Experimental allogenic penile transplantation

Experimental Models in Penile Transplantation: Translational Insights and Relevance to Clinical Application

Animal research is an essential contributor to the medical achievements of the last century. The first step of studying a disease in animals is the development of a model which is relevant to the clinical situation in humans. Thus, a good animal model is the sine qua non of the experimental research. This review aims to assess the contemporary literature on animal models for penile transplantation, examining their applicability and significance in the context of clinical scenarios. We also revisit, evaluate, and emphasize the interesting and important findings of certain animal models to bring the reader up to date from the perspective of allotransplantation. Their current and future clinical applicability and feasibility have been discussed, shedding light on worldwide experience in Vascularized Composite Allotransplantation (VCA).

Penile Microdissection: A Live Donor Feasibility Study in Feminizing Gender-Affirming Surgery

Femininizing gender affirmation surgery includes the creation of external female genitalia such as a new clitoris, labia, and vagina with removal of the glans and urethral remnants and full corpora cavernosa. We evaluated the possibility of using preserved cavernosal bodies with glans and urethral remnants for potential live-donor penile transplantation. Between March 2021 and February 2023, penile microvascular dissection followed by gender-affirming vaginoplasty was performed in 41 patients aged 18 to 57 years (mean 30.5 years). The mean follow-up was 15 months (ranging from 6 to 26 months). The removed penile entities were properly measured. The corpora cavernosa were completely preserved in all cases; the length of remaining anterior urethra ranged from 12.70 cm to 16.40 cm, while the mean glans remnant volume was 85.37% of the total volume. All patients reported satisfactory results after gender-affirming vaginoplasty. Microvascular penile dissection in gender-affirming vaginoplasty is simple and safe, suggesting a good possibility of using the full corpora cavernosa, glans, and anterior urethra remnants for live-donor penile transplantation.

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.

Vascularized composite allotransplantation of the penis: current status and future perspectives

Given the multifunctional role of the penis in daily life, penile loss can be a physically and emotionally devastating injury. Options to restore penile loss have traditionally relied on autogenous free flap, local flaps, and skin grafts. These techniques provide satisfactory outcomes but carry high rates of urologic and prosthesis-related complications. Vascularized composite allotransplantation may offer a novel solution for these patients through reconstruction with true penile tissue. Still, penile transplants pose ethical, logistical, and psychosocial challenges. These obstacles are made more complex by the limited cases detailed in published literature. A review of the literature was conducted to assay current practices for penile reconstruction. Most modern complex penile reconstructions utilize autogenous pedicled or free tissue flaps, which may be harvested from a variety of donor sites. A total of five penile transplants have been described in the literature. Of these, four report satisfactory outcomes. The advent of genital allotransplantation has recently broadened the landscape of treatment for penile loss. Reconstruction using true penile tissue through vascularized penile allotransplantation has the possibility to engender increased penile function, sensation, and overall quality of life.

A novel rat microsurgical model to study the immunological characteristics of male genital tissue in the context of penile transplantation

Penis transplantation represents an exciting new avenue for restoration of male genitalia and function after devastating tissue loss. This animal model is designed to fill a critical void to study immunologic aspects related to reconstructive transplantation of male genitalia. A rat penile graft dissection was designed based on the internal pudendal arteries and dorsal penile vein and includes the skin of the prepuce. A nonsuture cuff technique was used to anastomose the graft vessels to the recipient superficial epigastric and femoral vessels. Seventy-seven penile transplantations were performed. Graft design yields suitable caliber and length of vessels at the radix of the penis. Anastomosis of the dorsal penile vein and the internal pudendal arteries insures optimal graft perfusion. The nonsuture cuff technique allows for successful microvascular anastomosis by a single surgeon with an average overall operative time of 2.5 h. Long-term graft survival (>30 days) was observed in syngeneic transplants. We have established a robust murine model with ideal vascular perfusion of penile tissue to study the unique immunobiology of male genitourinary allotransplantation. Heterotopic inset further allows for visual monitoring of graft viability, while the native penis serves as an optimal control.

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.

Ushering in the era of penile transplantation

Penile transplantation is a novel approach to management of penile loss in the developing field of composite tissue allotransplantation (CTA). Prior management for significant penile loss has been free flap phalloplasty with issues related to function, cosmesis, and functional loss from the location of flap harvest. Transplantation has been an evolving field with advancement in CTA over the past several decades leading to the option of penile transplant. Management of penile injury with replantation provided some preliminary groundwork on the technical aspects for penile transplantation. Additionally, penile transplantation raises many ethical, emotional, and psychological considerations with need for patience amidst ongoing advancement within the field.

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.

