Advances in the development of experimental composite tissue transplantation models

Composite tissue xenopreservation: Preliminary results of staged VCA in rat to mouse model

BACKGROUND

The time between procurement and transplantation of composite tissues, especially regarding the limited donor pool, is a challenge effecting the outcomes of the transplantation. Current preservation techniques mainly include either cold preservation with a solution or machine perfusion using blood or certain oxygen-carrying solutions. However, none enables preservation beyond 24 h. Increasing this time to several days will provide better usage of the donor pool, safer transplantation of VCA with significant muscle content, and gives time to stabilize a patient before long surgical procedures. Herein, we described a novel strategy of xenopreservation (preservation via xenotransplantation) to preserve composite tissues for 7 days, followed by staged transplantation.

MATERIALS AND METHODS

We used two concordant species, female Sprague Dawley rats (n = 10) and female CF-1 mice (n = 10) in this study. Four of pair of animals are used for anatomical study. The groin flap of the rat was used as a xenograft and xenotransplanted to the neck area of the carrier mouse. Cyclosporine (CsA) was administered used as immunosuppressant. After 7 days of preservation on the mouse neck, xenotransplanted groin flap (called xenopreserved flap) was re-harvested, skin and vessels samples were collected for histopathological evaluation, and the xenopreserved flap was transplanted to the donor rat's opposite groin area. Anastomoses were performed between the flap's pedicle and the femoral vessels. Clinical observation regarding inflammation and tissue perfusion of the xenopreserved flap was monitored daily. Fifteen days after the second surgical procedure, the rats were euthanized, and skin and vessel samples were collected. Histologic evaluation, including inflammatory cell numbers, was performed. Wilcoxon test was used to compare the changes in inflammation severity and p < .05 was set for statistical significance.

RESULTS

All xenopreserved groin flaps except one survived. Mean lymphocyte count before the second operation (at the end of the xenopreservation procedure) was 20,22 ± 0.44 and reduced to 13,14 ± 0.47 at the end of 15 days, and the difference was statistically significant (p < .05).

CONCLUSION

This proof-of-concept study with preliminary results showed that xenotransplantation might be a novel strategy for preservation of VCA for a certain period of time. However, additional translational studies are needed to modulate the tissue changes following xenopreservation.

Reciprocal Donor-Recipient Strain Combinations Present Different Vascularized Composite Allotransplantation Outcomes in Rodent Models

BACKGROUND

Although vascularized composite allotransplantation (VCA) has been the focus of many animal studies, further research is needed to determine the potential for a generalized model and immunosuppression regimen that applies across different donor-recipient combinations. In this study, the authors evaluated the outcome of VCAs performed on reciprocal rodent donor-recipient combinations.

METHODS

VCA was performed in rats using Lewis and Brown Norway (BN) donor-recipient pairs, under the previously reported antilymphocyte serum/cyclosporine/adipose-derived stem cell regimen. Similarly, a published co-stimulatory blockade/rapamycin regimen was performed on the mouse VCA model between Balb/C and C57BL/6 strains.

RESULTS

To accommodate the active behaviors of BN recipients, the allograft had to be modified and inset to the neck instead of to the groin. The tolerogenic regimen did not provide the same benefits for BN rats as it did for Lewis recipients. Increasing antilymphocyte serum dose and extending the duration of cyclosporine administration from 10 to 21 days significantly prolonged allograft survival and induced donor-specific tolerance. In mice, the co-stimulatory blockade/rapamycin regimen produced inferior VCA outcomes in BALB/c recipients than in C57BL/6 recipients. In both rats and mice, the authors identified an association between the tolerance outcome and the peripheral chimerism measured on postoperative day 30.

CONCLUSIONS

Reciprocal donor-recipient combinations led to different responses toward the immunosuppression regimen and varied VCA outcomes. Sustained donor chimerism that remained in circulation for 1 month after surgery supported long-term VCA survival. Modification of the model and immunosuppression regimen accordingly is recommended.

