Immunosuppression and Rejection in Human Hand Transplantation

Translational bioengineering strategies for peripheral nerve regeneration: opportunities, challenges, and novel concepts

Peripheral nerve injuries remain a challenging problem in need of better treatment strategies. Despite best efforts at surgical reconstruction and postoperative rehabilitation, patients are often left with persistent, debilitating motor and sensory deficits. There are currently no therapeutic strategies proven to enhance the regenerative process in humans. A clinical need exists for the development of technologies to promote nerve regeneration and improve functional outcomes. Recent advances in the fields of tissue engineering and nanotechnology have enabled biomaterial scaffolds to modulate the host response to tissue repair through tailored mechanical, chemical, and conductive cues. New bioengineered approaches have enabled targeted, sustained delivery of protein therapeutics with the capacity to unlock the clinical potential of a myriad of neurotrophic growth factors that have demonstrated promise in enhancing regenerative outcomes. As such, further exploration of combinatory strategies leveraging these technological advances may offer a pathway towards clinically translatable solutions to advance the care of patients with peripheral nerve injuries. This review first presents the various emerging bioengineering strategies that can be applied for the management of nerve gap injuries. We cover the rationale and limitations for their use as an alternative to autografts, focusing on the approaches to increase the number of regenerating axons crossing the repair site, and facilitating their growth towards the distal stump. We also discuss the emerging growth factor-based therapeutic strategies designed to improve functional outcomes in a multimodal fashion, by accelerating axonal growth, improving the distal regenerative environment, and preventing end-organs atrophy.

Evaluating Treatment Preferences and Perceptions of a Prosthetic Versus a Transplanted Hand: A Conjoint Analysis-Based Study

INTRODUCTION

This study used a conjoint analysis-based survey to assess which factors are most influential when considering treatment with a prosthesis or transplant after a unilateral hand amputation.

METHODS

Overall, 469 respondents were recruited using Amazon Mechanical Turk and asked to assume that they experienced a hand amputation. To determine preferences for a prosthetic, respondents chose among 11 pairs of alternatives with variations in the following attributes: appearance, function, maintenance, and learning time. Respondents were then presented with descriptions of the risks and outcomes of hand transplantation. The most compelling reasons for and against a transplant were determined and characteristics predictive of support for a transplant were identified.

RESULTS

The most important attributes for a prosthesis were "lifelike appearance" and "myolectric function." For hand transplantation, respondents were most concerned about immunosuppression side effects (n = 323, 69%) and the intense nature of surgery (n = 275, 59%), whereas the most positive benefit was the concept of the transplant being "natural" (n = 339, 72%). When faced with the choice of a hand transplant or a prosthetic, approximately 50% of respondents chose a transplantation. Younger age, previous medical experiences, a perceived "familiarity with medical issues," and the regular attendance of religious services were associated with strong support for a hand transplantation (P < 0.01).

CONCLUSIONS

When considering a hand prosthesis, respondents are motivated most by appearance and function. Meanwhile, with hand transplantation, the risks of immunosuppression and the intense nature of surgery and recovery are predominant concerns. These findings may help inform patient-physician discussions when considering treatment after unilateral hand amputation.

Noninvasive evaluation of intragraft immune responses in upper extremity transplantation

In vascularized composite allotransplantation (VCA), invasive tissue biopsies remain the gold standard in diagnosing rejection carrying significant morbidity. We aimed to show feasibility of tape-stripping for noninvasive immune monitoring in VCA. Tape-stripping was performed on allografts and native skin of upper extremity transplant recipients. Healthy nontransplanted individuals served as controls. The technique was also used in swine on naïve skin in nontransplanted animals, native skin of treated, transplanted swine, nonrejecting VCAs, and rejecting VCAs. Extracted protein was analyzed for differences in cytokine expression using Luminex technology. Significantly decreased levels of INFγ and IL-1Ra were seen between human allograft samples and native skin. In swine, rejecting grafts had increased IL-1Ra compared to naïve and native skin, decreased levels of GM-CSF compared to native skin, and decreased IL-10 compared to nonrejecting grafts. Unsupervised hierarchical clustering revealed rejecting grafts separated from the nonrejecting (P = 0.021). Variable importance in projection scores identified GM-CSF, IL-1Ra, and IL-2 as the most important profiles for group discrimination. Differences in cytokine expression are detectable in human VCA patient native skin and VCA graft skin using a noninvasive tape-stripping method. Swine studies suggest that differences in cytokines between rejecting and nonrejecting grafts are discernable.

