Vascularized Composite Allotransplantation: Alternatives and Catch-22s

Optimized Decellularization of a Porcine Fasciocutaneaous Flap

Reconstructive techniques to repair severe tissue defects include the use of autologous fasciocutaneous flaps, which may be limited due to donor site availability or lead to complications such as donor site morbidity. A number of synthetic or natural dermal substitutes are in use clinically, but none have the architectural complexity needed to reconstruct deep tissue defects. The perfusion decellularization of fasciocutaneous flaps is an emerging technique that yields a scaffold with the necessary composition and vascular microarchitecture and serves as an alternative to autologous flaps. In this study, we show the perfusion decellularization of porcine fasciocutaneous flaps using sodium dodecyl sulfate (SDS) at three different concentrations, and identify that 0.2% SDS results in a decellularized flap that is efficiently cleared of its cellular material at 86%, has maintained its collagen and glycosaminoglycan content, and preserved its microvasculature architecture. We further demonstrate that the decellularized graft has the porous structure and growth factors that would facilitate repopulation with cells. Finally, we show the biocompatibility of the decellularized flap using human dermal fibroblasts, with cells migrating as deep as 150 µm into the tissue over a 7-day culture period. Overall, our results demonstrate the promise of decellularized porcine flaps as an interesting alternative for reconstructing complex soft tissue defects, circumventing the limitations of autologous skin flaps.

Design of a Multiparametric Perfusion Bioreactor System for Evaluating Sub-Normothermic Preservation of Rat Abdominal Wall Vascularized Composite Allografts

Static cold storage (SCS), the current clinical gold standard for organ preservation, provides surgeons with a limited window of time between procurement and transplantation. In vascularized composite allotransplantation (VCA), this time limitation prevents many viable allografts from being designated to the best-matched recipients. Machine perfusion (MP) systems hold significant promise for extending and improving organ preservation. Most of the prior MP systems for VCA have been built and tested for large animal models. However, small animal models are beneficial for high-throughput biomolecular investigations. This study describes the design and development of a multiparametric bioreactor with a circuit customized to perfuse rat abdominal wall VCAs. To demonstrate its concept and functionality, this bioreactor system was employed in a small-scale demonstrative study in which biomolecular metrics pertaining to graft viability were evaluated non-invasively and in real time. We additionally report a low incidence of cell death from ischemic necrosis as well as minimal interstitial edema in machine perfused grafts. After up to 12 h of continuous perfusion, grafts were shown to survive transplantation and reperfusion, successfully integrating with recipient tissues and vasculature. Our multiparametric bioreactor system for rat abdominal wall VCA provides an advanced framework to test novel techniques to enhance normothermic and sub-normothermic VCA preservations in small animal models.

What is needed to ensure long-term sustainability for the field of vascularized composite allotransplantation?

The field of vascularized composite allotransplantation (VCA) has demonstrated remarkable advances since its inception with some excellent long-term results in a variety of graft types. However, unlike solid organ transplantation, it has yet to become mainstream. We therefore discuss strategies on ensuring long-term sustainability by addressing continued clinical developments of VCA to improve the risk-to-benefit balance, importance of public support, improved policy and financial support, and need for a bridge to the future of transplant surgery. There has been headway on all fronts and collaboration among the VCA centers for centralization of data and incorporation of patient voices will be essential for continued progress.

Video Messaging to Increase Vascularized Composite Allograft Donation Willingness in United States Military Veterans

Expansion of vascularized composite allograft (VCA) transplantation depends on the public's willingness to donate VCA organs, including face, extremities, and genitourinary organs. This study evaluated the effectiveness of video messaging on VCA donation willingness in US military veterans, a key stakeholder in VCA transplantation.

Methods

Participants (n = 556) were randomized to 1 of 3 VCA video messaging interventions (informational, testimonial, or blended), a general (non-VCA) organ donation video message, or a control (nondonation) video message. Questionnaires were completed at pre- and postintervention and at 3-wk follow-up.

Results

Veterans exposed to any VCA video messaging were more likely to express VCA donation willingness (69%, n = 203/296) than those exposed to general donation messaging (53%, n = 47 of 89; P = 0.006) or No Donation Messaging (37%, n = 36 of 97; P < 0.001). A significantly higher proportion of participants who received Blended VCA Messaging were willing to be VCA donors, compared with the Informational VCA Messaging group (79% versus 61%, P = 0.006). Each VCA messaging video resulted in a significant pre- to postintervention increase in the proportion of participants willing to donate their own face, hands, and legs (P < 0.03).

