Gonadal dysfunction and infertility in kidney transplant patients receiving sirolimus

Targeted treatments for vascular malformations: current state of the art

Vascular malformations, which arise from anomalies in angiogenesis, encompass capillary, lymphatic, venous, arteriovenous, and mixed malformations, each affecting specific vessel types. Historically, therapeutic options such as sclerotherapy and surgery have shown limited efficacy in complicated malformations. Most vascular malformations stem from hereditary or somatic mutations akin to oncogenic alterations, activating the PI3K-AKT-mTOR, RAS-MAPK-ERK, and G-protein coupled receptor pathways. Recognizing the parallels with oncogenic mutations, we emphasize the potential of targeted molecular inhibitors in the treatment of vascular malformations by repurposing anticancer drugs. This review delves into the recent development and future use of such agents for the management of slow- and fast-flow vascular malformations, including in more specific situations, such as prenatal treatment and the management of associated coagulopathies.

Research progress on the role of autophagy in the development of varicocele

Varicocele (VC) is a common cause of infertility in men. Pathophysiological changes caused by VC, such as testicular hypoxia, high temperatures, oxidative stress, abnormal reproductive hormones, and Cd accumulation, can induce autophagy, thus affecting the reproductive function in patients with this condition. Autophagy regulators can be classified as activators or inhibitors. Autophagy activators upregulate autophagy, reduce the damage to the testis and epididymis, inhibit spermatogenic cell apoptosis, and protect fertility. In contrast, autophagy inhibitors block autophagy and aggravate the damage to the reproductive functions. Therefore, elucidating the role of autophagy in the occurrence, development, and regulation of VC may provide additional therapeutic options for men with infertility and VC. In this review, we briefly describe the progress made in autophagy research in the context of VC.

Role of Macroautophagy in Mammalian Male Reproductive Physiology

Physiologically, autophagy is an evolutionarily conserved and self-degradative process in cells. Autophagy carries out normal physiological roles throughout mammalian life. Accumulating evidence shows autophagy as a mechanism for cellular growth, development, differentiation, survival, and homeostasis. In male reproductive systems, normal spermatogenesis and steroidogenesis need a balance between degradation and energy supply to preserve cellular metabolic homeostasis. The main process of autophagy includes the formation and maturation of the phagophore, autophagosome, and autolysosome. Autophagy is controlled by a group of autophagy-related genes that form the core machinery of autophagy. Three types of autophagy mechanisms have been discovered in mammalian cells: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy is classified as non-selective or selective. Non-selective macroautophagy randomly engulfs the cytoplasmic components in autophagosomes that are degraded by lysosomal enzymes. While selective macroautophagy precisely identifies and degrades a specific element, current findings have shown the novel functional roles of autophagy in male reproduction. It has been recognized that dysfunction in the autophagy process can be associated with male infertility. Overall, this review provides an overview of the cellular and molecular basics of autophagy and summarizes the latest findings on the key role of autophagy in mammalian male reproductive physiology.

Cancer Treatment-Related Ovarian Dysfunction in Women of Childbearing Potential: Management and Fertility Preservation Options

PURPOSE

To review the complex concerns of oncofertility created through increased cancer survivorship and the long-term effects of cancer treatment in young adults.

DESIGN

Review chemotherapy-induced ovarian dysfunction, outline how fertility may be addressed before treatment initiation, and discuss barriers to oncofertility treatment and guidelines for oncologists to provide this care to their patients.

CONCLUSION

In women of childbearing potential, ovarian dysfunction resulting from cancer therapy has profound short- and long-term implications. Ovarian dysfunction can manifest as menstrual abnormalities, hot flashes, night sweats, impaired fertility, and in the long term, increased cardiovascular risk, bone mineral density loss, and cognitive deficits. The risk of ovarian dysfunction varies between drug classes, number of received lines of therapy, chemotherapy dosage, patient age, and baseline fertility status. Currently, there is no standard clinical practice to evaluate patients for their risk of developing ovarian dysfunction with systemic therapy or means to address hormonal fluctuations during treatment. This review provides a clinical guide to obtain a baseline fertility assessment and facilitate fertility preservation discussions.

Mechanisms of Male Reproductive Toxicity of Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDE) are a group of flame retardants used in a variety of artificial materials. Despite being phased out in most industrial countries, they remain in the environment and human tissues due to their persistence, lipophilicity, and bioaccumulation. Populational and experimental studies demonstrate the male reproductive toxicity of PBDEs including increased incidence of genital malformations (hypospadias and cryptorchidism), altered weight of testes and other reproductive tissues, altered testes histology and transcriptome, decreased sperm production and sperm quality, altered epigenetic regulation of developmental genes in spermatozoa, and altered secretion of reproductive hormones. A broad range of mechanistic hypotheses of PBDE reproductive toxicity has been suggested. Among these hypotheses, oxidative stress, the disruption of estrogenic signaling, and mitochondria disruption are affected by PBDE concentrations much higher than concentrations found in human tissues, making them unlikely links between exposures and adverse reproductive outcomes in the general population. Robust evidence suggests that at environmentally relevant doses, PBDEs and their metabolites may affect male reproductive health via mechanisms including AR antagonism and the disruption of a complex network of metabolic signaling.

