Sheep Model for Uterine Transplantation: The Best Option Before Starting a Human Program

A Sustainable Translational Sheep Model for Planned Cesarean Delivery of Contraction-Free Ewes

We evaluated whether the sheep constitutes a useful translational model to evaluate anatomical and surgical aspects of cesarean delivery (CD) from a human medical perspective with the aim of both maternal and neonatal well-being. Our hypothesis was that CD in contraction-free ewes is not associated with major complications. Primary endpoint was the transferability of anatomical conditions and surgical techniques of CD from the ewe to the human. Secondary endpoints were maternal and fetal survival, occurrence of retained fetal membranes, metritis, mastitis, or wound infections. Forty-eight Merino ewes were delivered by CD after 95% gestation (142-144 days). Both ewes and newborn lambs were cared for intensively after the delivery. Ovine uterine anatomy during CD appeared slightly different but comparable to the human uterus. Uterine incisions were mostly performed in the uterine horns, not in the uterine corpus. The ovine uterine wall is thinner than in humans. All ewes survived without any major complications. Seventy-seven (88.5%) out of 87 live-born lambs survived without any complications. The contraction-free ewe constitutes an appropriate and safe model to evaluate anatomical and surgical aspects of CD from a human medical perspective. We present a step-by-step manual for successfully planned cesarean delivery for sheep including the perioperative management illustrated with photographs and a five-minute video. With adequate planning and a reasonable number of staff, it is possible to safeguard both maternal and neonatal survival. This sustainable translational medicine model offers additional potential for the offspring to be used for further research studies (e.g., transgenerational inheritance research).

Uterus transplantation: from research, through human trials and into the future

Women suffering from absolute uterine factor infertility (AUFI) had no hope of childbearing until clinical feasibility of uterus transplantation (UTx) was documented in 2014 with the birth of a healthy baby. This landmark accomplishment followed extensive foundational work with a wide range of animal species including higher primates. In the present review, we provide a summary of the animal research and describe the results of cases and clinical trials on UTx. Surgical advances for graft removal from live donors and transplantation to recipients are improving, with a recent trend away from laparotomy to robotic approaches, although challenges persist regarding optimum immunosuppressive therapies and tests for graft rejection. Because UTx does not involve transplantation of the Fallopian tubes, IVF is required as part of the UTx process. We provide a unique focus on the intersection between these two processes, with consideration of when oocyte retrieval should be performed, whether, and for whom, preimplantation genetic testing for aneuploidy should be used, whether oocytes or embryos should be frozen and when the first embryo transfer should be performed post-UTx. We also address the utility of an international society UTx (ISUTx) registry for assessing overall UTx success rates, complications, and live births. The long-term health outcomes of all parties involved-the uterus donor (if live donor), the recipient, her partner and any children born from the transplanted graft-are also reviewed. Unlike traditional solid organ transplantation procedures, UTx is not lifesaving, but is life-giving, although as with traditional types of transplantation, costs, and ethical considerations are inevitable. We discuss the likelihood that costs will decrease as efficiency and efficacy improve, and that ethical complexities for and against acceptability of the procedure sharpen the distinctions between genetic, gestational, and social parenthood. As more programs wish to offer the procedure, we suggest a scheme for setting up a UTx program as well as future directions of this rapidly evolving field. In our 2010 review, we described the future of clinical UTx based on development of the procedure in animal models. This Grand Theme Review offers a closing loop to this previous review of more than a decade ago. The clinical feasibility of UTx has now been proved. Advancements include widening the criteria for acceptance of donors and recipients, improving surgery, shortening time to pregnancy, and improving post-UTx management. Together, these improvements catalyze the transition of UTx from experimental into mainstream clinical practice. The procedure will then represent a realistic and accessible alternative to gestational surrogacy for the treatment of AUFI and should become part of the armamentarium of reproductive specialists worldwide.

Anatomic characteristics and novel transplantation model of the canine uterus

Background

In Vietnam, the rate of absolute uterine factor infertility is increasing, but no study has been published on uterine transplantation. The present study was designed to comprehensively observe the canine uterine anatomy and to examine the possibility of using a living canine donor for uterine transplantation training and further research.

Methods

Ten female Vietnamese mixed-breed dogs were sacrificed for anatomical research, and 15 additional pairs were used to evaluate the novel uterine transplant model.