Pharmacokinetics and Biodistribution of Tacrolimus after Topical Administration: Implications for Vascularized Composite Allotransplantation

AIM

The high doses of oral tacrolimus (TAC) (1,2) necessary to prevent acute rejection (AR) after vascularized composite allotransplantation (VCA) are associated with systemic adverse effects. The skin is the most antigenic tissue in VCA and the primary target of AR. However, the short-term use of topical TAC (Protopic®), as an off-label adjunct to oral TAC, to treat AR episodes pro re nata (PRN), has yielded inconsistent results. There is lack of data on the pharmacokinetics and tissue distribution of topical TAC in VCA, that hampers our understanding of the reasons for unreliable efficacy. Toward this goal, we evaluated the ability of topical TAC to achieve high local tissue concentrations at the site of application with low systemic concentrations.

MATERIALS AND METHODS

We assessed the pharmacokinetics and tissue distribution of topical TAC (Protopic®, 0.03%) after single or repeated topical application in comparison to those after systemic delivery in rats. Animals received a single topical application of TAC ointment (Group 1) or an intravenous (IV) injection of TAC (Group 2) at a dose of 0.5 mg/kg. In another experiment, animals received daily topical application of TAC ointment (Group 3), or daily intraperitoneal (IP) injection of TAC (Group 4) at a dose of 0.5 mg/kg for 7 days. TAC concentrations in blood and tissues were analyzed by Liquid Chromatography-Mass Spectrometry (LC/MS-MS).

RESULTS

Following single topical administration, TAC was absorbed slowly with a Tmax of 4 h and an absolute bioavailability of 11%. The concentrations of TAC in skin and muscle were several folds higher than whole blood concentrations. Systemic levels remained subtherapeutic (< 3 ng/ml) with repeated once daily applications.

CONCLUSION

Topical application of TAC ointment (Protopic®, 0.03%) at a dose of 0.5 mg/kg/day provided high concentrations in the local tissues with low systemic exposure. Repeated topical administration of TAC is well tolerated with no local or systemic adverse effects. This study confirms the feasibility of topical application of TAC for site specific graft immunosuppression and enables future applications in VCA.

Building a Hand and Upper Extremity Transplantation Program: Lessons Learned From the First 20 Years of Vascularized Composite Allotransplantation

Background: Upper extremity transplantation is a quality-of-life enhancing treatment for select patients with upper extremity loss. This article reviews the preoperative, intraoperative, and postoperative challenges in the upper extremity transplantation process and the lessons learned from the first 2 decades of hand transplantation. Methods: Key components of the author's hand transplantation protocol including patient selection, donor screening, surgical rehearsal, donor procurement, transplantation, immunosuppression, and patient outcome reporting/follow-up are reported to assist other teams who wish to establish a hand transplantation program. Results: There have been many advancements in the first 20 years of hand transplantation including better patient selection criteria, the recent addition of pediatric patients, improved surgical techniques such as the use of virtual surgical planning, and improved immunosuppression protocols. Improvement has also taken place in the tracking and reporting of hand transplant outcomes, but more work is clearly needed to fully define the benefits of transplantation, especially for pediatric patients. Conclusions: Over the past 20 years, significant progress has been made in upper extremity transplantation although a number of challenges remain including how to best document and share outcome measures, optimize immunosuppression, and diagnose/treat rejection. The authors encourage upper extremity transplant programs to report their experience and protocols to advance hand transplantation as standard of care for properly selected individuals.

Prosthetic Rehabilitation and Vascularized Composite Allotransplantation following Upper Limb Loss

BACKGROUND

Upper limb loss is a devastating condition with dramatic physical, psychological, financial, and social consequences. Improvements in the fields of prosthetics and vascularized composite allotransplantation have opened exciting new frontiers for treatment and rehabilitation following upper limb loss. Each modality offers a unique set of advantages and limitations with regard to the restoration of hand function following amputation.