Fertility preservation for pediatric patients with hemoglobinopathies: Multidisciplinary counseling needed to optimize outcomes

Hemoglobinopathies are autosomal recessive disorders that occur when genetic mutations negatively impact the function of hemoglobin. Common hemoglobinopathies that are clinically significant include sickle cell disease, alpha thalassemia, and beta thalassemia. Advancements in disease-modifying and curative treatments for the common hemoglobinopathies over the past thirty years have led to improvements in patient quality of life and longevity for those who are affected. However, the diseases, their treatments and cures pose infertility risks, making fertility preservation counseling and treatment an important part of the contemporary comprehensive patient care. Sickle cell disease negatively impacts both male and female infertility, primarily by testicular failure and decreased ovarian reserve, respectively. Fertility in both males and females with beta thalassemia major are negatively impacted by iron deposition due to chronic blood transfusions. Hematopoietic stem cell transplant (HSCT) is currently the only curative treatment for SCD and transfusion dependent beta thalassemia. Many of the conditioning regimens for HSCT contain chemotherapeutic agents with known gonadotoxicity and whole-body radiation. Although most clinical studies on toxicity and impact of HSCT on long-term health do not evaluate fertility, gonadal failure is common. Male fertility preservation modalities that exist prior to gonadotoxic treatment include sperm banking for pubertal males and testicular cryopreservation for pre-pubertal boys. For female patients, fertility preservation options include oocyte cryopreservation and ovarian tissue cryopreservation. Oocyte cryopreservation requires controlled ovarian hyperstimulation (COH) with ten to fourteen days of intensive monitoring and medication administration. This is feasible once the patient has undergone menarche. Follicular growth is monitored via transvaginal or transabdominal ultrasound, and hormone levels are monitored through frequent blood work. Oocytes are then harvested via a minimally invasive approach under anesthesia. Complications of COH are more common in patients with hemoglobinopathies. Ovarian hyperstimulation syndrome creates a greater risk to patients with underlying vascular, pulmonary, and renal injury, as they may be less able to tolerate fluids shifts. Thus, it is critical to monitor patients undergoing COH closely with close collaboration between the hematology team and the reproductive endocrinology team. Counseling patients and families about future fertility must take into consideration the patient's disease, treatment history, and planned treatment, acknowledging current knowledge gaps.

Long-term treatment with chloroquine increases lifespan in middle-aged male mice possibly via autophagy modulation, proteasome inhibition and glycogen metabolism

Previous studies have shown that the polyamine spermidine increased the maximum life span in C. elegans and the median life span in mice. Since spermidine increases autophagy, we asked if treatment with chloroquine, an inhibitor of autophagy, would shorten the lifespan of mice. Recently, chloroquine has intensively been discussed as a treatment option for COVID-19 patients. To rule out unfavorable long-term effects on longevity, we examined the effect of chronic treatment with chloroquine given in the drinking water on the lifespan and organ pathology of male middle-aged NMRI mice. We report that, surprisingly, daily treatment with chloroquine extended the median life span by 11.4% and the maximum life span of the middle-aged male NMRI mice by 11.8%. Subsequent experiments show that the chloroquine-induced lifespan elevation is associated with dose-dependent increase in LC3B-II, a marker of autophagosomes, in the liver and heart that was confirmed by transmission electron microscopy. Quite intriguingly, chloroquine treatment was also associated with a decrease in glycogenolysis in the liver suggesting a compensatory mechanism to provide energy to the cell. Accumulation of autophagosomes was paralleled by an inhibition of proteasome-dependent proteolysis in the liver and the heart as well as with decreased serum levels of insulin growth factor binding protein-3 (IGFBP3), a protein associated with longevity. We propose that inhibition of proteasome activity in conjunction with an increased number of autophagosomes and decreased levels of IGFBP3 might play a central role in lifespan extension by chloroquine in male NMRI mice.

Dosing-time dependent testicular toxicity of everolimus in mice

The circadian timing system controls many biological functions in mammals including drug metabolism and detoxification, cell cycle events, and thus may affect pharmacokinetics, target organ toxicity and efficacy of medicines. Selective mTOR (mammalian target of rapamycin) inhibitor everolimus is an immunosuppressant and anticancer drug that is effective against several cancers. The aim of this study was to investigate dosing-time dependent testicular toxicity of subacute everolimus administration in mice. C57BL/6 J male mice were synchronized with Light-Dark (12h:12 h) cycle, with Light-onset at Zeitgeber Time (ZT)-0. Everolimus (5 mg/kg/day) was administered orally to mice at ZT1_rest-span or ZT13_{activity-span} for 4 weeks. Body weight loss, clinical signs, changes in testicular weights, testis histology, spermatogenesis and proliferative activity of germinal epithelium of seminiferous tubules were examined. Steady-state everolimus concentrations in testes were determined with validated HPLC method. Everolimus toxicity was less severe following dosing at ZT13 compared to ZT1, as shown with least body weight loss (p<0.001), least reductions in testes weights (p<0.001) and least histopathological findings. Everolimus-induced histological changes on testes included vacuolisation and atrophy of germinal epithelium, and loss of germinal cell attachment. The severity of everolimus-induced histological toxicity on testes was significantly more evident in mice treated at ZT1 than ZT13 (p<0.001). Spermatogenic cell population significantly decreased when everolimus administered at ZT1 compared to ZT13 (p<0.001). Proliferative activity of germinal epithelium was significantly decreased due to treatment at ZT1 compared to ZT13 (p<0.001). Everolimus concentrations in testes indicated a pronounced circadian variation, which was greater in mice treated at ZT1 compared to ZT13 (p<0.05). Our study revealed dosing-time dependent testicular toxicity of everolimus in mice, which was greater in severity when everolimus administered at early rest-span (daytime-ZT1) than early activity-span (nighttime-ZT13). These findings support the concept of everolimus chronotherapy for minimizing reproductive toxicity and increasing the tolerability of everolimus, as a clinical advantage.