Results

The anatomic features of the canine uterus differed considerably from those of the human uterus, with the uterine vessels originating from branches of the pudendal vessels (also known as the vaginal vessels). The uterine vascular pedicle had a small diameter (1 to 1.5 mm for arteries and 1.2 to 2.0 mm for veins) and required manipulation under a microscope. To perform uterine transplantation, the donor specimen's artery and vein lengths were successfully reconstructed by anastomosis between both sides of the vasculature using autologous Y-shaped subcutaneous veins. The living-donor uterine transplantation model constructed in this study was feasible, with the transplanted uterus surviving in 86.7% of cases (13/15).

Conclusions

Uterine transplantation was successfully performed in a Vietnamese canine living donor model. This model could be helpful in uterine transplantation training and improve the transplantation success rate in humans.

Whole-organ decellularization of the human uterus and in vivo application of the bio-scaffolds in animal models

PURPOSE

The aim of this investigation was to design a perfusion-based decellularization protocol to provide whole human uterine bio-scaffolds with preserved structural and componential characteristics and to investigate the in vivo properties of the decellularized tissues.

METHODS

Eight human uteri, donated by brain-dead patients, were decellularized by perfusion of sodium dodecyl sulfate (SDS) through the uterine arteries using a peristaltic pump. The bio-scaffolds were evaluated and compared with native human uterus regarding histological, immunohistochemical, structural, and bio-mechanical properties, in addition to CT angiographies to examine the preservation of the vascular networks. Subsequently, we obtained acellular patches and implanted them on uterine defects of female Wistar rats to investigate the bio-compatibility and regenerative potential of the bio-scaffolds. Finally, we performed immunostaining to investigate the potential role of circulating stem cells in recellularization of the implanted bio-scaffolds.

RESULTS

The outcomes of this investigation confirmed the efficacy of the proposed protocol to provide whole human uterine scaffolds with characteristics and extra-cellular matrix components similar to the native human uterus. Subsequent in vivo studies demonstrated the bio-compatibility and the regenerative potential of the scaffolds and suggested a signaling pathway as an underlying mechanism for the regenerative process.

CONCLUSIONS

To the best of our knowledge, this investigation provides the first efficient perfusion-based decellularization protocol for the human uterus to obtain whole-organ scaffolds. The outcomes of this investigation could be employed in future human uterus tissue engineering studies which could ultimately result in the development of novel treatments for female infertile patients.

Involving Animal Models in Uterine Transplantation

Background

Absolute uterine factor infertility affects 0. 2% women of childbearing age around the world. Uterine transplantation (UTx) is a promising solution for many of them since the first birth from UTx was described by the Swedish team in 2014. The success of Utx in humans has become possible after a systematic and meticulous approach involving years of research on animal models. To date, more than 80 UTx procedures have been performed worldwide and 30 children were born.

Material and Method

This review summarizes the research preparation conducted in animals before beginning UTx in humans. It focuses on the advantages and limits of each animal model, their place in surgical training, and current contribution in research to improve UTx successes in humans. The different steps in the process of UTx have been analyzed, such as imaging, surgery, ischemia-reperfusion effects, rejection markers, immunosuppressive treatment, and pregnancy.

Conclusion

Animal models have played an essential role in the implementation of UTx, which is a highly complex procedure. While respecting the 3R requirements (replacement, refinement, and reduction), the surgical training using large animal models, such as notably ewes remain irreplaceable for teams wishing to initiate a UTx program. Furthermore, animal models are still mandatory in current research to improve the success rates of UTx in humans as well as to reduce the morbidity associated with this experimental infertility treatment.

Uterus procurement from deceased donor for transplantation

Women with absolute uterine factor infertility cannot get pregnant. The current experience in uterine transplantation is limited and the use of a deceased donor uterus in this area is incipient after some initial unsuccessful attempts. The birth of healthy babies through this modality in four different centers has given a new impetus to the use of this transplantation technique. We aimed to develop a technique for uterus procurement and preparation for transplantation from a brain dead donor. Fifteen uteri were retrieved from multi-organ donor patients, 10 of these were used in bench surgeries with the proposed technique. All procedures were performed after obtaining family's consent. This study allowed the clinical use of two of the 15 organs that were procured for transplantation. One of these organs resulted in the first live birth worldwide using a uterus transplanted from a deceased donor, a landmark in reproductive medicine. Another outcome was the optimization of the surgical technique involving less manipulation of the uterine vascular pedicles. The success of this novel technique suggests that the proposed model can be replicated and optimized further to facilitate the transplantation of uterus from deceased donors.

