Key psychosocial challenges in vascularized composite allotransplantation

Psychosocial factors are important elements in the assessment and follow-up care for vascularized composite allotransplantation(VCA) and require multidisciplinary evaluation protocols. This review will highlight differences between VCA with solid organ transplantation(SOT), provide information on the psychosocial selection of VCA candidates, ethical issues, psychological outcomes, and on the need for multicenter research. VCA is primarily a life-enhancing procedure to improve recipients' quality of life and psychological well-being and it represents a potential option to provide reproduction in case of penile or uterine transplantation. The risk benefit ratio is distinctly different than SOT with candidates desiring life enhancing outcomes including improved body image, return to occupations, restored touch, and for uterine transplant, pregnancy. The Chauvet Workgroup has been convened with membership from a number of transplant centers to address these issues and to call for multicenter research. A multicenter research network would share similar evaluation approaches so that meaningful research on psychosocial variables could inform the transplant community and patients about factors that increase risk of non-adherence and other adverse psychosocial and medical outcomes.

PARATHYROID GLAND ALLOTRANSPLANTATION IN RATS USING A NUDE MOUSE INTERIM HOST SYSTEM

Donor rat parathyroid gland(PTG)was first transplanted into the nude mouse interim hostsystem.After 100 days the PTG was re-transplanted into eligible recipients.The resultsshow that mean survival time of recipient rats may be remarkably prolonged.

The Characteristics of Acute Rejection after Limb Allotransplantation in Rats─An Experimental Study

To study the characteristics of acute rejection after limb allotransplantation, 29 male Sprague Dawley rats were randomly divided into 2 groups, with 15 rats in control group and 14 rats in experimental group. Each rat in control group underwent limb replantation. Each rat in experimental group received limb transplantation from Wistar rat. No immnosuppressive drugs were used after operation. The circulation of the transplanted limb, time and signs of rejection, histopathological changes in the tissues of the limb graft when rejected and survival time of limb grafts were evaluated. In the control group, no signs of rejection were observed, the circulation of each replanted limb was normal, it could survive for a longer time. The experimental group showed clinical signs of rejection (sub dermal edema and erythema) after a mean time of 3.36±1.15 days, and the mean survival time of the allografts was only 7±0.78 days. Histopathological examination showed most violent rejection reaction in skin. It is concluded that with Wistar to SD limb transplantation without use of immunosuppression, rejection of the grafts would occur after a mean time of 3.36±1.15days; the earliest signs of rejection were edema and erythema of the skin, skin being the most representative component of limb graft rejection.

Recovery of nigrostriatal dopaminergic system insufficiency by allotransplantation of embryonic brain tissue

In an experiment in rats with electrolytic lesion of the compact part of substantia nigra (SN) and after allotransplantation of the embryonic tissue of SN in the caudate nucleus the features of movement and emotional behavior in the Open Field Test (OFT), the rotation movements caused by an administration of amphetamine, a content of catecholamines in the caudate nucleus, hypothalamus and blood plasma have been investigated. It is shown that the electrolytic lesion causes violations of the statokinetic reflexes, the horizontal and the vertical movement activity, enhances the rotatory behavior, slow the orienttate-searching and the emotional reactions that combined with disbalance in dopamine-and noradrenalinetransmitter systems functioning. Allotransplantation of the embryonic dofaminsynthesizing brain tissue contributes to the restoration of movement activeity and its specific neurotransmitter ensuring.

Allotransplantation of adult spinal cord tissues after complete transected spinal cord injury: long-term survival and functional recovery in canines

Spinal cord injury(SCI), especially complete transected SCI, leads to loss of cells and extracellular matrix and functional impairments. In a previous study, we transplanted adult spinal cord tissues(aSCTs) to replace lost tissues and facilitate recovery in a rat SCI model. However, rodents display considerable differences from human patients in the scale, anatomy and functions of spinal cord systems, and responses after injury. Thus, use of a large animal SCI model is required to examine the repair efficiency of potential therapeutic approaches. In this study, we transplanted allogenic aSCTs from adult dogs to the lesion area of canines after complete transection of the thoracic spinal cord, and investigated the long-term cell survival and functional recovery. To enhance repair efficiency, a growth factor cocktail was added during aSCT transplantation, providing a favorable microenvironment. The results showed that transplantation of a SCTs, in particular with the addition of growth factors, significantly improves locomotor function restoration and increases the number of neurofilament-, microtubule-associated protein2-, 5-hydroxytryptamine-, choline acetyltransferase-and tyrosine hydroxylase-positive neurons in the lesion area at 6 months post-surgery. In addition, we demonstrated that donor neurons in a SCTs can survive for a long period after transplantation. This study showed for the first time that transplanting aSCTs combined with growth factor supplementation facilitates reconstruction of injured spinal cords, and consequently promotes long lasting motor function recovery in a large animal complete transected SCI model, and therefore could be considered as a possible therapeutic strategy in humans.

