Ex Vivo Model of Human Penile Transplantation and Rejection: Implications for Erectile Tissue Physiology

Ethical stakes of penile transplantation: A literature review

BACKGROUND

Vascularized composite allotransplantation has become an alternative reconstruction technique for patients with a severe loss of substance. Today, five human penile transplantations have been reported. The objective of this literature review is to offer an updated overview of the technical and ethical questions surrounding penile transplantation compared with conventional phalloplasty.

MATERIAL AND METHODS

A systematic review was conducted of the literature from 2000 to 2020. A search of PubMed was performed using the keywords: "penile transplantation," "penis transplantation," and "penile vascularized composite allotransplantation." The criteria for the analysis were the type of study, surgical techniques, and ethical concerns.

RESULTS

Thirty-six articles were selected. These articles include reviews, case report, editorials, and preclinical studies. The first article was published in 2003, but the number of articles has increased after the second human transplantation in South Africa in 2014. Surgical techniques and the medication management specific to each team were successful in the 5 transplant cases, but several complications were noted.

CONCLUSION

Two decades of successful penile transplantations have proven the technique to be a viable solution to treat a penile amputation, allowing for a better esthetic and sensitive outcome paired with the possibility of natural urinary and erectile functions. Psychological impact of penile transplantation, selection of patients, complications of immunosuppressive therapies, and surgical technicity are the biggest penile transplantation challenges. Further experimental studies are necessary to produce standardized protocols to safely include penile transplantation in the conventional treatment of a penile amputation.

Penile allotransplantation: early outcomes from reported cases and survivorship considerations

Vascular composite allografts are at the forefront of medical and surgical innovation. With this new technique and the ability to transplant a face, hands, an abdominal wall, a uterus, or even a penis, patients can undergo operations that may drastically improve their quality of life. Although this process presents significant opportunities it is not always an easy road and requires significant upfront counseling and life-long immunosuppression. Often the recovery course is long, with functionality taking months to years to gain. Immunosuppression must be used to prevent rejection of the allograft although it has serious long-term side-effects. Only five patients have undergone penile allotransplantation but reported outcomes from these small numbers have nonetheless offered significant lessons with each patient. While the operation is still in its infancy, it is certain that shared experiences by surgical teams will yield improved outcomes in the future.

The Baltimore Criteria for an ethical approach to penile transplantation: a clinical guideline

Significant advances and increasing acceptance of vascularized composite allotransplantation (VCA) have contributed to emerging success of penile transplantation. The aims of penile transplantation are fourfold: adequate urinary function, enabling natural erections, restoration of erogenous sensation and appearance of external male genitalia. Successful penile transplantation also requires limiting risks and managing complications of lifelong immunosuppression. Given the limited experience with this procedure, potential recipients must understand that penile transplantation is not currently standard of care and long-term functional outcomes are unknown. Moreover, these transplants are associated with complex ethical issues. Nevertheless, as the efficacy and safety of penile transplantation are being evaluated, clear indications for transplant are needed. Although preliminary recommendations have been proposed, a more comprehensive framework is needed. We performed a literature review for English language publications related to penile transplantation and ethics. Based on the results of the search, a review of prior recommendations, and our experience performing the first whole male genital allotransplantation including penis, scrotum and abdominal wall; screening and identifying potential donors and recipients for the procedure; and addressing the associated ethical issues, we propose guidelines for responsible penile transplantation: The Baltimore Criteria for an Ethical Approach to Penile Transplantation.

The Urogenital Epithelium and Corporal Tissues Are the Primary Targets of Rejection in Penile Vascularized Composite Allotransplantation: A New Real-Time Tissue-Based Monitoring System

BACKGROUND

Although significant surgical advances have been made in the form of microvascular surgery and autologous free tissue transfer, penile reconstruction still poses several difficult challenges. Although interest in penile vascularized composite allotransplantation has grown since the first attempted transplant in 2006, little is known regarding the kinetics of rejection and subsequent function of penile allografts. The penis contains multiple tissue types that are not qualified by the Banff 2007 vascularized composite allotransplantation classification system, including urogenital mucosal epithelium and erectile tissues. In this study, the authors investigate the propagation of rejection and the resultant function following rejection in rat and human penile tissues.

