Report (2017) of the International Registry on Hand and Composite Tissue Allotransplantation (IRHCTT)

Designer Organs: Ethical Genetic Modifications in the Era of Machine Perfusion

Gene therapy is a rapidly developing field, finally yielding clinical benefits. Genetic engineering of organs for transplantation may soon be an option, thanks to convergence with another breakthrough technology, ex vivo machine perfusion (EVMP). EVMP allows access to the functioning organ for genetic manipulation prior to transplant. EVMP has the potential to enhance genetic engineering efficiency, improve graft survival, and reduce posttransplant complications. This will enable genetic modifications with a vast variety of applications, while raising questions on the ethics and regulation of this emerging technology. This review provides an in-depth discussion of current methodologies for delivering genetic vectors to transplantable organs, particularly focusing on the enabling role of EVMP. Organ-by-organ analysis and key characteristics of various vector and treatment options are assessed. We offer a road map for research and clinical translation, arguing that achieving scientific benchmarks while creating anticipatory governance is necessary to secure societal benefit from this technology.

Decellularization of Human Digits: A Step Towards Off-the-Shelf Composite Allograft Transplantation

The field of reconstructive surgery faces significant challenges in addressing limb loss and disfigurement, with current organ preservation methods limited by short storage times. Decellularization offers a promising solution for generating engineered alternatives for reconstructive surgery by removing cellular material while preserving the extracellular matrix (ECM) and providing scaffolds for tissue regeneration. In this study, we developed a robust protocol for decellularizing whole digits from long-term freezer storage, achieving the successful removal of cellular material with intact ECM. Digit angiography confirmed the preservation of vascular integrity, facilitating future perfusion for recellularization. Quantitative analysis revealed significantly lower DNA content in decellularized tissues, indicating effective decellularization. Furthermore, extracellular matrix analysis showed the preservation of collagen, elastin, and glycosaminoglycans (GAGs) contents. Histological examination confirmed the reduction in cellularity and maintenance of tissue architecture in decellularized digits. Mechanical strength testing of decellularized digit tendons proved consistent with that of native digits. Our findings highlight the potential of decellularized digits as versatile platforms for tissue engineering and regenerative medicine. Moving forward, further optimization of protocols and collaborative efforts are essential for translating these findings into clinical practice, offering innovative solutions for reconstructive surgery and limb transplantation.

Tacrolimus-loaded Drug Delivery Systems in Vascularized Composite Allotransplantation: Lessons and Opportunities for Local Immunosuppression

Long-term systemic immunosuppression is needed for vascularized composite allotransplantation (VCA). The high rate of acute rejection episodes in the first posttransplant year, the development of chronic rejection, and the adverse effects that come along with this treatment, currently prevent a wider clinical application of VCA. Opportunistic infections and metabolic disturbances are among the most observed side effects in VCA recipients. To overcome these challenges, local immunosuppression using biomaterial-based drug delivery systems (DDS) have been developed. The aim of these systems is to provide high local concentrations of immunosuppressive drugs while reducing their systemic load. This review provides a summary of recently investigated local DDS with different mechanisms of action such as on-demand, ultrasound-sensitive, or continuous drug delivery. In preclinical models, ranging from rodent to porcine and nonhuman primate models, this approach has been shown to reduce systemic tacrolimus (TAC) load and adverse effects, while prolonging graft survival. Localized immunosuppression using biomaterial-based DDS represents an encouraging approach to enhance graft survival and reduce toxic side effects of immunosuppressive drugs in VCA patients. Preclinical models using TAC-releasing DDS have demonstrated high local immunosuppressive effects with a low systemic burden. However, to reduce acute rejection events in translational animal models or in the clinical reality, the use of additional low-dose systemic TAC treatment may be envisaged. Patients may benefit through efficient graft immunosuppression and survival with negligible systemic adverse effects, resulting in better compliance and quality of life.

Sex and Gender Differences in Face and Upper Extremity Allotransplantation: A Narrative Review of Implications and Impact

Sex and gender differences play a significant role in vascularized composite allotransplantation (VCA), impacting both surgical outcomes and postoperative care. While sex refers to biological distinctions and gender encompasses life experiences and behaviors, both factors are closely interrelated in transplantation. Biological sex differences, such as immune responses, hormonal fluctuations, and anatomical features influence graft adaptation and healing, while both sex and gender-specific factors affect psychological and functional recovery. Studies indicate that men have higher mortality and reoperation rates, whereas women are more susceptible to adverse effects from immunosuppressive therapies. Unlike solid organ transplantation (SOT), which is primarily lifesaving, VCA focuses on life-enhancing outcomes, requiring careful attention to patients' social, psychological, and functional well-being. Lifelong immunosuppression in VCA carries risks, including infections and cancer, complicating patient management. Psychological readiness is crucial for candidate selection and long-term success, with women often expressing greater concerns about outcomes. Although no significant gender differences in functional recovery have been observed, individualized rehabilitation plans based on anatomical and physiological differences remain essential for optimal recovery.

Ischemia Time in Extremity Allotransplantation: A Comprehensive Review

In response to the widespread occurrence of limb loss and the transformative potential of extremity vascularized composite allotransplantation (VCA), we examine the impact of warm and cold ischemia duration on limb survival and functional recovery. Our insights into warm ischemia are largely derived from relevant literature on replantation and revascularization. Studies indicate that achieving reperfusion within 5 to 6 hours of warm ischemia is critical for limb survival, and within 3 hours for curbing significant functional deficits. For limbs preserved in static cold conditions, as is standard practice in VCA, reperfusion should be attained within 10 to 12 hours of cold ischemia. However, our analysis exposes a lack of data on extremity functional recovery following cold ischemia, particularly in humans or large animal models. This underscores a gap in the literature that could guide clinical ischemia management in VCA if addressed. We anticipate optimal functional recovery between 3 and 6 hours of cold ischemia, as supported by outcomes in rats. Prolonged ischemia times are also associated with graft rejection, posing unique challenges to VCA. Tissues exhibit diverse responses, with muscle and nerve being highly susceptible to ischemic damage, and skin acquiring heightened immunogenicity. Ischemia management emerges as a focus for future policy and research initiatives. On the horizon, exploring updated transplantation protocols, vascular shunts, stabilizing perfusion solutions, and subnormothermic machine perfusion could mitigate ischemic damage and enhance clinical outcomes in extremity VCA.

Lymph Node Inclusion in a Modified Osteomyocutaneous Allograft for Vascularized Composite Allotransplantation: Establishment and Feasibility Assessment in a Pig Model

Background

Representative translational animal models play a key role in vascularized composite allotransplantation (VCA) research. A composite porcine hindlimb flap, previously described, is a relevant preclinical model. However, its bulkiness and the absence of critical immunologic tissues make it less suitable for investigating the unique immunologic features of VCA. We aimed to further develop this model by reducing its bulkiness and by including donor-draining lymph nodes.