The effect of paternal exposure to immunosuppressive drugs on sexual function, reproductive hormones, fertility, pregnancy and offspring outcomes: a systematic review

BACKGROUND

Information regarding the possible influence of immunosuppressive drugs on male sexual function and reproductive outcomes is scarce. Men diagnosed with immune-mediated diseases and a wish to become a father represent an important neglected population since they lack vital information to make balanced decisions about their treatment.

OBJECTIVE AND RATIONALE

The aim of this research was to systematically review the literature for the influence of paternal immunosuppressive drug use on many aspects of male sexual health, such as sexual function, fertility, pregnancy outcomes and offspring health outcomes.

SEARCH METHODS

A systematic literature search was performed in the bibliographic databases: Embase (via Elsevier embase.com), MEDLINE ALL via Ovid, Cochrane Central Register of Trials (via Wiley) and Web of Science Core Collection. Additionally, Google Scholar and the Clinical trial registries of Europe and the USA were searched. The databases were searched from inception until 31 August 2019. The searches combined keywords regarding male sexual function and fertility, pregnancy outcomes and offspring health with a list of immunosuppressive drugs. Studies were included if they were published in English and if they included original data on male human exposure to immunosuppressive drugs. A meta-analysis was not possible to perform due to the heterogeneity of the data.

OUTCOMES

A total of 5867 references were identified, amongst which we identified 161 articles fulfilling the eligibility criteria. Amongst these articles, 50 included pregnancy and offspring outcomes and 130 included sexual health outcomes. Except for large Scandinavian cohorts, most of the identified articles included a small number of participants. While a clear negative effect on sperm quality was evident for sulfasalazine and cyclophosphamide, a dubious effect was identified for colchicine, methotrexate and sirolimus. In three articles, exposure to tumour necrosis factor-α inhibitors in patients diagnosed with ankylosing spondylitis resulted in improved sperm quality. The information regarding pregnancy and offspring outcomes was scant but no large negative effect associated with paternal immunosuppressive drug exposure was reported.

WIDER IMPLICATIONS

Evidence regarding the safety of immunosuppressive drugs in men with a wish to become a father is inconclusive. The lack of standardisation on how to evaluate and report male sexual function, fertility and reproduction as study outcomes in men exposed to immunosuppressive drugs is an important contributor to this result. Future research on this topic is needed and should be preferably done using standardised methods.

Infertility in Female and Male Solid Organ Recipients - From Diagnosis to Treatment: An Up-To-Date Review of the Literature

Around 20% to 30% of patients after solid organ transplantation are of reproductive age. The estimated rate of infertility in this group is slightly higher than in the general population. Choosing the optimal moment for pregnancy in transplanted patients plays a pivotal role, regardless of the method of conception. The first part of this article presents an up-to-date review of the problem of infertility in female and male solid organ recipients, with special attention to the influence of specific immunosuppressive drugs on semen parameters. The second part discusses the current knowledge regarding infertility treatment and the results of assisted reproductive techniques in this specific group of patients.

Despite restoring gonadal functions after transplantation, the patients should be informed about possible negative effects of medications on fertility, course of pregnancy, and the fetus. Interdisciplinary care should always be provided for infertile graft recipients, especially women, as it ensures safety both for the graft and for the potential gestation. The process of infertility diagnosis and tools used for that purpose are the same in transplanted patients as in the general population. The treatment with assisted reproductive techniques is acceptable and gives favorable results as long as patients are managed rationally, with special attention paid to prevention of iatrogenic complications.

Paternity in male kidney transplant recipients: a French national survey, the PATeRNAL study

Background

There is concern about the impact of immunosuppressive agents taken by male kidney transplant (KT) recipients on the risk of foetal malformations. The aim of our survey was to estimate the paternity rate and the outcomes of pregnancies fathered by kidney transplanted males.

Methods

This survey analysed 1332 male KT recipients older than 18 years, followed in 13 centres in France. A self-reported questionnaire was used to collect data on the patients, treatments at the time of conception and the pregnancy outcomes.

Results

The study included data on 349 children from 404 pregnancies fathered by 232 male KT recipients. The paternity rate was 17% (95% CI [15–20]). There were 37 (9%, 95% CI [7–12]) spontaneous abortions, 12 (3%, 95% CI [2–5]) therapeutic abortions, 2 (0.5%, 95% CI [0.1–1]) still births, and 13 (4%, 95% CI [2–6]) malformations reported. Compared to the general population, there was no difference in the proportion of congenital malformations nor unwanted outcomes whether the father was exposed or not to immunosuppressive agents.

Conclusions

This survey does not provide any warning signal that pregnancies fathered by male patients exposed to immunosuppressive agents, notably the debated MMF/MPA, have more complications than pregnancies in the general population.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s12882-020-02115-x.