METHODS

Presented in this article is a discussion outlining the complex considerations and decisions encountered when determining patient appropriateness for either prosthetic rehabilitation or vascularized composite allotransplantation following upper limb loss. In this review, the authors examine how psychosocial factors, nature of injury, rehabilitation course, functional outcomes, and risks and benefits may affect overall patient selection for either rehabilitative approach.

RESULTS

This review summarizes the current state of the literature. Advancements in both prosthetic and biological strategies demonstrate promise with regard to facilitating rehabilitation following upper limb loss. However, there remains a dearth of research directly comparing outcomes in prosthetic rehabilitation to that following upper extremity transplantation.

CONCLUSIONS

Few studies have performed a direct comparison between patients undergoing vascularized composite allotransplantation and those undergoing prosthetic rehabilitation. Upper extremity transplantation and prosthetic reconstruction should not be viewed as competing options, but rather as two treatment modalities with different risk-to-benefit profiles and indications.

Graft-implanted, enzyme responsive, tacrolimus-eluting hydrogel enables long-term survival of orthotopic porcine limb vascularized composite allografts: A proof of concept study

Background

Currently, patients receiving vascularized composite allotransplantation (VCA) grafts must take long-term systemic immunosuppressive therapy to prevent immunologic rejection. The morbidity and mortality associated with these medications is the single greatest barrier to more patients being able to receive these life-enhancing transplants. In contrast to solid organs, VCA, exemplified by hand or face transplants, allow visual diagnosis of clinical acute rejection (AR), directed biopsy and targeted graft therapies. Local immunosuppression in VCA could reduce systemic drug exposure and limit adverse effects. This proof of concept study evaluated, in a large animal forelimb VCA model, the efficacy and tolerability of a novel graft-implanted enzyme-responsive, tacrolimus (TAC)—eluting hydrogel platform, in achieving long-term graft survival.

Methods

Orthotopic forelimb VCA were performed in single haplotype mismatched mini-swine. Controls (n = 2) received no treatment. Two groups received TAC hydrogel: high dose (n = 4, 91 mg TAC) and low dose (n = 4, 49 mg TAC). The goal was to find a dose that was tolerable and resulted in long-term graft survival. Limbs were evaluated for clinical and histopathological signs of AR. TAC levels were measured in serial blood and skin tissue samples. Tolerability of the dose was evaluated by monitoring animal feeding behavior and weight.

Results

Control limbs underwent Banff Grade IV AR by post-operative day six. Low dose TAC hydrogel treatment resulted in long-term graft survival time to onset of Grade IV AR ranging from 56 days to 93 days. High dose TAC hydrogel also resulted in long-term graft survival (24 to 42 days), but was not well tolerated.

Conclusion

Graft-implanted TAC-loaded hydrogel delays the onset of Grade IV AR of mismatched porcine forelimb VCA grafts, resulting in long term graft survival and demonstrates dose-dependent tolerability.

Abdominal wall allotransplantation

Allotransplantation of vascularized composite tissue is a new field of transplantation surgery. One application of this technique is abdominal wall transplantation used as a supplementary procedure to the transplantation of visceral organs in patients with abdominal compartment deficits. As abdominal wall closure problems are experienced in around 30-40% of such patients, peer reviewed conclusions on the viability of various options, are important for an informed choice of possible procedures. This review focuses on the abdominal wall allotransplantion procedure. Our search provided 35 appropriate references which we used to support our findings as follows: abdominal wall transplantation was performed in 33 patients at seven centres. Of these, 30 had a full thickness abdominal wall transplanted from the same donor, 3 from a second donor. Three had visceral organ transplants and in addition, the posterior sheet of the rectus muscle fascia. In summary, our findings were that abdominal wall allotransplantation does not jeopardize the outcome of visceral organs transplantation. There is no higher risk of complications or rejection of the visceral organs. There have been no fatalities as a direct result of complications due to abdominal wall transplantation. Finally, the transplanted abdominal wall may provide an early warning of rejection before diagnostic tests on the bowel are symptomatic.

