Impact of Donor Bone Marrow on Survival of Composite Tissue Allografts

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL RELEVANCE STATEMENT

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

The Positive Impact of Donor Bone Marrow Cells Transplantation into Immunoprivileged Compartments on the Survival of Vascularized Skin Allografts

Using the vascularized skin allograft (VSA) model, we compared the tolerogenic effects of different allogeneic bone marrow transplantation (BMT) delivery routes into immunoprivileged compartments under a 7-day protocol immunosuppressive therapy. Twenty-eight fully MHC mismatched VSA transplants were performed between ACI (RT1^a) donors and Lewis (RT1¹) recipients in four groups of seven animals each, under a 7-day protocol of alfa/beta TCRmAb/CsA (alpha/beta-TCR monoclonal antibodies/Cyclosporine A therapy). Donor bone marrow cells (BMC) (100 × 106 cells) were injected into three different immunoprivileged compartments: Group 1: Control, without cellular supportive therapy, Group 2: Intracapsular BMT, Group 3: Intragonadal BMT, Group 4: Intrathecal BMT. In Group 2, BMC were transplanted under the kidney capsule. In Group 3, BMC were transplanted into the right testis between tunica albuginea and seminiferous tubules, and in Group 4, cells were injected intrathecally. The assessment included: skin evaluation for signs and grade of rejection and immunohistochemistry for donor cells engraftment into host lymphoid compartments. Donor-specific chimerism for MHC class I (RT1^a) antigens and the presence of CD4⁺/CD25⁺ T cells were assessed in the peripheral blood of recipients. The most extended allograft survival, 50–78 days, was observed in Group 4 after intrathecal BMT. The T cells CD4⁺/CD25⁺ in the peripheral blood were higher after intrathecal BMC injection than other experimental groups at each post-transplant time point. Transplantation of BMC into immunoprivileged compartments delayed rejection of fully mismatched VSA and induction of robust, donor-specific chimerism.

Vascularized Thymosternal Composite Tissue Allo- and Xenotransplantation in Nonhuman Primates: Initial Experience

Background:

Vascularized composite allotransplantation is constrained by complications associated with standard immunosuppressive strategies. Vascularized thymus and bone marrow have been shown to promote prolonged graft survival in composite organ and soft-tissue vascularized composite allotransplantation models. We report development of a nonhuman primate vascularized thymosternal composite tissue transplant model as a platform to address donor-specific immune tolerance induction strategies.

Methods:

Vascularized thymosternal allograft (skin, muscle, thymus, sternal bone) was transplanted between MHC-mismatched rhesus monkeys (feasibility studies) and baboons (long-term survival studies), with end-to-side anastomoses of the donor aorta and SVC to the recipient common femoral vessels. A male allograft was transplanted to a female’s lower abdominal wall, and clinically applicable immunosuppression was given. Skin biopsies and immunological assays were completed at regular intervals, and chimerism was quantified using polymerase chain reaction specific for baboon Y chromosome.

Results:

Four allo- and 2 xenotransplants were performed, demonstrating consistent technical feasibility. In 1 baboon thymosternal allograft recipient treated with anti-CD40–based immunosuppression, loss of peripheral blood microchimerism after day 5 was observed and anticipated graft rejection at 13 days. In the second allograft, when cutaneous erythema and ecchymosis with allograft swelling was treated with anti-thymocyte globulin starting on day 6, microchimerism persisted until immunosuppression was reduced after the first month, and the allograft survived to 87 days, 1 month after cessation of immunosuppression treatment.

Conclusions:

We established both allo- and xeno- composite vascularized thymosternal transplant preclinical models, which will be useful to investigate the role of primarily vascularized donor bone marrow and thymus.

Immunosuppression and monitoring of rejection in hand transplantation

Advances in vascularized composite allotransplantation over the last decade have achieved significant milestones in basic science and translational research, as well as clinically with highly encouraging functional and immunologic outcomes. However, certain immunologic challenges remain. In particular, although tolerance has been induced to nearly all components of a hand allograft in experimental models, the skin component may still be subject to acute rejection episodes. Currently, conventional immunosuppressive protocols have been successful at preventing allograft loss; however, they have not prevented episodes of acute skin rejection. Furthermore, the profound side effect profile of the life-long, high-dose, multidrug immunosuppression regimen that is necessary to maintain a viable graft alters the risk to benefit ratio of this non-life-saving procedure. Therefore, there must be a concerted effort in the scientific community to develop novel protocols to either minimize immunosuppression or to induce tolerance to the allograft to promote the widespread application of this life-changing procedure.

