A local drug delivery system prolongs graft survival by dampening T cell infiltration and neutrophil extracellular trap formation in vascularized composite allografts.

Introduction: The standard treatment for preventing rejection in vascularized composite allotransplantation (VCA) currently relies on systemic immunosuppression, which exposes the host to well-known side effects. Locally administered immunosuppression strategies have shown promising results to bypass this hurdle. Nevertheless, their progress has been slow, partially attributed to a limited understanding of the essential mechanisms underlying graft rejection. Recent discoveries highlight the crucial involvement of innate immune components, such as neutrophil extracellular traps (NETs), in organ transplantation. Here we aimed to prolong graft survival through a tacrolimus-based drug delivery system and to understand the role of NETs in VCA graft rejection. Methods: To prevent off-target toxicity and promote graft survival, we tested a locally administered tacrolimus-loaded on-demand drug delivery system (TGMS-TAC) in a multiple MHC-mismatched porcine VCA model. Off-target toxicity was assessed in tissue and blood. Graft rejection was evaluated macroscopically while the complement system, T cells, neutrophils and NETs were analyzed in graft tissues by immunofluorescence and/or western blot. Plasmatic levels of inflammatory cytokines were measured using a Luminex magnetic-bead porcine panel, and NETs were measured in plasma and tissue using DNA-MPO ELISA. Lastly, to evaluate the effect of tacrolimus on NET formation, NETs were induced in-vitro in porcine and human peripheral neutrophils following incubation with tacrolimus. Results: Repeated intra-graft administrations of TGMS-TAC minimized systemic toxicity and prolonged graft survival. Nevertheless, signs of rejection were observed at endpoint. Systemically, there were no increases in cytokine levels, complement anaphylatoxins, T-cell subpopulations, or neutrophils during rejection. Yet, tissue analysis showed local infiltration of T cells and neutrophils, together with neutrophil extracellular traps (NETs) in rejected grafts. Interestingly, intra-graft administration of tacrolimus contributed to a reduction in both T-cellular infiltration and NETs. In fact, in-vitro NETosis assessment showed a 62-84% reduction in NETs after stimulated neutrophils were treated with tacrolimus. Conclusion: Our data indicate that the proposed local delivery of immunosuppression avoids off-target toxicity while prolonging graft survival in a multiple MHC-mismatch VCA model. Furthermore, NETs are found to play a role in graft rejection and could therefore be a potential innovative therapeutic target.

A World Update of Progress in Lower Extremity Transplantation: What's Hot and What's Not.

ABSTRACT: The field of vascularized composite allotransplantation (VCA) is the new frontier of solid organ transplantation (SOT). VCA spans life-enhancing/life-changing procedures such as upper extremity, craniofacial (including eye), laryngeal, tracheal, abdominal wall, penis, and lower extremity transplants. VCAs such as uterus transplants are life giving unlike any other SOT. Of all VCAs that have shown successful intermediate- to long-term graft survival with functional and immunologic outcomes, lower extremity VCAs have remained largely underexplored. Lower extremity transplantation (LET) can offer patients with improved function compared to the use of conventional prostheses, reducing concerns of phantom limb pain and stump complications, and offer an option for eligible amputees that either fail prosthetic rehabilitation or do not adapt to prosthetics. Nevertheless, these benefits must be carefully weighed against the risks of VCA, which are not trivial, including the adverse effects of lifelong immunosuppression, extremely challenging perioperative care, and delayed nerve regeneration. There have been 5 lower extremity transplants to date, ranging from unilateral or bilateral to quadrimembral, progressively increasing in risk that resulted in fatalities in 3 of the 5 cases, emphasizing the inherent risks. The advantages of LET over prosthetics must be carefully weighed, demanding rigorous candidate selection for optimal outcomes.

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.

Cell-Based Therapies Induce Tolerance of Vascularized Composite Allotransplants: A Systematic Review.

