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.

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.

Current opinion: advances in machine perfusion and preservation of vascularized composite allografts - will time still matter?

PURPOSE OF REVIEW

A major hurdle hindering more widespread application of reconstructive transplantation is the very limited cold ischemia time (CIT) of vascularized composite allografts (VCAs). In this review, we discuss cutting edge machine perfusion protocols and preservation strategies to overcome this limitation.

RECENT FINDINGS

Several preclinical machine perfusion studies have demonstrated the multifactorial utility of this technology to extend preservation windows, assess graft viability prior to transplantation and salvage damaged tissue, yet there are currently no clinically approved machine perfusion protocols for reconstructive transplantation. Thus, machine perfusion remains an open challenge in VCA due to the complexity of the various tissue types. In addition, multiple other promising avenues to prolong preservation of composite allografts have emerged. These include cryopreservation, high subzero preservation, vitrification and nanowarming. Despite several studies demonstrating extended preservation windows, there are several limitations that must be overcome prior to clinical translation. As both machine perfusion and subzero preservation protocols have rapidly advanced in the past few years, special consideration should be given to their potential complementary utilization.

SUMMARY

Current and emerging machine perfusion and preservation technologies in VCA have great promise to transform the field of reconstructive transplantation, as every extra hour of CIT helps ease the complexities of the peri-transplant workflow. Amongst the many advantages, longer preservation windows may allow for elective procedures, improved matching, establishment of novel immunomodulatory protocols and global transport of grafts, ultimately enabling us the ability to offer this life changing procedure to more patients.

A Novel Sutureless Anastomotic Device in a Swine Model: A Proof of Concept Study

INTRODUCTION

Vascular reconstruction requires technical expertise and is often time consuming. As a novel alternative to traditional hand-sewn vascular anastomoses, the VasoLock (VL), is a nonabsorbable, sutureless anastomosis device with traction anchors designed to hold free artery ends together. These anchors do not penetrate the vessel wall but adhere by leveraging the elasticity of the vessels to fasten blood vessels together. This pilot study assesses the performance and patency of this novel device in a porcine model of femoral artery injury.

METHODS

Female swine (n = 7) underwent femoral artery exposure for a total of 10 VL implanted. Study animals underwent hemodilution to a target hematocrit of 15% and ROTEM was used to assess coagulopathy, followed by an arterial injury via transection. The VL was inserted without any sutures. Flow-probe monitors were positioned proximal and distal to the device and flow rates were measured continuously for a total of 90 min. Flow was analyzed and presented as a ratio of distal to proximal flow with the slope of this ratio across time subsequently determined. Angiographic assessment was completed to evaluate for patency and technical complications after 90 min of implant.

RESULTS

The average animal weight was 44.1 ± 3.2 kg. The average mean arterial pressure at the time of implant was 51.2 ± 7.8 mmHg, median heart rate was 77.4 (IQR = 77.25-157.4) beats per minute, and average temperature was 36.1 ± 1.5°C. The baseline hematocrit was 13.5 ± 3.0%, average pH was 7.20 ± 0.1, average clotting time was 154.1 ± 58.7 s and average clot formation time was 103.4 ± 10.9 s all demonstrating the acidotic, hypothermic, and coagulopathic state of the swine at the time of insertion. During the 90-min observation period, the average flow gradient identified across the VL was 0.99 ± 0.24, indicating no significant change in flow across the VL. The average slope of the gradients was 0.0005 (P = 0.22), suggesting the ratio of proximal and distal flow did not change over the 90 min. Following 90 min of dwell time, all VL were patent without technical complication. Angiographic assessment at 90 min demonstrated no evidence of dissection, device migration, arterial extravasation, or thromboembolism with any of the 10 devices.

CONCLUSIONS

This pilot study demonstrated technical feasibility of the novel VL device over a 90-min observation period. All VL were patent and no negative events or complications were identified. This technology demonstrated significant promise in a coagulopathic state: additional investigation, involving long-term survival, is warranted for further validation.

Polyethylene Glycol Fusion Restores Axonal Continuity and Improves Return of Function in a Rat Median Nerve Denervation Model

BACKGROUND

Polyethylene glycol (PEG) can fuse severed closely-apposed axolemmas and restore axonal continuity. We evaluated the effects of PEG-fusion on functional recovery in a rodent forelimb model of peripheral nerve injury.

METHODS

The median nerves of male Lewis rats (n=5 per group) were transected and repaired with standard suture repair (SR), SR with PEG (PEG), or SR with PEG and 1% methylene blue (PEG+MB); a sham surgery group was also included. Proximal stimulation produced compound nerve (CAPS) and muscle (CMAPs) action potentials recorded distally. The contralateral limb of each animal acted as an internal control for grip strength measurements.

RESULTS

CAPs and CMAPs immediately returned in all PEG and PEG+MB animals, but not in SR animals. PEG and PEG+MB groups demonstrated earlier return of function by post-operative day (POD) 7 (62.6 ±7.3% and 50.9 ±6.7% of contralateral limb grip strength, respectively) compared to SR group, in which minimal return of function was not measurable until POD 21. At POD 98, the PEG group grip strength recovered to 77.2 ±2.8% while the PEG+MB grip strength recovered to 79.9 ±4.4%, compared to 34.9 ±1.8% recovery in the SR group (p<0.05). The PEG and PEG+MB groups reached 50% of the Sham group grip strength on POD 3.8 and 6.3, respectively, whereas the SR group did not reach 50% grip strength recovery of the Sham group throughout the study period.

CONCLUSION

PEG-fusion plus neurorrhaphy with or without methylene blue re-established axonal continuity, shortened recovery time, and augmented functional recovery compared to suture neurorrhaphy alone.

Methods of ex vivo analysis of tissue status in vascularized composite allografts

Vascularized composite allotransplantation can improve quality of life and restore functionality. However, the complex tissue composition of vascularized composite allografts (VCAs) presents unique clinical challenges that increase the likelihood of transplant rejection. Under prolonged static cold storage, highly damage-susceptible tissues such as muscle and nerve undergo irreversible degradation that may render allografts non-functional. Skin-containing VCA elicits an immunogenic response that increases the risk of recipient allograft rejection. The development of quantitative metrics to evaluate VCAs prior to and following transplantation are key to mitigating allograft rejection. Correspondingly, a broad range of bioanalytical methods have emerged to assess the progression of VCA rejection and characterize transplantation outcomes. To consolidate the current range of relevant technologies and expand on potential for development, methods to evaluate ex vivo VCA status are herein reviewed and comparatively assessed. The use of implantable physiological status monitoring biochips, non-invasive bioimpedance monitoring to assess edema, and deep learning algorithms to fuse disparate inputs to stratify VCAs are identified.

Ethical and Psychosocial Factors in the Decision-Making and Informed Consent Process for Upper Extremity Vascularized Composite Allotransplantation: A Mixed-Methods Study

Although upper extremity (UE) vascularized composite allotransplantation (VCA) aims to improve quality of life, relatively few have been performed worldwide to support evidence-based treatment and informed decision-making.

Methods

We qualitatively examined factors contributing to anticipated and actual decision-making about UE VCA and perceptions of the elements of informed consent among people with UE amputations, and UE VCA candidates, participants, and recipients through in-depth interviews. Thematic analysis was used to analyze qualitative data.

Results

Fifty individuals participated; most were male (78%) and had a mean age of 45 y and a unilateral amputation (84%). One-third (35%) were "a lot" or "completely" willing to pursue UE VCA. UE VCA decision-making themes included the utility of UE VCA, psychosocial impact of UE VCA and amputation on individuals' lives, altruism, and anticipated burden of UE VCA on lifestyle. Most respondents who underwent UE VCA evaluation (n = 8/10) perceived having no reasonable treatment alternatives. Generally, respondents (n = 50) recognized the potential for familial, societal, cultural, medical, and self-driven pressures to pursue UE VCA among individuals with amputations. Some (n = 9/50, 18%) reported personally feeling "a little," "somewhat," "a lot," or "completely" pressured to pursue UE VCA. Respondents recommended that individuals be informed about the option of UE VCA near the amputation date.

