Allogeneic vascularized transplantation of human femoral diaphyses and total knee joints--first clinical experiences

Immune Rejection of Cartilage in a Swine Vascularized Composite Allotransplantation Model

BACKGROUND

Cartilage is a crucial tissue in vascularized composite allotransplantation (VCA) and plays a pivotal role in restoring motor function, especially in joint allotransplantation. Nevertheless, our understanding of immune rejection in cartilage remains limited and contentious. This study seeks to investigate the immune rejection of cartilage in a large animal model of VCA.

METHODS

Cartilage, including articular cartilage and meniscus, as well as skin, muscle and lymph node, was retrieved from a swine heterotopic VCA graft when the skin of the graft suffered from grade III-IV rejection. Histologic examination, transmission electron microscopy and immunofluorescent staining were used to investigate immune rejection.

RESULTS

Histologic examination revealed the infiltration of inflammatory cells and tissue destruction in cartilage. Transmission electron microscopy confirmed tissue damage and necrosis in cartilage. However, cartilage exhibited milder tissue damage when compared to rejected skin and muscle. Immunofluorescent staining revealed the activation of both the innate and adaptive immune systems, accompanied by an up-regulation of cell death biomarkers, including apoptosis and pyroptosis, in the rejected cartilage.

CONCLUSION

Our study demonstrates that cartilage is not immunologically privileged and undergoes immune rejection concurrently with skin and muscle in the VCA graft, though with less severe inflammation and rejection.

Challenges and opportunities in vascularized composite allotransplantation of joints: a systematic literature review

Background

Joint allotransplantation (JA) within the field of vascularized composite allotransplantation (VCA) holds great potential for functional and non-prosthetic reconstruction of severely damaged joints. However, clinical use of JA remains limited due to the immune rejection associated with all forms of allotransplantation. In this study, we aim to provide a comprehensive overview of the current state of JA through a systematic review of clinical, animal, and immunological studies on this topic.

Methods

We conducted a systematic literature review in accordance with the PRISMA guidelines to identify relevant articles in PubMed, Cochrane Library, and Web of Science databases. The results were analyzed, and potential future prospects were discussed in detail.

Results

Our review included 14 articles describing relevant developments in JA. Currently, most JA-related research is being performed in small animal models, demonstrating graft survival and functional restoration with short-term immunosuppression. In human patients, only six knee allotransplantations have been performed to date, with all grafts ultimately failing and a maximum graft survival of 56 months.

Conclusion

Research on joint allotransplantation has been limited over the last 20 years due to the rarity of clinical applications, the complex nature of surgical procedures, and uncertain outcomes stemming from immune rejection. However, the key to overcoming these challenges lies in extending graft survival and minimizing immunosuppressive side effects. With the emergence of new immunosuppressive strategies, the feasibility and clinical potential of vascularized joint allotransplantation warrants further investigation.

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

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

Autogenous Arteriovenous Bundle Implantation Maintains Viability Without Increased Immune Response in Large Porcine Bone Allotransplants

BACKGROUND

Transplantation of living allogeneic bone segments may permit reconstruction of large defects, particularly if viability is maintained without immunosuppression. Development of a new autogenous osseous blood supply accomplishes this goal in rodent experimental models. This study evaluates potential systemic and local inflammatory responses to this angiogenesis in a large-animal model.

METHODS

Vascularized allogeneic tibia segments were transplanted orthotopically into matched tibial defects in Yucatan minipigs. Microvascular anastomoses of bone nutrient artery and vein were supplemented by intramedullary placement of an autogenous arteriovenous (AV) bundle in group 1. Group 2 served as a no-angiogenesis control. A 3-drug immunosuppression regimen was withdrawn after 2 weeks. During the 20-week survival period, periodic leukocyte counts and inflammatory cytokine levels were measured. Thereafter, osteocyte survival was quantified and transplant rejection graded by histologic examination and quantitative real-time polymerase chain reaction of immunologic markers.

RESULTS

Both groups developed an initial systemic response, which resolved after 4 to 6 weeks. No differences were seen in blood cytokine levels. Interleukin 2 expression was diminished in group 1 tibiae. As expected, nutrient pedicles had thrombosed without sustained immunosuppression, occluded by intimal hyperplasia. In group 1, angiogenesis from the autogenous AV bundle resulted in significantly less osteonecrosis (P = .04) and fibrosis (P = .02) than group 2 allotransplants.

CONCLUSIONS

Systemic immune responses to large-bone allotransplants were not increased by generation of an autogenous osseous blood supply within porcine tibial bone allotransplants. Implanted AV bundles diminished inflammation and fibrosis and improved bone viability when compared to no-angiogenesis controls.

Transplant chimerism in porcine structural vascularized bone allotransplants

BACKGROUND

Bone allotransplant viability can be maintained long-term by implanting arteriovenous (AV) bundles and creating an autogenous neoangiogenic circulation. Only short-term immunosuppression is required. This study investigates the origin of viable osteocytes observed in areas of active bone remodeling in orthotopically transplanted tibiae in a Yucatan mini-pig model.

METHODS

Segmental tibial defects created in female Yucatan minipigs (N = 14) were reconstructed with a matched vascularized composite allotransplant from a male donor. The circulation was microsurgically restored, with simultaneous autogenous AV-bundle implantation in group 1 (N = 7). A ligated AV-bundle was implanted as a no-angiogenesis control in group 2 (N = 7). After 20-weeks, repopulation of the allotransplant was assessed by real-time qPCR measurement of relative copy numbers of a Y chromosome-specific gene (SRY) and an autosomal housekeeping gene, ribosomal protein L4 (RPL4). A lower SRY/RPL4 ratio demonstrates replacement of male allogeneic cells with female, autogenous cells in the sample. Genomic DNA was extracted from cross-sections of the allotransplant, liver and spleen. Additionally, areas of new bone formation within the allotransplant were sampled by laser capture microdissection. A comparison was made between groups as well as male control samples. RNA was extracted from bone as well, as a measure of metabolically active cells.