Methods

We conducted an anatomic study by harvesting 11 porcine osteomyocutaneous flaps (4 conventional and 7 modified techniques), which were characterized by computed tomography. Furthermore, 8 allotransplantations were performed in Swiss landrace pigs. After the procedure, animals were assigned to a model development and control group (N = 4 per group). No immunosuppression was given, and animals were followed up until grade 3 rejection.

Results

With the modified technique, the flap weight was significantly reduced with a mean weight of 831 g, corresponding to 1.8% total body weight versus 1710 g in the conventional technique, representing 4.2% of total body weight (P < 0.0001). The muscle/bone ratio was reduced from 8.24 (conventional) to 2.92 (modified), (P = 0.03). Histologically, graft-draining lymph nodes showed typical changes related to rejection and no signs of ischemia after in vivo transplantation.

Conclusions

By modifying the surgical technique, the bulkiness of the flap was markedly reduced, without impairing its vascularization and reliably including vascularized graft-draining lymph nodes. Our modified VCA model in the pig presents distinct advantages for surgery as well as immunologic analysis, warranting a large-scale use for experimental reconstructive transplantation studies.

Transcriptome profiling of immune rejection mechanisms in a porcine vascularized composite allotransplantation model

Background

Vascularized composite allotransplantation (VCA) offers the potential for a biological, functional reconstruction in individuals with limb loss or facial disfigurement. Yet, it faces substantial challenges due to heightened immune rejection rates compared to solid organ transplants. A deep understanding of the genetic and immunological drivers of VCA rejection is essential to improve VCA outcomes.

Methods

Heterotopic porcine hindlimb VCA models were established and followed until reaching the endpoint. Skin and muscle samples were obtained from VCA transplant recipient pigs for histological assessments and RNA sequencing analysis. The rejection groups included recipients with moderate pathological rejection, treated locally with tacrolimus encapsulated in triglycerol-monostearate gel (TGMS-TAC), as well as recipients with severe end-stage rejection presenting evident necrosis. Healthy donor tissue served as controls. Bioinformatics analysis, immunofluorescence, and electron microscopy were utilized to examine gene expression patterns and the expression of immune response markers.

Results

Our comprehensive analyses encompassed differentially expressed genes, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes pathways, spanning various composite tissues including skin and muscle, in comparison to the healthy control group. The analysis revealed a consistency and reproducibility in alignment with the pathological rejection grading. Genes and pathways associated with innate immunity, notably pattern recognition receptors (PRRs), damage-associated molecular patterns (DAMPs), and antigen processing and presentation pathways, exhibited upregulation in the VCA rejection groups compared to the healthy controls. Our investigation identified significant shifts in gene expression related to cytokines, chemokines, complement pathways, and diverse immune cell types, with CD8 T cells and macrophages notably enriched in the VCA rejection tissues. Mechanisms of cell death, such as apoptosis, necroptosis and ferroptosis were observed and coexisted in rejected tissues.

Conclusion

Our study provides insights into the genetic profile of tissue rejection in the porcine VCA model. We comprehensively analyze the molecular landscape of immune rejection mechanisms, from innate immunity activation to critical stages such as antigen recognition, cytotoxic rejection, and cell death. This research advances our understanding of graft rejection mechanisms and offers potential for improving diagnostic and therapeutic strategies to enhance the long-term success of VCA.

Reaching New Heights: A Comprehensive Study of Hand Transplantations in Korea after Institutionalization of Hand Transplantation Law

PURPOSE

With the revision of the Organ and Transplantation Act in 2018, the hand has become legal as an area of transplantable organs in Korea. In January 2021, the first hand allotransplantation since legalization was successfully performed, and we have performed a total of three successful hand transplantation since then. By comparing and incorporating our experiences, this study aimed to provide a comprehensive reconstructive solution for hand amputation in Korea.

MATERIALS AND METHODS

Recipients were selected through a structured preoperative evaluation, and hand transplantations were performed at the distal forearm level. Postoperatively, patients were treated with three-drug immunosuppressive regimen, and functional outcomes were monitored.

RESULTS

The hand transplantations were performed without intraoperative complications. All patients had partial skin necrosis and underwent additional surgical procedures in 2 months after transplantation. After additional operations, no further severe complications were observed. Also, patients developed acute rejection within 3 months of surgery, but all resolved within 2 weeks after steroid pulse therapy. Motor and sensory function improved dramatically, and patients were very satisfied with the appearance and function of their transplanted hands.

CONCLUSION

Hand transplantation is a viable reconstructive option, and patients have shown positive functional and psychological outcomes. Although this study has limitations, such as the small number of patients and short follow-up period, we should focus on continued recovery of hand function, and be careful not to develop side effects from immunosuppressive drugs. Through the present study, we will continue to strive for a bright future regarding hand transplantation in Korea.

The Nuances of Hand Transplantation After Sepsis

Vascularized composite allotransplantation (VCA) of the upper extremity is an established restorative procedure for selected patients with acquired upper limb loss. The majority of upper limb VCAs performed worldwide have been for victims of various forms of trauma. However, in the developed world, amputation following severe sepsis seems to be an increasingly common indication for referral to hand transplant programs. Unlike trauma patients with isolated limb injuries, patients with amputations as a complication of sepsis have survived through a state of global tissue hypoperfusion and multisystem organ failure with severe, enduring effects on the entire body's physiology. This article reviews the unique considerations for VCA candidacy in postsepsis patients with upper limb amputation. These insights may also be relevant to postsepsis patients undergoing other forms of transplantation or to VCA patients requiring additional future solid organ transplants.

Defining chronic rejection in vascularized composite allografts - do we have reliable surrogates to look for?

PURPOSE OF REVIEW

Chronic rejection (CR) is a major threat in the field of vascularized composite tissue allografts (VCAs) as it causes graft dysfunction and usually graft loss. Unfortunately, knowledge of CR in VCA is incomplete because of the limited number of VCA recipients, the heterogeneous nature of VCAs and the short follow-up.

RECENT FINDINGS

The diagnosis of CR in VCA has relied on clinical and pathological findings. Clinical changes include graft fibrosis, dyschromia and ischemic/necrotic ulcerations. Pathological changes primarily affect allograft vessels and manifest with graft vasculopathy (i.e. myo-intimal proliferation and luminal narrowing of allograft vessels, leading to graft ischemia). Attempts are made to diagnose CR with non- or minimally-invasive techniques, such as imaging studies (ultrasound biomicroscopy, functional magnetic resonance imaging) and serum biomarkers. These techniques provide interesting results and further insight into the mechanisms of CR in VCA.

SUMMARY

The diagnosis of CR in VCA still relies mainly on clinicopathological graft alterations; unfortunately, these become overt rather late during the rejection process, when reversal of CR is problematic. More recent, minimally- or non-invasive techniques have provided encouraging results, but their usefulness in the diagnosis of CR requires further studies. These data highlight the paramount importance of CR prevention.