INTRODUCTION: Vascularized composite allotransplantation (VCA) is the transplantation of multiple tissue types as a solution for devastating injuries. Despite the highly encouraging functional outcomes of VCA, the consequences of long-term immunosuppression remain the main obstacle in its application. In this review, we provide researchers and surgeons with a summary of the latest advances in the field of cell-based therapies for VCA tolerance. METHODS: Four electronic databases were searched: PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature , and Web of Science. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analysis as the basis of our organization. RESULTS: Hematopoietic stem cells prolonged VCA survival. A combination of immature dendritic cells and tacrolimus was superior to tacrolimus alone. T cell Ig domain and mucin domain modified mature dendritic cells increased VCA tolerance. Bone marrow-derived mesenchymal stem cells prolonged survival of VCAs. A combination of adipose-derived mesenchymal stem cells, cytotoxic T-lymphocyte antigen 4 immunoglobulin, and antilymphocyte serum significantly improved VCA tolerance. Ex-vivo allotransplant perfusion with recipient's bone marrow-derived mesenchymal stem cells increased VCA survival. Recipient's adipose-derived mesenchymal stem cells and systemic immunosuppression prolonged VCA survival more than any of those agents alone. Additionally, a combination of peripheral blood mononuclear cells shortly incubated in mitomycin and cyclosporine significantly improved VCA survival. Finally, a combination of donor recipient chimeric cells, anti-αß-T cell receptor (TCR), and cyclosporine significantly prolonged VCA tolerance. CONCLUSIONS: Evidence from animal studies shows that cell-based therapies can prolong survival of VCAs. However, there remain many obstacles for these therapies, and they require rigorous clinical research given the rarity of the subjects and the complexity of the therapies. The major limitations of cell-based therapies include the need for conditioning with immunosuppressive drugs and radiation, causing significant toxicity. Safety concerns also persist as most research is on animal models. While completely replacing traditional immunosuppression with cell-based methods is unlikely soon, these therapies could reduce the need for high doses of immunosuppressants and improve VCA tolerance.

Machine Perfusion Enables 24-h Preservation of Vascularized Composite Allografts in a Swine Model of Allotransplantation.

The current gold standard for preserving vascularized composite allografts (VCA) is 4°C static cold storage (SCS), albeit muscle vulnerability to ischemia can be described as early as after 2 h of SCS. Alternatively, machine perfusion (MP) is growing in the world of organ preservation. Herein, we investigated the outcomes of oxygenated acellular subnormothermic machine perfusion (SNMP) for 24-h VCA preservation before allotransplantation in a swine model. Six partial hindlimbs were procured on adult pigs and preserved ex vivo for 24 h with either SNMP (n = 3) or SCS (n = 3) before heterotopic allotransplantation. Recipient animals received immunosuppression and were followed up for 14 days. Clinical monitoring was carried out twice daily, and graft biopsies and blood samples were regularly collected. Two blinded pathologists assessed skin and muscle samples. Overall survival was higher in the SNMP group. Early euthanasia of 2 animals in the SCS group was linked to significant graft degeneration. Analyses of the grafts showed massive muscle degeneration in the SCS group and a normal aspect in the SNMP group 2 weeks after allotransplantation. Therefore, this 24-h SNMP protocol using a modified Steen solution generated better clinical and histological outcomes in allotransplantation when compared to time-matched SCS.

Depletion of donor dendritic cells ameliorates immunogenicity of both skin and hind limb transplants.