CLINICAL RELEVANCE STATEMENT

Various donor-recipient combinations respond differently to the immunosuppression regimens. Maintaining donor chimerism for 30 days after surgery improves VCA survival. It is recommended to tailor the immunosuppression regimen based on the recipient's background to optimize outcomes.

The Positive Impact of Donor Bone Marrow Cells Transplantation into Immunoprivileged Compartments on the Survival of Vascularized Skin Allografts

Using the vascularized skin allograft (VSA) model, we compared the tolerogenic effects of different allogeneic bone marrow transplantation (BMT) delivery routes into immunoprivileged compartments under a 7-day protocol immunosuppressive therapy. Twenty-eight fully MHC mismatched VSA transplants were performed between ACI (RT1^a) donors and Lewis (RT1¹) recipients in four groups of seven animals each, under a 7-day protocol of alfa/beta TCRmAb/CsA (alpha/beta-TCR monoclonal antibodies/Cyclosporine A therapy). Donor bone marrow cells (BMC) (100 × 106 cells) were injected into three different immunoprivileged compartments: Group 1: Control, without cellular supportive therapy, Group 2: Intracapsular BMT, Group 3: Intragonadal BMT, Group 4: Intrathecal BMT. In Group 2, BMC were transplanted under the kidney capsule. In Group 3, BMC were transplanted into the right testis between tunica albuginea and seminiferous tubules, and in Group 4, cells were injected intrathecally. The assessment included: skin evaluation for signs and grade of rejection and immunohistochemistry for donor cells engraftment into host lymphoid compartments. Donor-specific chimerism for MHC class I (RT1^a) antigens and the presence of CD4⁺/CD25⁺ T cells were assessed in the peripheral blood of recipients. The most extended allograft survival, 50–78 days, was observed in Group 4 after intrathecal BMT. The T cells CD4⁺/CD25⁺ in the peripheral blood were higher after intrathecal BMC injection than other experimental groups at each post-transplant time point. Transplantation of BMC into immunoprivileged compartments delayed rejection of fully mismatched VSA and induction of robust, donor-specific chimerism.

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 past the present and the future of face transplantation

PURPOSE OF REVIEW

Face transplantation represents vascularized composite allotransplantation (VCA) organ and became one of the most rewarding reconstructive options for severely disfigured patients. This review summarizes the past, current and future challenges of face transplantation, based on our experience and literature reports.

RECENT FINDINGS

In 2005, first partial face transplantation was reported by French team. In 2008, we have performed the US first near-total face transplantation. Currently, more than 40 face transplant cases were reported worldwide. Based on the outcomes of our three patients and the literature reports, face transplantation improved aesthetics, function and the quality of life of face transplant patients. However, there are still many challenges encountered including the side effects of immunosuppressive protocols, the psychological and social problems as well as the financial challenges which need to be address in the near future to maintain face transplantation in the armamentarium of reconstructive surgery.

SUMMARY

Currently, feasibility of face transplantation was confirmed; however, the life-long immunosuppressive protocols bearing serious side effects are still required to prevent face rejection. Thus, for the future of face and other VCA, novel approaches of cell-based therapies or engineered scaffolds should be developed to make face transplantation safer.

Heterotopic Transplantation of Allogeneic Vertical Rectus Abdominis Myocutaneous Flaps in Miniature Swine

BACKGROUND

Vascularized composite tissue allotransplantation (VCA) opens new possibilities for reconstruction of complex tissue defects, including upper extremity and facial transplantation. The main challenges in VCA transplantation are the side effects of long-term immunosuppression and chronic graft rejection. Translational preclinical animal models are crucial for VCA research to improve clinical outcomes and to study underlying immunologic mechanisms. Herein, we describe a novel, large animal, non-bone-bearing VCA model in inbred, swine leukocyte antigen-typed miniature swine.

METHODS

Transplantation of vertical rectus abdominis myocutaneous (VRAM) flaps was performed between fully swine leukocyte antigen-mismatched miniature swine. The flaps were transferred to the posterolateral aspect of the neck of recipients and anastomosed to the common carotid artery and internal jugular vein. Different immunosuppressive drug regimens were used. Clinical graft evaluation was performed daily, and punch biopsies were taken for histology.