Mycophenolic Acid for Topical Immunosuppression in Vascularized Composite Allotransplantation: Optimizing Formulation and Preliminary Evaluation of Bioavailability and Pharmacokinetics

Mycophenolic acid (MPA), is the active form of the ester prodrug mycophenolate mofetil (MMF). MMF is an FDA approved immunosuppressive drug that has been successfully used in systemic therapy in combination with other agents for the prevention of acute rejection (AR) following solid organ transplantation (SOT) as well as in vascularized composite allotransplantation (VCA). Systemic use of MMF is associated with gastrointestinal adverse effects. Topical delivery of the prodrug could thus provide graft-targeted immunosuppression while minimizing systemic drug exposure. Our goal was to develop a topical formulation of MPA with optimal in vitro/in vivo characteristics such as release, permeation, and tissue bioavailability to enable safety and efficacy evaluation in clinical VCA.

Permeation studies were performed with a solution of MPA (10 mg/ml). In vitro release and permeation studies were performed for different semisolid formulations (Aladerm, Lipoderm, emollient, and VersaBase) of MPA (1% w/w) using a Franz Diffusion Cell System (FDCS). In vivo pharmacokinetic characterization of MPA release from Lipoderm was performed in rats.

MPA in solution exhibited a steady state flux (3.8 ± 0.1 µg/cm²/h) and permeability (1.1 × 10⁻⁷ ± 3.2 × 10⁻⁹ cm/s). MPA in Lipoderm exhibited a steady state flux of 1.12 ± 0.24 µg/cm²/h, and permeability of 6.2 × 10⁻⁰⁹ ± 1.3 × 10⁻⁹ cm/s across the biomimetic membrane. The cumulative release of MPA from Lipoderm, showed a linear single-phase profile with a R² of 0.969. In vivo studies with MPA in Lipoderm showed markedly higher local tissue MPA levels and lower systemic MPA exposure as compared to values obtained after intravenous delivery of the same dose of drug (p < 0.05).

We successfully developed for the first time, a topical formulation of MPA in Lipoderm with optimal in vitro/in vivo permeability characteristics and no undesirable local or systemic adverse effects in vivo. Our study provides key preliminary groundwork for translational efficacy studies of topical MPA in pre-clinical large animal VCA models and for effectiveness evaluation in patients receiving VCA.

Blood product utilization in human upper-extremity transplantation: challenges, complications, considerations, and transfusion protocol conception

BACKGROUND

Upper-extremity transplantation (UET) is a reality. Immunologic, functional, and graft survival outcomes have been encouraging. However, these complex reconstructions have unique considerations that pose distinct challenges. Transplant programs have reported morbidity and mortality due to significant intraoperative blood losses, but similar data are scant during other phases of recovery. We report experience from two centers on complete blood component demands and utilization with UET.

STUDY DESIGN AND METHODS

Inpatient medical records of UET recipients from intraoperative (time from initiation of transplant surgery to exit from the operative suite) and postoperative (exit from the operative suite to discharge from the hospital) phases were retrospectively reviewed.

RESULTS

Six patients received various UETs and mean (±SD) postoperative hospital stay was 46 (±14.4) days. Mean (±SD) intraoperative blood unit utilization was 14.8 (±10.2) red blood cells (RBCs), 10.5 (±11.8) plasma, 0.8 (±1.2) platelets (PLTs), and 0.3 (±0.8) cryoprecipitate units. Mean postoperative blood unit utilization was 9.3 (±10.4) RBCs, 5.3 (±6.7) plasma, 1.2 (±2.0) PLTs, and 0.7 (±1.6) cryoprecipitate units. Both intraoperative and postoperative blood utilization for unilateral versus bilateral transplant were different, but not significantly so. However, total inpatient blood use in bilateral transplants was significantly greater than in unilateral transplants.

CONCLUSION

Substantial blood loss may occur in UET and require transfusion of many blood components, primarily RBCs and plasma. We propose an UET transfusion protocol and suggest that centers preparing to perform these transplants should actively engage the transfusion medicine service to ensure availability and access to appropriate blood components for the entire hospitalizations of these unique patients.

Postoperative Management of Composite Tissue Graft Transplantation

Composite tissue allotransplantation (CTA) is the transplantation of body structures such as the limbs, larynx, abdominal wall, tendons, and face. This chapter discusses the general and specific postoperative management of patients following CTA.