Acute cellular rejection remains a significant obstacle affecting successful outcomes of organ transplantation including vascularized composite tissue allografts (VCA). Donor antigen presenting cells (APCs), particularly dendritic cells (DCs), orchestrate early alloimmune responses by activating recipient effector T cells. Employing a targeted approach, we investigated the impact of donor-derived conventional DCs (cDCs) and APCs on the immunogenicity of skin and skin-containing VCA grafts, using mouse models of skin and hind limb transplantation. By post-transplantation day 6, skin grafts demonstrated severe rejections, characterized by predominance of recipient CD4 T cells. In contrast, hind limb grafts showed moderate rejection, primarily infiltrated by CD8 T cells. Notably, the skin component exhibited heightened immunogenicity when compared to the entire VCA, evidenced by increased frequencies of pan (CD11b-CD11c+), mature (CD11b-CD11c+MHCII+) and active (CD11b-CD11c+CD40+) DCs and cDC2 subset (CD11b+CD11c+ MHCII+) in the lymphoid tissues and the blood of skin transplant recipients. While donor depletion of cDC and APC reduced frequencies, maturation and activation of DCs in all analyzed tissues of skin transplant recipients, reduction in DC activities was only observed in the spleen of hind limb recipients. Donor cDC and APC depletion did not impact all lymphocyte compartments but significantly affected CD8 T cells and activated CD4 T in lymph nodes of skin recipients. Moreover, both donor APC and cDC depletion attenuated the Th17 immune response, evident by significantly reduced Th17 (CD4+IL-17+) cells in the spleen of skin recipients and reduced levels of IL-17E and lymphotoxin-α in the serum samples of both skin and hind limb recipients. In conclusion, our findings underscore the highly immunogenic nature of skin component in VCA. The depletion of donor APCs and cDCs mitigates the immunogenicity of skin grafts while exerting minimal impact on VCA.

Acute Rejection Rates in Vascularized Composite Allografts: A Systematic Review of Case Reports.

INTRODUCTION: Vascularized Composite Allografts (VCA) are usually performed in a full major histocompatibility complex mismatch setting, with a risk of acute rejection depending on factors such as the type of immunosuppression therapy and the quality of graft preservation. In this systematic review, we present the different immunosuppression protocols used in VCA and point out relationships between acute rejection rates and possible factors that might influence it. METHODS: This systematic review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. We systematically searched Medline (PubMed), Embase, and The Cochrane Library between November 2022 and February 2023, using following Mesh Terms: Transplant, Transplantation, Hand, Face, Uterus, Penis, Abdominal Wall, Larynx, and Composite Tissue Allografts. All VCA case reports and reviews describing multiple case reports were included. RESULTS: We discovered 211 VCA cases reported. The preferred treatment was a combination of antithymocyte globulins, mycophenolate mofetil (MMF), tacrolimus, and steroids; and a combination of MMF, tacrolimus, and steroids for induction and maintenance treatment, respectively. Burn patients showed a higher acute rejection rate (P = 0.073) and were administered higher MMF doses (P = 0.020). CONCLUSIONS: In contrast to previous statements, the field of VCA is not rapidly evolving, as it has encountered challenges in addressing immune-related concerns. This is highlighted by the absence of a standardized immunosuppression regimen. Consequently, more substantial data are required to draw more conclusive results regarding the immunogenicity of VCAs and the potential superiority of one immunosuppressive treatment over another. Future efforts should be made to report the VCA surgeries comprehensively, and muti-institutional long-term prospective follow-up studies should be performed to compare the number of acute rejections with influencing factors.

The contribution of the donor vascularised hand and face allograft in transplant rejection: An immunological perspective.

Overcoming immunological rejection remains a barrier to the safe adoption of Vascularised Composite Allotransplantation (VCA). To mitigate this risk, clinical protocols have been derived from solid organ transplantation, targeting recipient immunomodulation, yet VCA is unique. Face and hand composite allografts are composed of multiple different tissues, each with their own immunological properties. Experimental work suggests that allografts carry variable numbers and populations of donor leukocytes in an organ specific manner. Ordinarily, these passenger leukocytes are transferred from the donor graft into the recipient circulation after transplantation. Whether alloantigen presentation manifests as acute allograft rejection or transplant tolerance is unknown. This review aims to characterise the immunological properties of the constituent parts of the donor face and hand, the potential fate of donor leukocytes and to consider theoretical graft specific interventions to mitigate early rejection.

Lymphadenopathy and lymph node rejection following facial vascularized composite allotransplantation.