RESULTS

Ten VRAM transplants were performed. The mean ischemia time was 89.4 min (SD ± 47), mean pedicle length 7.5 cm (SD ± 2), mean venous diameter 2.5 mm (SD ± 0.4), and mean arterial diameter 2.2 mm (SD ± 0.3). Follow-up demonstrated good correlation between clinical appearance and progression of graft rejection confirmed by histologic assessment. Complications were intraoperative cardiac arrest in one recipient and one flap loss due to venous compromise.

CONCLUSIONS

VRAM transplantation in miniature swine is an appropriate preclinical VCA model, with the advantage of good clinical and histologic correlation during the course of rejection, as well as easy access to the graft. The availability of inbred, haplotyped animals allows studies across different major histocompatibility complex barriers in a non-bone-bearing VCA.

Validation of Animal Models for Facial Transplantation Research

BACKGROUND

The development of consistent animal experimental models is important for continued research on specific biological and immunologic aspects of vascularized composite allografts. It is also important for the translation of immune regulation and tolerance induction strategies and treatment ideas from bench to bedside. The purpose of our study is to provide an outline of the use of animal models in simulated facial transplant surgery and to investigate the feasibility of animal model use.

METHODS

The animals underwent hemifacial flap transplant surgery. The flaps were placed on the external carotid artery and external jugular vein of the donor animal. Twenty-one procedures were performed in 4 different animals (6 rats, 5 rabbits, 6 dogs, 4 pigs). Two experienced plastic surgeons and 5 students performed allotransplant.

RESULTS

All 4 models were suitable for facial allotransplant with different anatomic characteristics. Average feasibility scores were 4.8 for pigs, 3.6 for rabbits, 3.2 for dogs, and 3.4 for rats. Evaluations concluded that pigs were the most practical and realistic models for facial allotransplant training. Other models achieved validation thresholds.

CONCLUSIONS

This study is the first comparative validation assessment of animal models used in facial allotransplant. It supports the use of pig models for surgical skills training. Pigs were the preferred simulation models, while rats, rabbits, and dogs were considered inferior models for transplant simulation.

Neo-Angiogenesis, Transplant Viability, and Molecular Analyses of Vascularized Bone Allotransplantation Surgery in a Large Animal Model

Vascularized composite allotransplantation of bone is a possible alternative treatment for large osseous defects but requires life-long immunosuppression. Surgical induction of autogenous neo-angiogenic circulation maintains transplant viability without this requirement, providing encouraging results in small animal models [1-3]. A preliminary feasibility study in a swine tibia model demonstrated similar findings [4, 5]. This study in swine tibial allotransplantation tests its applicability in a pre-clinical large animal model. Previously, we have demonstrated bone vascularized composite allotransplantation (VCA) survival was not the result of induction of tolerance nor an incompetent immune system [1]. Fourteen tibia vascularized bone allotransplants were microsurgically transplanted orthotopically to reconstruct size-matched tibial defects in Yucatan miniature swine. Two weeks of immunosuppression was used to maintain allotransplant pedicle patency during angiogenesis from a simultaneously implanted autogenous arteriovenous bundle. The implanted arteriovenous bundle was patent in group 1 and ligated in group 2 (a neo-angiogenesis control). At twenty weeks, we quantified the neo-angiogenesis and correlated it with transplant viability, bone remodeling, and gene expression. All patent arteriovenous bundles maintained patency throughout the survival period. Micro-angiographic, osteocyte cell count and bone remodeling parameters were significantly higher than controls due to the formation of a neo-angiogenic autogenous circulation. Analysis of gene expression found maintained osteoblastic and osteoclastic activity as well as a significant increase in expression of endothelial growth factor-like 6 (EGFL-6) in the patent arteriovenous bundle group. Vascularized composite allotransplants of swine tibia maintained viability and actively remodeled over 20 weeks when short-term immunosuppression is combined with simultaneous autogenous neo-angiogenesis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:288-296, 2020.