Conclusions

Our study identified psychosocial and other factors affecting decision-making about UE VCA, which should be addressed to enhance informed consent. Study participants' perceptions and preferences about UE VCA suggest re-examination of assumptions guiding the UE VCA clinical evaluation process.

The Effects of Growth Hormone on Nerve Regeneration and Alloimmunity in Vascularized Composite Allotransplantation

BACKGROUND

Poor outcomes in functional recovery following upper extremity transplantation are largely due to denervation-induced muscle atrophy that occurs during the prolonged period of nerve regeneration. Growth hormone (GH) has well-established trophic effects on neurons, myocytes, and Schwann cells and represents a promising therapeutic approach to address this challenge. This study sought to confirm the positive effects of GH treatment on nerve regeneration and functional recovery and to evaluate the effects of GH treatment on the immune response in the setting of vascularized composite allotransplantation.

METHODS

Rats underwent orthotopic forelimb transplantation across a full MHC-mismatch and received either porcine-derived growth hormone or no treatment (n=18 per group). Functional recovery was measured using electrically-stimulated grip strength testing. Animals were monitored for clinical and subclinical signs of rejection.

RESULTS

Neuromuscular junction reinnervation and grip strength were improved in GH-treated animals (p=0.005; p=0.08). No statistically significant differences were seen in muscle atrophy, degree of myelination, axon diameter, and axon counts between groups. The rates of clinical and histological rejection did not significantly differ among groups.

CONCLUSIONS

Our findings alleviate concern for increased risk of transplant rejection during GH therapy and therefore support the translation of growth hormone as a therapeutic method to promote improved functional recovery in upper extremity transplantation.

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.

Patient preferences of patient selection criteria for upper extremity vascularized composite allotransplantation: A qualitative study

Background

Upper extremity vascularized composite allotransplantation is a life-enhancing reconstructive treatment option that aims to improve recipients' quality of life and maximize function. This study assessed upper extremity vascularized composite allotransplantation patient selection criteria perceptions among individuals with upper extremity limb loss. The perceptions of individuals with upper extremity limb loss on patient selection criteria may enable vascularized composite allotransplantation centers to improve criteria to avoid mismatched expectations about the posttransplant vascularized composite allotransplantation experience and outcomes. Realistic patient expectations may increase patient adherence, improve outcomes, and reduce vascularized composite allotransplantation graft loss.

Methods

We conducted in-depth interviews with civilian and military service members with upper extremity limb loss and upper extremity vascularized composite allotransplantation candidates, participants, and recipients from three US institutions. Interviews assessed perceptions of patient selection criteria for suitability as a candidate for upper extremity vascularized composite allotransplantation. Thematic analysis was used to analyze qualitative data.

Results

A total of 50 individuals participated (66% participation rate). Most participants were male (78%), White (72%), with a unilateral limb loss (84%), and a mean age of 45 years. Six themes emerged regarding upper extremity vascularized composite allotransplantation patient selection criteria, including support for candidates who: (1) are of younger age, (2) are in good physical health, (3) have mental stability, (4) are willing to "put in the work," (5) have specific amputation characteristics, and (6) have sufficient social support. Patients had preferences about selecting candidates with unilateral versus bilateral limb loss.

Conclusions

Our findings suggest that numerous factors, including medical, social, and psychological characteristics, inform patients' perceptions of patient selection criteria for upper extremity vascularized composite allotransplantation. Patient perceptions of patient selection criteria should inform the development of validated screening measures that optimize patient outcomes.

Biomaterials-based immunomodulation enhances survival of murine vascularized composite allografts

Vascularized composite allotransplantation (VCA) is a restorative option for patients suffering from severe tissue defects not amenable to conventional reconstruction. However, the toxicities associated with life-long multidrug immunosuppression to enable allograft survival and induce immune tolerance largely limit the broader application of VCA. Here, we investigate the potential of targeted immunomodulation using CTLA4-Ig combined with a biological porcine-derived extracellular matrix (ECM) scaffold that elicits a pro-regenerative Th2 response to promote allograft survival and regulate the inflammatory microenvironment in a stringent mouse orthotopic hind limb transplantation model (BALB/c to C57BL/6). The median allograft survival time (MST) increased significantly from 15.0 to 24.5 days (P = 0.0037; Mantel-Cox test) after adding ECM to the CTLA4-Ig regimen. Characterization of the immune infiltration shows a pro-regenerative phenotype prevails over those associated with inflammation and rejection including macrophages (F4/80^hi+CD206^hi+MHCII^low), eosinophils (F4/80^lowSiglec-F⁺), and T helper 2 (Th2) T cells (CD4⁺IL-4⁺). This was accompanied by an increased expression of genes associated with a Type 2 polarized immune state such as Il4, Ccl24, Arg1 and Ym1 within the graft. Furthermore, when ECM was applied along with a clinically relevant combination of CTLA4-Ig and Rapamycin, allograft survival was prolonged from 33.0 to 72.5 days (P = 0.0067; Mantel-Cox test). These studies implicate the clinical exploration of combined regimens involving local application of pro-regenerative, immunomodulatory biomaterials in surgical wound sites with targeted co-stimulatory blockade to reduce adverse effects of immunosuppression and enhance graft survival in VCA.

Hickman Catheter Use for Long-Term Vascular Access in a Preclinical Swine Model

Central venous catheters (CVCs) are invaluable devices in large animal research as they facilitate a wide range of medical applications, including blood monitoring and reliable intravenous fluid and drug administration. Specifically, the tunneled multi-lumen Hickman catheter (HC) is commonly used in swine models due to its lower extrication and complication rates. Despite fewer complications relative to other CVCs, HC-related morbidity presents a significant challenge, as it can significantly delay or otherwise negatively impact ongoing studies. The proper insertion and maintenance of HCs is paramount in preventing these complications, but there is no consensus on best practices. The purpose of this protocol is to comprehensively describe an approach for the insertion and maintenance of a tunneled HC in swine that mitigates HC-related complications and morbidity. The use of these techniques in >100 swine has resulted in complication-free patent lines up to 8 months and no catheter-related mortality or infection of the ventral surgical site. This protocol offers a method to optimize the lifespan of the HC and guidance for approaching issues during use.

Real-Time Monitoring Using Multiplexed Multi-Electrode Bioelectrical Impedance Spectroscopy for the Stratification of Vascularized Composite Allografts: A Perspective on Predictive Analytics

Vascularized composite allotransplantation addresses injuries to complex anatomical structures such as the face, hand, and abdominal wall. Prolonged static cold storage of vascularized composite allografts (VCA) incurs damage and imposes transportation limits to their viability and availability. Tissue ischemia, the major clinical indication, is strongly correlated with negative transplantation outcomes. Machine perfusion and normothermia can extend preservation times. This perspective introduces multiplexed multi-electrode bioimpedance spectroscopy (MMBIS), an established bioanalytical method to quantify the interaction of the electrical current with tissue components, capable of measuring tissue edema, as a quantitative, noninvasive, real-time, continuous monitoring technique to provide crucially needed assessment of graft preservation efficacy and viability. MMBIS must be developed, and appropriate models explored to address the highly complex multi-tissue structures and time-temperature changes of VCA. Combined with artificial intelligence (AI), MMBIS can serve to stratify allografts for improvement in transplantation outcomes.