Uterus transplantation in a sheep model: novel surgical technique with long-term survival and uterus vitality. First case series in Argentina

OBJECTIVE

To develop a sheep autologous uterus transplantation (UT) program with an innovative surgical technique and assess long term uterus vitality and animal survival.

METHODS

A novel surgical technique consisting of the procurement of the complete uterus and the two ovaries, back table vascular reconstruction, and subsequent implantation in the same animal, performing only two arterial and two venous anastomoses.

RESULTS

Four autologous transplantations were performed; anesthesia and surgery were well tolerated by all the animals without complications. Direct observation and Doppler US performed a week after UT and laparoscopy performed three months later confirmed uterus vitality. All animals were alive more than a year after transplantation.

CONCLUSIONS

Our study was the first to describe a novel surgical technique for sheep uterus autologous transplantation in Latin America, showing long-term survival and uterus vitality.

Uterine transplant: an ethical framework analysis from a Middle Eastern perspective

BACKGROUND

Significant advances in infertility treatment have been achieved over the past several decades, but women with uterine dysfunction, anomaly, or agenesis still need support to carry a pregnancy to term. Recently, advancements in surgical, anesthetic and immunosuppressive therapy have brought the idea of successful uterine transplant closer to reality, but many challenges must be overcome before uterine transplant can become more common, including ethical challenges related to the study and the conduct of this procedure.

METHODS

This was an updated ethical analysis of uterine transplant from a Middle Eastern perspective, using an established ethical framework that has been adapted for the analysis of research in non-Western cultures and developing countries.

RESULTS

Using the ethical framework, this analysis explored research developments in uterine transplant to date, using the following categories: collaborative partnership, social value, scientific validity, a fair selection of study population, favorable risk-benefit ratio, independent review, informed consent, and respect for recruited participants. The analysis revealed a significant need for region- and religion-specific ethical guidelines for uterine transplant procedures.

CONCLUSIONS

The horizons of research need to expand by addressing and researching the ethical issues related to uterine transplant trials and clinical procedures.

LIMITATIONS

Limitations included the challenges related to applying ethical analyses to work in developing countries, and the fact that this analysis was based on the views and interpretations of a single researcher.

Towards uterus tissue engineering: a comparative study of sheep uterus decellularisation

Uterus tissue engineering may dismantle limitations in current uterus transplantation protocols. A uterine biomaterial populated with patient-derived cells could potentially serve as a graft to circumvent complicated surgery of live donors, immunosuppressive medication and rejection episodes. Repeated uterine bioengineering studies on rodents have shown promising results using decellularised scaffolds to restore fertility in a partially impaired uterus and now mandate experiments on larger and more human-like animal models. The aim of the presented studies was therefore to establish adequate protocols for scaffold generation and prepare for future in vivo sheep uterus bioengineering experiments. Three decellularisation protocols were developed using vascular perfusion through the uterine artery of whole sheep uteri obtained from slaughterhouse material. Decellularisation solutions used were based on 0.5% sodium dodecyl sulphate (Protocol 1) or 2% sodium deoxycholate (Protocol 2) or with a sequential perfusion of 2% sodium deoxycholate and 1% Triton X-100 (Protocol 3). The scaffolds were examined by histology, extracellular matrix quantification, evaluation of mechanical properties and the ability to support foetal sheep stem cells after recellularisation. We showed that a sheep uterus can successfully be decellularised while maintaining a high integrity of the extracellular components. Uteri perfused with sodium deoxycholate (Protocol 2) were the most favourable treatment in our study based on quantifications. However, all scaffolds supported stem cells for 2 weeks in vitro and showed no cytotoxicity signs. Cells continued to express markers for proliferation and maintained their undifferentiated phenotype. Hence, this study reports three valuable decellularisation protocols for future in vivo sheep uterus bioengineering experiments.

[Orthotopic uterus transplantation. Sheep model experiment, Cali (Colombia)]

OBJECTIVE

It has been recommended that professionals who are planning to perform uterine transplantation should first carry out animal experiments. This paper describes the procedure for uterine transplant in sheep, as well as short and medium-term results.