Patient definitions of transplant success in upper extremity vascularized composite allotransplantation: A mixed-methods study

Objective

Upper extremity vascularized composite allotransplantation is an innovative treatment option for people with upper extremity amputations. Limited patient-relevant long-term outcomes data about transplant success may impede patients' informed treatment decision-making. We assessed perceptions of what constitutes upper extremity vascularized composite allotransplantation success among individuals with upper extremity amputations.

Methods

This multisite study entailed interviews and focus groups with individuals with upper extremity amputations and upper extremity vascularized composite allotransplantation candidates, participants, and recipients. We examined perceptions of transplant success and preferences for five upper extremity vascularized composite allotransplantation outcomes. Qualitative data were analyzed using thematic analysis; and quantitative data were analyzed using descriptive statistics.

Results

In all, 50 individuals participated in interviews (61.7% participation rate), and 37 participated in nine focus groups (75.5% participation rate). Most were White (72%, 73%), had a mean age of 45 and 48 years, and had a unilateral amputation (84%, 59%), respectively. Participants conceptualized upper extremity vascularized composite allotransplantation success as transplant outcomes: (1) restoring function and sensation to enable new activities; (2) accepting the transplanted limb into one's identity and appearance; (3) not having transplant rejection; (4) attaining greater quality of life compared to prosthetics; and (5) ensuring benefits outweigh risks. Participants rated their most important upper extremity vascularized composite allotransplantation outcomes as follows: not having transplant rejection, not developing health complications, grasping objects, feeling touch and temperature, and accepting the upper extremity vascularized composite allotransplantation into your identity.

Conclusion

Individuals with upper extremity amputations maintain several conceptions of vascularized composite allotransplantation success, spanning functional, psychosocial, clinical, and quality of life outcomes. Providers should address patients' conceptions of success to improve informed consent discussions and outcomes reporting for upper extremity vascularized composite allotransplantation.

Tolerance of a Vascularized Composite Allograft Achieved in MHC Class-I-mismatch Swine via Mixed Chimerism

Background

Vascularized composite allografts (VCAs) allow reconstruction of devastating injuries and amputations, yet require lifelong immunosuppression that is associated with significant morbidity. Induction of immune tolerance of VCAs would permit widespread use of these procedures. VCAs are acquired from deceased donors most likely to be fully-MHC-mismatched (in contrast to living-related renal transplant donor-recipient pairs matched at one MHC haplotype). After achieving VCA tolerance in a swine model equivalent to clinical living-related renal transplants (single-haplotype MHC mismatches: e.g., “mother-daughter”/haploidentical), we tested our protocol in MHC class I, class II, and fully-MHC-mismatched pairs. Although class II mismatched swine demonstrated similar results as the haploidentical scenario (stable mixed chimerism and tolerance), our protocol failed to prevent rejection of class I and full mismatch VCAs. Here, we describe a new adapted conditioning protocol that successfully achieved tolerance across MHC class-I-mismatch barriers in swine.

Methods

Swine were treated with non-myeloablative total body and thymic irradiation two days prior to infusion of bone marrow cells from an MHC class I-mismatched donor. They also received a short-term treatment with CTLA4-Ig (Belatacept^®) and anti-IL6R mAb (Tociluzimab^®) and were transplanted with an osteomyocutaneous VCA from the same donor.

Results

Stable mixed chimerism and tolerance of MHC class-I-mismatched VCAs was achieved in 3 recipients. Allograft tolerance was associated with a sustained lack of anti-donor T cell response and a concomitant expansion of double negative CD4^-CD8^- T cells producing IL-10.

Conclusions

This study demonstrates the first successful mixed chimerism-induced VCA tolerance in a large animal model across a MHC class-I-mismatch. Future studies aimed at fully-mismatched donor-recipient pairs are under investigation with this protocol.

Bionic Prostheses: The Emerging Alternative to Vascularised Composite Allotransplantation of the Limb

Twenty years have surpassed since the first vascularised composite allotransplantation (VCA) of the upper limb. This is an opportunity to reflect on the position of VCA as the gold standard in limb reconstruction. The paucity of recipients, tentative clinical outcomes, and insufficient scientific progress question whether VCA will remain a viable treatment option for the growing numbers of amputees. Bionic technology is advancing at a rapid pace. The prospect of widely available, affordable, safely applied prostheses with long-standing functional benefit is appealing. Progress in the field stems from the contributions made by engineering, electronic, computing and material science research groups. This review will address the ongoing reservations surrounding VCA whilst acknowledging the future impact of bionic technology as a realistic alternative for limb reconstruction.

Induction of Endotoxin Tolerance Delays Acute Rejection in a Hindlimb Transplantation Model in Rats

BACKGROUND

Acute rejection is seen in 85 percent of composite vascular allogeneic transplants despite long-term immunosuppression. Recently, it was reported that the induction of endotoxin tolerance prolonged heart allograft survival in mice. However, it produced side effects in all the animals secondary to the inflammatory reaction. Galactomannan has shown endotoxin tolerance without this side effect in vitro. The authors hypothesized that galactomannan-induced endotoxin tolerance delays acute rejection in vascular allogeneic transplantation without the side effects produced by lipopolysaccharide.

METHODS

Twenty-four rat hindlimb transplants were divided into four groups according to the preconditioning received: control, lipopolysaccharide (0.16 ml/kg), galactomannan 72 hours before (galactomannan-72) (8 ml/kg), and galactomannan 24 hours before (galactomannan-24) (8 ml/kg). Median acute rejection time, weight loss, and diarrheal episodes were monitored. Blood samples were collected at 0, 7, 21, 30, 45, and 60 days. Plasma cytokines (i.e., tumor necrosis factor alpha, interferon gamma), peripheral chimerism, and lymphocyte percentages were analyzed.

RESULTS

Median allograft survival was 40 days (range, 40 to 44 days) in the control group, 68 days (range, 61 to 71 days) in the lipopolysaccharide group, and 70 days (range, 69 to 73 days) in both galactomannan groups (p = 0.001). Weight loss was higher in the lipopolysaccharide group (p < 0.001), as was the 83.3 percent rate of diarrheal episodes (control, 0 percent, p = 0.015; galactomannan-72, 0 percent, p = 0.015; and galactomannan-24, 16.7 percent, p = 0.02). Preconditioned rats had higher peripheral blood chimerism (lipopolysaccharide, 2.30 ± 0.13 percent; galactomannan-72, 2.63 ±1.46 percent; and galactomannan-24, 2.47 ± 0.19 percent) compared to the control group (2.06 ± 0.36 percent) (lipopolysaccharide, p = 0.04; galactomannan-72, p = 0.002; and galactomannan-24, p = 0.002).

CONCLUSIONS

Induction of endotoxin tolerance delays acute rejection in the rat hindlimb transplantation model. Galactomannan preconditioning has no lipopolysaccharide side effects and was equally effective in delaying acute rejection.