A Patient-Centered Website (Within Reach) to Foster Informed Decision-making About Upper Extremity Vascularized Composite Allotransplantation: Development and Usability Study

BACKGROUND

Upper extremity (UE) vascularized composite allotransplantation (VCA; hand transplantation) is a reconstructive treatment option for patients with UE loss. Approximately 37 UE VCAs have been performed in the United States to date; thus, little is known about long-term psychosocial outcomes and whether the benefits outweigh the risks. To make an informed treatment decision, patients must understand the procedure, risks, and potential benefits of UE VCA. However, few educational resources are publicly available providing unbiased, comprehensive information about UE VCA.

OBJECTIVE

This paper described the development of a neutral, and accessible, educational website supporting informed decision-making about UE VCA as a treatment option for individuals with UE amputations.

METHODS

Website content development was informed by 9 focus groups conducted with individuals with UE amputations at 3 study sites. After initial website development, we conducted usability testing to identify ways to improve navigability, design, content, comprehension, and cultural sensitivity. Participants were administered the After-Scenario Questionnaire to assess user performance after completing navigational tasks, System Usability Scale to measure the perceived usability of the website, and Net Promoter Score to measure user satisfaction. Quantitative data were analyzed using descriptive statistics. Qualitative data were analyzed using rapid thematic analysis.

RESULTS

A total of 44 individuals with UE amputations participated in focus groups (n=37, 84%) and usability testing (n=14, 32%). Most participants in the focus groups and usability testing were male (24/37, 65% and 11/14, 79%, respectively) and White (27/37, 73% and 9/14, 64%, respectively), had unilateral limb loss (22/37, 59% and 12/14, 86%, respectively), and had mean ages of 48 (SD 9.2) and 50 (SD 12.0) years, respectively. Focus group results are organized into accessibility, website design, website development, website tone and values, sitemap, terminology, images and videos, and tables and graphics. Usability testing revealed that participants had a positive impression of the website. The mean After-Scenario Questionnaire score of 1.3 to 2.3 across task scenarios indicated high satisfaction with website usability, the mean System Usability Scale score of 88.9 indicated user satisfaction with website usability, and the mean Net Promoter Score of 9.6 indicated that users were enthusiastic and would likely refer individuals to the website.

CONCLUSIONS

The findings suggest that our educational website, Within Reach, provides neutral, patient-centered information and may be a useful resource about UE VCA for individuals with UE amputations, their families, and health care professionals. Health care professionals may inform UE VCA candidates about Within Reach to supplement current VCA education processes. Within Reach serves as a resource about treatment options for patients preparing for scheduled or recovering from traumatic UE amputations. Future research should assess whether Within Reach improves knowledge about UE VCA and enhances informed decision-making about UE VCA as a treatment option.

Development of a rat forelimb vascularized composite allograft (VCA) perfusion protocol

Vascularized composite allografts (VCAs) refer to en bloc heterogenous tissue that is transplanted to restore form and function after amputation or tissue loss. Rat limb VCA has emerged as a robust translational model to study the pathophysiology of these transplants. However, these models have predominately focused on hindlimb VCAs which does not translate anatomically to upper extremity transplantation, whereas the majority of clinical VCAs are upper extremity and hand transplants. This work details our optimization of rat forelimb VCA procurement and sub-normothermic machine perfusion (SNMP) protocols, with results in comparison to hindlimb perfusion with the same perfusion modality. Results indicate that compared to hindlimbs, rat forelimbs on machine perfusion mandate lower flow rates and higher acceptable maximum pressures. Additionally, low-flow forelimbs have less cellular damage than high-flow forelimbs based on oxygen uptake, edema, potassium levels, and histology through 2 hours of machine perfusion. These results are expected to inform future upper extremity VCA preservation studies.

Lessons learned from the first 15 years of penile transplantation and updates to the Baltimore Criteria

Since 2006, five penis transplants have been performed worldwide. Mixed outcomes have been reported, and two of the five penile transplants have required explantation. However, the long-term outcomes have been encouraging when compliance is implemented, whether standard induction and triple therapy maintenance, or single therapy maintenance. Follow-up monitoring of transplant recipients has enabled a synthesis of technical considerations for surgical success and has shown stable leukocyte counts and renal function after a donor bone-marrow-based immunomodulatory regimen followed by tacrolimus monotherapy as long as 3 years post-transplant, as well as continuous nerve regeneration of penile allografts 3 years post-transplant. Areas of uncertainty include the ethics of donor-recipient colour mismatch, surveillance for sexually transmitted infections and how to optimize patient compliance. Questions also remain with respect to the long-term immunological sequelae of penile tissue, functional outcomes, psychosocial implications and patient selection. Patient counselling should be modified to mention the possibility of long-term improvement in nerve regeneration and sufficient renal function with single-therapy maintenance, and to build a longitudinal dialogue and partnership between the patient and the multidisciplinary care team regarding the risks of sexually transmitted infection instead of surveillance.

Donor derived hematopoietic stem cell niche transplantation facilitates mixed chimerism mediated donor specific tolerance

Compelling experimental evidence confirms that the robustness and longevity of mixed chimerism (MC) relies on the persistence and availability of donor-derived hematopoietic stem cell (HSC) niches in recipients. Based on our prior work in rodent vascularized composite allotransplantation (VCA) models, we hypothesize that the vascularized bone components in VCA bearing donor HSC niches, thus may provide a unique biologic opportunity to facilitate stable MC and transplant tolerance. In this study, by utilizing a series of rodent VCA models we demonstrated that donor HSC niches in the vascularized bone facilitate persistent multilineage hematopoietic chimerism in transplant recipients and promote donor-specific tolerance without harsh myeloablation. In addition, the transplanted donor HSC niches in VCA facilitated the donor HSC niches seeding to the recipient bone marrow compartment and contributed to the maintenance and homeostasis of stable MC. Moreover, this study provided evidences that chimeric thymus plays a role in MC-mediated transplant tolerance through a mechanism of thymic central deletion. Mechanistic insights from our study could lead to the use of vascularized donor bone with pre-engrafted HSC niches as a safe, complementary strategy to induce robust and stable MC-mediated tolerance in VCA or solid organ transplantation recipients.

Public Perceptions and Information Needs of VCA Transplantation and Donation: A Mixed Methods Study

Vascularized Composite Allotransplantation (VCA) involves transplantation of multiple tissues from a donor to a recipient (e.g., skin, muscle, bone). Little is known about the US public’s perceptions of and attitudes toward VCA organ donation. This multi-site, cross-sectional, mixed methods study involved focus groups and surveys to assess members of the general public’s attitudes about VCA, and willingness and barriers to donate VCA organs. Qualitative data were analyzed by thematic analysis; quantitative data were analyzed by descriptive statistics. In focus groups (n = 6, 42 participants), most participants were female (57%) and Black (62%) with mean age of 42.6 years. Three main themes emerged: 1) awareness and perceptions of VCA, 2) purpose of VCA donation, 3) and barriers to VCA donation. Participants had heard little about VCA and sought information about VCA donation. Participants perceived VCA as challenging their concepts of “normality” and voiced concerns that VCA would create “Frankenstein[s].” Barriers to VCA donation included disruptions to end-of-life arrangements and information gaps regarding the donation process. Participants reported moderate to high willingness to donate their hands (69%) and face (50%) Public education efforts should address the specific needs and concerns of the public to facilitate VCA donation and family authorization.

Information needs and development of a question prompt sheet for upper extremity vascularized composite allotransplantation: A mixed methods study

Background

People with upper extremity (UE) amputations report receiving insufficient information about treatment options. Furthermore, patients commonly report not knowing what questions to ask providers. A question prompt sheet (QPS), or list of questions, can support patient-centered care by empowering patients to ask questions important to them, promoting patient-provider communication, and increasing patient knowledge. This study assessed information needs among people with UE amputations about UE vascularized composite allotransplantation (VCA) and developed a UE VCA-QPS.