The miracle of face transplantation after 10 years

INTRODUCTION

At the 10th year anniversary of the first face transplantation, there are currently 36 patients worldwide, who are the recipients of faces coming from human donors.

AREAS OF AGREEMENT

Despite the initial debates and ethical concerns, face transplantation became a clinical reality with satisfactory functional outcomes.

AREAS OF CONTROVERSY

The areas of controversy still include the impact of lifelong immunosuppression on otherwise healthy patients as well as the selection process of face transplant candidates.

GROWING POINTS

Other concerns include financial support for this new generation of transplants as well as social reintegration and patients return to work after face transplantation.

AREAS TIMELY FOR DEVELOPING RESEARCH

Based on over 20 years of research experience in the field of vascularized composite allotransplantation, and clinical experience as a leading surgeon of the US first face transplantation, this review will summarize the well-known facts as well as unexpected outcomes and challenges of face transplantation.

Experimental Forelimb Allotransplantation in Canine Model

As reconstructive transplantation is gaining popularity as a viable alternative for upper limb amputees, it is becoming increasingly important for plastic surgeons to renew surgical skills and knowledge of this area. Forelimb allotransplantation research has been performed previously in rodent and swine models. However, preclinical canine forelimb allotransplantation studies are lacking in the literature. The purpose of this paper is to provide an overview of the surgical skills necessary to successfully perform forelimb transplantation in canines as a means to prepare for clinical application. A total of 18 transplantation operations on canines were performed. The recipient limb was shortened at the one-third proximal forearm level. The operation was performed in the following order: bones (two reconstructive plates), muscles and tendons (separately sutured), nerves (median, ulnar, and radial nerve), arteries (two), and veins (two). The total mean time of transplantation was 5 hours ± 30 minutes. All of the animals that received transplantation were treated with FK-506 (tacrolimus, 2 mg/kg) for 7 days after surgery. Most allografts survived with perfect viability without vascular problems during the early postoperative period. The canine forelimb allotransplantation model is well qualified to be a suitable training model for standard transplantation and future research work.

Vascularized composite allotransplantation: a new concept in musculoskeletal regeneration

Over the past 20 years, the fields of biomaterial sciences and tissue engineering have evolved into new clinically relevant applications including regenerative medicine and cell based therapies. Tissue engineering therapies are based on different types of materials and scaffolds combined with cells and submitted to engineering processes in order to create bio-scaffolds which will improve or replace biological functions. Despite the effort, only a few therapies, such as bone, cartilage and nerve, succeeded in clinical applications. Furthermore, the major drawback in standard application of these therapies was the critical size defects which could be covered with engineered materials, as well as inability to provide sustainable vascular supply to the created bio-scaffolds. In 1998, the first successful hand transplantation was performed in France, and the field of vascularized composite allotransplantation (VCA) was introduced into the armamentarium of reconstructive surgery (Dubernard in Am J Transplant 5(6):1580-1, 2005; Petruzzo et al. in Am J Transplant 6(7):1718-24, 2006; Lanzetta et al. in Transplantation 79(9):1210-4, 2005). As a result, a new generation of transplants including hand, face, larynx abdominal wall, lower extremities and penile transplantation became available to patients who had lost these unique organs and were previously unable to achieve restored function using standard reconstructive procedures. Ethical debate on the need for life-long immunosuppressive therapy to prevent rejection of the VCA overshadowed the success of face and hand transplants. Thus, a new, challenging opportunity developed to combine approaches of tissue engineering and regenerative medicine and ultimately restore the framework, function, aesthetics and survival of the VSA transplants. This overview presents the unique opportunities of merging established and new technologies into the burgeoning field of reconstructive transplantation.

A vascularized elbow allotransplantation model in the rat

BACKGROUND

The aim of this research was to develop a rat model for vascularized composite allotransplantation (VCA) of the elbow.

METHODS

We developed an animal model for VCA of the elbow in rats. Microvascular VCA was performed in 9 rats across a major histocompatibility barrier. Three different immunosuppressive regimens were provided. Joint mobility and weight-bearing capability were assessed throughout 90 days of life. Pedicle patency, bone blood flow, and histologic analyses were performed.

