased tendency of apoptosis in fetal Leydig cells was observed.

Retinoblastoma protein represses E2F3 to maintain Sertoli cell quiescence in mouse testis.

Maintenance of the differentiated state and cell cycle exit in adult Sertoli cells depends on tumor suppressor retinoblastoma protein (RB, also known as RB1). We have previously shown that RB interacts with transcription factor E2F3 in the mouse testis. Here, we investigated how E2f3 contributes to adult Sertoli cell proliferation in a mouse model of Sertoli cell-specific knockout of Rb by crossing these mice with an E2f3 knockout mouse line. In the presence of intact RB, E2f3 was redundant in Sertoli cells. However, in the absence of RB, E2f3 is a key driver for cell cycle re-entry and loss of function in adult Sertoli cells. Knockout of E2f3 in Sertoli cells rescued the breakdown of Sertoli cell function associated with Rb loss, prevented proliferation of adult Sertoli cells and restored fertility of the mice. In summary, our results show that RB-mediated repression of E2F3 is critical for the maintenance of cell cycle exit and terminal differentiation in adult mouse Sertoli cells.

Developmental effects of imatinib mesylate on follicle assembly and early activation of primordial follicle pool in postnatal rat ovary.

Imatinib mesylate is an anti-cancer agent that competitively inhibits several receptor tyrosine kinases (RTKs). RTKs play important roles in the regulation of primordial follicle formation, the recruitment of primordial follicles into the pool of growing follicles and maturation of the follicles. In the present study, we investigated the effects of the tyrosine kinase inhibitor imatinib on primordial follicle assembly and early folliculogenesis in postnatal rats. Female Sprague-Dawley rats were treated with either imatinib (150mg/kg) or placebo (water) on postnatal days 2-4. Bilateral ovariectomy was performed on postnatal day 2 and 5. Histology, immunohistochemistry, and mRNA analysis were performed. Imatinib treatment was associated with increased density of the multi-oocyte follicles (P<0.01), oogonia (p<0.01) and germline clusters (P<0.05), decreased activation of primordial follicles, increased expression of c-Kit and AMH, and decreased protein expression of Kit-ligand and GDF9 when compared to age-matched controls. In conclusion, imatinib affects folliculogenesis in postnatal rat ovaries by delaying the cluster breakdown, follicular assembly and early activation of the primordial follicle pool.

Minimal residual disease of leukemia and the quality of cryopreserved human ovarian tissue in vitro.

Auto-transplant of cryopreserved ovarian tissue in leukemia patients carries a risk to reintroduce malignant cells. Maturation of ovarian follicles in vitro is a promising strategy to overcome the leukemic cell contamination. The follicle development and survival in 14 cryopreserved ovarian tissues with leukemia-specific PCR marker was evaluated after 7 or 14 days culture. Minimal residual disease (MRD) quantification was assessed by real-time quantitative PCR in order to identify the MRD positive (n = 6) and negative (n = 8) samples and to monitor levels of MRD before and after culture. The morphology of ovarian follicles were studied by light microscopy. After culture, no statistical significant differences were detected in follicle densities between MRD positive- and negative samples. Ovarian MRD either decreased below undetectable or fluctuated near the baseline level after 7 and 14 days in culture. This study provides quantitative in vitro evidence that leukemia contamination does not affect the follicle survival in cryopreserved ovarian tissue.

Effect of Previous Chemotherapy on the Quality of Cryopreserved Human Ovarian Tissue In Vitro.