Setting the Goals in the Management of Mutilated Injuries of the Hand-Impressions Based on the Ganga Hospital Experience

Mutilated injuries need to be treated aggressively and appropriately to avoid amputation or severe disability in the individual. Assessment of the management of these injuries on a global level reveals that there is a gap between the need and availability of the skilled manpower to manage these injuries. There is also a gap in the utilization of the available services. These gaps need to be covered or narrowed as far as possible. Although some measures need policy changes and improvement of health care delivery infrastructure, simpler measures taken at the final health care delivery level can significantly improve the final outcome.

Hand Transplantation Versus Hand Prosthetics: Pros and Cons

Composite tissue transplantation and new developments in the field of prosthetics have opened new frontiers in the restoration of function among upper limb amputees. It is now possible to restore hand function in affected patients; however, the indications, advantages, and limitations for either hand transplantation or prosthetic fitting must be carefully considered depending on the level and extent of the limb loss. Hand transplantation allows comprehensive hand function to be restored, yet composite tissue transplantation comes with disadvantages, making this method a controversial topic in the hand surgical community. Alternatively, prosthetic limb replacement represents the standard of care for upper limb amputees, but results in the known limitations of function, sensation, and usage. The indication for hand transplantation or prosthetic fitting strongly depends on the level of amputation, as well as on the extent (unilateral/bilateral) of the amputation. In this review, we discuss the advantages and disadvantages of hand transplantation and prosthetic replacement for upper limb amputees in general, as well as in regard to the different levels of amputation.

Simultaneous transplantation of hematopoietic stem cells and a vascularized composite allograft leads to tolerance

BACKGROUND

We have previously demonstrated that tolerance to a vascularized composite allograft (VCA) can be achieved after the establishment of mixed chimerism. We test the hypothesis that tolerance to a VCA in our dog leukocyte antigen-matched canine model is not dependent on the previous establishment of mixed chimerism and can be induced coincident with hematopoietic cell transplantation (HCT).

METHODS

Eight dog leukocyte antigen-matched, minor antigen mismatched dogs received 200 cGy of radiation and a VCA transplant. Four dogs received donor bone marrow at the time of VCA transplantation (group 1), whereas a second group of four dogs did not (group 2). All recipients received a limited course of postgrafting immunosuppression. All dogs that received HCT and VCA were given donor, third-party, and autologous skin grafts.

RESULTS

All group 1 recipients were tolerant to their VCA (>62 weeks). Three of the four dogs in group 2 rejected their VCA transplants after the cessation of immunosuppression. Biopsies obtained from the muscle and skin of VCA from group 1 showed few infiltrating cells compared with extensive infiltrates in biopsies of VCA from group 2. Compared with autologous skin and muscle, elevated levels of CD3+ FoxP3+ T-regulatory cells were found in the skin and muscle obtained from the VCA of HCT recipients. All group 1 animals were tolerant to their donor skin graft and promptly rejected the third-party skin grafts.

CONCLUSION

These data demonstrated that donor-specific tolerance to all components of the VCA can be established through simultaneous nonmyeloablative allogeneic HCT and VCA transplantation protocol.

Facial and hand allotransplantation

Vascularized composite allotransplantation (VCA) is a novel therapeutic option for treatment of patients suffering from limb loss or severe facial disfigurement. To date, 72 hand and 19 facial transplantations have been performed worldwide. VCA in hand and facial transplantation is a complex procedure requiring a multidisciplinary team approach and extensive surgical planning. Despite good functional outcome, courses after hand and facial transplantation have been complicated by skin rejection. Long-term immunosuppression remains a necessity in VCA for allograft survival. To widen the scope of these quality-of-life-improving procedures, minimization of immunosuppression to limit risks and side effects is needed.