RESULTS

Laser-captured areas of new bone formation in animals with both normal and ligated AV-bundles were found to have significantly lower relative copy numbers of SRY (p = 0.03) than control specimens from male bone, indicating replacement by female (autogenous) bone-forming cells. Analysis of an entire segment of the allotransplant from Group 1 was similarly reduced (p = 0.04), unlike that from Group 2. RNA expression of SRY was observed in both groups. No chimerism could be found in non-bone tissues (liver and spleen).

CONCLUSION

We observed a significant level of transplant chimerism in areas of new bone formation sampled by laser capture microdissection. The migration of autogenous cells including osteocytes was seen in both groups. Survival of some allogeneic (male) cells was also demonstrable. No microchimerism was found in liver and spleen.

A Flow Dynamic Rationale for Accelerated Vascularized Composite Allotransplant Rejection

BACKGROUND

From 1996 to 2000, Diefenbeck et al. carried out six knee vascularized composite allotransplants. The allotransplants were composed of bone, soft tissue, and femoral vascular pedicle (25 to 40 cm). All rejected between 14 and 56 months. Failures were attributed to chronic rejection. In 2008, the Louisville team lost their fourth patient's hand transplant at 8 months. During the rejection workup, intraoperative findings noted a thickened arterial pedicle attributed to intimal hyperplasia with significant fibrotic perivascular tissue and a near "no-flow phenomenon." No cutaneous rejection was appreciated and failure was attributed to chronic rejection.

METHODS

Data were collected from two teams, one in Germany and the other in Louisville, Kentucky. The population under study consisted of the six knee and one hand transplants. The factor of interest was the long donor arterial pedicle. The outcome measurements were transplant survival time and histopathologic results.

RESULTS

There are only seven published vascularized composite allotransplant cases where a donor artery longer than 25 cm was used. This cohort represents a 100 percent accelerated failure rate. The cause of these losses remains unexplained. The donor arteries suffered from T-cell-mediated rejection and ischemia-induced media/adventitial necrosis.

CONCLUSIONS

We hypothesize that the donor artery rejected at an accelerated rate because of ischemia caused by disruption of the external vasa vasorum in conjunction with intimal hyperplasia induced by T-cell-mediated rejection that led to disruption of the Windkessel effect. Loss of this effect presented as intimal hyperplasia accelerated by ischemia causing an expedited transplant failure.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Bone vascularized composite allotransplantation model in swine tibial defect: Evaluation of surgical angiogenesis and transplant viability

INTRODUCTION

In prior small animal studies, we maintained vascularized bone allotransplant viability without long-term immunotherapy. Instead, an autogenous neoangiogenic circulation is created from implanted vessels, sufficient to maintain bone viability with only 2 weeks immunosupression. Blood flow is maintained despite rejection of the allogeneic vascular pedicle thereafter. We have previously described a large animal (swine) pre-clinical model, reconstructing tibial defects with vascularized tibial allotransplants. In this manuscript, autologous angiogenesis is evaluated in this model and correlated with bone viability.

MATERIALS AND METHODS

Allogeneic tibial segments were transplanted across a major swine leukocyte antigen mismatch. Microvascular repair of the bone VCA pedicle was combined with intraosseous implantation of an autogenous arteriovenous (AV) bundle. The bundle was ligated in group 1 (n = 4), and allowed to perfuse in group 2 (n = 4). Three-drug immunotherapy was given for 2 weeks. At 16 weeks micro-CT angiography quantified neoangiogenic vessel volume. Bone viability, rejection grade, and bone healing were analyzed.

RESULTS

A substantial neoangiogenic circulation developed from the implanted AV-bundle in group 2, with vessel density superior to ligated AV-bundle controls (0.11 ± 0.05 vs. 0.01 ± 0.01, P = .029). Bone allotransplant viability was also significantly enhanced by neoangiogenesis (78.7 ± 4.4% vs. 27.7 ± 5.8%, P = .028) with higher bone healing scores (21.4 ± 2.9 vs. 12.5 ± 3.7, P = .029). Ligated control tibias demonstrated disorganized bone morphology and higher local inflammation (P = .143).

CONCLUSION

Implantation of autogenous AV bundles into vascularized bone allotransplants resulted in the rapid formation of a neoangiogenic autogenous blood supply in a swine tibia model that maintained bone viability, improved bone healing, and minimized rejection.