BACKGROUND: Apart from the skin, little is known about the immunological processes in deeper tissues, which are typically not accessible to biopsy and inspection, of vascularized composite allografts (VCAs). Face transplant patients develop prominent adenopathy shortly after transplantation that resolves over time. The mechanisms underlying this process are not understood. MATERIALS AND METHODS: A retrospective cohort study was conducted on 9 patients who underwent 10 facial VCAs at the Brigham and Women's Hospital, Boston, MA, between April 2009 and July 2019. Clinical, radiological, and histological data related to lymphadenopathy of the head and neck were reviewed. RESULTS: Patients who received donor-derived lymph nodes (LNs) developed bilateral lymphadenopathy of the submental or submandibular superficial LNs. Median time of presentation was POD18 (range POD6-POM3). Notably, bilateral adenopathy of the neck was not observed in later stages of follow-up (mean follow-up, 115 months). Histology of 3 LNs showed increased histiocytes and apoptosis, with the features reminiscent of necrotizing histiocytic lymphadenitis, and B and T lymphocytes (mostly CD8 + T) admixed with CD163 + histiocytes and dendritic cells. Molecular chimerism analysis in one case showed the coexistence of donor (81%) and recipient (19%) derived lymphocytes. Granzyme B (GZMB) expression confirmed the presence of increased cytotoxic T cells in this LN sample. CONCLUSION: Our data suggested the involvement of an immunological process within the donor-derived LNs after facial allotransplantation between the recipient and donor cells. GZMB expression suggested LN rejection that can occurred independently of skin rejection. This finding supports the need to better define the role of donor-derived immune cells in the context of allograft rejection.

Implications of an Altered Gut Microbiome in Rat Experimental Vascularized Composite Transplantation.

OBJECTIVES: Vascularized composite allotransplantation is a reconstructive option after severe injury but is fraught with complications, including transplant rejection due to major histocompatibility complex mismatch in the context of allogeneic transplant, which in turn is due to altered immuno-inflammation secondary to transplant. The immunosuppressant tacrolimus can prevent rejection. Because tacrolimus is metabolized predominantly by the gut, this immunosuppressant alters the gut microbiome in multiple ways, thereby possibly affecting immunoinflammation. MATERIALS AND METHODS: We performed either allogeneic or syngeneic transplant with or without tacrolimus in rats. We quantified protein-level inflammatory mediators in the skin, muscle, and plasma and assessed the diversity of the gut microbiome through 16S RNA analysis at several timepoints over 31 days posttransplant. RESULTS: Statistical analysis highlighted a complex interaction between major histocompatibility complex and tacrolimus therapy on the relative diversity of the microbiome. Time-interval principal component analysis indicated numerous significant differences in the tissue characteristics of inflammation and gut microbiome that varied over time and across experimental conditions. Classification and regression tree analysis suggested that both inflammatory mediators in specific tissues and changes in the gut microbiome are useful in characterizing the temporal dynamics of posttransplant inflammation. Dynamic network analysis highlighted unique changes in Methanosphaera that were correlated with Peptococcusin allogeneic transplants with and without tacrolimus versus Prevotella in syngeneic transplant with tacrolimus, suggesting that alterations in Methanosphaera might be a biomarker of vascularized composite allotransplant rejection. CONCLUSIONS: Our results suggest a complex interaction among major histocompatibility complex, local and systemic immuno-inflammation, and tacrolimus therapy and highlight the potential for novel insights into vascularized composite allotransplant from computational approaches.

OPTN/SRTR 2022 Annual Data Report: Vascularized Composite Allograft.

This year's chapter on vascularized composite allograft (VCA) encompasses reviews of data collected from 2014 (when VCA was included in the Final Rule) through 2022. The present Annual Data Report shows that the number of VCA recipients in the United States continues to be small and has remained consistent from the prior report. The data continue to be limited by sample size, with trends persistently demonstrating a predominance of White males in the young/middle-aged population as both donors and recipients for nonuterus VCA transplants, and White women younger than 35 years as the predominant recipients of uterus transplant. Similar to the 2021 report, there were only eight failed uterus grafts and one failed nonuterus VCA graft reported from 2014 through 2022. Standardization of definitions of success and failure as well as outcome measures for the different VCA types remain unmet needs in VCA transplantation.

Topical Tacrolimus and Mycophenolic Acid Therapy Synergizes with Low Dose Systemic Immunosuppression to Sustain Vascularized Composite Allograft Survival.