Conclusions

Brief educational videos focused on VCA transplantation can have a demonstrable and verifiable impact on rates of VCA donation willingness in veterans.

Recipient Selection Criteria for Facial Transplantation: A Systematic Review

BACKGROUND

Recipient selection is an important determinant of surgical outcomes in facial transplantation (FT). Appropriately, each FT program develops their own guidelines for recipient selection criteria. Currently, there is no resource to simultaneously assess and identify similarities and differences between these guidelines. Such information could be useful in distinguishing areas of FT that are well understood from those that could benefit from further exploration.

METHODS

We performed a systematic review of the scientific literature from inception to June 18, 2021, using Pubmed, Embase, Cochrane Library, and Scopus to identify articles pertaining to recipient selection criteria. Clinical trials were identified through the Clinicaltrials.gov registry. United States and international program websites were reviewed for patient-facing information.

RESULTS

Our systematic review yielded 90 suitable articles, 8 clinical trials, and 7 program websites containing the recipient selection criteria of 24 different FT programs. The most reported on recipient criteria were age, positive human immunodeficiency viral status (HIV+), positive hepatitis C viral status, psychosocial stability, and medical compliance. Other criteria were rarely addressed, such as blindness and recipient immune status.

CONCLUSIONS

Guidelines among different face transplant programs are changing over time. We found consensus on certain recipient selection criteria, but the majority remain program or surgeon dependent, emphasizing that FT is still an evolving procedure. Although most programs reported on their recipient selection criteria, the rationale was often missing. Further discussion about recipient selection criteria and the reasoning behind employing or changing them will help advance the field.

Addressing common orthopaedic calamities with microsurgical solutions

Reconstructive microsurgery has been an essential aspect of orthopaedic surgery and extremity reconstruction since the introduction of the operating microscope in the mid-20^th century. The reconstructive ladder ranges from simple healing by secondary intention to complex procedures such as free tissue transfer and vascularized composite allotransplantation. As orthopaedic surgery has evolved over the past 60 years, so too have the reconstructive microsurgical skills that are often needed to address common orthopaedic surgery problems. In this article, we will discuss a variety of complex orthopaedic surgery scenarios ranging from trauma to infection to tumor resection as well as the spectrum of microsurgical solutions that can aid in their management.

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.

Engineering Vascularized Composite Allografts Using Natural Scaffolds: A Systematic Review

INTRODUCTION

Vascularized Composite Allotransplantation refers to the transplantation of multiple tissues as a functional unit from a deceased donor to a recipient with a severe injury. These grafts serve as potential replacements for traumatic tissue losses. The main problems are the consequences of the long immunosuppressive drugs medications and the lake of compatible donor. To avoid these limitations, decellularization/recellularization constitute an attractive approach. The aim of decellularization/recellularization technology is to develop immunogenic free biological substitutes that will restore, maintain, or improve tissue and organ's function.

METHODS

A PubMed search was performed for articles on decellularization and recellularization of composite tissue allografts between March and February 2021, with no restrictions in publication year. The selected reports were evaluated in terms of decellularization protocols, assessment of decellularized grafts, and evaluation of their biocompatibility and repopulation with cells both in vitro and in vivo.

RESULTS

The search resulted in a total of 88 articles. Each article was reviewed, 77 were excluded and the remaining 11 articles reported decellularization of 12 different vascular composite allografts in humans (four), large animals (three), and small animals (rodents) (five). The decellularization protocol for vascularized composite allotransplantation varies slightly between studies, but majority of the reports employ 1% sodium dodecyl sulfate as the main reagent for decellularization. The immunological response of the decellularized scaffolds remains poorly evaluated. Few authors have been able to attempt the recellularization and transplantation of these scaffolds. Successful transplantation seems to require prior recellularization.

CONCLUSION

Decellularization/recellularization is a promising, growing, emerging developing research field in vascular composite allotransplantation.

Facial Transplantation: Principles and Evolving Concepts

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Appreciate the evolution and increasing complexity of transplanted facial allografts over the past two decades. 2. Discuss indications and contraindications for facial transplantation, and donor and recipient selection criteria and considerations. 3. Discuss logistical, immunologic, and cost considerations in facial transplantation, in addition to emerging technologies used. 4. Understand surgical approaches and anatomical and technical nuances of the procedure. 5. Describe aesthetic, functional, and psychosocial outcomes of facial transplantation reported to date.