Recipient-derived angiogenesis with short term immunosuppression increases bone remodeling in bone vascularized composite allotransplantation: A pilot study in a swine tibial defect model

Current vascularized composite allotransplantation (VCA) transplantation protocols rely upon life-long immune modulation to maintain tissue perfusion. Alternatively, bone-only VCA viability may be maintained in small animal models using surgical angiogenesis from implanted autogenous vessels to develop a neoangiogenic bone circulation that will not be rejected. This study tests the method's efficacy in a large animal model as a bridge to clinical practice, quantifying the remodeling and mechanical properties of porcine tibial VCAs. A segmental tibial defect was reconstructed in Yucatan miniature swine by transplantation of a matched tibia segment from an immunologically mismatched donor. Microsurgical repair of nutrient vessels was performed in all pigs, with simultaneous intramedullary placement of an autogenous arteriovenous (AV) bundle in Group 2. Group 1 served as a no-angiogenesis control. All received 2 weeks of immunosuppression. After 16 weeks, micro-CT and histomorphometric analyses were used to evaluate healing and remodeling. Axial compression and nanoindentation studies evaluated bone mechanical properties. Micro-CT analysis demonstrated significantly more new bone formation and bone remodeling at the distal allotransplant/recipient junction and on the endosteal surfaces of Group 2 tibias (p = 0.03). Elastic modulus and hardness were not adversely affected by angiogenesis. The combination of 2 weeks of immunosuppression and autogenous AV-bundle implantation within a microsurgically transplanted tibial allotransplant permitted long-term allotransplant survival over the study period of 16 weeks in this large animal model. Angiogenesis increased bone formation and remodeling without adverse mechanical effects. The method may allow future composite-tissue allotransplantation of bone without the risks associated with long-term immunosuppression. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1242-1249, 2017.

Orthotopic Hind Limb Transplantation in the Mouse

In vivo animal model systems, and in particular mouse models, have evolved into powerful and versatile scientific tools indispensable to basic and translational research in the field of transplantation medicine. A vast array of reagents is available exclusively in this setting, including mono- and polyclonal antibodies for both diagnostic and interventional applications. In addition, a vast number of genotyped, inbred, transgenic, and knock out strains allow detailed investigation of the individual contributions of humoral and cellular components to the complex interplay of an immune response and make the mouse the gold standard for immunological research. Vascularized Composite Allotransplantation (VCA) delineates a novel field of transplantation using allografts to replace "like with like" in patients suffering traumatic or congenital tissue loss. This surgical methodological protocol shows the use of a non-suture cuff technique for super-microvascular anastomosis in an orthotopic mouse hind limb transplantation model. The model specifically allows for comparison between established paradigms in solid organ transplantation with a novel form of transplants consisting of various different tissue components. Uniquely, this model allows for the transplantation of a viable vascularized bone marrow compartment and niche that have the potential to exert a beneficial effect on the balance of immune acceptance and rejection. This technique provides a tool to investigate alloantigen recognition and allograft rejection and acceptance, as well as enables the pursuit of functional nerve regeneration studies to further advance this novel field of transplantation.

Vascularized composite tissue allotransplantation--state of the art

Vascularized composite tissue allotransplantation is a viable treatment option for injuries and defects that involve multiple layers of functional tissue. In the past 15 yr, more than 150 vascularized composite allotransplantation (VCA) surgeries have been reported for various anatomic locations including - but not limited to - trachea, larynx, abdominal wall, face, and upper and lower extremities. VCA can achieve a level of esthetic and functional restoration that is currently unattainable using conventional reconstructive techniques. Although the risks of lifelong immunosuppression continue to be an important factor when evaluating the benefits of VCA, reported short- and long-term outcomes have been excellent, thus far. Acute rejections are common in the early post-operative period, and immunosuppression-related side effects have been manageable. A multidisciplinary approach to the management of VCA has proven successful. Reports of long-term graft losses have been rare, while several factors may play a role in the pathophysiology of chronic graft deterioration in VCA. Alternative approaches to immunosuppression such as cellular therapies and immunomodulation hold promise, although their role is so far not defined. Experimental protocols for VCA are currently being explored. Moving forward, it will be exciting to see whether VCA-specific aspects of allorecognition and immune responses will be able to help facilitate tolerance induction.

Facial transplantation

The face has functional and aesthetic importance. It represents the most identifiable aspect of an individual's physical being. Its role in a person's identity and ability to communicate can therefore not be overstated. The face also plays an important role in certain functional needs such as speech, communicative competence, eye protection, and emotional expressiveness. The latter function bears significant social and psychological import, because two thirds of our communication takes place through nonverbal facial expressions. Accordingly, the significance of reconstruction of the face is indisputable. Yet despite application of meticulous techniques and the development of innovative approaches, full functional and aesthetic reconstruction of the face remains challenging. This is because optimal reconstruction of specialized units of the face have to address both the functional and aesthetic roles of the face.

Past, present, and future prospects for inducing donor-specific transplantation tolerance for composite tissue allotransplantation

Composite tissue allotransplantation (CTA) is among the most immunologically complex and newest transplant fields. Although the field has made considerable advances, there are still concerns that these procedures are performed to enhance quality-of-life issues and are not lifesaving procedures that restore physiologic function. Two challenges limit the widespread application of CTA; the first is chronic rejection, the most prevailing cause of organ allograft failure after transplantation; the second barrier is the numerous health complications associated with lifelong immunosuppressive therapy. Several tolerance-inducing strategies, including costimulatory blockade, T-cell depletion, mixed chimerism, and gene targeting of transplanted organs, have the potential to induce lifelong tolerance to organ allografts without chronic immunosuppression. Effective clinical tolerance protocols that improve CTA acceptance and offer an alternative to the requirement for chronic immunosuppressive therapy could be a major advance in the field. Tolerance would allow allotransplantation to provide a currently unmet need for reconstruction of large tissue defects. This article reviews the history of CTA, current challenges and complications, and offers future directions for CTA research in strategies to induce tolerance.