The rapamycin analog Everolimus reversibly impairs male germ cell differentiation and fertility in the mouse†

Sirolimus, also known as rapamycin, and its closely related rapamycin analog (rapalog) Everolimus inhibit "mammalian target of rapamycin complex 1" (mTORC1), whose activity is required for spermatogenesis. Everolimus is Food and Drug Administration approved for treating human patients to slow growth of aggressive cancers and preventing organ transplant rejection. Here, we test the hypothesis that rapalog inhibition of mTORC1 activity has a negative, but reversible, impact upon spermatogenesis. Juvenile (P20) or adult (P>60) mice received daily injections of sirolimus or Everolimus for 30 days, and tissues were examined at completion of treatment or following a recovery period. Rapalog treatments reduced body and testis weights, testis weight/body weight ratios, cauda epididymal sperm counts, and seminal vesicle weights in animals of both ages. Following rapalog treatment, numbers of differentiating spermatogonia were reduced, with concomitant increases in the ratio of undifferentiated spermatogonia to total number of remaining germ cells. To determine if even low doses of Everolimus can inhibit spermatogenesis, an additional group of adult mice received a dose of Everolimus ∼6-fold lower than a human clinical dose used to treat cancer. In these animals, only testis weights, testis weight/body weight ratios, and tubule diameters were reduced. Return to control values following a recovery period was variable for each of the measured parameters and was duration and dose dependent. Together, these data indicate rapalogs exerted a dose-dependent restriction on overall growth of juvenile and adult mice and negative impact upon spermatogenesis that were largely reversed; following treatment cessation, males from all treatment groups were able to sire offspring.

Sirolimus and mTOR Inhibitors: A Review of Side Effects and Specific Management in Solid Organ Transplantation

Inhibitors of mechanistic target of rapamycin (mTOR inhibitors) are used as antiproliferative immunosuppressive drugs and have many clinical applications in various drug combinations. Experience in transplantation studies has been gained regarding the side effect profile of these drugs and the potential benefits and limitations compared with other immunosuppressive agents. This article reviews the adverse effects of mTOR inhibitors in solid organ transplantation, with special attention given to mechanisms hypothesized to cause adverse events and their management strategies.

New insights into the role of mTORC1 in male fertility in zebrafish

Mechanistic target of rapamycin complex 1 (mTORC1) plays crucial roles in male fertility. In mammals, deregulation of mTORC1 led to disordered spermatogonia proliferation and spermatogenesis, which eventually caused infertility in males. However, its roles in male fertility of non-mammalian species remain unclarified. In the present study, it was found that treatment of rapamycin, an mTORC1 inhibitor, resulted in infertility with decreased milt production and sperm motility in zebrafish. However, it is surprising to find that spermatogenesis was normal in these fish. All types of germ cells were found and the proliferation of spermatogonia and spermatocyte were normal. These results suggested that maturation of sperm may be impaired in males treated with rapamycin. Increased apoptosis was found surrounding the lumen containing spermatozoa, implicating a loss of Sertoli cells in testes treated with rapamycin. Moreover, LH/hCG mediated up-regulation of steroidogenic genes was abolished. The expression of npr and ar induced by LH/hCG was also blocked, which further suppressed the signaling of progestin and androgen. Collectively, mTORC1 maintains male fertility via different mechanisms in fish and mammals. mTORC1 is dispensable for spermatogenesis in zebrafish, but possibly supports the maintenance of Sertoli cells and mediates the signaling of hormones, which are crucial for sperm maturation.

Evidence-based practice: Guidance for using everolimus in combination with low-exposure calcineurin inhibitors as initial immunosuppression in kidney transplant patients

The mammalian target of rapamycin (mTOR) inhibitor, everolimus, in combination with reduced-exposure calcineurin inhibitor (CNI), has been demonstrated in clinical trials to have comparable efficacy in low-to-moderate immunological risk kidney transplant recipients to the Standard of Care, mycophenolic acid (MPA) in combination with standard-exposure CNI. Current treatment guidelines consider mTOR inhibitors to be a second-line therapy in the majority of cases; however, given that everolimus-based regimens are associated with a reduced rate of viral infections after transplantation, their wider use could have great benefits for kidney transplant patients. In this evidence-based practice guideline, we consider the de novo use of everolimus in kidney transplant recipients. The main outcomes of our consideration of the available evidence are that: 1. Everolimus, in combination with reduced-exposure CNI and low dose steroids, is a suitable regimen for the prophylaxis of kidney transplant rejection in the majority of low-to-moderate immunological risk adult patients, with individualized management; 2. Induction with either basiliximab or rabbit anti-thymocyte globulin is an effective therapy for kidney transplant recipients when initiating an everolimus-based, reduced-exposure CNI regimen; and 3. An individualized approach should be adopted when managing kidney transplant recipients on everolimus-based therapy.