METHODS

Experimental surgery study in sheep subjected to uterine explantation and transplant. Four 40-50 kg sheep received uteri transplantation (orthotopic) from four live donors. End-to-side vascular anastomosis was used, the vagina was sutured on one plane and the uterus was fixed to the pelvic wall. Complications and 180-day evolution are described.

RESULTS

Transplant surgery was accomplished in the 4 sheep. Surgical time in the first procedure was 240 minutes, while the last procedure lasted 185 minutes. Warm ischemia time was reduced from 42 to 22 minutes. One sheep died on the seventh postoperative day due to an intraoperative complication unrelated to the vascular anastomosis. A second sheep developed local vaginal infection treated with metronidazole and evolved satisfactorily. No transplant rejection had occurred in the remaining 3 sheep after 6 months.

CONCLUSIONS

The ovine model allowed surgical training in experimental uterine transplant surgery. For the authors, it offered an opportunity to gain knowledge and make progress towards future uterus transplantation in women with uterine factor infertility in Colombia.

[Uterus transplantation, current prospect and future indications. State of art with review of literature]

OBJECTIVES

The aim of this review is to summarize the development of UT on worldwide and to develop the new questions posed by this technique in 2020.

METHODS

According to the PRISMA model, via Pubmed, we searched for publications containing the keywords: uterus transplantation; UT and cryopreservation from 2000 to 2020.

RESULTS

At least 76 UTx have been carried out around the world and 19 healthy babies were born. The main indication remains the uterine agenesis (MRKH Syndrome>85% cases) then the history of hysterectomy (hemorrhage of the delivery or cervical cancer) and the non-functional uterus (Asherman's syndrome, diffuse adenomyosis). The 2 types of donors (living and deceased) are developed representing respectively 75% and 25% of the TU; the success rate in terms of return of rules is better in the living donor group and is 79% vs 68% in the deceased donor group. The choice of donor type must take into account the constraints of both procedures. Surgical complications (grade III) for the donor are estimated to be 14% mainly represented by ureter wounds. Technical simplifications concerning the venous return of the graft but also the carrying out of robot-assisted surgery would reduce the operating time for the donor and facilitate the collection process.

CONCLUSION

TU is a complementary alternative to GPA and adoption allowing patients to be surrogates, legal and biological of the baby. An extension of the indications to patients with non absolute uterine infertility is in the process of democratization.

Human uterine vasculature with respect to uterus transplantation: A comprehensive review

Due to the novelty of uterus transplantation, data on preferable inflow and outflow of the graft are limited. This paper reviews the technique, type of vessels and the outcome. A systematic search of the PubMed database was conducted. We extracted and analyzed data on the arteries and veins utilized, types of anastomosis, types of donors, complications and the outcome. Thirty eight sources reported 51 human uterine transplantations, 10 graft thromboses and 25 live births. Inflow was established with two uterine arteries (UA) with/without the anterior division of the internal iliac artery in 62% (n = 31) of cases, two UA arteries with a segment/patch of the internal iliac artery in 34% (n = 17) of cases or two UA with a conduit in 4% of cases (n = 2). Both cases with a conduit developed thrombosis (n = 2). Arterial thrombosis/ischemia developed in 8 of the 51 cases. In 50% of cases with arterial thrombosis, atherosclerosis was identified as a possible cause. Outflow was established by two internal iliac veins with patches/segments in 27.5% of cases (n = 14) followed by two utero-ovarian veins in 25.5% (n = 13). Venous thrombosis occurred in 3 of the 51 cases. Uterine arteries with/without anterior division of the internal iliac artery were the most frequent arteries used for inflow and produced the highest patency rate. The presence of atherosclerosis and complex arterial reconstruction was associated with a high rate of arterial thrombosis. None of the veins utilized in the procedures appeared to be superior. There are insufficient data to draw a definite conclusion.

Novel Technique in a Sheep Model of Uterine Transplantation

INTRODUCTION

Uterine transplantation (UTx) is a surgical therapeutic modality designed for the treatment of patients with exclusive uterine factor infertility. Experimental models are paramount to study this transplant modality, and as the ewes' uteri are very similar to that of humans, they are frequently used with this purpose. The aim of this study is to describe a novel technical variation for UTx in sheep.