A modified vascularized whole knee joint allotransplantation model in the rat

Previous papers have shown surgical neoangiogenesis to allow long-term bone allotransplant survival without immunosuppression. Whole joint composite tissue allotransplants (CTA) might be treated similarly. A novel rat knee CTA model is described for further study of the roles of neoangiogensis in joint allotransplant survival and adjustment of immunosuppression. Microvascular knee CTA was performed in nine rats across a major histocompatibility barrier with both pedicle repair and implantation of host-derived arteriovenous ("a/v") bundles. In the control group (N = 3), the pedicle was ligated. Immunosuppression was given daily. Joint mobility, weight-bearing, pedicle patency, bone blood flow, and sprouting from a/v bundles were assessed at 3 weeks. All but the nonrevascularized control knees had full passive motion and full weight bearing. One nutrient pedicle thrombosed prematurely. Blood flow was measurable in transplants with patent nutrient pedicles. Implanted a/v bundles produced new vascular networks on angiography. This new rat microsurgical model permits further study of joint allotransplantation. Patency of both pedicles and implanted a/v bundles was maintained, laying a foundation for future studies.

Living bone allotransplants survive by surgical angiogenesis alone: development of a novel method of composite tissue allotransplantation

BACKGROUND

Segmental bone defects pose reconstructive challenges. Composite tissue allotransplantation offers a potential solution but requires long-term immunosuppression with attendant health risks. This study demonstrates a novel method of composite-tissue allotransplantation, permitting long-term drug-free survival, with use of therapeutic angiogenesis of autogenous vessels to maintain circulation.

METHODS

Ninety-three rats underwent femoral allotransplantation, isotransplantation, or allografting. Group-1 femora were transplanted across a major histocompatibility complex barrier, with microsurgical pedicle anastomoses. The contralateral saphenous artery and vein (termed the AV bundle) of the recipient animal were implanted within the medullary canal to allow development of an autogenous circulation. In Group 2, allotransplantation was also performed, but with AV bundle ligation. Group 3 bones were frozen allografts rather than composite-tissue allotransplantation femora, and Group 4 bones were isotransplants. Paired comparison allowed evaluation of AV bundle effect, bone allogenicity (isogeneic or allogeneic), and initial circulation and viability (allotransplant versus allograft). Two weeks of immunosuppression therapy maintained blood flow initially, during development of a neoangiogenic autogenous blood supply from the AV bundle in patent groups. At eighteen weeks, skin grafts from donor, recipient, and third-party rats were tested for immunocompetence and donor-specific tolerance. At twenty-one weeks, bone circulation was quantified and new bone formation was measured.

RESULTS

Final circulatory status depended on both the initial viability of the graft and the successful development of neoangiogenic circulation. Median cortical blood flow was highest in Group 1 (4.6 mL/min/100 g), intermediate in Group 4 isotransplants (0.4 mL/min/100 g), and absent in others. Capillary proliferation and new bone formation were generally highest in allotransplants (15.0%, 6.4 μm³/μm²/yr) and isotransplants with patent AV bundles (16.6%, 50.3 μm³/μm²/yr) and less in allotransplants with ligated AV bundles (4.4%, 0.0 μm³/μm²/yr) or allografts (8.1%, 24.1 μm³/μm²/yr). Donor and third-party-type skin grafts were rejected, indicating immunocompetence without donor-specific tolerance.

CONCLUSIONS

In the rat model, microvascular allogeneic bone transplantation in combination with short-term immunosuppression and AV bundle implantation creates an autogenous neoangiogenic circulation, permitting long-term allotransplant survival with measurable blood flow.

Hand transplantation and vascularized composite tissue allografts in orthopaedics and traumatology

Composite tissue allograft (CTA) is defined as heterologous transplantation of a complex comprising skin and subcutaneous, neurovascular and mesenchymal tissue. Such techniques allow complex reconstruction using matched tissue, without donor site morbidity. The potential indications in orthopaedics-traumatology could in the future be more frequent than the present indications of heart, lung, liver, kidney and pancreas transplantation. International clinical experience clearly demonstrates the feasibility of CTA, both surgically and immunologically. However, immunosuppression remains indispensable, exposing the patient to risks that are not acceptable for purely functional surgery, except in very particular indications. The main hope for the future lies in induction of graft-specific tolerance.

Tacrolimus (FK506): Safety and Applications in Reconstructive Surgery

Tacrolimus (FK506) is a macrolide immunosuppressive drug that is approved for the prevention of allograft rejection. It is a standard component of immunosuppressive regimens currently in use for organ and reconstructive tissue transplants. The experimental literature has demonstrated potential efficacy in the management of other diseases for which transplantation does not play a role. The ability of tacrolimus to modulate the immune system and inhibit T cell activation provides a potential benefit for the treatment of disorders in which autoimmune phenomena are central to their pathogenesis such as rheumatoid arthritis and inflammatory bowel disease. Tacrolimus also has well-established neuroprotective and neuroregenerative properties through both similar and different mechanisms that have been extensively demonstrated in both small and large animal models. However, as a potent immunosuppressive agent, it can cause serious adverse effects, some of which are irreversible and potentially life threatening. This article reviews its safety under different therapeutic requirements and applications in both allogeneic and autogenous tissue reconstruction.

[Organ transplantation, composite tissue allotransplantation, and plastic surgery]

Transplantations play an increasing role for plastic reconstructive surgeons. The increasing number of solid organ transplantations and the improved long-term survival rates lead to increased numbers of these patients also undergoing plastic and reconstructive procedures. Free flap transfer in solid organ transplant patients is feasible with no higher risk to both transplant function and postoperative complications than for nontransplant patients, even during immune suppression. Composite tissue allotransplantation (CTA) is an evolving field in plastic reconstructive surgery with hands, arms, partial faces, abdominal walls, and knee joints being transferred in clinical settings. However only an interdisciplinary approach using all available resources in highly selected patients after exhausting all other plastic reconstructive procedures is able to achieve reasonable results. The potential complications of long-term immune suppression and patient compliance have to be balanced with the expected and achieved functional result of CTA, whose procedures must be discussed as a potential tissue or organ transplantation, given the legal and logistic implications. The interdisciplinary cooperation of transplant surgeons, microsurgeons, psychologists, and ergo- and physiotherapists is mandatory to achieve successful CTA results.