Upper extremity transplantation: current concepts and challenges in an emerging field

Loss of an isolated upper limb is an emotionally and physically devastating event that results in significant impairment. Patients who lose both upper extremities experience profound disability that affects nearly every aspect of their lives. While prosthetics and surgery can eventually provide the single limb amputee with a suitable assisting hand, limited utility, minimal haptic feedback, weight, and discomfort are persistent problems with these techniques that contribute to high rates of prosthetic rejection. Moreover, despite ongoing advances in prosthetic technology, bilateral amputees continue to experience high levels of dependency, disability, and distress. Hand and upper extremity transplantation holds several advantages over prosthetic rehabilitation. The missing limb is replaced with one of similar skin color and size. Sensibility, voluntary motor control, and proprioception are restored to a greater degree, and afford better dexterity and function than prosthetics. The main shortcomings of transplantation include the hazards of immunosuppression, the complications of rejection and its treatment, and high cost. Hand and upper limb transplantation represents the most commonly performed surgery in the growing field of Vascularized Composite Allotransplantation (VCA). As upper limb transplantation and VCA have become more widespread, several important challenges and controversies have emerged. These include: refining indications for transplantation, optimizing immunosuppression, establishing reliable criteria for monitoring, diagnosing, and treating rejection, and standardizing outcome measures. This article will summarize the historical background of hand transplantation and review the current literature and concepts surrounding it.

A critical analysis of rejection in vascularized composite allotransplantation: clinical, cellular and molecular aspects, current challenges, and novel concepts

Advances in microsurgical techniques and immunomodulatory protocols have contributed to the expansion of vascularized composite allotransplantation (VCA) with very encouraging immunological, functional, and cosmetic results. Rejection remains however a major hurdle that portends serious threats to recipients. Rejection features in VCA have been described in a number of studies, and an international consensus on the classification of rejection was established. Unfortunately, current available diagnostic methods carry many shortcomings that, in certain cases, pose a great diagnostic challenge to physicians especially in borderline rejection cases. In this review, we revisit the features of acute skin rejection in hand and face transplantation at the clinical, cellular, and molecular levels. The multiple challenges in diagnosing rejection and in defining chronic and antibody-mediated rejection in VCA are then presented, and we finish by analyzing current research directions and novel concepts aiming at improving available diagnostic measures.

Site-specific immunosuppression in vascularized composite allotransplantation: prospects and potential

Skin is the most immunogenic component of a vascularized composite allograft (VCA) and is the primary trigger and target of rejection. The skin is directly accessible for visual monitoring of acute rejection (AR) and for directed biopsy, timely therapeutic intervention, and management of AR. Logically, antirejection drugs, biologics, or other agents delivered locally to the VCA may reduce the need for systemic immunosuppression with its adverse effects. Topical FK 506 (tacrolimus) and steroids have been used in clinical VCA as an adjunct to systemic therapy with unclear beneficial effects. However, there are no commercially available topical formulations for other widely used systemic immunosuppressive drugs such as mycophenolic acid, sirolimus, and everolimus. Investigating the site-specific therapeutic effects and efficacy of systemically active agents may enable optimizing the dosing, frequency, and duration of overall immunosuppression in VCA with minimization or elimination of long-term drug-related toxicity.

Hand disease in scleroderma: a clinical correlate for chronic hand transplant rejection

Abstract

Chronic rejection remains a potential long-term consequence of hand composite tissue allotransplantation (CTA). Scleroderma has already been proposed as a model for chronic facial allograft rejection based on potential parallels of observed progression of disease and pathophysiology course. This study proposes a similar model for how chronic rejection may manifest itself in the context of hand CTA through the functional and psychological assessment of patients with scleroderma, should it occur.

Methods

100 consecutive patients with a clinical diagnosis of scleroderma were recruited into the study. Subjective assessment of static hand disfigurement was carried out through the use of standardised digital photographs. Hand function was assessed through the measurement of active range of motion (AROM) and using the activities of daily living (ADL) and Disabilities of the Arm, Shoulder & Hand (DASH) questionnaire. Psychological and quality of life evaluation comprised the Hospital Anxiety Depression Scale (HADS) and the SF36 health survey.

Results

Examination of standardised digital photographs of subjects revealed a variety of hand changes characteristic of scleroderma, ranging from mild to moderate through to severe. Objective assessment of hand disfigurement did not correlate with duration of disease, nor psychological distress. However, individuals with worsening disfigurement demonstrated poorer AROM. Longitudinally no deterioration in terms of function was seen over time in terms of the DASH and ADL results. Nevertheless deterioration of function did have a significant impact on quality of life. Overall HADS showed 22% of individuals as suffering from clinical levels of anxiety and 10% from clinical depression.