Rabies virus transmission via solid organs or tissue allotransplantation

Background:Rabies,for which the mortality rate is almost 100%,is a zoonotic viral disease that can be transmitted via solid organs or tissue allotransplantation.Dozens of deaths from rabies via solid organs or tissues allotransplantation(ROTA)have been documented during the last decades.In 2015 and 2016,two cases of rabies virus transmission via solid organs or tissue allotransplantation were reported in China,which further underscore the risk and importance of this special type of rabies for organ transplant recipients.Main text:From 1978 to 2017,at least 13 cases of ROTA,causing dozens of deaths,have been reported worldwide,whether in the high-risk or low-risk countries of rabies.The reported incubation period of ROTA ranges from 11 days to more than 17 months,while the historical incubation period of rabies is generally considered to range from~1 week to several years.The pathogenesis of ROTA is not clear,but the use of post-exposure prophylaxis(PEP)can play a protective role in the transplant recipients.We also summarize reports about ROTA in China,combined with the actual situation regarding work on rabies surveillance and elimination,and suggest countermeasures for the prevention and control of ROTA in the future.Conclusions:Understanding the significance of ROTA,screening the suspected organs,assessing the risk and protecting the related population will be effective way to prevent and control further occurrence of ROTA.

Reviewing immunosuppressive regimens in animal models for vascularized composite allotransplantation

The development of vascularized composite allotransplantation (VCA) and its clinical need has led to the need for more animal models to study and perform the research required to further this specialty in terms of functional recovery and immunomodulatory improvements. Much of the animal models are reported in individual series in the literature but there has not been a review as such of these models. Here we present a compilation of the animal models reported in the literature thus far in VCA. A comprehensive review of the literature was performed for any studies which involved the use of animal models in various aspects of VCA research. The models were organized according to the type of VCA transplant, whether they were orthotopic or heterotopic, immunosuppressive regimen each study used and investigation purpose. Twenty-one facial transplant models were reported, 3 abdominal wall transplants, 4 penile transplantations, 21 uterus transplantations, 12 hindlimb transplantations and 4 myocutaneous flap transplantation animal models were reported. Primates, swine, rats, mice, rabbits, sheep and dog animal models in VCA were also reported. The most used immunosuppressive drugs are calcineurin inhibitor such as cyclosporin A and tacrolimus in these VCA animal models. They can significantly suppress lymphocyte function by blocking the phosphatase activity of calcineurin of lymphocytes. They are sometimes used combined with mycophenolate mofetil or steroids or antilymphocyte serum. The review of existing animal models will allow further research to be focused in other areas of VCA where there is a current paucity of literature. The immunosuppressive regimens used in each animal model can also be reviewed to determine which regimen works in which type of animal model which will save time and resources for future research.

Expanding the top rungs of the extremity reconstructive ladder:targeted muscle reinnervation,osseointegration,and vascularized composite allotransplantation

Osseointegration(OI),targeted muscle reinnervation(TMR),and vascularized composite allotransplantation(VCA)are just a few ways by which our reconstructive ladder is evolving.It is important to recognize that amputation does not necessarily denote failure,but surgeons should strive to find ways to provide these patients with means for obtaining better satisfaction and quality of life postoperatively.TMR and OI have added options for mutilating lower extremity injuries that necessitate amputation.More recently,the senior author(Levin LS)described the"penthouse"floor of the reconstructive ladder being VCA.Despite the advances in VCA over the last 20 years,there are many challenges that face this discipline including indications for patient selection,minimizing immunosuppressive regimens,standardizing outcome measures,establishing reliable protocols for monitoring,and diagnosing and managing rejection.Herein,the authors review TMR,OI,and VCA as additional higher rungs of the reconstructive ladder.