METHODS

Rejected human and rat penile tissues were examined using an ex vivo real-time tissue-based derivative of the classic mixed lymphocyte reaction assay to determine the interactions occurring between en bloc penile tissues and peripheral blood mononuclear cells (autologous and allogeneic). Correlative in vivo heterotopic rat penile vascularized composite allotransplantation was used to correlate ex vivo findings.

RESULTS

In both human and rat ex vivo systems and in vivo rat vascularized composite allotransplantation, the urethral mucosa was the first to undergo rejection-associated apoptosis. The urethral mucosa was the most immunogenic and led to the highest level of peripheral blood mononuclear cell proliferative generations in all systems, whereas the neural tissues of the penis remained immune privileged.

CONCLUSION

These findings are the first to describe the kinetics of rejection in both human and rat penile vascularized composite allotransplantation and that the urethral mucosa is the most antigenic, suffering the highest level of rejection-associated apoptosis and peripheral blood mononuclear cell proliferative aggregation.

Penile transplantation: the US experience and institutional program set-up

Penile transplantation using vascularized composite allografts is an emerging technique to treat genital loss. In the United States, this procedure has been performed successfully at Massachusetts General Hospital in a patient who had previously undergone treatment for penile cancer. The Johns Hopkins Medical Institutions has developed a research protocol to perform penile transplantation in patients with genital loss secondary to trauma. The process of selecting the appropriate candidate for genitourinary (GU) vascularized composite allograft surgery is rigorous including extensive physical examination, laboratory testing, imaging and psychological evaluations. After transplantation, limiting the potential complications associated with immunosuppression is critical given that the procedure is intended to improve quality of life and is not life-saving. Ultimately, penile transplant is a surgical intervention which may have numerous applications. Optimization of the pre-operative screening process, surgical technique, and immunosuppressive protocol is required to establish this method as the standard treatment for patients with genital loss and limited reconstructive options.

Penile Allotransplantation for Complex Genitourinary Reconstruction

PURPOSE

Reconstruction of complex functional structures is increasingly being performed with vascularized composite allotransplantation. Penile transplantation is a novel vascularized composite allotransplantation treatment option for severe penile tissue loss and disfigurement. Three allogeneic human penile transplantations have been reported. We review these cases as well as penile transplant indications, preclinical models and immunosuppression therapy.

MATERIALS AND METHODS

We performed a comprehensive literature review for the years 1970 to 2016 via MEDLINE®, PubMed® and Google with the key words "penis transplantation," "penile rejection," "penile replantation," "penile tissue loss" and "penis vascularized composite allotransplantation." Relevant articles, including original research, reviews and nonscientific press reports, were selected based on contents, and a review of this literature was generated.

RESULTS

Three human allogeneic penile transplantations have been performed to date, of which 1 was removed 14 days after transplantation. The second recipient reports natural spontaneous erections and impregnating his partner. All 3 patients were able to void spontaneously through the graft's urethra. The complexity of the transplant is determined by how proximally the penile shaft anastomosis is performed and additional pelvic tissue may be transplanted en bloc if needed.

CONCLUSIONS

Penile transplantation is a technically demanding procedure with significant ethical and psychosocial implications that can provide tissue and functional replacement, including urinary diversion and natural erections. It is unclear how rejection and immunosuppression may affect graft function. Better models and more preclinical research are needed to better understand and optimize penile transplantation.

Penile transplantation: an emerging option for genitourinary reconstruction

Penile transplantation is an emerging option for patients with severe genital defects not amenable to traditional reconstructive options. In this article, we discuss the burgeoning problem of severe male genitourinary trauma in the military, the limitations of traditional reconstructive options in addressing these problems, and the potential for penile transplantation to provide improved outcomes. We also review the preclinical research and limited worldwide experience with penile transplantation to date, including lessons learned, and discuss the many important technical, logistical, and ethical considerations pertaining to penile transplantation that must be addressed to maximize the likelihood of successful implementation.