Methods

This multi-site, cross-sectional, mixed-methods study involved in-depth and semi-structured interviews with people with UE amputations to assess information needs and develop a UE VCA-QPS. Qualitative data were analyzed by thematic analysis; quantitative data were analyzed by descriptive statistics. The initial UE VCA-QPS included 130 items across 18 topics.

Results

Eighty-nine people with UE amputations participated. Most were male (73%), had a mean age of 46 years, and had a unilateral (84%) and below-elbow amputation (56%). Participants desired information about UE VCA eligibility, evaluation process, surgery, risks, rehabilitation, and functional outcomes. After refinement, the final UE VCA-QPS included 35 items, across 9 topics. All items were written at a ≤ 6th grade reading level. Most semi-structured interview participants (86%) reported being ‘completely’ or ‘very’ likely to use a UE VCA-QPS.

Conclusion

People with UE amputations have extensive information needs about UE VCA. The UE VCA-QPS aims to address patients’ information needs and foster patient-centered care. Future research should assess whether the UE VCA-QPS facilitates patient-provider discussion and informed decision-making for UE VCA.

Special Considerations for Secondary Surgery After Upper Extremity Transplantation

BACKGROUND

Upper extremity (UE) transplantation is a complex undertaking that may require emergent or elective secondary surgery (SS) days to years following transplant. Various patient and transplantation may help determine what SS is needed. In this study, we characterize the SS needed by our UE transplant patients.

METHODS

We retrospectively reviewed 6 patients who underwent hand and UE transplantation by one of the authors. Transplantation and SS details were obtained from medical records. Hand and arm function was quantified both subjectively (patient-reports) and objectively (Disabilities of the Arm, Shoulder, and Hand Score; Carroll test; Action Research Arm Tests; Box and Block test).

RESULTS

Six patients underwent transplantation for a total of 10 transplanted limbs. Five transplants were performed below and 5 above the elbow. Mean time post-transplantation at last follow-up was 5 years (range: 1-9 years). In all, 66.7% of the patients required SS: total 7 surgeries comprising 13 procedures. The most common procedures were to improve hand function-nerve decompressions and tendon transfer, both in above-elbow transplant. Both patients showed a mean improvement of 15 points on Carroll scores. One above-elbow transplant had a brachioplasty for excess skin and another had a hematoma evacuation immediately after transplantation. Procedures in the below-elbow transplants included multiple incision and drainages for a septic wrist and an open reduction and internal fixation for a forearm fracture.

CONCLUSION

Patients receiving UE transplantation often require one or more secondary procedures which may vary with level of transplantation. Secondary surgery should be an important aspect of pretransplant planning and cost-effectiveness determinations.

LEVEL OF EVIDENCE

Level IV.

Hyperspectral Evaluation of the Human Liver During Major Resection

Objective

This study investigates the effects of PVE and vascular inflow control (VIC) on liver microperfusion and tissue oxygenation using hyperspectral imaging (HSI) technology.

Background

Mechanisms triggering future liver remnant (FLR) augmentation introduced by PVE have not been sufficiently studied in humans. Particularly, the arterial buffer response (ABR) of the liver might play a vital role.

Methods

Hyperspectral datacubes (TIVITA) acquired during 58 major liver resections were qualitatively and quantitatively analyzed for tissue oxygenation (StO2%), near-infrared (NIR) perfusion, organ-hemoglobin indices (OHI), and tissue-water indices (TWI). The primary study endpoint was measurement of hyperspectral differences in liver parenchyma subject to PVE and VIC before resection.

Results

HSI revealed parenchyma specific differences in StO2% with regard to the underlying disease (P < 0.001). Preoperative PVE (n = 23, 40%) lead to arterial hyperoxygenation and hyperperfusion of corresponding liver segments (StO2: 77.23% ± 11.93%, NIR: 0.46 ± 0.20[I]) when compared with the FLR (StO2: 66.13% ± 9.96%, NIR: 0.23 ± 0.12[I]; P < 0.001). In a case of insufficient PVE and the absence of FLR augmentation hyperspectral StO2 and NIR differences were absent. The hyperspectral assessment demonstrated increased liver tissue-oxygenation and perfusion in PVE-segments (n = 23 cases) and decreased total VIC in nonembolized FLR hemilivers (n = 35 cases; P < 0.001). Intraoperative HSI analysis of tumor tissue revealed marked tumor specific differences in StO2, NIR, OHI, and TWI (P < 0.001).

Conclusions

HSI allows intraoperative quantitative and qualitative assessment of microperfusion and StO2% of liver tissue. PVE lead to ABR-triggered tissue hyperoxygenation and cross-talk FLR augmentation. HSI furthermore facilitates intraoperative tumor tissue identification and enables image-guided liver surgery following VIC.

Intraoperative reperfusion assessment of human pancreas allografts using hyperspectral imaging (HSI)

Background

The most common causes of early graft loss in pancreas transplantation are insufficient blood supply and leakage of the intestinal anastomosis. Therefore, it is critical to monitor graft perfusion and oxygenation during the early post-transplant period. The goal of our pilot study was to evaluate the utility of hyperspectral imaging (HSI) in monitoring the microcirculation of the graft and adequate perfusion of the intestinal anastomosis during pancreatic allotransplantation.

Methods

We imaged pancreatic grafts and intestinal anastomosis in real-time in three consecutive, simultaneous pancreas-kidney transplantations using the TIVITA^® HSI system. Further, the intraoperative oxygen saturation (StO₂), tissue perfusion (near-infrared perfusion index, NIR), organ hemoglobin index (OHI), and tissue water index (TWI) were measured 15 minutes after reperfusion by HSI.

Results

All pancreas grafts showed a high and homogeneous StO₂ (92.6%±10.45%). Intraoperative HSI analysis of the intestinal anastomosis displayed significant differences of StO₂ (graft duodenum 67.46%±5.60% vs. recipient jejunum: 75.93%±4.71%, P<0.001) and TWI {graft duodenum: 0.63±0.09 [I (Index)] vs. recipient jejunum: 0.72±0.09 [I], P<0.001}. NIR and OHI did not display remarkable differences {NIR duodenum: 0.68±0.06 [I] vs. NIR jejunum: 0.69±0.04 [I], P=0.747; OHI duodenum: 0.70±0.12 [I] vs. OHI jejunum: 0.68±0.13 [I], P=0.449}. All 3 patients had an uneventful postoperative course with one displaying a Banff 1a rejection which was responsive to steroid treatment.

Conclusions

Our study shows that contact-free HSI has potential utility as a novel tool for real-time monitoring of human pancreatic grafts after reperfusion, which could improve the outcome of pancreas transplantation. Further investigations are required to determine the predictive value of intraoperative HSI imaging.

A systematic review of sutureless vascular anastomosis technologies

Vascular anastomoses typically involve a handsewn technique requiring significant surgical training, expertise, and time. The aim of our systematic review was to identify and describe sutureless vascular anastomosis techniques. We performed a systematic review of all sutureless vascular anastomosis technologies published in MEDLINE, PubMed, Embase, CINAHL, Cochrane, Web of Science, and Scopus Library databases and a patent review using US Patent and Trade Office Application, US Patent and Trademark Office Patent, Google Patents, Lens, Patent Quality Through Artificial Intelligence, SureChEMBL, and E-Space Net. Data from inclusion studies and patents published between January 1, 1980 and July 15, 2021 were abstracted to describe their category, anastomosis type and configuration, study types, and advantages and disadvantages encountered with each technology. Two hundred eleven original studies and 475 patents describing sutureless vascular anastomosis technologies were identified. In the literature, stents/stent-grafts/grafts (n = 61), lasers (n = 53), and couplers (n = 27) were the predominant device categories. In the patent review, adhesive technologies (n = 103), stents/stent-grafts/grafts (n = 68), and mechanical connectors (n = 61) predominated. The majority of studies involved in vivo animal studies (n = 193); 32.2% (n = 68) of investigations involved human trials; and 17.9% (n = 85) of patent technologies were approved by the US Food and Drug Administration. The main advantages described for sutureless anastomosis technologies included faster procedure time and greater patency rates compared with handsewn anastomoses. The main disadvantages included reduced vessel compliance, stenosis, leakage, and device costs. The appeal of sutureless technology is substantiated by numerous animal trials, but their use in humans remains limited. This may be a reflection of strict regulatory criteria and/or vascular complications associated with currently available technologies.