RESULTS

In the cyclosporine group, forelimb activity was recovered during the postoperative 90 days. The extremity that was operated on was used in daily activities. There was minimal motion or use of the limb in the cyclosporine taper and control groups. The vascular pedicles were patent at the time of death in the cyclosporine-treated group but not in the remaining groups. Micro-computed tomography scan performed 3 months after transplantation revealed union at the bone junctions, and the elbow joint appeared grossly normal on death in the cyclosporine treatment group only. Incomplete healing was observed in the other 2 groups, and the elbow joints were grossly destroyed. Histologic examination revealed normal cartilage and bone cells in the cyclosporine-treated group, whereas the nontreated groups demonstrated lymphocytic infiltration and loss of normal histologic features. Flow cytometry of blood samples obtained on days 14, 30, 60, and 90 showed no recipient cell chimerism in any of the groups.

CONCLUSIONS

We developed an animal model for elbow VCA. Immunosuppressed animals regained nearly normal function of forelimbs and maintained grossly normal elbow cartilage. Without cyclosporine treatment, the elbow transplants were rejected.

The unique immunobiology of the skin: implications for tolerance of vascularized composite allografts

PURPOSE OF REVIEW

Vascularized composite allograft (VCA) transplantation restores function and form following major soft tissue and musculoskeletal injury. Lifelong immunosuppression is necessary for graft function and survival but acute skin-targeted rejection episodes remain common. We review recent advances in skin immunobiology, emphasizing findings in clinical and experimental VCAs. We also highlight advances in immunotherapy and tolerance protocols with implications for the prevention of VCA rejection, and ultimately, induction of clinically applicable strategies for VCA tolerance.

RECENT FINDINGS

There is now an increasing appreciation for the role of skin-specific mechanisms, including lymphoid neogenesis, in VCA rejection. In contrast, expression of the regulatory master-switch FOXP3 was demonstrated to be significantly upregulated in the skin of tolerant VCAs in large animal models compared with normal skin and rejecting controls.

SUMMARY

Most VCA transplant centers continue to utilize antibody-mediated induction therapy and triple agent maintenance immunosuppression. Skin remains the primary target of rejection in VCAs, and current multicenter studies hope to elucidate the mechanisms involved. Proposed standardized procedures for skin biopsies, and diligent reporting of clinical data to the international registry, will be important to maximize the strength of these studies.

Impact of reconstructive transplantation on the future of plastic and reconstructive surgery

This article summarizes the current knowledge on the new developing field of reconstructive transplantation. A brief outline of vascularized composite allografts (VCA) such as human hand, face, larynx, and abdominal wall transplants is provided. The clinical applications and indications for these new reconstructive transplantation procedures are outlined. The advantages, disadvantages, and complications and concerns surrounding clinical VCA are discussed. Finally, the impact of reconstructive transplantation on the future of plastic and reconstructive surgery is presented.

Chimerism-based experimental models for tolerance induction in vascularized composite allografts: Cleveland clinic research experience

The preclinical experimental models of vascularized composite allografts (VCAs) have been rapidly developed for the assessment of immunomodulatory protocols for clinical application. Recently, researchers have focused on immunomodulatory protocols which overcome the immunologic barrier between the allogeneic donor and recipient and may lead to tolerance induction. In order to test the feasibility of chimerism induction, experimental VCAs have been performed in different models including rodents, large animals, and nonhuman primates. These models differ in the complexity of transplanted tissue and in their responses to immunomodulatory protocols. In most applications, VCA contains multiple-tissue components; however, each individual component of CTA possesses unique immunologic characteristics that ultimately contribute to the chimerism induction and successful outcome of the VCA. Heterogenic character and complexity of tissue components in different VCA models determine the quality and robustness of donor-specific chimerism. As introduced in experimental studies, variable immunomodulatory options have been studied to achieve tolerance to VCA in rodents and large animal models allowing for widespread application in clinic. In this paper, based on our own experience, we have analyzed the current knowledge of tolerance-inducing strategies via chimerism induction in VCA experimental models in the context of immunomodulatory protocols and VCA complexity and their relevance and applicability to clinical practice.

