Large-gap peripheral nerve repair using xenogeneic transplants in rhesus macaques.

Surgical intervention is required to successfully treat severe, large-gap (≥4 cm) peripheral nerve injuries. However, all existing treatments have shortcomings and an alternative to the use of autologous nerves is needed. Human and porcine nerves are physiologically similar, with comparable dimensions and architecture, presence and distribution of Schwann cells, and conserved features of the extracellular matrix (ECM). We report the repair of fully transected radial nerves in 10 Rhesus Macaques using viable, whole sciatic nerve from genetically engineered (GalT-KO), designated pathogen free (DPF) porcine donors. This resulted in the regeneration of the transected nerve, and importantly, recovery of wrist extension function, distal muscle reinnervation, and recovery of nerve conduction velocities and compound muscle action potentials similar to autologous controls. We also demonstrate the absence of immune rejection, systemic porcine cell migration, and detectable residual porcine material. Our preliminary findings support the safety and efficacy of viable porcine nerve transplants, suggest the interchangeable therapeutic use of cross-species cells, and highlight the broader clinical potential of xenotransplantation.

Immunological response in cynomolgus macaques to porcine α-1,3 galactosyltransferase knockout viable skin xenotransplants-A pre-clinical study.

BACKGROUND: Allogeneic skin recovered from human deceased donors (HDD) has been a mainstay interim treatment for severe burns, but unfortunately risk of infectious disease and availability limitations exist. Genetically engineered ɑ-1,3 galactosyltransferase knockout (GalT-KO) porcine source animals for viable skin xenotransplants may provide a promising clinical alternative. METHODS: Four cynomolgus macaque recipients received full-thickness surgical wounds to model the defects arising from excision of full-thickness burn injury and were treated with biologically active skin xenotransplants derived from GalT-KO, Designated Pathogen Free (DPF) miniature swine. Evaluations were conducted for safety, tolerability, and recipient immunological response. RESULTS: All skin xenotransplants demonstrated prolonged survival, vascularity, and persistent dermal adhesion until the study endpoint at post-operative day 30. No adverse outcomes were observed during the study. Varying levels of epidermolysis coincided with histologic detection of CD4+ and CD8+ T cells, and other cellular infiltrates in the epidermis. Recipient sera IgM and IgG demonstrated significant antibody immune response to non-α-1,3-galactose porcine xenoantigens. Separately, specific wound healing mediators were quantified. Neither porcine cell migration nor PERV were detected in circulation or any visceral organs. CONCLUSIONS: These results provide a detailed analysis of vital skin xenotransplants utilizing a non-human primate model to predict the anticipated immunological response of human patients. The lack of adverse rejection even in the presence of elevated Ig indicates this is a prospective therapeutic option. The findings reported here directly supported regulatory clearance for a first-in-man, Phase I xenotransplantation clinical trial.

Penis Transplantation: First US Experience.

OBJECTIVE: We describe the first successful penis transplant in the United States in a patient with a history of subtotal penectomy for penile cancer. BACKGROUND: Penis transplantation represents a new paradigm in restoring anatomic appearance, urine conduit, and sexual function after genitourinary tissue loss. To date, only 2 penis transplants have been performed worldwide. METHODS: After institutional review board approval, extensive medical, surgical, and radiological evaluations of the patient were performed. His candidacy was reviewed by a multidisciplinary team of surgeons, physicians, psychiatrists, social workers, and nurse coordinators. After appropriate donor identification and recipient induction with antithymocyte globulin, allograft procurement and recipient preparation took place concurrently. Anastomoses of the urethra, corpora, cavernosal and dorsal arteries, dorsal vein, and dorsal nerves were performed, and also inclusion of a donor skin pedicle as the composite allograft. Maintenance immunosuppression consisted of mycophenolate mofetil, tacrolimus, and methylprednisolone. RESULTS: Intraoperative, the allograft had excellent capillary refill and strong Doppler signals after revascularization. Operative reinterventions on postoperative days (PODs) 2 and 13 were required for hematoma evacuation and skin eschar debridement. At 3 weeks, no anastomotic leaks were detected on urethrogram, and the catheter was removed. Steroid resistant-rejection developed on POD 28 (Banff I), progressed by POD 32 (Banff III), and required a repeat course of methylprednisolone and antithymocyte globulin. At 7 months, the patient has recovered partial sensation of the penile shaft and has spontaneous penile tumescence. Our patient reports increased overall health satisfaction, dramatic improvement of self-image, and optimism for the future. CONCLUSIONS: We have shown that it is feasible to perform penile transplantation with excellent results. Furthermore, this experience demonstrates that penile transplantation can be successfully performed with conventional immunosuppression. We propose that our successful penile transplantation pilot experience represents a proof of concept for an evolution in reconstructive transplantation.

