Basic research on uterus transplantation in nonhuman primates in Japan

Keio Uterus Transplantation Research: From Basic Research toward Future Clinical Application

Uterus transplantation (UTx) is now a potential option to allow women with uterine factor infertility to give birth. However, UTx is still at an experimental stage, and basic animal studies, including in non-human primates, are needed for the accumulation of data prior to clinical application. Considering that UTx may provide new hope to Japanese women, we launched UTx research in 2009 and have since accumulated a large archive of results in the UTx research field. Furthermore, we have carried out various activities aimed at the implementation of clinical applications of UTx in Japan while clarifying the ethical and social issues involved. Currently, the clinical application of UTx in Japan is just around the corner, and it is expected that UTx research will develop further in the future. Herein, we summarize our basic experiences using non-human primates and our activities with the goal of future clinical applications.

Concerns Associated with Uterus Transplantation in Japan

Uterus transplantation (UTx) has seen increasing global adoption as an alternative for women with uterine factor infertility to achieve pregnancy. However, several medical, ethical, and social issues need to be addressed before UTx can be applied clinically. Since 2009, Japan has amassed a large database of basic research on UTx in non-human primates, but clinical application has not been realized because of conservative attitudes and prudent concerns. Nonetheless, UTx may be viable in Japan after comprehensive resolution of the concerns associated with this medical technology.

Urogenital Lesions in Nonhuman Primates at 2 National Primate Research Centers

Given their genetic and anatomic similarities to humans, nonhuman primates (NHPs) may serve as animal models for urogenital diseases of humans. The purpose of this study was to examine the frequency of spontaneous urogenital lesions occurring over a 30-year period at the Yerkes and Southwest National Primate Research Centers and to compare and contrast lesions occurring in Old World versus New World primates. Lesions occurring in the chimpanzee (Pan troglodytes), baboon (Papio spp.), rhesus macaque (Macaca mulatta), cynomolgus macaque (Macaca fascicularis), pig-tailed macaque (Macaca nemestrina), sooty mangabey (Cercocebus atys), common marmoset (Callithrix jacchus), cotton-top tamarin (Sanguinus oedipus), and squirrel monkey (Saimiri sciureus) are discussed. The most common lesions of the kidney were medullary amyloidosis, renal cysts, renal tubular degeneration, glomerulonephritis or glomerulopathy, nephritis, nephrocalcinosis, pyelonephritis, and hydronephrosis. Specific causes of renal tubular disease included pigmentary nephrosis and tubular lipidosis. Renal tumors, including renal adenoma and carcinoma, lymphoma, and nephroblastoma, were infrequent diagnoses in all species. Endometriosis was the most frequently diagnosed lesion of the female genital tract. Of the animals examined in this study, it was most frequent in Old World primates. Leiomyoma was the most common uterine tumor. Granulosa cell tumor was the most frequently observed neoplasm of the ovaries, followed by teratoma. Of animals included in the study, most ovarian tumors occurred in baboons. Neoplasms of the male reproductive tract included interstitial cell tumor, seminoma, penile squamous cell carcinoma, penile papilloma, and histiocytoma. In New World monkeys, renal lesions were reported more frequently than genital lesions.

First Successful Delivery after Uterus Transplantation in MHC-Defined Cynomolgus Macaques

Delivery following uterus transplantation (UTx)—an approach for treating uterine factor infertility—has not been reported in nonhuman primate models. Here, six female major histocompatibility complex (MHC)-defined cynomolgus macaques that underwent allogeneic UTx were evaluated. Antithymocyte globulin and rituximab were administered to induce immunosuppression and a triple maintenance regimen was used. Menstruation resumed in all animals with long-term survival, except one, which was euthanized due to infusion associated adverse reaction to antithymocyte globulin. Donor-specific antibodies (DSA) were detected in cases 2, 4, and 5, while humoral rejection occurred in cases 4 and 5. Post-transplant lymphoproliferative disorder (PTLD) developed in cases 2 and 3. Pregnancy was attempted in cases 1, 2, and 3 but was achieved only in case 2, which had haploidentical donor and recipient MHCs. Pregnancy was achieved in case 2 after recovery from graft rejection coincident with DSA and PTLD. A cesarean section was performed at full-term. This is the first report of a successful livebirth following allogeneic UTx in nonhuman primates, although the delivery was achieved via UTx between a pair carrying haploidentical MHCs. Experimental data from nonhuman primates may provide important scientific knowledge needed to resolve unsolved clinical issues in UTx.

Experimental techniques for the development of a uterus transplantation model in cynomolgus macaques

Uterus transplantation (UTx) is now a treatment for women with uterine factor infertility to have a child. However, UTx is still largely at the experimental stage, and many medical issues remain unsolved. Therefore, adequate studies in large animals including non-human primates are required for validation of these issues. UTx research, especially in non-human primates, can provide important information for its full establishment in humans due to the anatomical and physiological similarities between the two. We accumulated data from UTx studies using cynomolgus macaques since 2009 and established autologous and allogeneic UTx models which led to deliveries after performing the procedure. In this paper, we summarized key points to develop UTx models in cynomolgus macaques based on our experience. UTx models in non-human primates can surely contribute new and beneficial knowledge in this field and can be useful for the further development of UTx in humans.