Premature recruitment of oocyte pool and increased mTOR activity in Fmr1 knockout mice and reversal of phenotype with rapamycin

While mutations in the fragile X mental retardation-1 (FMR1) gene are associated with varying reproductive outcomes in females, the effects of a complete lack of FMR1 expression are not known. Here, we studied the ovarian and reproductive phenotypes in an Fmr1 knockout (KO) mouse model and the role of mammalian target of rapamycin (mTOR) signaling. Breeding, histologic and mTOR signaling data were obtained at multiple time points in KO and wild type (WT) mice fed a control or rapamycin (mTOR inhibitor) diet. KO mice showed an earlier decline in ovarian reserve than WT mice with an increased proportion of activated follicles. mTOR and phosphorylated S6 kinase (p-S6K) levels, a measure of downstream mTOR signaling, were elevated in the KO ovaries. Rapamycin blocked these effects in KO mice, and increased the primordial follicle pool and age of last litter in WT mice. Our data demonstrates an early decline in reproductive capacity in Fmr1 KO mice and proposes that premature recruitment of the primordial pool via altered mTOR signaling may be the mechanism. Reversal of phenotypes and protein levels in rapamycin-treated KO mice, as well as increased reproductive lifespan of rapamycin-fed WT mice, suggest the mTOR pathway as a potential therapeutic target.

Rapamycin inhibits spermatogenesis by changing the autophagy status through suppressing mechanistic target of rapamycin-p70S6 kinase in male rats

Rapamycin (sirolimus) is an antiproliferative drug that has been widely used in the clinic as an immunosuppressant and a potential anticancer agent. Certain reports have indicated that rapamycin may induce male infertility through impairing sperm quality. The present study investigated the mechanism of male infertility caused by rapamycin and examined whether withdrawal of rapamycin could recover the number of sperm in rats. Male Sprague-Dawley rats (n=100) were divided randomly into 5 groups: 3 rapamycin-treated groups (2, 4 and 6 mg/kg) and 2 control groups [Blank and dimethyl sulfoxide (DMSO)]. Organ coefficients of the testes, number of sperm and hematoxylin-eosin staining analyses demonstrated that rapamycin treatment markedly damaged the structure of the seminiferous tubule and reduced the number of sperm. Immunohistochemistry of mechanistic target of rapamycin (mTOR) and Ki67 in testes tissue, and western blotting of phosphorylated-p70S6K and p70S6K, supported the hypothesis that rapamycin causes sperm reduction through inhibiting proliferation of spermatogonia. Unfortunately, 24 weeks after cessation of rapamycin treatment, only the number of sperm in 2 mg/kg group was restored back to the normal level. In addition, to the best of our knowledge, the present study was the first to demonstrate that low doses rapamycin leads to activation of autophagy in rat testes. This may be a self-protective mechanism of the cell in response to external stress. Thus, spermatogenesis can be recovered in the testes from rats in the low dose group. High doses of rapamycin resulted in excessive consumption of autophagy proteins, and the damage could not be compensated. In addition, it was revealed that cell apoptosis increased after treatment with rapamycin. In conclusion, the present study demonstrated that rapamycin inhibits spermatogenesis through suppressing phosphorylation of p70S6K and changing the autophagy status, ultimately reducing the number of sperm. These findings provide important guidance for the clinical application of rapamycin.

mTORC1/2 inhibition preserves ovarian function and fertility during genotoxic chemotherapy

The ovary contains oocytes within immature (primordial) follicles that are fixed in number at birth. Activation of follicles within this fixed pool causes an irreversible decline in reproductive capacity, known as the ovarian reserve, until menopause. Premenopausal women undergoing commonly used genotoxic (DNA-damaging) chemotherapy experience an accelerated loss of the ovarian reserve, leading to subfertility and infertility. Therefore, there is considerable interest but little effective progress in preserving ovarian function during chemotherapy. Here we show that blocking the kinase mammalian/mechanistic target of rapamycin (mTOR) with clinically available small-molecule inhibitors preserves ovarian function and fertility during chemotherapy. Using a clinically relevant mouse model of chemotherapy-induced gonadotoxicity by cyclophosphamide, and inhibition of mTOR complex 1 (mTORC1) with the clinically approved drug everolimus (RAD001) or inhibition of mTORC1/2 with the experimental drug INK128, we show that mTOR inhibition preserves the ovarian reserve, primordial follicle counts, serum anti-Mullerian hormone levels (a rigorous measure of the ovarian reserve), and fertility. Chemotherapy-treated animals had significantly fewer offspring compared with all other treatment groups, whereas cotreatment with mTOR inhibitors preserved normal fertility. Inhibition of mTORC1 or mTORC1/2 within ovaries was achieved during chemotherapy cotreatment, concomitant with preservation of primordial follicle counts. Importantly, our findings indicate that as little as a two- to fourfold reduction in mTOR activity preserves ovarian function and normal birth numbers. As everolimus is approved for tamoxifen-resistant or relapsing estrogen receptor-positive breast cancer, these findings represent a potentially effective and readily accessible pharmacologic approach to fertility preservation during conventional chemotherapy.

Mammalian target of rapamycin (mTOR): a central regulator of male fertility?

Mammalian target of rapamycin (mTOR) is a central regulator of cellular metabolic phenotype and is involved in virtually all aspects of cellular function. It integrates not only nutrient and energy-sensing pathways but also actin cytoskeleton organization, in response to environmental cues including growth factors and cellular energy levels. These events are pivotal for spermatogenesis and determine the reproductive potential of males. Yet, the molecular mechanisms by which mTOR signaling acts in male reproductive system remain a matter of debate. Here, we review the current knowledge on physiological and molecular events mediated by mTOR in testis and testicular cells. In recent years, mTOR inhibition has been explored as a prime strategy to develop novel therapeutic approaches to treat cancer, cardiovascular disease, autoimmunity, and metabolic disorders. However, the physiological consequences of mTOR dysregulation and inhibition to male reproductive potential are still not fully understood. Compelling evidence suggests that mTOR is an arising regulator of male fertility and better understanding of this atypical protein kinase coordinated action in testis will provide insightful information concerning its biological significance in other tissues/organs. We also discuss why a new generation of mTOR inhibitors aiming to be used in clinical practice may also need to include an integrative view on the effects in male reproductive system.