BACKGROUND: Cryopreservation of ovarian tissue has been widely accepted as an option for fertility preservation among cancer patients. Some patients are exposed to chemotherapy prior to ovarian tissue cryopreservation. Consequently, assessment of the developmental capacity of human ovarian tissue after chemotherapy is of primary importance. MATERIALS: In order to study the impact of previous chemotherapy on in vitro development and viability of ovarian follicles, quality control samples from 34 female cancer patients at median age of 15 years (range 1‒35), cryopreserved for fertility preservation before (n = 14) or after (n = 20) initiation of chemotherapy, were thawed and cultured for 7 days. The morphology and developmental stages of ovarian follicles were studied by light microscopy before and after culture. Possible associations between follicular densities, age and exposure to alkylating agents, expressed as cyclophosphamide equivalent dose (CED) were tested. RESULTS: Exposure to chemotherapy significantly impaired the survival and development of ovarian follicles in culture. After seven days, significantly higher densities of intermediary, primary and secondary follicles and lower densities of atretic follicles was detected in the samples collected before chemotherapy. Increasing dose of alkylating agents was identified by multivariate linear regression analysis as an independent predictor of a higher density of atretic follicles, whereas increasing age of the patient predicted a better outcome with less follicle atresia and a higher density of maturing follicles. CONCLUSION: This study provides quantitative in vitro evidence of the impact of chemotherapy on developmental capacity of cryopreserved human ovarian tissue. The results indicate that fertility preservation should be carried out, if possible, before initiation of alkylating agents in order to guarantee better in vitro survival of ovarian follicles. In addition, ovarian samples from younger girls show lower viability and fewer developing follicles in culture.

Autologous ectopic grafting of cryopreserved testicular tissue preserves the fertility of prepubescent monkeys that receive sterilizing cytotoxic therapy.

Boys faced with future sterility as a result of the need of a sterilizing cancer therapy might avoid this fate by engraftment of cryopreserved immature testicular tissue after therapy is completed. Efforts to address this important survivorship issue have been encouraged by reports of the long-term survival and proliferation of human spermatogonia after xenotransplant of cryopreserved immature testicular tissue into immunocompromised murine hosts. However, spermatogenic arrest at the pachytene spermatocyte stage that occurs in this situation has been associated with a failure in sperm production. In this study, we used a prepubescent simian model to address the possibility that testicular tissue engraftment is insufficiently supported in the model to allow suitable maturation of germ cells. Briefly, we carried out autologous orthotopic grafting of cryopreserved testicular tissue from four prepubescent monkeys and one pubescent rhesus monkey after testicular irradiation and castration of the host animal. Five months after implantation of scrotal grafts, we determined that 3% to 7% of the autografts could be recovered with spermatogenesis proceeding through spermatozoa formation in 13% to 17% of the seminiferous tubules formed in the grafts. In contrast, Sertoli cell-only tubules were detected in parallel xenografts transplanted into immunocompromised mice. Our results show that cryopreservation of testicular tissue from prepubescent primates can maintain the fully functional capacity of spermatogonia to produce sperm, but that host conditions are critical for spermatogenic maturation. Furthermore, our results establish an initial perspective on the quantity of cryopreserved material needed to ensure success in preserving fertility through testicular tissue grafts.

Hedgehog signalling promotes germ cell survival in the rat testis.

Hedgehog (Hh) signalling has a crucial role in testis development. Sertoli cell-derived desert hedgehog (DHH) guides the formation of testis cords and differentiation of foetal-type Leydig cells. Dhh mutant mice are infertile due to a block in germ cell differentiation, hypogonadism and hypoandrogenism. Hh signalling pathway components are also expressed in postnatal testis. In the rat testis the transcription factor of the Hh pathway, glioma-associated oncogene homologue (GLI1), is expressed by a wide variety of germ cells. This suggests that Hh signalling is involved in spermatogenesis at many different levels. Our data show that canonical Hh signalling is turned off in early condensing spermatids that strongly express the negative regulator of the pathway, suppressor of fused (SUFU). Most of the Hh pathway specific mRNAs display the highest values in stages II-VI of the rat seminiferous epithelial cycle. The key endocrine regulator of germ cell differentiation, FSH, down-regulates Dhh mRNA levels in vitro. Hh signalling inhibition in vitro leads to massive apoptosis of germ cells. In prepubertal rat testis imatinib mesylate-induced inhibition of tyrosine kinases impinges on Dhh transcript levels and Hh signalling. Our data indicate that Hh signalling is part of the paracrine signalling network in the rat testis. It promotes the survival of germ cells and is suppressed by FSH.

Testicular recovery after irradiation differs in prepubertal and pubertal non-human primates, and can be enhanced by autologous germ cell transplantation.