AIM: The goal of this study was to evaluate whether topical administration of tacrolimus (TAC) and mycophenolic acid (MPA) at the transplant site enables vascularized composite allograft (VCA) survival with significant minimization of the dose and adverse effects of systemic TAC (STAC) immunosuppression. MATERIALS AND METHODS: Lewis (Lew) rats received orthotopic hind limb allotransplants from fully mismatched Brown Norway (BN) donors. Group 1 (Controls) received no treatment. Other groups were treated with STAC at a dose of 1 mg/kg/day for 7 days. On post-operative day (POD) 8, the STAC dose was dropped to 0.1 mg/kg/day for Group 2 and maintained at 1 mg/kg for Group 3. Group 4 received topical application of TAC and MPA on the transplanted (Tx) limb starting POD 8 without STAC. Group 5 received topical TAC and MPA on the contralateral non-Tx limb and Group 6 received topical TAC and MPA on the Tx limb starting POD 8 along with low dose STAC (0.1 mg/kg/day). Treatment was continued until the study end point was reached, defined as either grade 3 rejection or allograft survival exceeding 100 days. .We conducted sequential LC-MS/MS measurements to assess TAC and MPA concentrations in both blood/plasma and allograft tissues. Additionally, we evaluated markers indicative of organ toxicity associated with STAC immunosuppression. RESULTS: Compared to controls, topical therapy with TAC+MPA significantly prolonged allograft survival beyond 100 daysat very low dose STAC (0.1 mg/kg/day) (Group 6). The histopathological assessment of the grafts was consistent with the clinical outcomes. .Drug levels in blood/plasma remained low or undetectable, while allograft tissues showed higher drug concentrations compared to contralateral limb tissues (P<0.05). . Urinary creatinine clearance remained within the normal range at 2.5 mL/min. CONCLUSION: Combination therapy with topical TAC and MPA synergizes with a very low dose, corticosteroid- free-STAC regimen and facilitates rejection-free, prolonged VCA survival without morbidity.

First-in-Human Whole-Eye Transplantation: Ensuring an Ethical Approach to Surgical Innovation.

As innovations in the field of vascular composite allotransplantation (VCA) progress, whole-eye transplantation (WET) is poised to transition from non-human mammalian models to living human recipients. Present treatment options for vision loss are generally considered suboptimal, and attendant concerns ranging from aesthetics and prosthesis maintenance to social stigma may be mitigated by WET. Potential benefits to WET recipients may also include partial vision restoration, psychosocial benefits related to identity and social integration, improvements in physical comfort and function, and reduced surgical risk associated with a biologic eye compared to a prosthesis. Perioperative and postoperative risks of WET are expected to be comparable to those of facial transplantation (FT), and may be similarly mitigated by immunosuppressive protocols, adequate psychosocial support, and a thorough selection process for both the recipient and donor. To minimize the risks associated with immunosuppressive medications, the first attempts in human recipients will likely be performed in conjunction with a FT. If first-in-human attempts at combined FT-WET prove successful and the biologic eye survives, this opens the door for further advancement in the field of vision restoration by means of a viable surgical option. This analysis integrates recent innovations in WET research with the existing discourse on the ethics of surgical innovation and offers preliminary guidance to VCA programs considering undertaking WET in human recipients.

Banff 2022 Vascularized Composite Allotransplantation Meeting Report: Diagnostic criteria for vascular changes.

As more data become available, the Banff 2007 working classification of skin-containing vascularized composite allograft (VCA) pathology is expected to evolve and develop. This report represents the Banff VCA Working Group's consensus on the first revision of the 2007 scoring system. Prior to the 2022 Banff-CanXadian Society of Transplantation Joint Meeting, 83 clinicians and/or researchers were invited to a virtual meeting to discuss whether the 2007 Banff VCA system called for a revision. Unanimously, it was determined that the vascular changes were to be included in the first revision. Subsequently, 2 international online surveys, each followed by virtual discussions, were launched. The goals were (1) to identify which changes define severe rejection, (2) to grade their importance in the evaluation of severe rejection, and (3) to identify emerging criteria to diagnose rejection. A final hybrid (in-person and virtual) discussion at the Banff/Canadian Society of Transplantation Joint Meeting finalized the terminology, the definition, a scoring system, and a reporting system of the vascular changes. This proposal represents an international consensus on this topic and establishes the first revision of the Banff 2007 working classification of skin-containing vascularized composite allograft pathology.