CLINICAL RELEVANCE STATEMENT

The contributions of this experimental work are very incipient. Although the use of galactomannan in clinical practice requires more studies to assess its safety, there is no doubt that immunomodulation may be one of the responses that solve the problem of long-term immunosuppression.

Evaluation of Early Markers of Ischemia-reperfusion Injury and Preservation Solutions in a Modified Hindlimb Model of Vascularized Composite Allotransplantation

Background.

Ischemia-reperfusion injury plays an important role in vascularized composite allotransplantation (VCA). Currently, there is no ideal preservation solution for VCA. In this study, we investigated the effects of 4 different preservation solutions on different tissues within an allogeneic hindlimb rat model.

Methods.

Sprague Dawley rat hindlimbs were flushed and placed at 4°C for 6 h in heparinized saline, histidine-tryptophan-ketoglutarate, University of Wisconsin (UW), and Perfadex and heterotopically transplanted for ease of ambulation. Apoptosis, necrosis, and the extracellular matrix of the tissues within the allograft were analyzed 2 h posttransplantation using immunohistochemistry, terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate nick-end labeling (TUNEL) assay, and enzyme-linked immunoassay.

Results.

Higher expression of cleaved caspase 3, a significant increase of high-mobility group box 1 and TUNEL-positive apoptotic cells were observed in the muscle and vessels preserved with heparinized saline compared with UW and Perfadex following reperfusion. Higher expression of TUNEL-positive apoptotic cells was observed in the skin at 12 h of ischemia and in the nerve following reperfusion with histidine-tryptophan-ketoglutarate as a preservation solution.

Conclusions.

Our data suggest that UW and Perfadex are preferred solutions in VCA. The vessels within the allografts appear to be very susceptible, with laminins and CD31 playing a role in ischemia-reperfusion injury.

Pediatric Hand Transplantation: A Decision Analysis

Background: The first successful bilateral pediatric hand transplant was performed in 2015. Previous hand transplant decision analysis models have focused on the adult population. This model principally aimed to determine whether adverse outcomes associated with immunosuppression outweigh the benefits of performing bilateral hand transplant surgery in a pediatric candidate. The model also conceptualized the valuation of losing years of life and sought to determine the impact of that valuation on the surgical decision. Methods: A decision model compared undergoing bilateral hand transplant surgery with using prosthetics for an 8-year-old patient. The outcome measure used was quality adjusted life years (QALYs), and sensitivity analysis was performed on the immunosuppressive risks associated with the surgical decision, as well as the perceived valuation of aversion to life years lost. Results: The decision to perform surgery was marginally optimal compared to the prosthetic decision (50.11 QALY vs. 47.95 QALY). A Monte Carlo simulation revealed that this difference may be too marginal to detect an optimal decision (50.14 ± 8.28 QALY vs. 47.95 ± 2.12 QALY). Sensitivity analysis identified decision thresholds related to immunosuppression risks (P = 29% vs. P = 33% modeled), and a trend of increasing risk as a patient is more averse to losing life years. Conclusions: The marginally optimal treatment strategy currently is bilateral hand transplant, compared to prosthetics for pediatric patients. Key determinants of the future optimal strategy will be whether immunosuppressive regimens become safer, with a reduced risk of losing life years due to immunosuppressive complications, and whether prosthetics become more acceptable and enable higher functioning.

Software-based Detection of Acute Rejection Changes in Face Transplant

BACKGROUND

 An objective, non-invasive method for redness detection during acute allograft rejection in face transplantation (FT) is lacking.

METHODS

 A retrospective cohort study was performed with 688 images of 7 patients with face transplant (range, 1 to 108 months post-transplant). Healthy controls were matched to donor age, sex, and had no prior facial procedures. Rejection state was confirmed via tissue biopsy. An image-analysis software developed alongside VicarVision (Amsterdam, Netherlands) was used to produce R, a measure of differences between detectable color and absolute red. R is inversely proportional to redness, where lower R values correspond to increased redness. Linear mixed models were used to study fixed effect of rejection state on R values. Estimated marginal means of fitted models were calculated for pairwise comparisons.

RESULTS

 Of 688 images, 175, 170, 202, and 141 images were attributable to Banff Grade 0,1,2, and 3, respectively. Estimated change in R value of facial allografts decreased with increasing Banff Grade (p = 0.0001). The mean R value of clinical rejection (Banff Grade ⅔) (16.67, 95% Confidence Interval [CI] 14.79-18.58) was lower (p = 0.005) than non-rejection (Banff Grade 0/1) (19.38, 95%CI 17.43-21.33). Both clinical and non-rejection mean R values were lower (p = 0.0001) than healthy controls (24.12, 95%CI 20.96-27.28).

CONCLUSION

 This proof-of-concept study demonstrates that software-based analysis can detect and monitor acute rejection changes in FT. Future studies should expand on this tool's potential application in telehealth and as a screening tool for allograft rejection.

Face transplantation: A longitudinal histological study focusing on chronic active and mucosal rejection in a series with long-term follow-up

The 2007 Banff working classification of skin-containing Tissue Allograft Pathology addressed only acute T cell-mediated rejection in skin. We report the longitudinal long-term histological follow-up of six face transplant recipients, focusing on chronic and mucosal rejection. We identified three patterns suggestive of chronic rejection (lichen planus-like, vitiligo-like and scleroderma-like). Four patients presented lichen planus-like and vitiligo-like chronic rejection at 52 ± 17 months posttransplant with severe concomitant acute T cell-mediated rejection. After lichen planus-like rejection, two patients developed scleroderma-like alterations. Graft vasculopathy with C4d deposits and de novo DSA led to subsequent graft loss in one patient. Chronic active rejection was frequent and similar patterns were noted in mucosae. Concordance between 124 paired skin and mucosal biopsies acute rejection grades was low (κ = 0.2, p = .005) but most grade 0/I mucosal rejections were associated with grade 0/I skin rejections. We defined discordant (grade≥II mucosal rejection and grade 0/I skin rejection) (n = 55 [70%]) and concordant (grade≥II rejection in both biopsies) groups. Mucosal biopsies of the discordant group displayed lower intra-epithelial GranzymeB/FoxP3 ratios suggesting a less aggressive phenotype (p = .08). The grading system for acute rejection in mucosa may require phenotyping. Whether discordant infiltrates reflect a latent allo-immune reaction leading to chronic rejection remains an open question.

Long-term Outcomes After Facial Allotransplantation: Systematic Review of the Literature

BACKGROUND

Facial vascularized composite allotransplantation (fVCA) represents a reconstructive approach that enables superior improvements in functional and esthetic restoration compared with conventional craniomaxillofacial reconstruction. Outcome reports of fVCA are usually limited to short-term follow-up or single-center experiences. We merge scientific literature on reported long-term outcome data to better define the risks and benefits of fVCA.

METHODS

We conducted a systematic review of PubMed/MEDLINE databases in accordance with PRISMA guidelines. English full-text articles providing data on at least 1 unique fVCA patient, with ≥3 years follow-up, were included.