Ethical challenges in vascularized composite allotransplantation of the lower extremity:lessons learned from hand transplantation and implications for the future

Vascularized composite allotransplantation(VCA)is a novel surgical practice that involves the transplantation of multiple tissue types as a functional unit without the primary purpose of extending life.While VCA of the upper extremity is becoming increasingly accepted and performed,VCA of the lower extremity remains largely unexplored despite its acknowledged potential value.There are inherent ethical concerns surrounding VCA that are dominated by a conflict between the principles of beneficence and maleficence.The primary question is whether the quality-of-life benefits to the patient outweigh the risks associated with long-term immunosuppression for a non-lifesaving procedure.In addition,the ethical conversation involves concerns regarding informed consent,donor autonomy,patient privacy and public disclosure,patient selection,and unique considerations in the pediatric patient.Lower extremity VCA has additional ethical issues compared to upper extremity VCA,as current lower limb prostheses provide excellent,near baseline function that upper limb constructs have not yet been able to achieve.In this review,we discuss the ethical challenges of lower extremity VCA using available evidence for the upper extremity.We also compare ethical considerations of VCA of the extremity with other surgical alternatives to limb loss-namely,limb salvage and replantation-and address how the conversation may be altered with further advancements in immunosuppression and prosthetic technology.

Nerve regeneration in vascularized composite allotransplantation:current strategies and future directions

Vascularized composite allotransplantation(VCA)has emerged as a viable treatment option for limb and face reconstruction of severe tissue defects.Functional recovery after VCA requires not only effective immunosuppression,but also consideration of peripheral nerve regeneration to facilitate motor and sensory reinnervation of donor tissue.At the time of transplantation,the donor and recipient nerves are typically coapted in an end-to-end fashion.Following transplantation,there are no therapies available to enhance nerve regeneration and graft reinnervation,and functional outcomes are dependent on the recipients’innate regenerative capacities.Functional outcomes to date have been promising,but there is still much room for improvement,studies have demonstrated reliable return of protective sensation(pain,thermal,gross tactile),while discriminative sensation and motor function show more inconsistent results.In order to maximize the benefit afforded to the by VCA,we must develop consistent and reliable procedures and therapies to ensure effective nerve regeneration and functional outcomes.New technologies,such as nerve guidance conduits and fibrin glues,and the use of stem cells to facilitate nerve regeneration remain untested in VCA but are proving worthwhile in the context of peripheral nerve repair.VCA presents a unique set of challenges with regards to surgical techniques,postoperative regimen,and health of donor tissue.In this review,we discuss current challenges underlying achievement of nerve regeneration in VCA and discuss novel technologies and approaches to translate nerve regeneration into functional restoration.

Complex upper extremity injuries:targeted muscle reinnervation,free functional muscle transfer,and vascularized composite allotransplantation

Restoration of upper extremity function poses a unique surgical challenge.With considerations ranging from ensuring appropriate skeletal support and musculotendinous and ligamentous anatomy,restoring adequate vascularity and innervation,and providing sufficient soft tissue coverage,upper extremity injuries present a diverse range of reconstructive problems.Recent history has been marked by an expansion of novel techniques for addressing these complex issues.Sophisticated modalities,such as targeted muscle reinnervation,free functional muscle transfer,and vascularized composite allotransplantation,have become some of the most powerful tools in the armamentarium of the reconstructive surgeon.This review article aims to define the distinguishing features of each of these modalities and reviews some of their unique advantages and limitations.

Immunological protection of small bowel by simultaneously transplanted liver graft in pigs