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

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

Endothelial Stromal PD-L1 (Programmed Death Ligand 1) Modulates CD8+ T-Cell Infiltration After Heart Transplantation

BACKGROUND

The role of checkpoint axes in transplantation has been partially addressed in animal models but not in humans. Occurrence of fulminant myocarditis with allorejection-like immunologic features in patients under anti-PD1 (programmed death cell protein 1) treatment suggests a key role of the PD1/PD-L1 (programmed death ligand 1) axis in cardiac immune homeostasis.

METHODS

We cross-sectionally studied 23 heart transplant patients undergoing surveillance endomyocardial biopsy. Endomyocardial tissue and peripheral blood mononuclear cells were analyzed by flow cytometry. Multivariate logistic regression analyses including demographic, clinical, and hemodynamic parameters were performed. Murine models were used to evaluate the impact of PD-L1 endothelial graft expression in allorejection.

RESULTS

We found that myeloid cells dominate the composition of the graft leukocyte compartment in most patients, with variable T-cell frequencies. The CD (cluster of differentiation) 4:CD8 T-cell ratios were between 0 and 1.5. The proportion of PD-L1 expressing cells in graft endothelial cells, fibroblasts, and myeloid leukocytes ranged from negligible up to 60%. We found a significant inverse logarithmic correlation between the proportion of PD-L1+HLA (human leukocyte antigen)-DR+ endothelial cells and CD8+ T cells (slope, -18.3 [95% CI, -35.3 to -1.3]; P=0.030). PD-L1 expression and leukocyte patterns were independent of demographic, clinical, and hemodynamic parameters. We confirmed the importance of endothelial PD-L1 expression in a murine allogeneic heart transplantation model, in which Tie2Crepdl1fl/fl grafts lacking PD-L1 in endothelial cells were rejected significantly faster than controls.

CONCLUSIONS

Loss of graft endothelial PD-L1 expression may play a role in regulating CD8+ T-cell infiltration in human heart transplantation. Murine model results suggest that loss of graft endothelial PD-L1 may facilitate alloresponses and rejection.

A short course of tofacitinib sustains the immunoregulatory effect of CTLA4-Ig in the presence of inflammatory cytokines and promotes long-term survival of murine cardiac allografts

Costimulation blockade-based regimens are a promising strategy for management of transplant recipients. However, maintenance immunosuppression via CTLA4-Ig monotherapy is characterized by high frequency of rejection episodes. Recent evidence suggests that inflammatory cytokines contribute to alloreactive T cell activation in a CD28-independent manner, a reasonable contributor to the limited efficacy of CTLA4-Ig. In this study, we investigated the possible synergism of a combined short-term inhibition of cytokine signaling and CD28 engagement on the modulation of rejection. Our results demonstrate that the JAK/STAT inhibitor tofacitinib restored the immunomodulatory effect of CTLA4-Ig on mouse alloreactive T cells in the presence of inflammatory cytokines. Tofacitinib exposure conferred dendritic cells with a tolerogenic phenotype reducing their cytokine secretion and costimulatory molecules expression. JAK inhibition also directly affected T cell activation. In vivo, the combination of CTLA4-Ig and tofacitinib induced long-term survival of heart allografts and, importantly, it was equally effective when using grafts subjected to prolonged ischemia. Transplant survival correlated with a reduction in effector T cells and intragraft accumulation of regulatory T cells. Collectively, our studies demonstrate a powerful synergism between CTLA4-Ig and tofacitinib and suggest their combined use is a promising strategy for improved management of transplanted patients.

Unraveling the Crucial Roles of FoxP3+ Regulatory T Cells in Vascularized Composite Allograft Tolerance Induction and Maintenance

BACKGROUND

The role of regulatory T cells (Treg) in tolerance induction of vascularized composite allotransplantation (VCA) remains unclear. This study was designed to examine characteristics of Treg after VCA and their capacity to rescue allografts from rejection.

METHODS

Osteomyocutaneous allografts were transplanted from Balb/c to C57BL/6 mice. All mice received costimulatory blockade and a short course of rapamycin. To elucidate the role of Treg for tolerance induction, Treg depletion was performed at postoperative day (POD) 0, 30, or 90. To assess capacity of Treg to rescue allografts from rejection, an injection of 2 × 106 Treg isolated from tolerant mice was applied.

RESULTS

Eighty percent of VCA recipient mice using costimulatory blockade and rapamycin regimen developed tolerance. The tolerant recipients had a higher ratio of circulating Treg to effector T cells and elevated interleukin-10 at POD 30. A significantly higher rejection rate was observed when Treg were depleted at POD 30. But Treg depletion at POD 90 had no effect on tolerance. Treg from tolerant recipients showed stronger suppressive potential and the ability to rescue allografts from rejection. Furthermore, transplanted Treg-containing skin grafts from tolerant mice delayed rejection elicited by adoptively transferred effector T cells to Rag2-/- mice.

CONCLUSIONS

Circulating Treg are crucial for inducing VCA tolerance in the early posttransplant phase, and allograft-residing Treg may maintain tolerance. Treg may, therefore, serve as a potential cellular therapeutic to improve VCA outcomes.

Method, Material, and Machine: A Review for the Surgeon Using Three-Dimensional Printing for Accelerated Device Production

BACKGROUND

Physicians are at the forefront of identifying innovative targets to address current medical needs. 3D printing technology has emerged as a state-of-the-art method of prototyping medical devices or producing patient-specific models that is more cost-efficient, with faster turnaround time, in comparison to traditional prototype manufacturing. However, initiating 3D printing projects can be daunting due to the engineering learning curve, including the number of methodologies, variables, and techniques for printing from which to choose. To help address these challenges, we sought to create a guide for physicians interested in venturing into 3D printing.

STUDY DESIGN

All commercially available, plug-and-play, material and stereolithography printers costing less than $15,000 were identified via web search. Companies were contacted to obtain quotes and information sheets for all printer models. The qualifying printers' manufacturer specification sheets were reviewed, and pertinent variables were extracted.

RESULTS

We reviewed 309 commercially available printers and materials and identified 118 printers appropriate for clinicians desiring plug-and-play models for accelerated device production. We synthesized this information into a decision-making tool to choose the appropriate parameters based on project goals.

CONCLUSIONS

There is a growing clinical need for medical devices to reduce costs of care and increase access to personalized treatments; however, the learning curve may be daunting for surgeons. In this review paper, we introduce the "3Ms of 3D printing" for medical professionals and provide tools and data sheets for selection of commercially available, affordable, plug-and-play 3D printers appropriate for surgeons interested in innovation.