RESULTS

The search yielded 1812 articles, of which 28 were ultimately included. We retrieved data on 23 fVCA patients with mean follow-up of 5.3 years. More than half of the patients showed improved quality of life, eating, speech, and motor and sensory function following fVCA. On average, the patients had 1 acute cell-mediated rejection and infectious episode per year. The incidence rates of acute rejection and infectious complications were high within first-year posttransplant but declined thereafter. Sixty-five percent of the patients developed at least 1 neoplastic or metabolic complication after transplantation. Chronic vascular rejection was confirmed in 2 patients, leading to allograft loss after 8 and 9 years. Two patient deaths occurred 3.5 and 10.5 years after transplant due to suicide and lung cancer, respectively.

CONCLUSIONS

Allograft functionality and improvements in quality of life suggest a positive risk-benefit ratio for fVCA. Recurrent acute rejection episodes, chronic rejection, immunosuppression-related complications, and heterogeneity in outcome reporting present ongoing challenges in this field.

Preservation solutions for attenuation of ischemia-reperfusion injury in vascularized composite allotransplantation

Vascularized composite allotransplantation represents the final level of the reconstructive ladder, offering treatment options for severe tissue loss and functional deficiencies. Vascularized composite allotransplantation is particularly susceptible to ischemia–reperfusion injury and requires preservation techniques when subjected to extended storage times prior to transplantation. While static cold storage functions to reduce ischemic damage and is widely employed in clinical settings, there exists no consensus on the ideal preservation solution for vascularized composite allotransplantation. This review aims to highlight current clinical and experimental advances in preservation solution development and their critical role in attenuating ischemia–reperfusion injury in the context of vascularized composite allotransplantation.

In Vivo Activity of Genetically Modified Cells Preseeded in Rat Vascularized Composite Allografts

OBJECTIVE

Transplantation of the hand or face, known as vascularized composite allotransplantation (VCA), has revolutionized reconstructive surgery. Notwithstanding, there are still several areas of improvement to mitigate immune rejection while sparing systemic adverse effects. The goal of this study was to evaluate the engraftment and viability of a genetically modified cell population pre-engrafted into a VCA transplant, to potentially act as a local biosensor to report and modify the graft in vivo. A rat fibroblast cell line genetically modified to secrete Gaussia-Luciferase (gLuc), which served as a constitutive biomarker of cells, was incorporated into a VCA to study the viability of biosensor cells in a syngeneic rat heterotopic partial hindlimb transplantation model.

RESULTS

Five perfusions were first performed as engineering runs to have a stable limb perfusion protocol, followed by 3 perfusions to analyze the cell engraftment during machine perfusion, and finally 4 perfusions to study in vivo persistence of the cell biosensors. Blood samples were collected to monitor gLuc secretion during perfusion and postoperatively. A time-dependent increase in gLuc secretion in the limb perfusion outflow during machine perfusion indirectly verified the presence of biosensors within the graft. After the ex vivo perfusion, VCA hindlimbs were analyzed for near infrared fluorescence emission that showed a presence of dyed engineered cells in all areas of the limbs. Postoperatively, gLuc was detectable 4 to 5 days after transplantation (W = 16, P = .02857). This study demonstrated that engineered cells could be successfully preimplanted into VCAs-an important step toward development of an in vivo biosensor platform to use in modulating acute VCA outcomes.

Intergender Hand Transplant: A Sex Congruent Hand Transformation

ABSTRACT

Hand and upper-extremity transplantation restore severely damaged limbs that cannot be repaired with conventional surgical techniques. Over the past 20 years, more than 200 vascularized composite allotransplantations have been performed worldwide, among them 7 were cases of sex unmatched hand transplants. The long term effects of recipient sex hormones and nerve regeneration on the sexually dimorphic physical features of donor upper extremity have not been described previously. We report a case of sex congruent transformation of hand morphology in an intergender hand transplant.

Biomarker and surrogate development in vascularised composite allograft transplantation: Current progress and future challenges

Vascularised composite allograft (VCA) transplantation is now a feasible reconstructive option for patients who have suffered significant soft tissue injuries. However, despite numerous technical advances in the field over two decades, a number of challenges remain, not least the management of transplant rejection. Part of the difficulty faced by clinicians is the early recognition and prevention of acute rejection episodes. Whilst this is potentially easier in VCAs than solid organ transplants, due to their visible skin component, at present the only validated method for the diagnosis of acute rejection is histological examination of a tissue biopsy. The aim of this review article is to provide an evidence-based overview of progress in the field of VCA biomarker discovery, including immune cell subsets, immune cell effector pathways, and circulating markers of allograft damage, and to discuss future challenges in the field.

Graft vasculopathy in upper extremity allotransplantation: Results of a retrospective high-resolution ultrasonographic study

Graft vasculopathy (GV) is the most severe pathologic change of chronic rejection in vascularized composite allotransplantation. Since 2012, the intimal media thickness (IMT) of radial and ulnar arteries was annually monitored by high-resolution ultrasonography in seven bilateral upper extremity transplant (UET) patients. We also investigated the IMT of seven matched healthy subjects (controls). No significant difference between IMT values of controls and UET patients was found. The median IMT values of recipient radial and ulnar arteries were 0.23 mm and 0.25 mm, respectively, while the median IMT values of grafted radial and ulnar arteries were 0.27 mm and 0.30 mm, respectively. There was a statistically significant difference in the IMT values of the grafted and recipient ulnar arteries (p = .043), but this difference was no longer significant when patient #2 was excluded. He showed a significant difference between recipient and grafted arteries and significantly higher IMT values (p = .001) of his grafted arteries compared with those of all transplanted patients. This patient developed GV leading to graft loss 11 years after the transplantation. In conclusion, this study showed a significant IMT increase in an UET recipient who developed GV.

Abdominal Wall Transplantation: Indications and Outcomes

Purpose of Review

This article aims to review published outcomes associated with full-thickness vascularized abdominal wall transplantation, with particular emphasis on advances in the field in the last 3 years.

Recent Findings

Forty-six full-thickness vascularized abdominal wall transplants have been performed in 44 patients worldwide. Approximately 35% of abdominal wall transplant recipients will experience at least one episode of acute rejection in the first year after transplant, compared with rejection rates of 87.8% and 72.7% for hand and face transplant respectively. Recent evidence suggests that combining a skin containing abdominal wall transplant with an intestinal transplant does not appear to increase sensitization or de novo donor-specific antibody formation.

Summary

Published data suggests that abdominal wall transplantation is an effective safe solution to achieve primary closure of the abdomen after intestinal or multivisceral transplant. However, better data is needed to confirm observations made and to determine long-term outcomes, requiring standardized data collection and reporting and collaboration between the small number of active transplant centres around the world.