The history of human composite tissue allotransplantation

Restoration of amputations and disfigurement are represented in ancient mythology, but the modern history of composite tissue allotransplantation begins with World War II injuries that generated seminal immunologic experiments by Medawar and co-workers. These studies led to the first successful human allografts in the 1950s by Peacock with composite tissue and Murray and co-workers with solid organs. Pharmacologic immunosuppression brought rapid growth of solid organ transplantation over the next 50 years, but composite tissue transplantation virtually disappeared. This evolution was judged to be a consequence of the greater antigenicity of skin, which that was insurmountable by the available immunosuppression. In the mid-1990s, progress in immunosupression allowed skin-bearing grafts, led by successful hand transplants, which produced a renaissance in composite tissue allotransplantation. Since then, graft types have expanded to over 10, and graft numbers to over 150, with success rates that equal or exceed solid organs. The field has emerged as one of the most exciting in contemporary medicine, although accompanied by substantial challenges and controversy. This paper reviews the origins and progress of this field, assessing its potential for future evolution.

Hand transplantation in the United States: experience with 3 patients

BACKGROUND

Composite tissue allotransplantation (CTA) is a newly emerging field of transplantation that involves the simultaneous transfer of multiple tissues with differing antigenicity. Hand transplantation, the most widely recognized form of CTA, aims to improve function and the quality of life of upper limb amputees.

METHODS

In 1999, an institutional review board-approved hand transplantation protocol was implemented at the Jewish Hospital, University of Louisville. Suitable patients were evaluated and underwent hand transplantation. The surgical technique was akin to that used in limb reimplantation, and the immunosuppression protocol used was similar to renal transplantation.

RESULTS

Between 1999 and 2006, 3 patients underwent hand transplantation at our center. Although episodes of acute rejection were seen in all patients during the early postoperative period, only 1 immunologic event occurred after the first year. Graft function improved with time period. Carroll test scores were superior to those recorded with a prosthesis at the end of 1 year. Additionally, recovery of protective sensation was seen in all 3 patients and limited discriminatory sensation in 2. Complications related to immunosuppression have included cytomegalovirus infection in 2 patients, diabetes in 1, hyperlipidemia in 2, and osteonecrosis in 1. At a follow-up of 8, 6, and 1 year(s), all the recipients are healthy and have returned to a productive life.

CONCLUSIONS

The long-term success reported here should encourage wider application of the CTA in general and hand transplantation in particular. Methods of minimizing long-term immunosuppression need to be pursued.

Composite tissue transplantation: a rapidly advancing field

Composite tissue allotransplantation (CTA) is emerging as a potential treatment for complex tissue defects. It is currently being performed with increasing frequency in the clinic. The feasibility of the procedure has been confirmed through 30 hand transplantation, 3 facial reconstructions, and vascularized knee, esophageal, and tracheal allografts. A major drawback for CTA is the requirement for lifelong immunosuppression. The toxicity of these agents has limited the widespread application of CTA. Methods to reduce or eliminate the requirement for immunosuppression and promote CTA acceptance would represent a significant step forward in the field. Multiple studies suggest that mixed chimerism established by bone marrow transplantation promotes tolerance resulting in allograft acceptance. This overview focuses on the history and the exponentially expanding applications of the new frontier in CTA transplantation: immunology associated with CTA; preclinical animal models of CTA; clinical experience with CTA; and advances in mixed chimerism-induced tolerance in CTA. Additionally, some important hurdles that must be overcome in using bone marrow chimerism to induce tolerance to CTA are also discussed.

Chimerism and bone marrow based therapies in transplantation

Composite tissue allotransplantation holds a great potential for providing increased knowledge of anatomy and microsurgical experience for life-enhancing reconstructions. Many transplant cases around the world have made this a clinical reality at the present time. Composite tissue allotransplants contain multiple tissue types, including bone, muscle, vessels, nerves, skin, and immune cells and bear a huge antigenic load. Although immunosuppressive drugs are applied successfully to prevent allograft rejection, their side effects pose a barrier to worldwide use. Bone marrow therapy in many tolerance induction protocols, therefore, provides a guide to reaching the target of permanent immunotolerance. Multiple studies suggest that bone marrow is immunomodulatory and may facilitate allograft acceptance. In this review, bone marrow based therapy protocols of clinical and experimental models are presented in two major categories: solid organ and composite tissue transplantation.

Effects of bisphosphonate treatment on bone repair under immunosuppression using cyclosporine A in adult rats

The effect of cyclosporine A on bone turnover remains unclear. Using adult rats with vascularized bone transplantation, we show that long-term cyclosporine A administration increases bone turnover and zoledronic acid treatment enhances the reconstruction of cyclosporine A-administered skeleton. Bisphosphonates might be efficacious in human bone repair under immunosuppression using cyclosporine A.

INTRODUCTION

Bisphosphonate treatment effectively prevents bone loss after transplantation. However, recent evidence from gain- and loss-of-function experiments has indicated that calcineurin inhibitors, such as cyclosporine A (CsA), reduce bone turnover, and severely suppressed bone turnover might delay the union of human fractured bone. The purpose of this study was to investigate the effects of bisphosphonate treatment on the repair of CsA-administered skeleton.