Developing online communication training to request donation for vascularized composite allotransplantation (VCA): improving performance to match new US organ donation targets.

BACKGROUND: Approaching families of dying or newly deceased patients to donate organs requires specialized knowledge and a mastery of relational communication. As the transplantation field has progressed, Donation Professionals (DPs) are also leading conversations with family decision makers (FDMs) about the donation of uncommon anatomical gifts, such as face, hands, genitalia, referred to as Vascularized Composite Allotransplants (VCA) without much training or experience. To address the need for training, we adapted and beta tested an evidenced-based communication training program for donation discussions to VCA requests. The overarching goal of Communicating Effectively about Donation for Vascularized Composite Allotransplantation (CEaD-VCA) is to increase the number of VCA authorizations and to improve the socioemotional outcomes of FDMs. METHODS: We developed CEaD-VCA, an online, on-demand training program based on the previously tested, evidenced-based communication skills training program designed to train DPs to have conversations about solid organ donation. The training was modified utilizing data from a national telephone survey with DPs and results of 6 focus groups conducted with members of the general public. The survey and focus groups assessed knowledge, attitudes, and barriers to VCA donation. The training was shaped by a partnership with a leading industry partner, the Gift of Life Institute.™ RESULTS: Using the results as a guide, the existing CEaD training program, consisting of interactive eLearning modules, was adapted to include technical information about VCA, foundational communication skills, and two interactive example VCA donation request scenarios to facilitate active learning. Forty-two DPs from two partner Organ Procurement Organizations (OPOs) participated in the beta test of CEaD-VCA. Pre- and post-test surveys assessed the impact of the training. CONCLUSIONS: The training was scored highly by DPs in effectiveness and ease of use. This project created a standardized, accessible, and comprehensive training for DPs to communicate about VCA donation. CEaD-VCA is an example of how to develop a communication skills training for difficult conversations utilizing input from stakeholders, guided by communication theory. It also demonstrates how gaps in communication skills during medical education can be filled utilizing advanced online Learning Management Systems. The training specifically addresses new CMS rules concerning OPO performance metrics.

Local Delivery of Adipose Stem Cells Promotes Allograft Survival in a Rat Hind-Limb Model of Vascularized Composite Allotransplantation.

BACKGROUND: Adipose stem cells (ASCs) are a promising cell-based immunotherapy because of their minimally invasive harvest, high yield, and immunomodulatory capacity. In this study, the authors investigated the effects of local versus systemic ASC delivery on vascularized composite allotransplant survival and alloimmune regulation. METHODS: Lewis rats received hind-limb transplants from Brown Norway rats and were administered donor-derived ASCs (passage 3 or 4, 1 × 10 6 cells/rat) locally in the allograft, or contralateral limb, or systemically at postoperative day 1. Recipients were treated intraperitoneally with rabbit anti-rat lymphocyte serum on postoperative days 1 and 4 and daily tacrolimus for 21 days. Limb allografts were monitored for clinical signs of rejection. Donor cell chimerism, immune cell differentiation, and cytokine expression in recipient lymphoid organs were measured by flow cytometric analysis. The immunomodulation function of ASCs was tested by mixed lymphocyte reaction assay and ASC stimulation studies. RESULTS: Local-ASC-treated recipients achieved significant prolonged allograft survival (85.7% survived >130 days; n = 6) compared with systemic-ASC and contralateral-ASC groups. Secondary donor skin allografts transplanted to the local-ASC long-term surviving recipients accepted permanently without additional immunosuppression. The increases in donor cell chimerism and regulatory T-cells were evident in blood and draining lymph nodes of the local-ASC group. Moreover, mixed lymphocyte reaction showed that ASCs inhibited donor-specific T-cell proliferation independent of direct ASC-T-cell contact. ASCs up-regulated antiinflammatory molecules in response to cytokine stimulation in vitro. CONCLUSION: Local delivery of ASCs promoted long-term survival and modulated alloimmune responses in a full major histocompatibility complex-mismatched vascularized composite allotransplantation model and was more effective than systemic administration. CLINICAL RELEVANCE STATEMENT: ASCs are a readily available and abundant source of therapeutic cells that could decrease the amount of systemic immunosuppression required to maintain limb and face allografts.