BACKGROUND: Although infertility is a serious concern in survivors of pediatric cancers, little is known about the influence of the degree of sexual maturation at the time of irradiation on spermatogenic recovery after treatment. Thus, we address this question in a non-human primate model, the rhesus monkey (Macaca mulatta). METHODS: Two pubertal (testis size 3 and 6.5 ml, no sperm in ejaculate) and four prepubertal (testis size 1 ml, no sperm in ejaculate) macaques were submitted to a single fraction of testicular irradiation (10 Gy). Unilateral autologous transfer of cryopreserved testis cells was performed 2 months after irradiation. Testicular volume, histology and semen parameters were analyzed to assess irradiation effects and testicular recovery. RESULTS: Irradiation provoked acute testis involution only in the two pubertal monkeys. Subsequently, testis sizes recovered and sperm was present in the ejaculates. Longitudinal outgrowth of seminiferous tubules continued, and, in testes without autologous cell transfer, 4-22% of tubular cross sections showed spermatogenesis 2 years after irradiation. In contrast, the four prepubertal monkeys showed neither a detectable involution as direct response to irradiation, nor a detectable growth of seminiferous tubules later. However, two of these animals showed spermarche 2 years after irradiation, and 8-12% of tubules presented spermatogenesis. One prepubertally irradiated monkey presented fast growth of one testis after cell transfer, and showed spermarche 1 year after irradiation. The infused testis had spermatogenesis in 70% of the tubules. The contralateral testis remained smaller. CONCLUSION: We conclude that irradiation before puberty has a severe detrimental effect on outgrowth of seminiferous tubules. But, within the seminiferous epithelium, spermatogenetic recovery occurs at a low rate with no detectable relation to the maturity of the epithelium at irradiation. We also show that autologous testis cell transplantation can enhance spermatogenesis, but only in isolated cases.

Effect of childhood acute lymphoblastic leukemia therapy on spermatogonia populations and future fertility.

CONTEXT: Isolation of spermatogonial stem cells before potentially sterilizing cancer therapy, followed by transplantation of these cells into the testis after such treatment, may be an effective approach to prevent infertility among prepubertal boys suffering from acute lymphoblastic leukemia (ALL). A key clinical consideration in this context is the timing of biopsy, if collection of spermatogonia could be delayed from diagnosis to the later phase of leukemia treatment, better patient selection could be offered. OBJECTIVE: The objective of the study was to examine the routine testicular biopsy material collected to detect testicular leukemia to evaluate if treatment for leukemia affects numbers and maturation of the spermatogonia during the prepubertal period. DESIGN AND PARTICIPANTS: The study involved 28 testicular biopsies from 23 prepubertal boys treated for ALL. OUTCOME MEASURE: Samples were stained immunohistochemically to evaluate the expression of the spermatogonial markers MAGE 4A, OCT4, CD9, and AP2gamma, and of the Sertoli cell marker WT-1. To relate these findings to gonadal function after sexual maturation, the surviving patients were evaluated as adults. RESULTS: Several MAGE 4A-, CD9-, or OCT4-positive spermatogonia were detected in testicular biopsies after standard risk therapy without cyclophosphamide, whereas their numbers were significantly reduced in six patients receiving high-risk ALL therapy involving cyclophosphamide. No significant alteration in spermatogonial numbers was associated with testicular leukemia. All patients not treated with cyclophosphamide recovered normal testicular function, with normal sperm quality and endocrine function. CONCLUSION: Treatment for childhood leukemia without high-dose cyclophosphamide seldom depletes the spermatogonial stem cell pool totally.

Functional in vitro model to examine cancer therapy cytotoxicity in maturing rat testis.