METHODS

After skeletal reconstruction by vascularized tibial grafting, adult recipient rats were treated with intramuscular CsA (10 mg/kg/day) and low-dose (0.2 microg/kg/week) or high-dose (2 microg/kg/week) subcutaneous zoledronic acid alone or in combination for 8 weeks. Biochemical parameters were measured in blood and urine. The reconstructed skeleton was analyzed using soft X-ray, histology, dual energy X-ray absorptiometry, and three-point bending test.

RESULTS

CsA induced mild renal dysfunction, hyperparathyroidism and high bone turnover. High-dose zoledronic acid delayed cortical bone union at the distal host-graft junction, but its combination with CsA did not cause such a delay. High-dose zoledronic acid prevented CsA-induced bone loss and bone fragility in the reconstructed skeleton.

CONCLUSION

In this rat model, long-term CsA administration increases bone turnover, at least partly, through hyperparathyroidism and high-dose zoledronic acid treatment does not impair the union of CsA-administered bone.

Allogreffe de mains: expérience lyonnaise

Hand allograft is a method in the stage of clinical experimentation, which is reserved in France for the treatment of bilateral traumatic amputees. This study reports the Lyon team experience, which is pioneer in this domain. Four patients (3 males and 1 female) underwent seven (one unilateral and three bilateral) hand transplantations from September 1998 to February 2007. The level of amputation was at the wrist or at the mid-forearm. Delay since hand loss ranged from 2.5 to 9 years. The surgical protocol was elaborated and planned case by case. All recipients received the same immunosuppressive treatment. Episodes of acute rejection were observed in the first 3 months after transplantation, which were easily managed after a few days increasing oral prednisone doses and applying topical immunosuppressants. Currently the patients receive the doses of immunosuppressants comparable to those in kidney-grafted patients. We have not registered any severe complication of immunosuppressive treatment up till now (7 years follow-up for the earliest graft). We performed analytical and functional clinical, as well as questionnaire evaluation of patients. The first case (unilateral graft) resulted in graft failure at 2 years due to non-compliance of the patient. The three bilateral graftees demonstrate a favorable evolution despite some immunological (hyperglycemia, serum sickness) and surgical (thrombosis, osteomyelitis, skin loss) complications, which could be managed. The middle and long-term follow-up evaluation revealed good to excellent sensorimotor recovery of 4 hands in both male recipients (4 and 7 years) with satisfactory social adaptation, higher or equal to those expected after post-traumatic replantations at the equivalent level and higher to those obtained with currently available myoelectric prosthesis. The last patient, a young female who has been grafted in February 2007, receives ongoing reeducation course and shows normal progress of functional restoration of both hands. The encouraging results of this clinical experimentation make us currently consider hand allografting as reasonable and useful both for the patients and for evolution of research in composite tissues allotransplantation (CTA). Further long-term careful research and worldwide monitoring of all patients with hand allografts is required to, on the one part, state on the authorization of this surgery, and, on the other part, to better elucidate the mechanisms of successful CTA.

Transplantation of the hand, face, and composite structures: evolution and current status

This article reviews the world experience in the newly emerging field of composite tissue allotransplantation. These allografts contain multiple tissues that are usually musculoskeletal structures with a skin or epithelial surface, such as hand, facial structures, larynx, tongue, ear, knee/femur, abdominal wall, and penis. They represent a new transplantation field, with only a 10-year experience and just over 50 clinical cases. This review of the 10-year world experience found uniform technical success, immunologic biology, and immunosuppression regimens very similar to solid organ transplants, and success strongly correlated with adherence to guidelines for psychiatric screening, thorough preparation of patient and families, intense postoperative monitoring, and assurance of medication access. All failures reported have been caused by lapses in these parameters. This early experience shows a great potential for application of these new procedures to the most challenging reconstructive needs.

[Experimental and clinical experience of composite tissues allotransplantation in reconstructive surgery]

Composite tissue allotransplantation (CTA) is a new concept in reconstructive surgery to improve major physical defects with no current solution. Although not a life-saving procedure, tissue replacement by CTA offers great potential for improving quality of life but relies on lifelong immunotherapy. This new practice has become achievable with the refinement of microsurgical techniques, with experience gained from limb and scalp replantations, with the development of organ transplantation and the release of new immunosuppressive drugs. Experimental and clinical research made it possible. The first human cases of CTA proved the reality and the feasibility of the concept. While the early functional results of these allografts are encouraging, they will need to be assessed in the long-term, and development of less toxic - more efficient immonu-suppressive drugs will be a permanent requisite to the broadening of CTA. Although long-term outcome and potential adverse effects of chronic immunosuppression remain uncertain, as for organ transplantation, CTA is already a potential solution for some highly selected patients carrying physical disabilities such as large facial defects and bilateral hand amputation.

Outcome of allogeneic vascularized knee transplants

Transplantation of vascularized knee joints is a novel approach in Composite Tissue Allotransplantation (CTA). In 1996 our group started a clinical knee transplantation project and six transplantations have been performed since. Key problems identified early were the monitoring of acute rejection and choice of an immunosuppressive regime. One graft was lost due to postoperative infection and one due to of noncompliance where the patient discontinued the immunosuppressant regime. In three cases late rejection lead to necrosis and graft dysfunction after 15, 16 and 24 months, respectively. Exit-strategies were arthrodesis in one patient and Above Knee Amputation in two cases. With retrospective analysis after initial five cases the treatment protocol was improved. The immunosuppressive drug regime was altered, femoral diaphysis and knee joint grafting was combined and a vascularized block of donor skin and subcutaneous tissue was harvested with the graft (sentinel skin graft). The sentinel skin graft enabled us to monitor acute rejection by clinical and histological examination and avoid late rejection by rapid treatment with high dose steroids. In summary, over a four-year period, one of six allogeneic vascularized knee transplants has survived, one was lost from a surgical site infection, one by noncompliance and three by late rejection. Analysis of our data leads us to suggest that knee transplantation should be limited to a combined injury consisting of extensive loss of cartilage and bone, deficient extensor mechanism and soft tissue and skin defects without any signs of infection. Transplantation should only be taken into consideration as last option before Above Knee Amputation in an otherwise healthy patient under 35 years of age.