Penis Allotransplantation in Beagle Dog

This is an original research of penis allotransplantation. The paper presents an experiment allogenic penis transplantation model in Beagles, with a focus on recovery of blood supply and changes in tissue architecture. Twenty adult Beagles were allocated to 10 pairs for penile transplantation. After operation, the skin and glans were observed. If adverse symptoms occurred, the transplanted penis was resected and pathologically examined. Frequency of urination, urinary stream, and patency level were recorded 7 days after transplantation. Cystourethrography was performed on Day 10. The transplanted penises were resected on Day 14 for pathological examination. The research showed that transplanted penises survived after allotransplantation, and the dogs regained urination ability. Penis autotransplantation in Beagles is feasible. This preliminary study shows a potential for application of this new procedure for penis transplantation in humans.

A Review of Transplantation Practice of the Urologic Organs: Is It Only Achievable for the Kidney?

Transplantation is a viable treatment option for failure of most major organs. Within urology, transplantation of the kidney and ureter are well documented; however, evidence supporting transplantation of other urologic organs is limited. Failure of these organs carries significant morbidity, and transplantation may have a role in management. This article reviews the knowledge, research, and literature surrounding transplantation of each of the urologic organs. Transplantation of the penis, testicle, urethra, vas deferens, and bladder is discussed. Transplantation attempts have been made individually with each of these organs. Penile transplantation has only been performed once in a human. Testicular transplantation research was intertwined with unethical lucrative pursuits. Interest in urethra, bladder, and vas deferens transplantation has decreased as a result of successful surgical reconstructive techniques. Despite years of effort, transplantations of the penis, testicle, urethra, vas deferens, and bladder are not established in current practice. Recent research has shifted toward techniques of reconstruction, tissue engineering, and regenerative medicine.

Penile autotransplantation in rats: An animal model

CONTEXT

Penile allotransplantation might be a viable option for patients who need penile reconstruction.

AIMS

A successful autotransplantation rat model is the first step toward proceeding for allotransplantation. We herein evaluate autotransplantation following transaction of the rat penis just distal to the urethral bulb.

SETTINGS AND DESIGN

Experimental animal study.

MATERIALS AND METHODS

Five Sprague-Dawely rats weighing 520 g (SD 19) were used. Utilizing a magnification of 6-40, transection and immediate anastomosis of the tunica albuginea, urethra, dorsal vein and nerves were carried out. Vesicostomy was made to divert urine. The glandular skin was sutured to the perineum and the abdominal wall was closed in layers.

STATISTICAL ANALYSIS USED

Descriptive statistics.

RESULTS

Average surgery time was 8 h. The first two rats had no vesicostomy and died in the first postoperative day from retention. Three rats tolerated well the procedure and survived to the end point. One rat was sacrificed at day 10 and histopathology showed 30-50% necrosis of the implanted penis. Another rat was sacrificed at day 20 and showed normal cavernous tissue. The fifth rat was sacrificed 3 months postoperatively and showed evidence of moderate corporal fibrosis. Urethral fistula and necrosis of corpus spongiosum, dorsal nerve necrosis and dorsal vein occurred in all animals.

CONCLUSIONS

Penile autotransplantation in rats is feasible and provides the basis for evaluation of the corpora cavernosa in an allotransplantation model. Long-term urethral continuity and dorsal neurovascular bundle survival in this model is difficult to establish.

Ethical issues in penile transplantation

This article provides an overview of the ethical issues associated with penile transplantation, a form of composite tissue allografting. There is only one reported case of human penile transplantation, and, as such, this technique is considered to be experimental. The ethical issues at stake involve both the graft donor and the graft recipient. With regard to the recipient, there are significant concerns relating to surgical risks and benefits, informed consent, body image (including surgical expectations and outcomes) and compliance. Donor issues may include family consent and privacy, as well as graft harvesting (leaving the donor cadaver without a penis). Many of these ethical issues can be explored during the recipient's assessment and consent process. Because no medium-term or long-term outcome data for this procedure exist-only one such operation has ever been performed-the burdens and ethical issues concerning penile transplantation remain unknown.

Rat Penis as a Replantation Model

The aim of this study is to assess the feasibility of rat penile replantation as a new microsurgical training model. The study was performed in 2 parts. ANATOMIC STUDIES: Fifteen Wistar albino rats were used to study and document the penile vascular anatomy. In 5 rats, dissections were performed after colored silicone injections, while 5 rats were operated under anesthesia to develop the strategy of flap elevation. In the remaining 5 rats, microangiographic study was performed with silicone-lead oxide mixture. FLAP STUDIES: As flap studies in 5 rats, penis were elevated based on right-side internal pudendal artery and internal pudendal vein and resutured. In 6 rats, penis were elevated as free flaps, and in 3 rats the penis were implanted in right thigh of the rats being the femoral artery and vein recipient. In the remaining 3 rats, penis were resutured in their original place, with saphenous artery and vein being the recipient and rerouted to the pubic region. At postoperative fifth day, the penis were examined for viability, and selected ones were histologically examined. Rat penis has a dual blood supply from bilateral internal pudendal arteries. Venous drainage is via both crural veins and dorsal vein. One side of the internal pudendal artery and anastomotic vein (branch of pudendal plexus) may be used as the vascular pedicle of the flap. Rat penis may be successfully elevated as a free flap and also may be replanted in its original place.