Childhood cancer treatment can lead to infertility. Organ culture of early postnatal testicular tissue might provide a valuable approach to the study of acute testicular toxicity. The aim of the present study was to develop a functional in vitro organ culture method, in order to identify sensitive target cells to doxorubicin-induced cytotoxicity in immature rat testis during germ cell migration prior initiation of the first wave of spermatogenesis. Testicular tissue fragments from 5-day-old Sprague-Dawley rats were cultured in the absence or presence of doxorubicin (40 and 100ng/ml) and morphology, apoptosis, proliferation and testosterone secretion was analyzed. Postnatal testicular development proceeded normally in control samples for 48h in vitro. In these untreated culture conditions germ and Sertoli cell numbers and germ cell migration were comparable to in vivo. Germ cells were the primary, most sensitive targets for in vitro-induced doxorubicin (100ng/ml) toxicity and their death was not associated with any morphological defects in the Sertoli cells. Organ culture which reduces the need of animal experimentation can be used to study the cytotoxic effects of doxorubicin on the immature testis.

Adult reproductive functions after early postnatal inhibition by imatinib of the two receptor tyrosine kinases, c-kit and PDGFR, in the rat testis.

Imatinib mesylate (Glivec, STI 571; Novartis), a small-molecular analog of ATP that potently inhibits the tyrosine kinase activities of Bcr-Abl, PDGFR-alpha, PDGFR-beta, c-Fms, Arg and c-kit, is one of the novel molecularly targeted agents being introduced into cancer therapy. Stem cell factor (SCF)/c-kit and platelet-derived growth factor (PDGF) signaling pathways regulate postnatal formation of the pools of spermatogonial stem cells and Leydig cells in the rat testis. The effect of short postnatal imatinib exposure on fertility of the male rats and offspring of these animals were investigated. Imatinib significantly reduced the litter size sired by the treated animals and led to permanently slightly elevated serum levels of the gonadotropins. Testicular morphology and mRNA levels of ligands and receptors involved in stem cell factor/c-kit and PDGF signaling returned to control levels, and the offsprings were born healthy. Our findings indicate that treatment of cancer with certain molecularly targeted drugs may have latent effects on testicular development by inhibiting specific physiological signaling pathways.

Inhibition of tyrosine kinases PDGFR and C-Kit by imatinib mesylate interferes with postnatal testicular development in the rat.

The tyrosine kinase receptor c-kit and its interaction with the ligand, stem cell factor (SCF), play an essential role in the developing testis. C-kit is important for the development of the Leydig cells and for the migration, proliferation and survival of spermatogonia. Platelet-derived growth factor (PDGF) and its tyrosine kinase receptor (PDGFR) are important for the development of Leydig cells and myoid cells. The chemotherapeutic agent, imatinib mesylate (STI571, Glivec; Novartis) inhibits both of these tyrosine kinase receptors. Three-day treatment of immature male rats (SD) with imatinib (150 mg/kg) on postnatal days 5-7 delayed the formation of germ-line stem cell pool, reduced proliferation of type A spermatogonia and induced germ cell apoptosis. PDGFR-mediated proliferation of mesenchymal myoid precursors was also decreased and the length of the seminiferous cord was reduced. However, at the age of 11 weeks the exposed animals had normal epididymal sperm counts, whereas plasma levels of luteinizing hormone and follicle stimulating hormone were significantly increased. Imatinib serves as a good tool to study postnatal formation of the male germ-line stem cell pool and factors determining the final testicular size. As development of the human testis is controlled by the same mechanisms, further studies with primate and human models are needed to explore whether imatinib affects the testis in children as well.

Irradiation causes acute and long-term spermatogonial depletion in cultured and xenotransplanted testicular tissue from juvenile nonhuman primates.