Vascularised composite allotransplantation in solid organ transplant recipients: A systematic review

INTRODUCTION

A solid organ transplant (SOT) recipient, already taking immunosuppression, may represent the ideal candidate for vascularised composite allograft transplantation (VCA). However, concerns have been raised about the potential risk of SOT loss or the need for increased immunosuppression to sustain the VCA. This systematic review examines all published cases of SOT recipients who have received a VCA to establish associated morbidity and immunosuppression requirements.

METHODS

A systematic review was performed in accordance with the PRISMA guidelines. The PubMed, MEDLINE and EMBASE databases were searched for original articles published between January 1997 and May 2019. Only articles relating to patients who had received both a VCA and SOT with a reported follow up of greater than six months were included.

RESULTS

Fifteen articles were identified, including data from 39 VCAs in 37 patients. There was no increase in the number of SOT rejection episodes, complications such as post-transplant lymphoproliferative disorder or graft versus host disease, de novo donor specific HLA antibodies or short-term risks to the recipient when compared with SOT in isolation. One child required a sustained increase in their baseline immunosuppression following bilateral hand transplantation.

CONCLUSIONS

In this small heterogeneous cohort, the addition of a VCA to a SOT does not appear to increase the short-term risks to the SOT or the patient with comparable results to SOT in isolation. However, data are often poorly reported and longer-term follow up and uniform reporting of outcomes would be beneficial to more accurately assess the safety profile of combining VCA with SOT.

Hypothermic Ex Situ Perfusion of Human Limbs With Acellular Solution for 24 Hours

BACKGROUND

Machine perfusion (MP) has evolved as a promising approach for the ex situ preservation in organ transplantation. However, the literature on the use of MP in human vascularized composite allografts is scarce. The aim of this study was to evaluate the effects of hypothermic MP with an acellular perfusate in human upper extremities and compare with the current gold standard of static cold storage (SCS).

METHODS

Six upper extremities were assigned to either MP (n = 3) or SCS (n = 3) conditions for 24 h. MP-extremities were perfused with oxygenated Steen solution at a constant pressure of 30 mm Hg and 10°C.

RESULTS

Median total ischemia time was 213 min (range, 127-222 min). Myoglobin, creatine-kinase (CK) showed increased levels at the start of MP (medians: myoglobin: 4377 ng/mL, CK: 1442 U/L), peaking 6 h after perfusate exchange (medians: myoglobin: 9206 ng/mL, CK: 3995 U/L) at timepoint 24. Lactate levels decreased from a median of 6.9-2.8 mmol/L over time. Expression of hypoxia-inducible factor 1-alpha peaked in the SCS-group after 8 h, followed by a decrease. Increased hypoxia-inducible factor 1-alpha expression in the MP group was delayed until 20 h. Perfusion pressure, temperature, and circuit flow were maintained at median of 30.88 mm Hg, 9.77°C, and 31.13 mL/min, respectively. Weight increased 1.4% in the SCS group and 4.3% in the MP group over 24 h.

CONCLUSIONS

Hypothermic ex situ perfusion with an oxygenated acellular Steen solution may extend the allowable extracorporeal preservation time by a factor of 4-6 compared to SCS and holds promise to be beneficial for vascularized composite allograft recipients and victims of traumatic major limb amputation.

Toward Development of the Delayed Tolerance Induction Protocol for Vascularized Composite Allografts in Nonhuman Primates

BACKGROUND

Transplantation of vascularized composite allografts is limited mainly by the need for life-long immunosuppression. The consequent side effects and looming specter of chronic rejection portend eventual allograft loss. Development of tolerogenic protocols is thus of utmost importance to the field of vascularized composite allograft transplantation.

METHODS

With a modified delayed tolerance induction protocol, 10 cynomolgus macaques received hand (n = 2) or face vascularized composite allografts across both full and haploidentical major histocompatibility complex barriers before donor bone marrow transplantation at a later date. Protocol and for-cause allograft skin biopsies were performed for immunohistochemical analysis and analysis of donor-recipient leukocyte contribution; mixed chimerism in peripheral blood and in vitro immune responses were assessed serially.

RESULTS

Before bone marrow transplantation, maintenance immunosuppression for 4 months led to lethal complications, including posttransplant lymphoproliferative disorder (in two of four recipients), which necessitated early study termination. Shortening the maintenance period to 2 months was clinically relevant and allowed all subsequent subjects (n = 6) to complete the delayed tolerance induction protocol. Acute rejection developed within the first 2 to 4 weeks after transplantation, with corresponding near-complete turnover of allograft leukocytes from donor to recipient origin, but donor-specific antibodies remained negative. After bone marrow transplantation, mixed chimerism failed to develop, although carboxyfluorescein succinimidyl ester mixed lymphocyte reaction demonstrated generalized unresponsiveness. However, the accrual of subsequent rejection episodes eventually culminated in graft vasculopathy and irreversible allograft loss.

CONCLUSIONS

Despite the various advantages of the delayed tolerance induction protocol, it failed to reliably induce mixed chimerism and thus immunologic tolerance to vascularized composite allografts, given currently available immunosuppression treatment options. Ongoing work shows promise in overcoming these limitations.

Trauma-induced Rejection in Vascularized Composite Allotransplantation

: Vascularized composite allotransplantation (VCA) is a relatively new field in reconstructive medicine. Likely a result of the unique tissue composition of these allografts-including skin and often a bone marrow component-the immunology and rejection patterns do not always mimic those of the well-studied solid organ transplantations. While the number and type of VCAs performed is rapidly expanding, there is still much to be discovered and understood in the field. With more patients, new findings and patterns emerge and add to our understanding of VCA. Here, we present a case report of an upper extremity transplant recipient with trauma-induced rejection.

Emerging Ethical Challenges Raised by the Evolution of Vascularized Composite Allotransplantation

BACKGROUND

Despite early skepticism, the field of vascularized composite allotransplantation (VCA) has demonstrated feasibility. The ethics of VCA have moved past doubts about the morality of attempting such transplants to how to conduct them ethically.

METHODS

Leaders of each program performing and/or evaluating VCA in the United States were invited to participate in a working group to assess the state and future of VCA ethics and policy. Four meetings were held over the course of 1 year to describe key challenges and potential solutions.

RESULTS

Working group participants concluded that VCA holds great promise as treatment for patients with particular injuries or deficits, but the field faces unique challenges to adoption as standard of care, which can only be overcome by data sharing and standardization of evaluation and outcome metrics.

CONCLUSIONS

Adequate attention must be given to concerns including managing the uniquely intense physician-patient relationship, ethical patient selection, ensuring patients have adequate representation, informing and earning the trust of the public for donation, standardizing metrics for success, and fostering an environment of data sharing. These steps are critical to transitioning VCA from research to standard of care and to its insurance coverage inclusion.