Tissue engineering: bridging the gap between replantation and composite tissue allografts

This article explores issues related to tissue engineering and composite tissue allografts that employ physiologic and anatomic autogenous replicates to restore tissue loss. Composite tissue allotransplantation has become a controversial option for reconstruction, most prominently for reconstruction involving the hand and, recently, the face. While the side-effect profile of systemic immunosuppression continues to improve, the long-term risks of immunosuppression leaves composite tissue allotransplantation a domain for cautious exploration. Meanwhile, tissue engineering could, conceivably, be the gap between replantation and composite tissue allografts. Whereas the perils of immunosuppression may limit the routine use of allografts, employing constructions made of the patient's own cells negates the need for any antirejection therapy.

Tissue Transplantation in Plastic Surgery

The functional and aesthetic outcome following application of conventional reconstructive procedures or prosthetic materials is not satisfactory, especially in patients who have severe deformities and disabilities. Since the first successful hand transplantation in France in 1998, composite tissue allograft transplantation has gained a great deal of interest in the field of plastic surgery. It is obvious that composite tissue allograft transplantation will improve patients' life quality, but this might be at the expense of decreasing life expectancy. Currently, the main obstacle for composite tissue allograft transplantation is the use of life-long immunosuppression therapy because of their well-known side effects. In addition, the ethical, social, and psychologic issues are raised when discussing face transplantation. The long-term results of the recently performed partial face transplantations will be critical to judge the future applications of partial or total face transplantation.

Hand transplantation: the state-of-the-art

The feasibility of hand transplantation has been demonstrated, both surgically and immunologically. Levels of immunosuppression comparable to regimens used in solid organ transplantation are proving sufficient to prevent graft loss. Many patients have achieved discriminative sensibility and recovery of intrinsic muscle function. In addition to restoration of function, hand transplantation offers considerable psychological benefits. The recipient's pre-operative psychological status, his motivation and his compliance with the intense rehabilitation programme are key issues. While the induction of graft specific tolerance represents a hope for the future, immunosuppression currently remains necessary and carries significant risks. Hand transplantation should, therefore, only be considered a therapeutic option for a carefully selected group of patients.

Vascularized bone allotransplantation: current state and implications for future reconstructive surgery

This article focuses on current advances in musculoskeletal tissue allotransplantation, including strategies for maintaining tissue viability in the face of histocompatibility mismatch and resulting acute and chronic rejection responses. In particular, it introduces a novel concept developed in the authors' laboratory and currently under evaluation that may obviate the problem of chronic rejection. The authors have used therapeutic angiogenesis to develop a host-derived neoangiogenic circulation that maintains blood flow regardless of rejection. The replacement of the allogeneic vessels together with bone remodeling from host-derived cells eventually may largely replace the allogeneic osteocytes and bone with native bone.

Anatomic bases of vascularized elbow joint harvesting to achieve vascularized allograft

In order to later make precise the operative technique of free vascularized elbow allograft transfer, the anatomic conditions necessary for the success of such an operation are reviewed. The exact topography of the nutrient foramina of the humerus, radius, and ulna has been specified on 102 dry bones. The osseous resection at the recipient will have to be carried out on these aspects: nutrient foramina of the three bones of the elbow (at 9 cm from medial epicondyle for the humerus; at 8 cm for the two bones of forearm) in order to preserve diaphysary vascularization of the recipient. A study of arterial and venous vascularization carried out on 18 anatomic specimens showed that the osseous ends were irrigated by a periosteal arterial network and were drained in the centromedullary cavities. Systematization of the arteriovenous blood supply of the distal end of the humerus and proximal ends of the two forearm bones is proposed after dissection of 18 anatomic specimens. Arterial periosteal territories are defined. The importance of each peri articular arteriole is estimated according to the surface of its respective section. A radial, constant, and musculoperiosteal collateral artery from the brachial artery is described. It accounts for 12% (+/- 3%) of the total contribution. The recurrent radial artery is the most significant: 31% (+/- 9%) of the total contribution. The profunda brachii artery is negligible: 4% (+/- 2%) of the total contribution. As well for vascular as mechanical reasons, osteosynthesis will have to be carried out using screwed plates, the optimal location of which is specified according to the arterial periosteal cartography. Ulnar and radial nerves and, to a lesser extent, the median nerve can be harvested "en bloc" preserving their vascular supply in order to make vascularized grafts of them. Free vascularized elbow allograft transfer is technically possible, if one respects these anatomic bases.

Bilateral Vascularized Femoral Bone Transplant

We present a new model of vascularized bone marrow transplantation-bilateral vascularized femoral bone (BVFB) isograft transplant based on abdominal aorta and inferior vena cava. A total of 7 BVFB isograft transplants were performed between Lewis (RT1) rats. In the donor, both femoral bones were harvested based on the abdominal aorta and inferior vena cava. In the recipient, the harvested isograft transplants were transferred into the inguinal region (in 3 animals) and into the abdominal cavity (in 4 animals). The mean operation time was 3 hours and 35 minutes. The mean warm ischemic time was 35 minutes. The vascular pedicles of the transplants that were transferred into the inguinal region were thrombosed at day 7 posttransplantation. The vascular pedicles of transplants into the abdominal cavity were patent and the bones were viable during the follow-up period of 63 days posttransplant. We have confirmed the feasibility of BVFB transplantation based on abdominal aorta and inferior vena cava.