Autophagy in Diabetic Retinopathy

Autophagy is an important homeostatic cellular process encompassing a number of consecutive steps indispensable for degrading and recycling cytoplasmic materials. Basically autophagy is an adaptive response that under stressful conditions guarantees the physiological turnover of senescent and impaired organelles and, thus, controls cell fate by various cross-talk signals. Diabetic retinopathy (DR) is a serious microvascular complication of diabetes and accounts for 5% of all blindness. Although, various metabolic disorders have been linked with the onset of DR, due to the complex character of this multi-factorial disease, a connection between any particular defect and DR becomes speculative. Diabetes increases inflammation, advanced glycation end products (AGEs) and oxidative stress in the retina and its capillary cells. Particularly, a great number of evidences suggest a mutual connection between oxidative stress and other major metabolic abnormalities implicated in the development of DR. In addition, the intricate networks between autophagy and apoptosis establish the degree of cellular apoptosis and the progression of DR. Growing data underline the crucial role of reactive oxygen species (ROS) in the activation of autophagy. Depending on their delicate balance both redox signaling and autophagy, being detrimental or beneficial, retain opposing effects. The molecular mechanisms of autophagy are very complex and involve many signaling pathways cooperating at various steps. This review summarizes recent advances of the possible molecular mechanisms in autophagic process that are involved in pathophysiology of DR. In-depth analysis on the molecular mechanisms leading to autophagy in the retinal pigment epithelial (RPE) will be helpful to plan new therapies aimed at preventing or improving the progression of DR.

HCG-mediated activation of mTORC1 signaling plays a crucial role in steroidogenesis in human granulosa lutein cells

Luteinizing hormone/human chorionic gonadotropin stimulates progesterone biosynthesis in the corpus luteum by activating cyclic adenosine monophosphate/protein kinase A cascade. Recent studies have shown that cyclic adenosine monophosphate-mediated activation of protein kinase A interacts with the mammalian target of rapamycin signaling pathways. Furthermore, the use of mammalian target of rapamycin inhibitors for immunosuppression in transplant patients has shown adverse effects in reproductive functions. This study examined whether the mammalian target of rapamycin pathway plays any role in luteinizing hormone-mediated regulation of progesterone production. Human granulosa lutein cells were isolated from follicular aspirates of women undergoing in vitro fertilization. Cells were cultured for 72 h and treated with human chorionic gonadotropin (50 ng/ml) for different time periods with or without pretreatment with mammalian target of rapamycin complex 1 inhibitor, rapamycin, (20 nM) for 1 h. Expression of steroidogenic enzymes, including steroidogenic acute regulatory protein, cholesterol side chain cleavage enzyme, and 3β-hydroxysteroid dehydrogenase type 1 messenger RNA, were examined by real-time polymerase chain reaction after 6 h of human chorionic gonadotropin treatment. Expressions of phospho-ribosomal protein S6 kinase and cholesterol side chain cleavage enzyme were analyzed after 15 min and 24 h of human chorionic gonadotropin treatment, respectively. Progesterone production was analyzed by an enzyme immunoassay kit after human chorionic gonadotropin (50 ng/ml) or forskolin (10 μM) treatment for 24 h. Treatment with human chorionic gonadotropin increased the expression of downstream targets of mammalian target of rapamycin complex 1, as well as cholesterol side chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase type 1 and steroidogenic acute regulatory protein messenger RNAs. These increases were inhibited by rapamycin pretreatment. Increased progesterone production in response to treatment with human chorionic gonadotropin or forskolin was also blocked by rapamycin pretreatment. Our findings support a role for mammalian target of rapamycin complex 1 in regulating steroidogenesis in human granulosa lutein cells.

Management of side effects of mTOR inhibitors in tuberous sclerosis patients

mTOR inhibitors represent a relatively new therapeutic option in the management of patients affected by tuberous sclerosis complex (TSC). Randomized clinical trials support the use of everolimus in the treatment of subependymal giant cell astrocytomas (SEGA) and renal angiomyolipomas (AML) related to TSC. Accumulating data suggest also systemic disease-modifying potential of mTOR inhibitors. Given that increasing number of patients with TSC receive mTOR inhibitors, the issue of adverse events associated with this therapy becomes practically important. In the present study we provide the overview of clinical manifestations and therapeutic options for the most common adverse events related to mTOR inhibitors in TSC patients.