Tolerance induction strategies in vascularized composite allotransplantation: mixed chimerism and novel developments

Since the start of the clinical vascularized composite allotransplantation (VCA) era over a decade ago this field has witnessed significant developments in both basic and translational research. Transplant tolerance, defined as rejection-free acceptance of transplanted organs or tissues without long-term immunosuppression, holds the potential to revolutionize the field of VCA by removing the need for life-long immunosuppression. While tolerance of organ and vascularized composite transplants may be induced in small animal models by a variety of protocols, only mixed-chimerism-based protocols have successfully bridged the gap to preclinical study and to clinical trial in solid organ transplantation to date. In this paper we review the mixed-chimerism approach to tolerance induction, with specific reference to the field of VCA transplantation, and provide an overview of some novel cellular therapies as potential adjuvants to mixed chimerism in the development of tolerance induction protocols for clinical vascularized composite allotransplantation.

The need for inducing tolerance in vascularized composite allotransplantation

Successful hand and face transplantation in the last decade has firmly established the field of vascularized composite allotransplantation (VCA). The experience in VCA has thus far been very similar to solid organ transplantation in terms of the morbidity associated with long-term immunosuppression. The unique immunological features of VCA such as split tolerance and resistance to chronic rejection are being investigated. Simultaneously there has been laboratory work studying tolerogenic protocols in animal VCA models. In order to optimize VCA outcomes, translational studies are needed to develop less toxic immunosuppression and possibly achieve donor-specific tolerance. This article reviews the immunology, animal models, mixed chimerism & tolerance induction in VCA and the direction of future research to enable better understanding and wider application of VCA.

Animal models for basic and translational research in reconstructive transplantation

Reconstructive transplantation represents a bona fide option for select patients with devastating tissue loss, which could better restore the appearance, anatomy, and function than any other conventional treatment currently available. Despite favorable outcomes, broad clinical application of reconstructive transplantation is limited by the potential side effects of chronic multidrug immunosuppression. Thus, any reconstructive measures to improve these non-life-threatening conditions must address a delicate balance of risks and benefits. Today, several exciting novel therapeutic strategies, such as the implementation of cellular therapies including bone marrow or stem cells that integrate the concepts of immune regulation with those of nerve regeneration, are on the horizon. The development of reliable and reproducible small and large animal models is essential for the study of the unique immunological and biological aspects of vascularized composite allografts and to translate such novel immunoregulatory and tolerance-inducing strategies and therapeutic concepts from the bench to bedside. This review provides an overview of the multitude of small and large animal models that have been particularly designed for basic and translational research related to reconstructive transplantation.

The gracilis myocutaneous free flap in swine: an advantageous preclinical model for vascularized composite allograft transplantation research

Vascularized composite allotransplantation (VCA) has become a clinical reality, prompting research aimed at improving the risk-benefit ratio of such transplants. Here, we report our experience with a gracilis myocutaneous free flap in Massachusetts General Hospital miniature swine as a preclinical VCA model. Fourteen animals underwent free transfer of a gracilis myocutaneous flap comprised of the gracilis muscle and overlying skin, each tissue supplied by independent branches of the femoral vessels. End-to-end anastomoses were performed to the common carotid artery and internal jugular vein, or to the femoral vessels of the recipients. Thirteen of fourteen flaps were successful. A single flap was lost due to compromise of venous outflow. This model allows transplantation of a substantial volume of skin, subcutaneous tissue, and muscle. The anatomy is reliable and easily identified and harvest incurs minimal donor morbidity. We find this gracilis myocutaneous flap an excellent pre-clinical model for the study of vascularized composite allotransplantation.

Microvascular porcine model for the optimization of vascularized composite tissue transplantation

BACKGROUND

Devastating extremity injuries are prevalent but most often survivable on the modern battlefield. The complexity of these injuries requires advanced methods of reconstruction. This study is designed to validate the feasibility of gracilis myocutaneous flap transplantation via microvascular free tissue transfer in a porcine model. This model will facilitate study of autotransplant physiology as well as vascularized composite allotransplantation as an evolving method for reconstructing previously nonreconstructable injuries.