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.

International consensus recommendations on face transplantation: A 2-step Delphi study.

Face transplantation is a viable reconstructive approach for severe craniofacial defects. Despite the evolution witnessed in the field, ethical aspects, clinical and psychosocial implications, public perception, and economic sustainability remain the subject of debate and unanswered questions. Furthermore, poor data reporting and sharing, the absence of standardized metrics for outcome evaluation, and the lack of consensus definitions of success and failure have hampered the development of a "transplantation culture" on a global scale. We completed a 2-round online modified Delphi process with 35 international face transplant stakeholders, including surgeons, clinicians, psychologists, psychiatrists, ethicists, policymakers, and researchers, with a representation of 10 of the 19 face transplant teams that had already performed the procedure and 73% of face transplants. Themes addressed included patient assessment and selection, indications, social support networks, clinical framework, surgical considerations, data on patient progress and outcomes, definitions of success and failure, public image and perception, and financial sustainability. The presented recommendations are the product of a shared commitment of face transplant teams to foster the development of face transplantation and are aimed at providing a gold standard of practice and policy.

Vascularized Composite Allograft Versus Prosthetic for Reconstruction After Facial and Hand Trauma: Comparing Cost, Complications, and Long-term Outcome.

ABSTRACT: In the past decade, vascularized composite allotransplantation (VCA) has become clinical reality for reconstruction after face and hand trauma. It offers patients the unique opportunity to regain form and function in a way that had only been achieved with traditional reconstruction or with the use of prostheses. On the other hand, prostheses for facial and hand reconstruction have continued to evolve over the years and, in many cases, represent the primary option for patients after hand and face trauma. We compared the cost, associated complications, and long-term outcomes of VCA with prostheses for reconstruction of the face and hand/upper extremity. Ultimately, VCA and prostheses represent 2 different reconstructive options with distinct benefit profiles and associated limitations and should ideally not be perceived as competing choices. Our work adds a valuable component to the general framework guiding the decision to offer VCA or prostheses for reconstruction after face and upper extremity trauma.

Mimicking Clinical Rejection Patterns in a Rat Osteomyocutaneous Flap Model of Vascularized Composite Allotransplantation.

INTRODUCTION: Graft loss in vascularized composite allotransplantation (VCA) is more often associated with vasculopathy and chronic rejection (CR) than acute cellular rejection (ACR). We present a rat osteomyocutaneous flap model using titrated tacrolimus administration that mimics the graft rejection patterns in our clinical hand transplant program. Comparison of outcomes in these models support a role for ischemia reperfusion injury (IRI) and microvascular changes in CR of skin and large-vessel vasculopathy. The potential of the surgical models for investigating mechanisms of rejection and vasculopathy in VCA and treatment interventions is presented. MATERIALS AND METHODS: Four rodent groups were evaluated: syngeneic controls (Group 1), allogeneic transient immunosuppression (Group 2), allogeneic suboptimal immunosuppression (Group 3), and allogeneic standard immunosuppression (Group 4). Animals were monitored for ACR, vasculopathy, and CR of the skin. RESULTS: Transient immunosuppression resulted in severe ACR within 2 wk of tacrolimus discontinuation. Standard immunosuppression resulted in minimal rejection but subclinical microvascular changes, including capillary thrombosis and luminal narrowing in arterioles in the donor skin. Further reduction in tacrolimus dose led to femoral vasculopathy and CR of the skin. Surprisingly, femoral vasculopathy was also observed in the syngeneic control group. CONCLUSIONS: Titration of tacrolimus in the allogeneic VCA model resulted in presentations of rejection and vasculopathy similar to those in patients and suggests vasculopathy starts at the microvascular level. This adjustable experimental model will allow the study of variables and interventions, such as external trauma or complement blockade, that may initiate or mitigate vasculopathy and CR in VCA.