SUMMARY

This CME article highlights principles and evolving concepts in facial transplantation. The field has witnessed significant advances over the past two decades, with more than 40 face transplants reported to date. The procedure now occupies the highest rung on the reconstructive ladder for patients with extensive facial disfigurement who are not amenable to autologous reconstructive approaches, in pursuit of optimal functional and aesthetic outcomes. Indications, contraindications, and donor and recipient considerations for the procedure are discussed. The authors also review logistical, immunologic, and cost considerations of facial transplantation. Surgical approaches to allograft procurement and transplantation, in addition to technical and anatomical nuances of the procedure, are provided. Finally, the authors review aesthetic, functional, and psychosocial outcomes that have been reported to date.

Nuclear Receptor Subfamily 4 Group A Member 1 Overexpression Prolongs Free Flap Allotransplant Graft Survival by Inducing T-Cell Anergy in the Rat

BACKGROUND

New strategies to inhibit acute rejection are needed for further applications of composite tissue allotransplantation. The nuclear receptor subfamily 4 group A member 1 (NR4A1) is considered a key controller of maintaining tolerance homeostasis. However, the effect of NR4A1 in suppressing rejection responses after allotransplantation remains unknown.

METHODS

Brown Norway rat groin flaps were transplanted into Lewis rat recipients. The recipients were administrated cytosporone B, an NR4A1 activator. NR4A1 expression and graft survival time were assessed. T helper type 1 and regulatory T cell populations in the second lymphoid organ were detected by flow cytometry. Furthermore, a retrovirus containing NR4A1 was constructed and transfected to T cells in vitro. After stimulation, interleukin 2 and interferon gamma secretions were detected in the T cells.

RESULTS

Administration of cytosporone B activated NR4A1 expression in allotransplant recipients and was associated with prolonged survival time of the vascularized free flap allograft. T helper type 1 cells in the recipient secondary lymphoid organs were decreased, whereas the population of regulatory T cells did not change. Interleukin 2 and interferon gamma were suppressed in vitro in the T cells overexpressing NR4A1.

CONCLUSIONS

We demonstrated that the overexpressed NR4A1 is associated with suppressed graft rejection response. The suppression effect may attribute to induction of T-cell anergy and blockade of key immunologic cytokines.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

"Auricular reconstruction: A sociocultural, surgical and scientific perspective"

The functional and sociocultural role of the auricle has been prevalent in art, literature and history for millennia. It is no surprise, therefore, that auricular anomalies can be associated with affective disorders and impaired academic performance in children. The challenge of auricular reconstruction has captured the attention of surgical innovators for millennia with the earliest records of auricular reconstruction documented in the Edwin Smith Surgical Papyrus dating back to 3000 BCE. Since the 19th century, however, the interest in the ambition partial and total auricular reconstruction witnessed a rebirth, with refinements in frame construction, projection and skin coverage improving exponentially over the last two centuries. The gold standard auricular reconstruction practices today have their roots in these historical milestones, and form a solid foundation for the introduction of technological advancements such as 3D bioprinting and composite tissue allotransplantation into future auricular reconstruction practice. The aim of this review is to outline the sociocultural role of the auricle, the history and evolution of auricular reconstruction surgery and to provide an insight into potential future avenues of restoring auricular form and function.

The Baltimore Criteria for an ethical approach to penile transplantation: a clinical guideline

Significant advances and increasing acceptance of vascularized composite allotransplantation (VCA) have contributed to emerging success of penile transplantation. The aims of penile transplantation are fourfold: adequate urinary function, enabling natural erections, restoration of erogenous sensation and appearance of external male genitalia. Successful penile transplantation also requires limiting risks and managing complications of lifelong immunosuppression. Given the limited experience with this procedure, potential recipients must understand that penile transplantation is not currently standard of care and long-term functional outcomes are unknown. Moreover, these transplants are associated with complex ethical issues. Nevertheless, as the efficacy and safety of penile transplantation are being evaluated, clear indications for transplant are needed. Although preliminary recommendations have been proposed, a more comprehensive framework is needed. We performed a literature review for English language publications related to penile transplantation and ethics. Based on the results of the search, a review of prior recommendations, and our experience performing the first whole male genital allotransplantation including penis, scrotum and abdominal wall; screening and identifying potential donors and recipients for the procedure; and addressing the associated ethical issues, we propose guidelines for responsible penile transplantation: The Baltimore Criteria for an Ethical Approach to Penile Transplantation.