Mammalian target of rapamycin complex 1 (mTORC1) Is required for mouse spermatogonial differentiation in vivo

Spermatogonial stem cells (SSCs) must balance self-renewal with production of transit-amplifying progenitors that differentiate in response to retinoic acid (RA) before entering meiosis. This self-renewal vs. differentiation spermatogonial fate decision is critical for maintaining tissue homeostasis, as imbalances cause spermatogenesis defects that can lead to human testicular cancer or infertility. A great deal of effort has been exerted to understand how the SSC population is maintained. In contrast, little is known about the essential program of differentiation initiated by retinoic acid (RA) that precedes meiosis, and the pathways and proteins involved are poorly defined. We recently reported a novel role for RA in stimulating the PI3/AKT/mTOR kinase signaling pathway to activate translation of repressed mRNAs such as Kit. Here, we examined the requirement for mTOR complex 1 (mTORC1) in mediating the RA signal to direct spermatogonial differentiation in the neonatal testis. We found that in vivo inhibition of mTORC1 by rapamycin blocked spermatogonial differentiation, which led to an accumulation of undifferentiated spermatogonia. In addition, rapamycin also blocked the RA-induced translational activation of mRNAs encoding KIT, SOHLH1, and SOHLH2 without affecting expression of STRA8. These findings highlight dual roles for RA in germ cell development - transcriptional activation of genes, and kinase signaling to stimulate translation of repressed messages required for spermatogonial differentiation.

Nutritional signals and reproduction

There is extensive evidence that nutrition influences reproductive function in various mammalian species (agricultural animals, rodents and human). However, the mechanisms underlying the relationship between nutrition, energy metabolism and reproductive function are poorly understood. This review considers nutrient sensors as a molecular link between food molecules and consequences for female and male fertility. It focuses on the roles and the molecular mechanisms of some of the relevant hormones, such as insulin and adipokines, and of energy substrates (glucose, fatty acids and amino acids), in the gonadotropic axis (central nervous system and gonads). A greater understanding of the interactions between nutrition and fertility is required for both better management of the physiological processes and the development of new molecules to prevent or cure metabolic diseases and their consequences for fertility.

Long-term side effects of treatment with mTOR inhibitors in children after renal transplantation

BACKGROUND

mTOR inhibitors (mTORI) have emerged as alternative and additive immunosuppressive agents in pediatric renal transplantation (pRTx). Their immunosuppressive, anti-proliferative, and anti-neoplastic mechanisms have been described to be effective, whereas some side effects are alarming. In particular, growth and pubertal development are of concern. The aim of this study was to look for long-term side effects of mTORI therapy in pRTx.

PATIENTS AND METHODS

The retrospective analysis focused on side effects, growth, and pubertal development under mTORI therapy in 31 children. Eighteen children were routinely monitored for estradiol, testosterone, LH, and FSH levels.

RESULTS

The occurrence of bacterial infections, lymphoceles, myelosuppression, and the course of overall linear growth was comparable with other pediatric renal transplant cohorts. According to the clinical puberty status, all but one patient showed normal age-related development in parallel to normal serum hormone levels. Only one patient experienced cytomegaly virus infection under mTORI, no post-transplant lymphoproliferative disorders (PTLD) occurred.

CONCLUSIONS

Long-term mTORI therapy is safe in pRTx. No negative impact on growth and pubertal development was observed.

Outcomes of Pregnancies Fathered by Solid-Organ Transplant Recipients Exposed to Mycophenolic Acid Products

Context

In women, exposure to mycophenolic acid products during pregnancy results in an increase in both miscarriages and birth defects in the live born.

Objective

To describe the outcomes of pregnancies fathered by transplant recipients who were being maintained on mycophenolic acid products at the estimated time of conception and compare these pregnancies with pregnancies in the general population.

Methods

Data were collected by the National Transplantation Pregnancy Registry via questionnaires, telephone interviews, and medical records.

Results

One hundred fifty-two male transplant recipients with exposure to mycophenolic acid products fathered 205 pregnancies (208 outcomes, including 3 pairs of twins). Pregnancy outcomes included 194 live births with a prematurity rate of 10.8%, 14 spontaneous abortions, and no therapeutic abortions or stillbirths. Among the live births, 6 malformations were reported, for an incidence of 3.1%. No pattern of malformations was identified.

Conclusion

The outcomes of pregnancies fathered by transplant recipients treated with mycophenolic acid products appear similar to outcomes in the general population.

Low-dose oral sirolimus and the risk of menstrual-cycle disturbances and ovarian cysts: analysis of the randomized controlled SUISSE ADPKD trial

Sirolimus has been approved for clinical use in non proliferative and proliferative disorders. It inhibits the mammalian target of rapamycin (mTOR) signaling pathway which is also known to regulate ovarian morphology and function. Preliminary observational data suggest the potential for ovarian toxicity but this issue has not been studied in randomized controlled trials. We reviewed the self-reported occurrence of menstrual cycle disturbances and the appearance of ovarian cysts post hoc in an open label randomized controlled phase II trial conducted at the University Hospital Zürich between March 2006 and March 2010. Adult females with autosomal dominant polycystic kidney disease, an inherited kidney disease not known to affect ovarian morphology and function, were treated with 1.3 to 1.5 mg sirolimus per day for a median of 19 months (N = 21) or standard care (N = 18). Sirolimus increased the risk of both oligoamenorrhea (hazard ratio [HR] 4.3, 95% confidence interval [CI] 1.1 to 29) and ovarian cysts (HR 4.4, CI 1.1 to 26); one patient was cystectomized five months after starting treatment with sirolimus. We also studied mechanisms of sirolimus-associated ovarian toxicity in rats. Sirolimus amplified signaling in rat ovarian follicles through the pro-proliferative phosphatidylinositol 3-kinase pathway. Low dose oral sirolimus increases the risk of menstrual cycle disturbances and ovarian cysts and monitoring of sirolimus-associated ovarian toxicity is warranted and might guide clinical practice with mammalian target of rapamycin inhibitors.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00346918.