One-Stage Supramaximal Full-Thickness Wedge Resection of Vascular Lip Anomalies.

PURPOSE: Vascular lip anomalies include infantile hemangiomas, venous malformations, and arteriovenous malformations. Surgical management can be complicated by alterations in horizontal length, vertical height, and lip thickness from the underlying pathology. Additional reconstructive challenges include preservation of oral continence, vermillion definition, and the sublabial sulcus. This report describes a technique of supramaximal single-stage full-thickness wedge resection of these lesions. MATERIALS AND METHODS: A retrospective study approved by the institutional review board of patients who underwent full-thickness resection of vascular lip anomalies from December 2007 through February 2013 was performed. Patient demographics, final diagnosis, preoperative treatment, examination findings (pre- and postoperative), intraoperative management, and follow-up findings were reviewed. RESULTS: Eighteen patients (9 female) with a mean age of 25 ± 19.8 years (range, 3 to 70 yr) were identified. Underlying pathologies were arteriovenous malformation (6), port wine stain with secondary soft tissue hypertrophy (6), capillary malformation (1), venous malformation (3), and infantile hemangioma (2). Prior treatments included embolization, lasers, surgical excision, steroids, and propranolol; 8 patients were treatment naive. All patients underwent a single or double pentagonal-shaped wedge resection of the involved upper or lower lip. An average of 3.75 cm (41.7%; range, 20 to 70%) of horizontal lip length was excised. Four patients required additional concomitant debulking of the vermillion. No intraoperative complications were noted. Postoperatively, 1 patient developed wound dehiscence at 12 days and another had a midline depression with mild oral incontinence. Follow-up averaged 1,074 days (range, 371 to 1,777 days) and patients and their parents reported a high degree of satisfaction with the improvement in lip appearance and symmetry except for 1 patient who required further debulking. The sublabial sulcus and vermillion and cutaneous definition were preserved in all cases. CONCLUSION: Despite the traditional recommendation that no more than 30% of lip length be surgically removed, vascular lip anomalies result in tissue hypertrophy, horizontal elongation, ectropion labii, and tissue expansion that allow up to 70% of the lip to be excised.

SPLIT rectus abdominis myocutaneous double free flap for extremity reconstruction.

A Mathes and Nahai type III muscle, such as the rectus abdominis muscle, can be utilized to cover two separate wounds simultaneously utilizing its dual blood supply thereby minimizing donor site morbidity and operative time. We report a case for treatment of bilateral Gustillo type IIIB lower extremity injuries treated with a single rectus abdominis muscle split into two free flaps, with one based on the deep inferior epigastric vessels and one on the superior epigastric vessels to cover the contralateral wound. In our patient, both lower extremity wounds were covered with muscle flaps from the same donor site in a single operation, salvaging both limbs with progression to unassisted ambulatory status. We show in this case report that the utilization of the vascular anatomy of the rectus muscle allows for division of the flap into two flaps, permitting preservation of the contralateral abdominal wall integrity and coverage of two wounds with a single muscle.

Vital, Porcine, Gal-Knockout Skin Transplants Provide Efficacious Temporary Closure of Full-Thickness Wounds: Good Laboratory Practice-Compliant Studies in Nonhuman Primates.

Vital, genetically engineered porcine skin transplants have long been regarded as a promising treatment option for severe burn wounds. The objective of this two-part, preclinical study was to evaluate the ability of vital, split-thickness skin xenotransplants derived from designated pathogen-free, alpha 1,3 galactosyltransferase knockout miniature swine to provide temporary wound closure of full-thickness wound defects intended to model severe and extensive, deep partial- and full-thickness burn wounds. In part 1 of the study, four full-thickness wound defects were introduced in four cynomolgus macaques recipients and, then engrafted with two xenografts and two allografts to achieve temporary wound closure. On POD-15, autografts were used to achieve definitive wound closure and were observed until POD-22. In part 2 of the study, four additional subjects each received two full-thickness wound defects, followed by two xenografts to achieve temporary wound closure, and were observed postoperatively for 30 days without further intervention. All grafts were assessed for signs of adherence to the wound bed, vascularity, and signs of immune rejection via gross clinical and histological methods. Xenograft and allograft comparators were equivalent in part 1, and later autografts were otherwise indistinguishable. In part 2, all xenotransplants demonstrated adherence, vascularity, and survival until POD-30. These were unexpected results that exceed previously published findings in similar models. Furthermore, the ensuing GLP-study report directly supported regulatory clearance, permitting a phase I clinical trial. This solution holds great promise as an alternative to human cadaver allograft, the current standard of care for the treatment of severe burns.