BACKGROUND: A simultaneously transplanted liver shields a bowel graft from immunologic attack in small animals, while the possible immuno-tolerance induced by the liver in liver and small bowel transplantation (LSBT) is uncertain in large animal models. To investigate the clinically suspected beneficial effect of the liver on small bowel allograft, we developed a new model of composite LSBT in the pig. METHODS: Seventy outbred long-white pigs were randomized into four groups. LSBT without immunosuppressive treatment (n=10, group A); LSBT with routine immunosuppressive treatment (n=10, group B); LSBT with a lower dose of immunosuppressive treatment (n=10, group C); and small bowel segment allotransplantation without immunosuppressive treatment (n=10, group D). RESULTS: There was no remarkable difference in survival time between groups A and D (10.33 vs. 12.89 days, P>0.05), but the initial time of acute rejection of the intestinal graft in group A was clearly delayed when compared to group D (8.22 vs. 4.33 days, P<0.05), and the rejection scores in group A were remarkably lower than those in group D at each postoperative time point (0 vs. 0.44 on day 3, P<0.05; 0.22 vs. 1.78 on day 5, P<0.05; 1.11 vs. 2.56 on day 7, P<0.05). There were evident differences in postoperative survival time, initial time of acute rejection and postoperative rejection scores between groups A, B and C. Postoperative survival time (30.00 vs. 28.13 days, P>0.05), initial acute rejection time (25.40 vs. 22.13 days, P>0.05) or rejection score did not differ between groups B and C within one postoperative month. CONCLUSIONS: Compared to isolated segment small bowel allotransplantation, the intestinal graft in LSBT (group A) had a delayed initial time of acute rejection and a lower postoperative acute rejection score, and a lower dose of immunosuppressive treatment led to persistent graft immuno-tolerance in LSBT. Thus the simultaneously transplanted liver graft may reduce the risk of intestinal rejection and protect the bowel graft from severe acute rejection.

I-2190A Is a Potent Immunosuppressive Drug for Vascularized Heart Transplantation in Rats

The effect of a new immunosuppressant -I-2190A was tested in a rodent heart allograft model. Grafts were transplanted to recipients heterotopcally.There were 5 groups: group 1 received no immunosuppressive agents; group 2 was given CsA (2. 0 mg/kg, i. p.); group 3 was administered I-2190A (0. 1 mg/kg, i. p. ) in carboxymethyl cellulose (CMC); group 4 received injection of I-2190A (0. 5 mg/kg, i. p. in CMC) ; group 5 received the combination treatment of I-2190A (0. 1rug/kg) and CsA (2. 0 mg/kg). Immunosuppressants were discontinued 14 days after operation. No statistically significant difference in grafts median survival time (MST) was found between group 2 (9. 5 days) and group 1 (9days ). The MSTs of grafts in group 3 (22 days, P< 0. 05), group 4 (> 100 days, PRO. of ) and group 5 (M100 days, P< 0. 01 ) were significantly prolonged compared with control group 1 (9 days ). Our results suggest that I-2190A is a potent immunosuppressant able to significantly prolong heart allograft survival in rats after a short time treatment. Low-dose I-2190A could potentiate the effect of sub-therapeutic dose of CsA as well.

Face transplantation:Anesthetic challenges

Face transplantation is a complex vascular composite allotransplantation(VCA) surgery. It involves multiple types of tissue, such as bone, muscles, blood vessels, nerves to be transferred from the donor to the recipient as one unit. VCAs were added to the definition of organs covered by the Organ Procurement and Transplantation NetworkFinal Rule and National Organ Transplant Act. Prior to harvest of the face from the donor, a tracheostomy is usually performed. The osteotomies and dissection of the midface bony skeleton may involve severe hemorrhagic blood loss often requiring transfusion of blood products. A silicon face mask created from the facial impression is used to reconstruct the face and preserve the donor's dignity. The recipient airway management most commonly used is primary intubation of an existing tracheostoma with a flexometallic endotracheal tube. The recipient surgery usually averages to 19-20 h. Since the face is a very vascular organ, there is usually massive bleeding, both in the dissection phase as well as in the reperfusion phase. Prior to reperfusion, often, after one sided anastomosis of the graft, the contralateral side is allowed to bleed to get rid of the preservation solution and other additives. Intraoperative product replacement should be guided by laboratory values and point of care testing for coagulation and hemostasis. In face transplantation, bolus doses of pressors or pressor infusions have been used intraoperatively in several patients to manage hypotension. This article reviews the anesthetic considerations for management for face transplantation, and some of the perioperative challenges faced.