MATERIAL AND METHODS

A donor gracilis myocutaneous flap is procured from Yorkshire swine. The right external carotid artery and internal jugular vein are prepared as the recipient axis for microvascular anastomoses. Group 1 undergoes immediate microvascular anastomosis with resultant 1-h ischemic period. Group 2 undergoes delayed anastomosis with 3-h ischemic period. Markers of ischemia-reperfusion injury are evaluated after anastomosis and on postoperative days 1, 2, 7, and 14.

RESULTS

A novel porcine model for microvascular composite tissue transplantation is demonstrated. Ischemia period-dependent elevations in circulating biomarkers (lactate dehydrogenase [LDH], creatine kinase [CK], and aspartate transaminase [AST]) demonstrate the effects of prolonged ischemia. Both groups showed marked LDH elevation without significant statistical intergroup difference (P=0.250). The difference in CK and AST levels at 24h showed strong significance (P<0.0001).

CONCLUSIONS

A novel method of vascularized gracilis myocutaneous flap transplantation was validated in the Yorkshire swine. Assays for skeletal muscle tissue injury (LDH, CK, and AST) showed ischemia period-dependent response providing assessment of ischemia-reperfusion injury at the cellular level. Subsequent studies will evaluate agents that mitigate ischemia-reperfusion injury and transition these findings to potentiate vascularized composite allotransplantation.

Restoration of facial form and function after severe disfigurement from burn injury by a composite facial allograft

Composite facial allotransplantation is emerging as a treatment option for severe facial disfigurements. The technical feasibility of facial transplantation has been demonstrated, and the initial clinical outcomes have been encouraging. We report an excellent functional and anatomical restoration 1 year after face transplantation. A 59-year-old male with severe disfigurement from electrical burn injury was treated with a facial allograft composed of bone and soft tissues to restore midfacial form and function. An initial potent antirejection treatment was tapered to minimal dose of immunosuppression. There were no surgical complications. The patient demonstrated facial redness during the initial postoperative months. One acute rejection episode was reversed with a brief methylprednisolone bolus treatment. Pathological analysis and the donor's medical history suggested that rosacea transferred from the donor caused the erythema, successfully treated with topical metronidazol. Significant restoration of nasal breathing, speech, feeding, sensation and animation was achieved. The patient was highly satisfied with the esthetic result, and regained much of his capacity for normal social life. Composite facial allotransplantation, along with minimal and well-tolerated immunosuppression, was successfully utilized to restore facial form and function in a patient with severe disfigurement of the midface.

A new composite midface allotransplantation model with sensory and motor reinnervation

In this study, we extended application of face transplantation model in rat by incorporation of vascularized premaxilla, and nose with infraorbital and facial nerves for evaluation of allotransplanted sensory and motor nerve functional recovery. In group I (n = 3) the dissection technique is studied. In group II (n = 5) isotransplantations were performed. In group III (n = 5) allotransplantations were performed under Cyclosporin A monotherapy. Grafts; composed of nose, lower lip, and premaxilla; were dissected. Infraorbital nerve and facial nerve were included into the transplant. A heterotopic transplantation was performed to inguinal region of recipient. Nerve coaptations were performed between infraorbital-sapheneous nerve and facial-femoral nerve. CT scan, somatosensory-evoked potential testing (SSEP), motor-evoked potential testing (MEP), and microangiography were used for evaluation. All transplants survived indefinitely over 100 days. Microangiography showed preserved vascularization of the graft. Computed tomography revealed vital premaxillary bone segments. SSEP and MEP confirmed recovery of motor and sensory functions and latencies reached 67% of normal infraorbital nerve value and 70% of normal facial nerve value at 100 days post-transplant. We have introduced new midface transplant model of composite midface allograft with sensory and motor units. In this model, motor and sensory functional recovery was confirmed at 100 days post-transplant.