Clinical Impact of Cryopreservation on Split Thickness Skin Grafts in the Porcine Model.

Vital, genetically engineered, porcine xenografts represent a promising alternative to human cadaveric allografts (HCA) in the treatment of severe burns. However, their clinical value would be significantly enhanced if preservation and long-term storage-without the loss of cellular viability-were feasible. The objective of this study was to examine the direct impact of cryopreservation and the length of storage on critical in vivo and in vitro parameters, necessary for a successful, potentially equivalent substitute to HCA. In this study, vital, porcine skin grafts, continuously cryopreserved for more than 7 years were compared side-by-side to otherwise identically prepared skin grafts stored for only 15 minutes. Two major histocompatibility complex (MHC)-controlled donor-recipient pairs received surgically created deep-partial wounds and subsequent grafting with split-thickness porcine skin grafts, differentiated only by the duration of storage. Clinical and histological outcomes, as well as quantification of cellular viability via a series of 3-4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) assays, were assessed. No statistically significant differences were observed between skin grafts cryopreserved for 15 minutes vs 7 years. Parametric distinctions between xenografts stored for short- vs long-term durations could not be ascertained across independent clinical, histological, or in vitro evaluative methods. The results of this study validate the ability to reliably preserve, store, and retain the essential metabolic activity of porcine tissues after cryopreservation. Plentiful, safe, and readily accessible inventories of vital xenografts represent an advantageous solution to numerous limitations associated with HCA, in the treatment of severe burns.

A Comparative Examination of the Clinical Outcome and Histological Appearance of Cryopreserved and Fresh Split-Thickness Skin Grafts.

The clinical use of frozen, human allogeneic skin grafts is considered a suitable alternative to freshly harvested allogeneic skin grafts when the latter are not available. However, limited functional and histological information exists regarding the effects of cryopreservation on allogeneic skin grafts, especially those across mismatched histocompatibility barriers. Thus, we performed a side-by-side comparative study of fresh vs frozen skin grafts, across both minor and major histocompatibility barriers, in a miniature swine model. Since porcine skin shares many physical and immunological properties with human skin, our findings have relevance to current clinical practices involving allogeneic grafting and may support future, temporary wound therapies involving frozen xenografts, comprised genetically modified porcine skin. Four miniature swine underwent harvest and grafting of split-thickness skin, with and without cryopreservation, in order to observe autologous grafts and grafts across minor and major histocompatibility barriers. A biopsy of the grafts was done at regular intervals for study of architecture, vascularization, and outcomes. All grafts vascularized without technical complications. Differences were noted in the early appearance of some fresh vs frozen grafts, but no significant difference was observed in overall survival times in any of the experimental groups. These results demonstrate that despite early observable differences in the healing process, cryopreservation and thawing does not significantly affect long-term graft survival or time to rejection, thus supporting the clinical and experimental use of fresh and frozen split-thickness skin grafts as comparable and interchangeable.

External fixator kickstands for free soft tissue flap protection: case series and description of technique.

BACKGROUND: Protected elevation represents a critical component of postoperative care, particularly in posteriorly located flaps, to prevent pressure on the flap's vascular pedicle and ensure a successful skin graft. Although several short case series and technique papers have described kickstand placement to prevent heel ulcers as an adjuvant to fixator placement for fracture management, there remains a paucity of reports describing external fixator placement solely for extremity elevation and pressure alleviation in the postoperative care of flap coverage procedures. METHODS: Patients who underwent lower extremity free flap coverage procedures requiring temporary elevation were included. Age, diagnosis, soft tissue procedures performed, type of external fixator placed, duration of frame placement, mode of removal, and complications related to external fixator placement were documented. Patients requiring external fixator placement for fracture management were excluded. RESULTS: Twelve patients with 13 lower limb soft tissue defects were included in our case series. A thin-wire ring external fixator kickstand was applied in 5 limbs while the rest underwent placement of a uniplanar carbon fiber bar type external fixator kickstands. The average time for removal of the frames was 4 weeks. No complications were reported from kickstand placement. CONCLUSION: The use of external fixator kickstands is an effective and safe adjuvant to soft tissue flap procedures for the lower extremity. Our case series is the largest in the literature and first to address the technical considerations for frame placement, positioning, and removal for external fixator kickstands placed solely for flap coverage procedures. LEVEL OF EVIDENCE: Level IV, retrospective case series.