Local Immunosuppression for Vascularized Composite Allografts: Application of Topical FK506-TyroSpheres in a Nonhuman Primate Model

Transplantation of vascularized composite allografts (VCAs) provides a means of restoring complex anatomical and functional units following burns and other disfigurement otherwise not amenable to conventional autologous reconstructive surgery. While short- to intermediate-term VCA survival is largely dependent on patient compliance with medication, the myriad of side effects resulting from lifelong systemic immunosuppression continue to pose a significant challenge. Topical immunosuppression is therefore a logical and attractive alternative for VCA. Current formulations are limited though, by poor skin penetration but this may be mitigated by conjugation of immunosuppressive drugs to TyroSpheres for enhanced delivery. Therefore, we investigated the topical application of FK506-TyroSpheres (in the form of a gel dressing) in a clinically relevant nonhuman primate VCA model to determine if allograft survival could be prolonged at reduced levels of maintenance systemic immunosuppression. Six Major Histocompatibility Complex (MHC)-mismatched cynomolgus macaques (Macaca fascicularis) served as reciprocal donors and recipients of radial forearm fasciocutaneous flaps. Standard Bacitracin ointment and FK506-TyroSpheres were applied every other day to the VCAs of animals in groups 1 (controls, n = 2) and 2 (experimental, n = 4), respectively, before gradual taper of systemic FK506. Clinical features of VCA rejection still developed when systemic FK506 fell below 10 ng/ml despite application of FK506-TyroSpheres and prolonged VCA survival was not achieved. However, unwanted systemic FK506 absorption was avoided with TyroSphere technology. Further refinement to optimize local drug delivery profiles to achieve and maintain therapeutic delivery of FK506 with TyroSpheres is underway, leveraging significant experience in controlled drug delivery to mitigate acute rejection of VCAs.

Extended ex vivo normothermic perfusion for preservation of vascularized composite allografts

Ischemia and reperfusion injury remains a significant limiting factor for the successful revascularization of amputated extremities. Ex vivo normothermic perfusion is a novel approach to prolong the viability of the amputated limbs by maintaining physiologic cellular metabolism. This study aimed to evaluate the outcomes of extended ex vivo normothermic limb perfusion (EVNLP) in preserving the viability of amputated limbs for over 24 hours. A total of 10 porcine forelimbs underwent EVNLP. Limbs were perfused using an oxygenated colloid solution at 38°C containing washed RBCs. Five forelimbs (Group A) were perfused for 12 hours and the following 5 (Group B) until the vascular resistance increased. Contralateral forelimbs in each group were preserved at 4°C as a cold storage control group. Limb viability was compared between the 2 groups through assessment of muscle contractility, compartment pressure, tissue oxygen saturation, indocyanine green (ICG) angiography and thermography. EVNLP was performed for 12 hours in group A and up to 44 hours (24-44 hours) in group B. The final weight increase (-1.28 ± 8.59% vs. 7.28 ± 15.05%, P = .548) and compartment pressure (16.50 ± 8.60 vs. 24.00 ± 9.10) (P = .151) were not significantly different between the two groups. Final myoglobin and CK mean values in group A and B were: 875.0 ± 325.8 ng/mL (A) versus 1133.8 ± 537.7 ng/mL (B) (P = .056) and 53 344.0 ± 16 603.0 U/L versus 64 333.3 ± 32 481.8 U/L (P = .286). Tissue oxygen saturation was stable until the end in both groups. Infra-red thermography and ICG-angiography detected variations of peripheral limb perfusion. Our results suggest that extended normothermic preservation of amputated limbs is feasible and that the outcomes of prolonged EVNLP (>24 hours) are not significantly different from short EVNLP (12 hours).

The Evolving Clinical Presentation of Acute Rejection in Facial Transplantation

Importance

Acute rejection is one of the most frequent complications in facial transplantation, with potentially severe consequences for the recipient if overlooked. Clinical signs, such as erythema or edema, are helpful to diagnose acute rejection in the early follow-up stage; however, it is not well known whether these clinical signs remain reliable markers of acute rejection beyond the second posttransplant year.

Objective

To determine the diagnostic value of clinical signs of acute rejection after facial transplantation over time.

Design, Setting, and Participants

A retrospective, single-center cohort study was conducted of patients who underwent facial transplantation at Brigham and Women's Hospital between April 2009 and October 2014, with up to an 8-year follow-up. Medical records were reviewed until September 30, 2017. The medical records from 104 encounters with 7 patients who underwent partial or full facial transplantation were analyzed for symptoms of rejection, immunosuppressive therapy, and histopathologic findings.

Main Outcomes and Measures

The occurrence of 5 clinical signs of acute rejection were evaluated: erythema, edema, exanthema, suture line erythema, and mucosal lesions. Odds ratios (ORs) were calculated to determine the statistically significant association of these signs with the histopathologic diagnosis of rejection. In addition, tacrolimus blood levels, as a surrogate marker of immunosuppressive therapy, were evaluated.

Results

Of the 7 patients included in the study, 5 were men. The mean follow-up was 66 months (range, 35-101). Of 104 clinical encounters, 46 encounters (44.2%) represented rejection episodes and 58 encounters (55.8%) represented no-rejection episodes. Beyond 2 years posttransplantation, only erythema (OR, 6.53; 95% CI, 1.84-20.11; P = .004) and exanthema (OR, ∞; 95% CI, 2.2-∞; P = .004) were demonstrated to be reliable clinical signs of acute rejection in facial transplantation. There was also a statistically significant association of subtherapeutic tacrolimus levels with late rejection episodes (OR, 3.79; 95% CI, 1.25-12.88; P = .03). In addition, the occurrence of subclinical rejection was more frequent during later follow-up times (7 [24.1%] late rejections vs 1 [5.9%] early rejection). Five of 8 subclinical rejections (62.5%) were associated with subtherapeutic tacrolimus levels.

Conclusions and Relevance

Clinical signs of acute rejection in facial transplantation appear to be of limited diagnostic value, particularly after the second postoperative year. Until alternative biomarkers for rejection are identified, protocol skin biopsies will remain necessary for guiding assessments of allograft rejection.

Level of Evidence

3.

The histocompatibility and immunogenetics of hand transplantation

This short review will be concerned with the literature that has developed connected with the immunogenetic and tissue compatibility aspects of hand transplantation and will also draw on connected work in the more general area of vascularized composite allotransplantation (VCA) which includes face, abdominal wall uterus and larynx.

Blood proteome profiling using aptamer-based technology for rejection biomarker discovery in transplantation

Face transplantation is a promising solution for patients with devastating facial injuries who lack other satisfactory treatment options. At the same time, this type of transplantation is accompanied with high risks of acute transplant rejection. The limitations of traditional skin biopsy and the need to frequently monitor the condition of face transplant call for less invasive biomarkers to better diagnose and treat acute rejection. Discovery of peripheral serum proteins accurately reflecting the transplant status would represent a reasonable solution to meet this demand. However, to date, there is no clinical data available to address the feasibility of this approach. In this study, we used the next generation aptamer-based SOMAscan proteomics platform to profile 1305 proteins of peripheral blood serum in twenty-four samples taken from 6 patients during no-rejection, nonsevere rejection, and severe rejection episodes. Also, we provide a detailed description of biosample processing and all steps to generate and analyze the SOMAscan dataset with hope it will assist in performing biomarker discovery in other transplantation centers using this platform.