Noninvasive evaluation of intragraft immune responses in upper extremity transplantation

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

A Large-Scale Bank of Organ Donor Bone Marrow and Matched Mesenchymal Stem Cells for Promoting Immunomodulation and Transplant Tolerance

Induction of immune tolerance for solid organ and vascular composite allografts is the Holy Grail for transplantation medicine. This would obviate the need for life-long immunosuppression which is associated with serious adverse outcomes, such as infections, cancers, and renal failure. Currently the most promising means of tolerance induction is through establishing a mixed chimeric state by transplantation of donor hematopoietic stem cells; however, with the exception of living donor renal transplantation, the mixed chimerism approach has not achieved durable immune tolerance on a large scale in preclinical or clinical trials with other solid organs or vascular composite allotransplants (VCA). Ossium Health has established a bank of cryopreserved bone marrow (BM), termed "hematopoietic progenitor cell (HPC), Marrow," recovered from deceased organ donor vertebral bodies. This new source for hematopoietic cell transplant will be a valuable resource for treating hematological malignancies as well as for inducing transplant tolerance. In addition, we have discovered and developed a large source of mesenchymal stem (stromal) cells (MSC) tightly associated with the vertebral body bone fragment byproduct of the HPC, Marrow recovery process. Thus, these vertebral bone adherent MSC (vBA-MSC) are matched to the banked BM obtained from each donor, as opposed to third-party MSC, which enhances safety and potentially efficacy. Isolation and characterization of vBA-MSC from over 30 donors has demonstrated that the cells are no different than traditional BM-MSC; however, their abundance is >1,000-fold higher than obtainable from living donor BM aspirates. Based on our own unpublished data as well as reports published by others, MSC facilitate chimerism, especially at limiting hematopoietic stem and progenitor cell (HSPC) numbers and increase safety by controlling and/or preventing graft-vs.-host-disease (GvHD). Thus, vBA-MSC have the potential to facilitate mixed chimerism, promote complementary peripheral immunomodulatory functions and increase safety of BM infusions. Both HPC, Marrow and vBA-MSC have potential use in current VCA and solid organ transplant (SOT) tolerance clinical protocols that are amenable to "delayed tolerance." Current trials with HPC, Marrow are planned with subsequent phases to include vBA-MSC for tolerance of both VCA and SOT.

Long-term outcome after hand and forearm transplantation - a retrospective study

Between 2000 and 2014, five patients received bilateral hand (n = 3), bilateral forearm (n = 1), and unilateral hand (n = 1) transplants at the Innsbruck Medical University Hospital. We provide a comprehensive report of the long-term results at 20 years. During the 6-20 years follow-up, 43 rejection episodes were recorded in total. Of these, 27.9% were antibody-related with serum donor-specific alloantibodies (DSA) and skin-infiltrating B-cells. The cell phenotype in rejecting skin biopsies changed and C4d-staining increased with time post-transplantation. In the long-term, a change in hand appearance was observed. The functional outcome was highly depending on the level of amputation. The number and severity of rejections did not correlate with hand function, but negatively impacted on the patients´ well-being and quality of life. Patient satisfaction significantly correlated with upper limb function. One hand allograft eventually developed severe allograft vasculopathy and was amputated at 7 years. The patient later died due to progressive gastric cancer. The other four patients are currently rejection-free with moderate levels of immunosuppression. Hand transplantation remains a therapeutic option for carefully selected patients. A stable immunologic situation with optimized and individually adopted immunosuppression favors good compliance and patient satisfaction and may prevent development of DSA.

Adipose-derived stromal cells modulating composite allotransplant survival is correlated with B cell regulation in a rodent hind-limb allotransplantation model

Background

Our previous studies demonstrated that adipose-derived mesenchymal stromal cells (ASCs) have immunomodulatory effects that prolong allograft survival in a rodent hind-limb allotransplant model. In this study, we investigated whether the effects of immunomodulation by ASCs on allograft survival are correlated with B cell regulation.

Methods

B cells isolated from splenocytes were cocultured with ASCs harvested from adipose tissue from rodent groin areas for in vitro experiments. In an in vivo study, hind-limb allotransplantation from Brown-Norway to Lewis rats was performed, and rats were treated with ASCs combined with short-term treatment with anti-lymphocyte serum (ALS)/cyclosporine (CsA) as immunosuppressants. Peripheral blood and transplanted tissue were collected for further analysis.

Result

An in vitro study revealed that ASCs significantly suppressed lipopolysaccharide-activated B cell proliferation and increased the percentage of Bregs. The levels of immunoregulatory cytokines, such as TGF-β1 and IL-10, were significantly increased in supernatants of stimulated B cells cocultured with ASCs. The in vivo study showed that treatment with ASCs combined with short-term ALS/CsA significantly reduced the B cell population in alloskin tissue, increased the proportion of circulating CD45Ra⁺/Foxp3⁺ B cells, and decreased C4d expression in alloskin.

Conclusion

ASCs combined with short-term immunosuppressant treatment prolong allograft survival and are correlated with B cell regulation, C4d expression and the modulation of immunoregulatory cytokines.

Multiphase Assembly of Small Molecule Microcrystalline Peptide Hydrogel Allows Immunomodulatory Combination Therapy for Long-Term Heart Transplant Survival

Combination therapies that target multiple pathways involved in immune rejection of transplants hold promise for patients in need of restorative surgery. Herein, a noninteracting multiphase molecular assembly approach is developed to crystallize tofacitinib, a potent JAK1/3 inhibitor, within a shear-thinning self-assembled fibrillar peptide hydrogel network. The resulting microcrystalline tofacitinib hydrogel (MTH) can be syringe-injected directly to the grafting site during surgery to locally deliver the small molecule. The rate of drug delivered from MTH is largely controlled by the dissolution of the encapsulated microcrystals. A single application of MTH, in combination with systemically delivered CTLA4-Ig, a co-stimulation inhibitor, affords significant graft survival in mice receiving heterotopic heart transplants. Locoregional studies indicate that the local delivery of tofacitinib at the graft site enabled by MTH is required for the observed enhanced graft survival.

Identification and characterization of a large source of primary mesenchymal stem cells tightly adhered to bone surfaces of human vertebral body marrow cavities

Background:

Therapeutic allogeneic mesenchymal stromal cells (MSCs) are currently in clinical trials to evaluate their effectiveness in treating many different disease indications. Eventual commercialization for broad distribution will require further improvements in manufacturing processes to economically manufacture MSCs at scales sufficient to satisfy projected demands. A key contributor to the present high cost of goods sold for MSC manufacturing is the need to create master cell banks from multiple donors, which leads to variability in large-scale manufacturing runs. Therefore, the availability of large single donor depots of primary MSCs would greatly benefit the cell therapy market by reducing costs associated with manufacturing.

Methods:

We have discovered that an abundant population of cells possessing all the hallmarks of MSCs is tightly associated with the vertebral body (VB) bone matrix and only liberated by proteolytic digestion. Here we demonstrate that these vertebral bone-adherent (vBA) MSCs possess all the International Society of Cell and Gene Therapy-defined characteristics (e.g., plastic adherence, surface marker expression and trilineage differentiation) of MSCs, and we have therefore termed them vBA-MSCs to distinguish this population from loosely associated MSCs recovered through aspiration or rinsing of the bone marrow compartment.

Results:

Pilot banking and expansion were performed with vBA-MSCs obtained from 3 deceased donors, and it was demonstrated that bank sizes averaging 2.9 × 10⁸ ± 1.35 × 10⁸ vBA-MSCs at passage 1 were obtainable from only 5 g of digested VB bone fragments. Each bank of cells demonstrated robust proliferation through a total of 9 passages, without significant reduction in population doubling times. The theoretical total cell yield from the entire amount of bone fragments (approximately 300 g) from each donor with limited expansion through 4 passages is 100 trillion (1 × 10¹⁴) vBA-MSCs, equating to over 10⁵ doses at 10 × 10⁶ cells/kg for an average 70-kg recipient.

Discussion:

Thus, we have established a novel and plentiful source of MSCs that will benefit the cell therapy market by overcoming manufacturing and regulatory inefficiencies due to donor-to-donor variability.