Infertility is a serious late effect in childhood cancer survivors. Little is known about acute irradiation effects in immature primate testis. Radiation defects have previously only been studied in postpubertal primates. Here we use the juvenile rhesus monkey as a preclinical model. We expose fragments of testicular tissue to 0, 0.5, 1.0, and 4.0 Gy irradiation in vitro. We then maintain the fragments in organ culture for 24-48 h or xenograft the fragments into nude mice for 4 months. Histological endpoints were determined to explore the cellular responses to the irradiation. At the highest dose, irradiation provoked an acute depletion of A-spermatogonia and a rise of apoptotic germ and Sertoli cells in organ culture. A dose-dependent decrease in the number of seminiferous tubules containing type A dark and type A pale spermatogonia was observed in irradiated xenografts. The number of Sertoli-cell only tubules increased respectively. Outgrowth of grafts was affected by the 4-Gy dose. Our observations reveal that irradiation evoked an immediate and sustained depletion of A-spermatogonia. We conclude that spermatogonia in the juvenile primate testis are highly sensitive to irradiation and that spermatogonial depletion and cessation of proliferation is an acute response. In contrast to adult testes, where such damage is immediately visible, this damage in immature testes becomes apparent only when spermatogonial insufficiency leads to spermatogenic failure, and thus infertility, at the onset of puberty. Our methods are applicable to immature human testis and might serve as powerful tool to study irradiation toxicity in the juvenile human testis.

Expression and localization of androgen receptor-interacting protein-4 in the testis.

Androgen receptor-interacting protein 4 (ARIP4) belongs to the SNF2 family of proteins involved in chromatin remodeling, DNA excision repair, and homologous recombination. It is a DNA-dependent ATPase, binds to DNA and mononucleosomes, and interacts with androgen receptor (AR) and modulates AR-dependent transactivation. We have examined in this study the expression and cellular localization of ARIP4 during postnatal development of mouse testis. ARIP4 was detected by immunohistochemistry in Sertoli cell nuclei at all ages studied, starting on day 5, and exhibited the highest expression level in adult mice. At the onset of spermatogenesis, ARIP4 expression became evident in spermatogonia, pachytene, and diplotene spermatocytes. Immunoreactive ARIP4 antigen was present in Leydig cell nuclei. In Sertoli cells ARIP4 was expressed in a stage-dependent manner, with high expression levels at stages II-VI and VII-VIII. ARIP4 expression patterns did not differ significantly in testes of wild-type, follicle-stimulating hormone receptor knockout, and luteinizing hormone receptor knockout mice. In testes of hypogonadal mice, ARIP4 was found mainly in interstitial cells and exhibited lower expression in Sertoli and germ cells. In vitro stimulation of rat seminiferous tubule segments with testosterone, FSH, or forskolin did not significantly change stage-specific levels of ARIP4 mRNA. Heterozygous ARIP4(+/-) mice were haploinsufficient and had reduced levels of Sertoli-cell specific androgen-regulated Rhox5 (also called Pem) mRNA. Collectively, ARIP4 is an AR coregulator in Sertoli cells in vivo, but the expression in the germ cells implies that it has also AR-independent functions in spermatogenesis.

Doxorubicin induces apoptosis in germ line stem cells in the immature rat testis and amifostine cannot protect against this cytotoxicity.

The underlying primary damage to the seminiferous epithelium caused by chemotherapeutic regimens at childhood is largely unknown. The present investigation was designed to identify acute cytotoxic events in the testis caused by a single dose of doxorubicin. Male rats at 6, 16, and 24 days of age were injected with doxorubicin (3 mg/kg, i.p.) or vehicle (saline) alone and 24 and 48 hours later, the germ cell types and apoptotic cells in the seminiferous epithelium were examined. As indicated by microscopy and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling staining, an 8-fold increase in the number of apoptotic germ cells in the testes of 6-day-old rats was observed 48 hours after doxorubicin treatment. Spermatogonia migrating to the basement membrane were the primary cell type undergoing this induced apoptosis. A single dose of amifostine (200 mg/kg) administered i.p. 15 minutes before injection of doxorubicin provided no protection against this enhanced apoptosis. Under the same conditions, testicular levels of p53 and activated caspase 8 were elevated, whereas the level of murine double minute-2 was lowered. In contrast, doxorubicin treatment did not result in any significant change in the physiologic, stage-specific germ cell apoptosis occurring in the testes of 16- and 24-day-old rats. These observations suggest that the initiation phase of spermatogenesis is highly sensitive to doxorubicin-induced apoptosis. Gonocytes and early spermatogonia are the cell types that are vulnerable to this p53-trigged apoptosis, which results in a decrease in the size of the pool of germ-line stem cells. Amifostine fails to protect the germ cells against this cytotoxic insult.