Use of FK506 and bone marrow mesenchymal stem cells for rat hind limb allografts

Dark Agouti rat donor hind limbs were orthotopically transplanted into Lewis rat recipients to verify the effects of bone marrow mesenchymal stem cells on neural regeneration and functional recovery of allotransplanted limbs in the microenvironment of immunotolerance, bone marrow mesenchymal stem cells were intramuscularly （gluteus maximus） injected with FK506 （tacrolimus） daily, and were transplanted to the injured nerves. Results indicated that the allograft group not receiving therapy showed severe rejection, with transplanted limbs detaching at 10 days after transplantation with complete necrosis. The number of myelinated axons and Schwann cells in the FK506 and FK506 ＋ bone marrow mesenchymal stem cells groups were significantly increased. We observed a lesser degree of gastrocnemius muscle degeneration, and increased polymorphic fibers along with other pathological changes in the FK506 ＋ bone marrow mesenchymal stem cells group. The FK506 ＋ bone marrow mesenchymal stem cells group showed significantly better recovery than the autograft and FK506 groups. The results demonstrated that FK506 improved the immune microenvironment. FK506 combined with bone marrow mesenchymal stem cells significantly promoted sciatic nerve regeneration, and improved sensory recovery and motor function in hind limb allotransplant.

rFliC prolongs allograft survival in association with the activation of recipient Tregs in a TLR5-dependent manner

AIIorejection remains an obstacle for successful organ transplantation. Although different types of immunosuppressive agents are effective for controlling rejection and prolonging graft survival, drug treatment is limited because of side effects and toxicity. Therefore, it is necessary and urgent to identify new candidate drugs for inducing allotolerance. Recently, it has been reported that bacterial flagellin induces the immunosuppressive activity of regulatory T cells （Tregs） in humans in vitro. In the present study, we analyzed the effects of recombinant flagellin （rFliC） on allograft survival and explored the underlying mechanisms associated with the activation of recipient Tregs in a murine skin allotransplantation model. The results showed that rFliC administration （3 mg/kg, once per day for 3 days, i.p.） prolonged allograft survival （mean survival time： 18.4--.1.1 days） compared to the control group （10___0.7 days, P〈O.01）. Additionally, higher positive expression of Toll-like receptor 5 （TLR5） was detected within the allograft administered with rFliC. The frequency of CD4＋CD25＋Foxp3＋ Tregs; the expression of Treg-related factors TLR5, Foxp3, TGF-I^I and IL-IO; and the proliferation and suppression of Tregs were increased following rFliC administration compared to the control. Moreover, the increased expression of tolerance-related molecules and the proliferation of Tregs induced by rFliC were attenuated by an anti-TLR5 blocking antibody both in vivo and in vitro. In conclusion, rFliC administration prolongs the survival of allografts, which is associated with the activation of recipient Tregs in a TLR5-dependent manner, rFliC may be a new candidate for anti-allorejection therapy.

The intragraft vascularized bone marrow component plays a critical role in tolerance induction after reconstructive transplantation

The role of the vascularized bone marrow component as a continuous source of donor-derived hematopoietic stem cells that facilitate tolerance induction of vascularized composite allografts is not completely understood.In this study,vascularized composite tissue allograft transplantation outcomes between recipients receiving either conventional bone marrow transplantation(CBMT)or vascularized bone marrow(VBM)transplantation from Balb/c(H2d)to C57BL/6(H2b)mice were compared.Either high-or low-dose CBMT(1.5×10^(8)or 3×10^(7)bone marrow cells,respectively)was applied.In addition,recipients were treated with costimulation blockade(1 mg anti-CD154 and 0.5 mg CTLA4Ig on postoperative days 0 and 2,respectively)and short-term rapamycin(3 mg/kg/day for the first posttransplant week and then every other day for another 3 weeks).Similar to high-dose conventional bone marrow transplantation,5/6 animals in the vascularized bone marrow group demonstrated long-term allograft survival(>120 days).In contrast,significantly shorter median survival was noted in the low-dose CBMT group(~64 days).Consistently high chimerism levels were observed in the VBM transplantation group.Notably,low levels of circulating CD4^(+)and CD8^(+)T cells and a higher ratio of Treg to Teff cells were maintained in VBM transplantation and high-dose CBMT recipients(>30 days)but not in low-dose VBM transplant recipients.Donor-specific hyporesponsiveness was shown in tolerant recipients in vitro.Removal of the vascularized bone marrow component after secondary donor-specific skin transplantation did not affect either primary allograft or secondary skin graft survival.