MMP3 Is a Non-invasive Biomarker of Rejection in Skin-Bearing Vascularized Composite Allotransplantation: A Multicenter Validation Study

Background: There is unmet need for non-invasive immunomonitoring to improve diagnosis and treatment of acute rejection in vascularized composite allotransplantation (VCA). Circulating matrix metalloproteinase 3 (MMP3) was described as a candidate non-invasive biomarker to predict treatment response to acute rejection in clinical VCA. However, larger validation studies are yet to be reported to allow for more definitive conclusions.

Methods: We retrospectively measured MMP3 levels using ELISA in a total of 140 longitudinal serum samples from six internal and three external face transplant recipients, as well as three internal and seven external upper extremity transplant recipients. The control groups comprised serum samples from 36 kidney transplant recipients, 14 healthy controls, and 38 patients with autoimmune skin disease. A linear mixed model was used to study the effect of rejection state (pre-transplant, no-rejection, non-severe rejection (NSR), and severe rejection) on MMP3 levels.

Results: In VCA, MMP3 levels increased significantly (p < 0.001) between pre- and post-transplant no-rejection states. A further increase occurred during severe rejection (p < 0.001), while there was no difference in MMP3 levels between non-severe and no-rejection episodes. A threshold of 5-fold increase from pre-transplant levels could discriminate severe from NSR with 76% sensitivity and 81% specificity (AUC = 0.79, 95% CI = 0.65–0.92, p < 0.001). In kidney transplantation, the MMP3 levels were significantly (p < 0.001) elevated during antibody-mediated rejection but not during T-cell mediated rejection (TCMR) (p = 0.547). MMP3 levels in healthy controls and autoimmune skin disease patients were comparable with either pre-transplant or no-rejection/NSR episodes of VCA patients.

Conclusion: The results of this study suggest that serum MMP3 protein is a promising marker for stratifying patients according to severity of rejection, complementary to biopsy findings.

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 vasculopathy of vascularized composite allografts in humans: a literature review and retrospective study

Mechanisms of chronic rejection of vascularized composite allografts (VCA) remain poorly understood and likely present along a spectrum of highly varied clinicopathological findings. Across both animal and human VCA however, graft vasculopathy (GV) has been the most consistent pathological finding resulting clinically in irreversible allograft dysfunction and eventual loss. A literature review of all reported clinical VCA cases with documented GV up to December 2018 was thus performed to elucidate the possible mechanisms involved. Relevant data extracted include C4d deposition, donor-specific antibody (DSA) formation, extent of human leukocyte antigen (HLA) mismatch, pretransplant panel reactive antibody levels, induction and maintenance immunosuppression used, the number of preceding acute rejection episodes, and time to histological confirmation of GV. Approximately 6% (13 of 205) of all VCA patients reported to date developed GV at a mean of 6 years post-transplantation. 46% of these patients have either lost or had their VCAs removed. Neither C4d nor DSA alone was predictive of GV development; however, when both are present, VCA loss appears inevitable due to progressive GV. Of utmost concern, GV in VCA does not appear to be abrogated by currently available immunosuppressive treatment and is essentially irreversible by the time of diagnosis with allograft loss a likely eventuality.

Increased levels of circulating MMP3 correlate with severe rejection in face transplantation

Face transplantation is a viable treatment option for carefully selected patients with devastating injuries to the face. However, acute rejection episodes occur in more than 80% of recipients in the first postoperative year. Unfortunately, neither a correlation between histological grades of rejection and anti-rejection treatment nor systemic surrogate markers of rejection in face transplantation are established in clinical routine. Therefore, we utilized next generation aptamer-based SOMAscan proteomics platform for non-invasive rejection biomarker discovery. Longitudinal serum samples from face transplant recipients with long-term follow-up were included in this study. From the 1,310 proteins analyzed by SOMAscan, a 5-protein signature (MMP3, ACY1, IL1R2, SERPINA4, CPB2) was able to discriminate severe rejection from both no-rejection and nonsevere rejection samples. Technical validation on ELISA platform showed high correlation with the SOMAscan data for the MMP3 protein (r_s = 0.99). Additionally, MMP3 levels were significantly increased during severe rejection as compared to no-rejection (p = 0.0009) and nonsevere rejection (p = 0.0173) episodes. Pathway analyses revealed significant activation of the metallopeptidase activity during severe face transplant rejection. This pilot study demonstrates the feasibility of SOMAscan to identify non-invasive candidate biomarkers of rejection in face transplantation. Further validation in a larger independent patient cohort is needed.

Advances in machine perfusion, organ preservation, and cryobiology: potential impact on vascularized composite allotransplantation

PURPOSE OF REVIEW

In this review, we discuss novel strategies that allow for extended preservation of vascularized composite allografts and their potential future clinical implications for the field of vascularized composite allotransplantation (VCA).

RECENT FINDINGS

The current gold standard in tissue preservation - static cold preservation on ice - is insufficient to preserve VCA grafts for more than a few hours. Advancements in the field of VCA regarding matching and allocation, desensitization, and potential tolerance induction are all within reasonable reach to achieve; these are, however, constrained by limited preservation time of VCA grafts. Although machine perfusion holds many advantages over static cold preservation, it currently does not elongate the preservation time. More extreme preservation techniques, such as cryopreservation approaches, are, however, specifically difficult to apply to composite tissues as the susceptibility to ischemia and cryoprotectant agents varies greatly by tissue type.

SUMMARY

In the current scope of extended preservation protocols, high subzero approaches of VCA grafts will be particularly critical enabling technologies for the implementation of tolerance protocols clinically. Ultimately, advances in both preservation techniques and tolerance induction have the potential to transform the field of VCA and eventually lead to broad applications in reconstructive transplantation.

Outcomes after hand and upper extremity transplantation

Hand and upper extremity transplantation (HUET) has emerged as the most frequently performed reconstructive procedure in the burgeoning field of vascularized composite allotransplantation (VCA). VCA refers to a form of transplant with multiple tissue types that represents a viable treatment option for devastating injuries where conventional reconstruction would be unable to restore form and function. As hand transplantation becomes increasingly more common, discussions on advantages and disadvantages of the procedure seem to intensify. Despite encouraging functional outcomes, current immunosuppressive regimens with their deleterious side-effect profile remain a major concern for a life-changing but not life-saving type of transplant. In addition, a growing number of recipients with progressively longer follow-up prompt the need to investigate potential long-term sequelae, such as chronic rejection. This review will discuss the current state of HUET, summarizing outcome data on graft survival, motor and sensory function, as well as immunosuppressive treatment. The implications of these findings for VCA in terms of achievements and challenges ahead will then be discussed.