A drug safety evaluation of everolimus in kidney transplantation

INTRODUCTION

Calcineurin inhibitors (CNI) have greatly reduced the rate of acute rejection and improved short-term graft survival after organ transplantation, however, long-term survival has hardly changed since their introduction. CNIs are believed to contribute to graft fibrosis, have side effects that adversely affect cardiovascular risk, and are associated with an increased rate of post-transplant malignancies. Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, is not associated with graft fibrosis, has a superior cardiovascular risk profile to CNI therapy and has shown potential for the prevention and treatment of diverse forms of cancer.

AREAS COVERED

This review summarizes key aspects of everolimus, including its mechanism of action, pharmacokinetics, pharmacodynamics, drug-drug interactions and pivotal clinical studies with a focus on safety and efficacy.

EXPERT OPINION

Everolimus is effective in improving graft function in selected kidney transplant patients. Most adverse events are present for a short time after the introduction of everolimus, and are manageable. Everolimus has the potential to become an important agent in de novo and maintenance immunotherapy in kidney transplant recipients.

The impact of sirolimus on sex hormones in male adolescent kidney recipients

While it is known that sirolimus affects sex hormones in adult kidney transplant patients, there is a scarcity of data on its effects on sex hormone levels in adolescent kidney recipients. The objective of this study is to describe the impact of sirolimus on the sex hormones in this patient population. This is a retrospective review of male adolescent renal transplant patients transitioned to sirolimus. Baseline and subsequent annual testosterone levels were collected. Linear regression was undertaken to determine the predictors of testosterone levels. Four African Americans and 11 Caucasians, median age of 15 yr (11-18) in 2008, were included. Mean time post-transplant was 81 ± 37 months. Mean testosterone values were the following: 336 ± 135 ng/dL (n = 8) at baseline, 349 ± 130 ng/dL (n = 15) one yr later, and 360 ± 132 ng/dL (n = 13) two yr later (normal range for adult males: 350-970 ng/dL). Seven (47%) patients experienced a decrease in testosterone levels. Time on sirolimus was associated with decreased testosterone (r = 0.643, p = 0.010). Testosterone levels in pubertal male kidney transplant recipients on sirolimus may be suppressed, especially if they have been treated with sirolimus for several years. These data need to be confirmed in a larger study.

Potential Therapeutic Roles for Inhibition of the PI3K/Akt/mTOR Pathway in the Pathophysiology of Diabetic Retinopathy

Novel therapeutics such as inhibitors of PI3K/Akt/mTOR pathway presents a unique opportunity for the management of diabetic retinopathy (DR). Second generation mTOR inhibitors have the prospect to be efficacious in managing various stages of disease progression in DR. During early stages, the mTOR inhibitors suppress HIF-1α, VEGF, leakage, and breakdown of the blood-retinal barrier. These mTOR inhibitors impart a pronounced inhibitory effect on inflammation, an early component with diverse ramifications influencing the progression of DR. These inhibitors suppress IKK and NF-κB along with downstream inflammatory cytokines, chemokines, and adhesion molecules. In proliferative DR, mTOR inhibitors suppress several growth factors that play pivotal roles in the induction of pathological angiogenesis. Lead mTOR inhibitors in clinical trials for ocular indications present an attractive treatment option for chronic use in DR with favorable safety profile and sustained ocular pharmacokinetics following single dose. Thereby, reducing dosing frequency and risk associated with chronic drug administration.

Tacrolimus and sirolimus induce reproductive abnormalities in female rats

BACKGROUND

Immunosuppression medications contribute to posttransplant diabetes mellitus in patients and can cause insulin resistance in male rats. Tacrolimus (TAC)-sirolimus (SIR) immunosuppression is also associated with appearance of ovarian cysts in transplant patients. Because insulin resistance is observed in patients with polycystic ovary syndrome, we hypothesized that TAC or SIR may induce reproductive abnormalities.

METHODS

We monitored estrus cycles of adult female rats treated daily with TAC, SIR, and combination of TAC-SIR, or diluent (control) for 4 weeks. Animals were then challenged with oral glucose to determine their glucose and insulin responses, killed, and their blood and tissues, including ovaries and uteri harvested.

RESULTS

TAC and TAC-SIR treatments increased mean random glucose concentrations (P<0.05). TAC, SIR, and TAC-SIR treatments also increased the glucose response to oral glucose challenge (P<0.05). The insulin response to glucose was significantly higher in rats treated with SIR compared with TAC (P<0.05). TAC, SIR and TAC-SIR treatments reduced number of estrus cycles (P<0.05). The ovaries were smaller after SIR and TAC-SIR treatment compared with controls. The TAC and TAC-SIR treatment groups had fewer preovulatory follicles. Corpora lutea were present in all groups. Ovarian aromatase expression was reduced in the SIR and TAC-SIR treatment groups. A significant (P<0.05) reduction in uterine size was observed in all treatment groups when compared with controls.

CONCLUSION

In a model of immunosuppressant-induced hyperglycemia, both TAC and SIR induced reproductive abnormalities in adult female rats, likely through different mechanisms.