Public education materials about Vascular Composite Allotransplantation and donation in the United States: Current scope and limitations

As the field of Vascular Composite Allotransplantation (VCA) grows, demand for VCA donations will increase. The public should be made aware of this treatment option to support patients' informed decision-making and authorization for deceased donation. We assessed the availability and quality of existing VCA public education materials from organ procurement organizations (OPOs), transplant centers, the Organ Procurement and Transplant Network, Veterans Affairs, and the Department of Defense. A content analysis was performed to identify topics covered and important gaps. In total, 1314 public education materials were analyzed, including OPO Facebook posts (61.6%), OPO Twitter posts (29.9%), websites (6.4%), and written documents (eg, fact sheets, research reports) (2.1%). Upper extremity (34.7%) and face (34.5%) transplants were more commonly covered than reproductive (6.4%) or other VCA types (2.8%). Most materials (76.6%) referenced a specific VCA story. However, few materials described which patient population could benefit from VCA (eg, Veterans, amputees, burn victims, 16.4%), the authorization requirements for VCA donation (6.6%), or the appearance of transplanted VCA organs (1.2%). Current VCA public education materials do not adequately educate the public. More comprehensive education materials are needed to prepare the public to authorize VCA donation, become potential donors, or learn about transplant options.

Skin xenotransplantation: technological advances and future directions

PURPOSE OF REVIEW

To summarize the evolution of skin xenotransplantation and contextualize technological advances and the status of clinically applicable large animal research as well as prospects for translation of this work as a viable future treatment option.

RECENT FINDINGS

Porcine xenografts at the start of the millennium were merely biologic dressings subject to rapid rejection. Since then, numerous important advances in swine to nonhuman primate models have yielded xenotransplant products at the point of clinical translation. Critical genetic modifications in swine from a designated pathogen-free donor herd have allowed xenograft survival reaching 30 days without preconditioning or maintenance immunosuppression. Further, xenograft coverage appears not to sensitize the recipient to subsequent allograft placement and vice versa, allowing for temporary coverage times to be doubled using both xeno and allografts.

SUMMARY

Studies in large animal models have led to significant progress in the creation of living, functional skin xenotransplants with clinically relevant shelf-lives to improve the management of patients with extensive burns.

Latissimus Dorsi Myocutaneous Flap Procedure in a Swine Model

BACKGROUND

As surgical research expands in both breadth and scope, translational models become increasingly important. The accessibility, reproducibility, and clinical applicability of translational models is of vital importance to ensure adequate and accurate research. Though different flap models have been described, the literature lacks an in-depth, technical description of an easy large-animal preclinical model. We here describe the procedure for elevation of a latissimus dorsi flap in a swine. This flap contains muscle and skin that can be isolated on a vascular pedicle, transferred as a free flap, perfused, or innervated/denervated as dictated by the needs of the experiment.

METHODS

Five different latissimus dorsi flaps were elevated in miniature swine. Careful attention was paid to anatomical landmarks and optimal placement of incision, dissection, and retraction. Temporary ischemia with vascular clamping was performed along with serial digital and infrared imaging both intra- and postoperatively. In three of the flaps with induced ischemia, the animal was observed for a 30-day follow up with daily photodocumentation and intermittent biopsy.

RESULTS

A reproducible latissimus flap model was designed with optimized conditions. In the animals in which flaps were followed postoperatively, complete healing was seen within 30 days without evidence of procedure-related ischemia or loss of motor function.

CONCLUSION

We have identified and described a pre-clinical large animal flap model that can be easily reproduced for translational studies of multiple scientific areas including flap-based repair, ischemia, ischemia reperfusion, and operative technique. This provides an important model for ready replication in preclinical studies of many varieties.

Ischemia considerations for the development of an organ and tissue donor derived bone marrow bank

Background

Deceased organ donors represent an untapped source of therapeutic bone marrow (BM) that can be recovered in 3–5 times the volume of that obtained from living donors, tested for quality, cryopreserved, and banked indefinitely for future on-demand use. A challenge for a future BM banking system will be to manage the prolonged ischemia times that are inevitable when bones procured at geographically-dispersed locations are shipped to distant facilities for processing. Our objectives were to: (a) quantify, under realistic field conditions, the relationship between ischemia time and the quality of hematopoietic stem and progenitor cells (HSPCs) derived from deceased-donor BM; (b) identify ischemia-time boundaries beyond which HSPC quality is adversely affected; (c) investigate whole-body cooling as a strategy for preserving cell quality; and (d) investigate processing experience as a variable affecting quality.

Methods

Seventy-five bones from 62 donors were analyzed for CD34+ viability following their exposure to various periods of warm-ischemia time (WIT), cold-ischemia time (CIT), and body-cooling time (BCT). Regression models were developed to quantify the independent associations of WIT, CIT, and BCT, with the viability and function of recovered HSPCs.

Results

Results demonstrate that under “real-world” scenarios: (a) combinations of warm- and cold-ischemia times favorable to the recovery of high-quality HSPCs are achievable (e.g., CD34+ cell viabilities in the range of 80–90% were commonly observed); (b) body cooling prior to bone recovery is detrimental to cell viability (e.g., CD34+ viability < 73% with, vs. > 89% without body cooling); (c) vertebral bodies (VBs) are a superior source of HSPCs compared to ilia (IL) (e.g., %CD34+ viability > 80% when VBs were the source, vs. < 74% when IL were the source); and (d) processing experience is a critical variable affecting quality.

Conclusions

Our models can be used by an emerging BM banking system to formulate ischemia-time tolerance limits and data-driven HSPC quality-acceptance standards.

Psychosocial factors and medication adherence among recipients of vascularized composite allografts

Objectives

Psychosocial factors are important predictors of medication adherence, and subsequently graft survival, in solid organ transplantation. Early experiences suggest this may also be the case in vascularized composite allotransplantation.

Methods

Using validated tools, we surveyed upper extremity transplant recipients at two centers to assess depression (Patient Health Questionnaire-9), personality (Ten-Item Personality Inventory), anxiety (Generalized Anxiety Disorder 7-Item Scale), post-traumatic stress disorder (Primary Care Post-Traumatic Stress Disorder Screen for Diagnostic and Statistical Manual of Mental Disorders, 5th Edition), and social support (Multidimensional Scale of Perceived Social Support). Medication adherence among vascularized composite allotransplantation recipients at two centers was assessed by a member of the clinical research team using the recipients' medical records.

Results

Medication adherence was reported for 12 vascularized composite allotransplantation recipients, and 9 vascularized composite allotransplantation recipients completed psychosocial assessments. Most recipients were believed to be adherent to their immunosuppression, however, three recipients were believed to be non-adherent and a member of the clinical team had discussed non-adherence at least once with five recipients. Results from the psychosocial assessment (n = 9) indicated that eight participants had high levels of social support, and eight demonstrated high levels of conscientiousness which have been associated with better medication adherence in solid organ transplantation. However, three participants demonstrated mild anxiety, two demonstrated minimal symptoms of depression, and one demonstrated post-traumatic stress disorder which have been associated with worse medication adherence in solid organ transplantation.

Conclusion

These findings lay the groundwork for future assessments of the role psychosocial factors play in facilitating medication adherence and broader transplant outcomes.

Defining chronic rejection in vascularized composite allotransplantation-The American Society of Reconstructive Transplantation and International Society of Vascularized Composite Allotransplantation chronic rejection working group: 2018 American Society of Reconstructive Transplantation meeting report and white paper Research goals in defining chronic rejection in vascularized composite allotransplantation

Objectives:

This report summarizes a collaborative effort between the American Society of Reconstructive Transplantation and the International Society of Vascularized Composite Allotransplantation to establish what is known about chronic rejection in recipients of vascularized composite allografts, with an emphasis on upper extremity and face transplants. As a picture of chronic rejection in hand and face vascularized composite allografts emerges, the results will be applied to other types of vascularized composite allografts, such as uterine transplantation.

Methods:

The overall goal is to develop a definition of chronic rejection in vascularized composite allografts so that we can establish longitudinal correlates of factors such as acute rejection, immunosuppressive therapy, de novo donor-specific antibody and trauma/infection and other external factors on the development of chronic rejection. As Dr Kanitakis eloquently stated at the 2017 International Society of Vascularized Composite Allotransplantation meeting in Salzburg, “Before we can correlate causative factors of chronic rejection, we have to define what chronic rejection in VCA is.”