Conclusion

Chronic rejection has not yet occurred in any of the hand transplants performed to date. Scleroderma results in a spectrum of chronic functional and psychological disability that provides a model for the potential outcome of chronic hand allograft rejection. Findings from this study provide insight into the impact of this progressive disease for patients and contribute to the information and consent process for patients considering hand composite tissue transplantation.

Anesthetic management in upper extremity transplantation: the Pittsburgh experience

BACKGROUND

Hand/forearm/arm transplants are vascularized composite allografts, which, unlike solid organs, are composed of multiple tissues including skin, muscle, tendons, vessels, nerves, lymph nodes, bone, and bone marrow. Over the past decade, 26 upper extremity transplantations were performed in the United States. The University of Pittsburgh Medical Center has the largest single center experience with 8 hand/forearm transplantations performed in 5 recipients between January 2008 and September 2010. Anesthetic management in the emerging field of upper extremity transplants must address protocol and procedure-specific considerations related to the role of regional blocks, effects of immunosuppressive drugs during transplant surgery, fluid and hemodynamic management in the microsurgical setting, and rigorous intraoperative monitoring during these often protracted procedures.

METHODS

For the first time, we outline salient aspects of upper extremity transplant anesthesia based on our experience with 5 patients. We highlight the importance of minimizing intraoperative vasopressors and improving fluid management and blood product use.

RESULTS

Our approach reduced the incidence of perioperative bleeding requiring re-exploration or hemostasis and shortened in-hospital and intensive care unit stay. Functional, immunologic and graft survival outcomes have been highly encouraging in all patients.

CONCLUSIONS

Further experience is required for validation or standardization of specific anesthetic protocols. Meanwhile, our recommendations are intended as pertinent guidelines for centers performing these novel procedures.

Functional outcome after hand and forearm transplantation: what can be achieved?

The first successful hand transplant in the modern era of reconstructive transplantation was performed in 1998. Since then, more than 65 hand and upper limb transplantations have been performed around the globe, with encouraging results. The main goal of all upper limb transplantations is to enhance the patient's quality of life. The transplant must be successfully integrated into the patient's body and self-image and the recipient should be satisfied with the recovery of sensitivity and muscle function of the new limb. To achieve these goals, a proper and thorough design of the rehabilitation regimen is of critical importance.

Acute and chronic rejection in upper extremity transplantation: what have we learned?

To date, 78 upper extremity transplants have been performed in 55 recipients around the world. The purpose of this article is to provide an overview of acute and chronic rejection (CR) and to summarize collective insights in upper extremity transplantation. To date, almost all patients experienced AR that is pathophysiologically similar to that in solid organs. The spectre of chronic rejection is just emerging. Upper extremity transplantation has significant potential as a reconstructive option only if efforts are invested in strategies to reduce risks of prolonged immunosuppression and in approaches to better diagnose, monitor and treat AR and CR.

Hand allotransplantation

In the past decade, more than 100 different composite tissue allotransplantation (CTA) procedures have been performed around the world including more than 50 hand and 8 facial transplants with encouraging graft survival and excellent functional outcomes. Broader clinical application of CTA, however, continues to be hampered by requirement for long-term, high-dose, multidrug maintenance immunosuppression to prevent graft rejection mediated particularly by composite tissue allograft's highly immunogenic skin component. Medication toxicity could result in severe adverse events including metabolic and infectious complications or malignancy. Notably, unlike in solid organs, clinical success is dictated not only by graft acceptance and survival but also by nerve regeneration, which determines ultimate functional outcomes. Novel strategies such as cellular and biologic therapies that integrate the concepts of immune regulation with those of nerve regeneration have shown promising results in small and large animal models. Clinical translation of these insights to reconstructive transplantation and CTA could further minimize the need of immunosuppression and optimize functional outcomes. This will enable wider application of such treatment options for patients in need of complex reconstructive surgery for congenital deformities or devastating injuries that are not amenable to standard methods of repair.