Clinical features of irreversible rejection after allogeneic uterus transplantation in cynomolgus macaques

Uterus transplantation (UTx) is a potential option for women with uterine factor infertility to have a child. The clinical features indicating irreversible rejection of the uterus are unknown. In our experimental series of allogeneic UTx in cynomolgus macaques, six female macaques were retrospectively examined, which were unresponsive to treatment with immunosuppressants (i.e. irreversible rejection). Clinical features including general condition, hematology, uterine size, indocyanine green (ICG) fluorescence imaging by laparotomy, and histopathological findings of the removed uterus were evaluated. In all cases, general condition was good at the time of diagnosis of irreversible rejection and thereafter. Laboratory evaluation showed temporary increases in white blood cells, lactate dehydrogenase and C-reactive protein, then these levels tended to decrease gradually. In transabdominal ultrasonography, the uterus showed time-dependent shrinkage after transient swelling at the time of diagnosis of irreversible rejection. In laparotomy, a whitish transplanted uterus was observed and enhancement of the transplanted uterus was absent in ICG fluorescence imaging. Histopathological findings in each removed uterus showed hyalinized fibrosis, endometrial deficit, lymphocytic infiltration and vasculitis. These findings suggest that uterine transplantation rejection is not fatal, in contrast to rejection of life-supporting organs. Since the transplanted uterus with irreversible rejection atrophies naturally, hysterectomy may be unnecessary.

Long-Term Outcome and Rejection After Allogeneic Uterus Transplantation in Cynomolgus Macaques

Uterus transplantation (UTx) is an option for women with uterine factor infertility to have a child, but is still in the experimental stage. Therefore, allogeneic animal models of UTx are required for resolution of clinical issues. In this study, long-term outcomes were evaluated in four recipients (cases 1-4) after allogeneic UTx in cynomolgus macaques. Immunosuppression with antithymocyte globulin induction and a triple maintenance regimen was used. Postoperative ultrasonography and biopsy of the transplanted uterus and immunoserological examinations were performed. All four recipients survived for >3 months after surgery, but continuous menstruation did not resume, although temporary menstruation occurred (cases 1 and 2). All animals were euthanized due to irreversible rejection and no uterine blood flow (cases 1, 2 and 4) and post-transplant lymphoproliferative disorder (case 3). Donor-specific antibodies against MHC class I and II were detected in cases 1, 2 and 4, but not in case 3. Peripheral lymphocyte counts tended to elevate for CD3⁺, CD20⁺ and NK cells in conjunction with uterine rejection, and all animals had elevated stimulation indexes of mixed lymphocyte reaction after surgery. Establishment of allogeneic UTx in cynomolgus macaque requires further exploration of immunosuppression, but the clinicopathological features of uterine rejection are useful for development of human UTx.

The development of an extended normothermic ex vivo reperfusion model of the sheep uterus to evaluate organ quality after cold ischemia in relation to uterus transplantation

INTRODUCTION

Uterus transplantation has recently proved that infertility in women with uterine factor infertility can be cured. It is still an experimental procedure with numerous critical details remaining to be established, including tolerance to warm and cold ischemic insults. In preparation for human uterus transplantation trials, most teams use the sheep as a model system for research and team training, since the vasculature and the uterus is of similar size as in the human. We, therefore, aimed to develop an ex vivo sheep uterus reperfusion platform that mimics the reperfusion situation so that initial assessments and comparisons can be performed without the need for costly and labor-intensive in vivo transplantation experiments.

MATERIAL AND METHODS

Isolated sheep uteri were perfused with the preservation solution IGL-1 and were then exposed to cold ischemia for either 4 (n = 6) or 48 hours (n = 7). Uteri were then reperfused for 48 hours under normothermic conditions with an oxygenated recirculating perfusate containing growth factors and synthetic oxygen carriers. Histological and biochemical analysis of the perfusate was conducted to assess reperfusion injury.

RESULTS

Quantification of cell density indicated no significant edema in the myometrium or in the endometrium of uteri exposed to 4 hours cold ischemia and then a normothermic ex vivo reperfusion for 48 hours. Only the outer serosa layer and the inner columnar luminal epithelial cells were affected by the reperfusion. However, a much faster and severe reperfusion damage of all uterine layers were evident during the reperfusion experiment following 48 hours of cold ischemia. This was indicated by major accumulation of extracellular fluid, presence of apoptotic-labeled glandular epithelial layer and vascular endothelium. A significant accumulation of lactate was measured in the perfusate with a subsequent decrease in pH.

CONCLUSIONS

We developed a novel ex vivo sheep uterus model for prolonged perfusion. This model proved to be able to distinguish reperfusion injury-related differences associated to organ preservation. The experimental setup is a platform that can be used to conduct further studies on uterine ischemia- and reperfusion injury that may lead to improved human uterus transplantation protocols.

Current Progress in Uterus Transplantation Research in Asia

Uterus transplantation (UTx) is now a possible approach for women with absolute uterine factor infertility to deliver a child, following the first successful delivery by Brännström et al. in Sweden in September 2014. This remarkable achievement attracted major attention worldwide and caused many countries to prepare for UTx, including countries in Asia. To date, three groups have performed UTx in humans in Asia, and many others are aiming for the clinical application of UTx with accumulation of basic experimental data. Therefore, it is likely that UTx will expand rapidly in Asia in the near future, although this will depend on ethical, social and religious views in each country. With this background, herein we summarize the current progress of UTx in East, Southeast and South Asia, with the purpose of increasing understanding of the current status of basic and clinical UTx research in each country and sharing progress and knowledge to ensure future development of UTx research in Asia.