Results:

The first meeting report was presented at the sixth Biennial meeting of the American Society of Reconstructive Transplantation in November 2018. Based on collaborative efforts and descriptions of clinical cases of chronic rejection in vascularized composite allograft recipients, a working definition of chronic rejection in vascularized composite allografts with respect to overt functional decline, subclinical functional decline, histologic evidence without functional decline, and normal allograft function in the absence of histologic evidence of chronic rejection is proposed.

Conclusions:

It is the intent of this collaborative working group that these working definitions will help to focus ongoing research to define the incidence, risk factors and treatment regimens that will identify mechanisms of chronic rejection in vascularized composite allografts. As with all good research, our initial efforts have generated more questions than answers. We hope that this is the first of many updates.

Outcomes of simultaneous pancreas and kidney transplantation based on donor resuscitation

It has been hypothesized that transplanting simultaneous pancreas kidney (SPK) grafts from donors with a history of cardiac arrest and cardiopulmonary resuscitation (CACPR) leads to inferior posttransplant outcomes due to organ hypoperfusion during cardiac arrest and mechanical trauma during resuscitation. Using Scientific Registry of Transplant Recipients data, we identified 13 095 SPK transplants from 2000-2018, of which 810 (6.2%) were from donors with a history of CACPR. After inverse probability of treatment weighting on donor and recipient characteristics, we found that 1-, 5-, and 10-year patient (CACPR: 96.4%, 89.9%, and 78.9%; non-CACPR: 96.3%, 88.9%, and 76.0%; P = .3), death-censored pancreas graft survival (CACPR: 89.3%, 82.7%, 75.0%; non-CACPR: 89.9%, 82.7%, 76.3%; P = .7), and death-censored kidney graft survival (CACPR: 97.0%, 89.5%, 78.2%; non-CACPR: 96.9.9%, 88.7%, 80.0%; P = .4) were comparable between the two groups. There were no differences in the risk of pancreatitis (CACPR: 2.9%, non-CACPR: 2.4%; weighted OR = _0.74 1.22 _2.02 ; P = .4), anastomotic leak (CACPR: 1.6%, non-CACPR: 2.0%; weighted OR = _0.54 1.02 _1.93 ; P > .9), or median length of hospital stay (CACPR: 8 days, non-CACPR: 9 days; P = .6) for recipients of CACPR vs non-CACPR donors. Our findings suggest that CACPR donors could be used to expand the SPK donor pool without compromising short- or long-term outcomes.

Mechanisms and outcomes of the supercharged end-to-side nerve transfer: a review of preclinical and clinical studies

Proximal peripheral nerve injuries often result in poor functional outcomes, chiefly because of the long time period between injury and the reinnervation of distal targets, which leads to muscle and Schwann cell atrophy. The supercharged end-to-side (SETS) nerve transfer is a recent technical innovation that introduces donor axons distally into the side of an injured nerve to rapidly innervate and support end organs while allowing for additional reinnervation after a proximal repair at the injury site. However, the mechanisms by which donor axons grow within the recipient nerve, contribute to muscle function, and impact the regeneration of native recipient axons are poorly understood. This uncertainty has slowed the transfer's clinical adoption. The primary objective of this article is to comprehensively review the mechanisms underpinning axonal regeneration and functional recovery after a SETS nerve transfer. A secondary objective is to report current clinical applications in the upper limb and their functional outcomes. The authors also propose directions for future research with the aim of maximizing the clinical utility of the SETS transfer for peripheral nerve surgeons and their patients.

Induction of immunological tolerance to myelinogenic glial-restricted progenitor allografts

The immunological barrier currently precludes the clinical utilization of allogeneic stem cells. Although glial-restricted progenitors have become attractive candidates to treat a wide variety of neurological diseases, their survival in immunocompetent recipients is limited. In this study, we adopted a short-term, systemically applicable co-stimulation blockade-based strategy using CTLA4-Ig and anti-CD154 antibodies to modulate T-cell activation in the context of allogeneic glial-restricted progenitor transplantation. We found that co-stimulation blockade successfully prevented rejection of allogeneic glial-restricted progenitors from immunocompetent mouse brains. The long-term engrafted glial-restricted progenitors myelinated dysmyelinated adult mouse brains within one month. Furthermore, we identified a set of plasma miRNAs whose levels specifically correlated to the dynamic changes of immunoreactivity and as such could serve as biomarkers for graft rejection or tolerance. We put forward a successful strategy to induce alloantigen-specific hyporesponsiveness towards stem cells in the CNS, which will foster effective therapeutic application of allogeneic stem cells.

Efficacy of single-agent immunosuppressive regimens in a murine model of vascularized composite allotransplantation

We herein investigate the safety and efficacy of single-agent anti-rejection regimens in a mouse vascularized composite allotransplantation (VCA) model. Orthotopic hind-limb transplantations (Balb/c → C57BL/6) were performed using 6- to 8-week-old mice. A thirty-day regimen of either rapamycin, tacrolimus (both 1, 3, 5 mg/kg/day) or cyclosporine (25, 35, 50 mg/kg/day) was used. Primary endpoints were animal and graft survival, and secondary chimerism and regulatory T-cell levels. For rapamycin and tacrolimus given at 1, 3, and 5 mg/kg/day, median graft survival time (MST) was 23 days (18-28 days), 30 days (23-30 days), and 30 d (30-30 days) and 14 days (13-18 days), 30 days (16-30 days), and 30 days (30-30 days), respectively. For cyclosporine dosed at 25 and 35 mg/kg/day, MST was 15 days (12-18 days) and 21 days (14-27 days). Toxicity from CsA 50 mg/kg led to 100% mortality. Mixed chimerism levels were higher in rapamycin-treated animals than in tacrolimus-treated recipients (P = 0.029). Tacrolimus was superior in preventing leukocyte recruitment to the allograft. In murine VCA, no standardized immunosuppressive regimen exists, limiting comparability of outcomes and survival. Our data demonstrate that rapamycin and tacrolimus maintenance treatment at 5 mg/kg/day both yielded allograft survival (<grade 3 rejection) in all animals. Rapamycin displayed less toxicity and maintained mixed chimerism but was not as potent in controlling leukocyte recruitment compared with tacrolimus.

IL-10 signaling in T cells is essential for induction of transplant tolerance

Induction of long term transplant survival by “costimulation blockade” (CoB) regimens is impaired by inflammatory responses. We and others recently revealed new interrelations between inflammatory cytokines and interleukin 10 (IL-10) that alter the signaling outcome of the latter. In this study we investigated the role of IL-10 during transplant tolerance induction.

Using a murine full-mismatch skin transplantation model, we showed that IL-10 has a fundamental role in the protective effect of CoB. This tolerizing regimen also failed to be effective in recipient mice with T cell specific unresponsiveness to IL-10, revealing an unexpected important direct modulation of T cells by this cytokine. Accelerated rejection in these transgenic mice correlated with increased accumulation of T cells producing TNF-α, and IFN-γ, and a doubling of IL-17A secreting lymphocytes. We then investigated the mechanism behind modulation of T cells physiology by IL-10. Using in vitro generated rested-effector cells, we show that IL-10 did not reduce their signaling threshold nor their effector functions (cytokine secretion). Moreover, IL-10 did not promote the expression of inhibitory receptors. Instead, we discovered that IL-10 can completely neutralize the TLR-mediated (CD28 independent) costimulation of memory and effector T cells (a largely unexplored phenomenon). We have an ongoing RNAseq analysis to decipher this novel mechanism at the molecular level.

Overall, these results highlight the importance of IL-10 signaling for the therapeutic efficacy of CoB. A better understanding of the effects of this cytokine on T cells will reveal targets of strategies to sustain and potentially improve the clinical efficacy of CoB.