METHODS

This study was conducted at Laboratory of Medical Investigation 37 of the University of São Paulo School of Medicine in São Paulo, Brazil, and was approved by the Ethics Committee of Animal Use of the university. We used 3 adult female sheep that weighed approximately 45 kg and were not pregnant. We performed the technique of uterine autotransplantation with a novel technical variation that we called sequential vascularization: first, we performed the right uterine artery and vein anastomoses, after which the uterine graft was vascularized, and then the contralateral vascular anastomoses were performed.

CONCLUSION

We described 3 successful uterine autotransplants in sheep models with sequential vascularization. This variation technique will probably allow warm ischemia time in UTx to significantly decrease.

Intra- and Postoperative Blood Flow Monitoring in a Sheep Model of Uterus Transplantation

BACKGROUND

The introduction of the opportunity to transplant a viable uterus into women for fulfilling their desire to have a child has awakened high expectations worldwide.

MATERIALS AND METHODS

A sheep model was used to evaluate tools for optimizing measurement of blood flow in uterine transplantation. Intraoperatively, blood flow was measured using unidirectional Doppler and indocyanine green (ICG) fluorescence imaging. Postoperatively, an implantable Doppler probe served as a tool for clinical monitoring the patency of anastomosed vessels.

RESULTS

ICG imaging showed complete vascularization of the uterus before and in short-term evaluation after surgery. The implantable Doppler probe proved to be highly suitable for assessing patency of vessels in a non-invasive way. Results of histology, and real-time polymerase chain reaction demonstrated viability of the transplanted uterus.

CONCLUSION

Different methods to monitor vasculature patency have proven to be advantageous in supporting both surgeons and researchers in ensuring successful implementation of uterine transplantation.

Laparoscopic uterine graft procurement and surgical autotransplantation in ovine model

Currently, uterus transplantation (UTx) is a clinical option for infertile women. Over the past three decades, treating benign or malignant gynecological diseases with minimally invasive gynecological surgery has improved, providing significant advantages over conventional open surgery. This study addresses the method used for laparoscopic live-donor ovariohysterectomy and graft harvest from a sheep model. Using a microsurgical practice, ten grafts were autotransplanted after uterine perfusion. End-to-end anastomosis techniques were used to approximate veins and arteries. Follow-ups were carried out 2-months after surgery and postoperative studies included ultrasound scan, diagnostic hysteroscopy, vascular angiography, and exploratory laparoscopy. All transplants were completed without complications. After vascular anastomosis, total reperfusion of the tissue was accomplished in all animals without confirmation of arterial or venous thrombosis. Angiographic explorations did not show any statistically significant dissimilarity in the arterial diameters between the different examination times. 3-months after uterine transplantation all animals underwent assisted reproduction techniques. Patent uterine arteries were observed 4, 8 and 12 months after the transplant. 6-months after transplantation, six sheep (60%) became pregnant with assisted reproduction practices. We noticed an increase in the degree of fibrosis of the cervix samples in non-pregnant animals of the transplant group. Laparoscopic surgery can be an advantageous approach for the uterus retrieval procedure during uterine transplantation. However, larger sample sized reports are needed in order to accomplish validation, standardization and wider use of this route.

Basic research on uterus transplantation in nonhuman primates in Japan

Uterus transplantation (UTx) is now a potential option for women with uterine factor infertility to have a child. However, UTx is still in an experimental stage and basic animal studies including in nonhuman primates are needed for accumulation of data that will provide important information for establishment of UTx in humans. Herein, we summarized our experiences using cynomolgus macaques, with the goal of promoting further development of UTx studies in nonhuman primates. Our basic studies using cynomolgus macaques were summarized, including the results of other teams in nonhuman primates. Our team in Japan launched UTx research in 2009 using cynomolgus macaques and has accumulated a large archive of results in the UTx research field, including examination of uterine blood flow, surgical procedures of autologous and allogeneic UTx, organ perfusion methods in deceased donor models, immunological response and rejection and ischemia/reperfusion injury. We achieved the first delivery after autologous UTx in primates and the first periodic recovery of menstruation after allogeneic UTx in nonhuman primate models. Results from animal studies, including those in nonhuman primates, provide the basis for clinical application of UTx. Therefore, our accumulated data since 2009 and our basic experience in cynomolgus macaque are meaningful for future UTx trials in Japan. In addition, more validation in nonhuman primate models is needed for resolution of medical issues and further development of UTx in humans, despite clinical application of UTx in several countries.