Traumatic and trauma-related amputations: Part II: Upper extremity and future directions

Trauma is the most common reason for amputation of the upper extremity. The morphologic and functional distinctions between the upper and lower extremities render the surgical techniques and decision-making different in many key respects. Acceptance of the prosthesis and the outcomes are improved by performing a transradial rather than a more proximal amputation. Substantial efforts, including free tissue transfers when necessary, should be made to salvage the elbow. Careful management of the peripheral nerves is critical to minimize painful neuroma formation while preserving options for possible future utilization in targeted muscle reinnervation and use of a myoelectric prosthesis. Rapid developments with targeted muscle reinnervation, myoelectric prostheses, and composite tissue allotransplantation may dramatically alter surgical treatment algorithms in the near future for patients with severe upper-extremity trauma.

Composite tissue allotransplantation: hand transplantation and beyond

Recent advances in transplant immunology are shifting the focus from immunosuppression to immunoregulation, making composite tissue allotransplantation with novel and less potent immunosuppressive regimens a possibility. Hand transplantation has been the most frequently performed human composite tissue allotransplantation, with more than 50 upper extremity-based transplants done worldwide. Further research is needed regarding immunomodulating protocols, and careful oversight and individualized screening procedures will be required as patients seeking improved quality of life through human composite tissue allotransplantation come to accept a certain level of risk in these experimental procedures. Still, composite tissue allotransplantation offers to advance transplant medicine and reconstructive surgery.

Extremity war injuries: collaborative efforts in research, host nation care, and disaster preparedness

The fourth annual Extremity War Injuries (EWI) Symposium addressed ongoing challenges and opportunities in the management of combat-related musculoskeletal injury. The symposium, which also examined host-nation care and disaster preparedness and response, defined opportunities for synergy between several organizations with similar missions and goals. Within the Department of Defense, the Orthopaedic Extremity Trauma Research Program (OETRP) has funded basic research related to a series of protocols first identified and validated at prior EWI symposia. A well-funded clinical research arm of OETRP has been developed to help translate and validate research advances from each of the protocols. The Armed Forces Institute for Regenerative Medicine, a consortium of academic research institutions, employs a tissue-engineering approach to EWI challenges, particularly with regard to tissue loss. Programs within the National Institute of Arthritis and Musculoskeletal and Skin Diseases and throughout the National Institutes of Health have also expanded tissue-engineering efforts by emphasizing robust mechanistic basic science programs. Much of the clinical care delivered by US military medical personnel and nongovernmental agencies has been to host-nation populations; coordinating delivery to maximize the number of injured who receive care requires understanding of the breadth and scope of resources available within the war zone. Similarly, providing the most comprehensive care to the greatest number of injured in the context of domestic mass casualty requires discussion and planning by all groups involved.

Transgene expression in a model of composite tissue allotransplantation

BACKGROUND

Composite tissue allografting may be an ideal solution to many problems requiring reconstructive surgery. Unfortunately, complications associated with chronic immunocompromise are major impediments to widespread use of composite tissue allografting. Current immunosuppressive and immunomodulatory paradigms focus on modification of the recipient through global immunosuppression or donor/recipient chimerism. Alternatively, modifying the allograft to block rejection or promote tolerance could confine deleterious immunosuppressive effects to the graft or eliminate graft rejection. However, a technique introducing genetic information into the transplant is needed. The authors demonstrate the first model for expressing a gene of interest locally in a hind-limb transplant.

METHODS

Using a rat hind-limb transplant model, the authors tested the ability of naked DNA infusion, cationic polymer/DNA complex transfection, and adenoviral vector transduction to introduce genetic material into the composite tissue allograft. The marker genes luciferase and green fluorescent protein were used to follow gene expression.

RESULTS

Recombinant adenovirus showed rapid, high-level expression of marker genes in the graft, with no detectable expression in recipient animals. Expression was detectable at 18 hours and peaked at 7 days. Levels of expression were lower but above baseline at 4 weeks.

CONCLUSIONS

Using an adenoviral vector system, the authors have selectively introduced a marker gene (luciferase) into a transplanted hind-limb rat model. Expression was rapid and seen in a variety of cell types. Adenovirus infection had no impact on limb rejection. This method may be a powerful tool for genetically modifying composite tissue allografts and may contribute to immune tolerance and more widespread use of composite tissue allograft surgery.