From experimental rat hindlimb to clinical face composite tissue allotransplantation: Historical background and current status

The purpose of this article is to review the historical background and clinical status of composite tissue allotransplantation and to discuss the scientific evolution of clinical face transplantation. Composite tissue allotransplantation (CTA) rapidly progressed in the 1980s with the discovery of cyclosporine. Although the most success has been achieved with hand transplantation, others have made progress with allografts of trachea, peripheral nerve, flexor tendon apparatus, vascularized knee, larynx, abdominal wall, and most recently, partial face. The world's first partial face allotransplantation occurred in November 2005 in France. In April of 2006, there was a second performed in China. As of today, there are now multiple institutions with plans to attempt the world's first full facial/scalp transplant. Complete facial/scalp allotransplantation offers a viable alternative for unfortunate individuals suffering severe facial disfigurement and is a product of many decades of experimental research, beginning with rat hindlimb allografts.

Strategies for Tolerance Induction in Nonhuman Primates

Recent advances in the field of reconstructive surgery and immunology resulted in increased interest in composite tissue allograft (CTA) transplantation. Up to date, more than 50 CTA transplants have been reported in humans. A significant number of experimental studies on CTA transplants under different protocols of tolerance-inducting strategies have been reported in small-animal models. There is however, a limited number of CTA transplants performed in nonhuman primates. To reach the ultimate clinical success in CTA transplantation, more experimental studies on tolerance induction in nonhuman primates are needed to apply these immunomodulatory protocols to CTA transplants in humans. In this review, strategies for tolerance induction in the nonhuman primate model in solid organ and CTA transplants are presented in 3 major categories: chimerism induction, T-cell depletion, and costimulatory receptor blockade.

Bone quality and healing in a swine vascularized bone allotransplantation model using cyclosporine-based immunosuppression therapy

Although vascularized bone and joint allotransplantation is a promising new treatment option for reconstructing large bone defects, the need for immunosuppressive agents to prevent rejection in these procedures poses a major problem. This problem stems from the fact that several of these agents can cause harmful side effects, such as alterations in bone quality and healing. Therefore, the purpose of this study was to determine what effect the commonly used immunosuppressant regimen cyclosporine A-based combination therapy has on bone quality and healing. In 10 pigs, vascularized bone allografts with skin and muscle components (osteomyocutaneous free flaps) were transplanted from size-matched donor animals. Recipient animals received oral cyclosporine A/mycophenolate mofetil/prednisone therapy for 90 days. Bone quality was studied before and after transplantation by measuring the bone's acoustic velocity and density and calculating the bone's elastic coefficient. Bone healing was assessed using radiographic analysis. Four animals were lost as a result of graft rejection or immunosuppression-related complications before the 90-day endpoint of the study. Although bone specimens taken from the six animals that completed the 90-day protocol had histological signs of rejection, they all seemed to have normal bone healing. Posttransplant bone density values were significantly decreased (p < 0.05) (1544.7 +/- 47.5 kg/m3) as compared with pretransplant values (1722.7 +/- 44.1 kg/m3). Results of the acoustic velocity and elastic coefficients measurements showed a significant decrease (p < 0.05) in posttransplant values (from 3503.0 +/- 165.1 meters/sec to 2963.0 +/- 54.6 meters/sec and from 21.6 +/- 2.2 GPa to 13.6 +/- 0.5 GPa, respectively), indicating diminished bone quality. The findings indicate that cyclosporine A/mycophenolate mofetil/prednisone combination therapy is ineffective in preventing bone rejection, that it decreases bone quality, and that it is associated with systemic toxicity, suggesting that this immunosuppressive regimen at the doses used in this study is not ideal for vascularized bone allotransplantation procedures.

Perspectives on Hand Transplantation

The early experience of hand transplantation has yielded a mixture of successes and failures. No life-threatening adverse effects have been encountered from immunosuppression, yet additional medications were required in some cases with unknown long-term efficacy or side effects. Limited functional returns have been observed, but any effect of chronic rejection is too early to determine. Although the experience has confirmed the benefits of hand transplantation to patients and their families, the future of hand transplantation on a wide scale is dependent on further research to alter its risk-benefit balance.

New Surgical Approach in Facial Transplantation Extends Survival of Allograft Recipients

We have previously developed a composite total face-scalp allotransplantation model based on bilateral common carotid arteries (CCA) and external jugular veins. To decrease the mortality rates, different modifications of arterial anastomoses in the facial allograft recipients are presented. Eighteen full face-scalp allograft transplantations were performed across major histocompatibility (MHC) barriers between ACI (RT1) donors and Lewis (RT1) recipients. Bilateral CCA and bilateral external carotid arteries of the recipients were used as recipient vessels to vascularize the flap in 5 and 4 transplants, respectively. In 9 transplants, unilateral CCA of the recipients were used to vascularize the face/scalp flap. All the animals received CsA 16 mg/kg/d Sc, which was tapered over 4 weeks to 2 mg/kg/d. In transplants utilizing bilateral CCA, the survival rate of the animals was very short. Transplants in which unilateral CCA were used yielded 100% survivals over 200 days posttransplant. These modifications of arterial anastomoses have significantly improved survival of facial allograft recipients.