The need for inducing tolerance in vascularized composite allotransplantation

Successful hand and face transplantation in the last decade has firmly established the field of vascularized composite allotransplantation (VCA). The experience in VCA has thus far been very similar to solid organ transplantation in terms of the morbidity associated with long-term immunosuppression. The unique immunological features of VCA such as split tolerance and resistance to chronic rejection are being investigated. Simultaneously there has been laboratory work studying tolerogenic protocols in animal VCA models. In order to optimize VCA outcomes, translational studies are needed to develop less toxic immunosuppression and possibly achieve donor-specific tolerance. This article reviews the immunology, animal models, mixed chimerism & tolerance induction in VCA and the direction of future research to enable better understanding and wider application of VCA.

Animal models for basic and translational research in reconstructive transplantation

Reconstructive transplantation represents a bona fide option for select patients with devastating tissue loss, which could better restore the appearance, anatomy, and function than any other conventional treatment currently available. Despite favorable outcomes, broad clinical application of reconstructive transplantation is limited by the potential side effects of chronic multidrug immunosuppression. Thus, any reconstructive measures to improve these non-life-threatening conditions must address a delicate balance of risks and benefits. Today, several exciting novel therapeutic strategies, such as the implementation of cellular therapies including bone marrow or stem cells that integrate the concepts of immune regulation with those of nerve regeneration, are on the horizon. The development of reliable and reproducible small and large animal models is essential for the study of the unique immunological and biological aspects of vascularized composite allografts and to translate such novel immunoregulatory and tolerance-inducing strategies and therapeutic concepts from the bench to bedside. This review provides an overview of the multitude of small and large animal models that have been particularly designed for basic and translational research related to reconstructive transplantation.

The current state of hand transplantation

Hand transplantation is the most common form of modern composite tissue allotransplantation. Successful application of this technology requires a multidisciplinary approach incorporating not only skilled hand surgeons, transplant surgeons, and transplant immunologists, but also hand therapists, psychiatrists, medical specialists, anesthesiologists, and others. Functional outcomes can be life changing for properly selected candidates. Hand transplantation is becoming more common, with more centers offering this relatively new reconstructive modality. Its success depends on proper patient selection, a technically successful operation, postoperative rehabilitation, and an immunotherapy protocol that prevents rejection but has minimal or acceptable morbidity.

Full face transplant: the first case report

BACKGROUND

Since 2005, 11 human face transplants have been performed. In each, varying amounts of tissue have been transplanted. Herein we report a "full" face transplant including all intact aesthetic and functional units.

METHODS

On March 27, 2010, we performed a full face transplant, including all the soft tissues and part of the underlaying bony structure, at the University Hospital Vall d'Hebron, Barcelona, Spain. The donor was a 41-year-old male, who died from a massive brain hemorrhage. The recipient was a 30-year-old male with a severe facial deformity caused by a ballistic trauma in 2005. Harvest and subsequent implant took 24 hours. The patient received initial induction (Thymoglobulin 2 mg/kg/iv; Prednisone 1 gm/iv) and maintenance (Prednisone 1 mg/kg/24hours, Tacrolimus 10-15 ng/mL/PO, and Mycophenolate mofetil 2g/daily/PO) immunosuppression and Infection prophylaxis (Valganciclovir and Co-trimoxazole).

RESULTS

There were no intraoperative complications. Postoperative complications included; venous anastomoses thrombosis, acute oro-cutaneous fistula, right parotid sialocele and 2 acute rejection episodes, which were resolved by revision of the anastomosis, profuse irrigation and immunotherapy adjustment, respectively. The patient was discharged from the hospital at 4 months posttransplant with; near-total sensation and partial-motor recovery, no psychological complications and excellent acceptance of his new facial appearance.

CONCLUSIONS

The early success described in this case report demonstrates the technical and clinical feasibility of transplanting all the tissues of the with all its aesthetic and functional units intact.

Hand allotransplantation

In the past decade, more than 100 different composite tissue allotransplantation (CTA) procedures have been performed around the world including more than 50 hand and 8 facial transplants with encouraging graft survival and excellent functional outcomes. Broader clinical application of CTA, however, continues to be hampered by requirement for long-term, high-dose, multidrug maintenance immunosuppression to prevent graft rejection mediated particularly by composite tissue allograft's highly immunogenic skin component. Medication toxicity could result in severe adverse events including metabolic and infectious complications or malignancy. Notably, unlike in solid organs, clinical success is dictated not only by graft acceptance and survival but also by nerve regeneration, which determines ultimate functional outcomes. Novel strategies such as cellular and biologic therapies that integrate the concepts of immune regulation with those of nerve regeneration have shown promising results in small and large animal models. Clinical translation of these insights to reconstructive transplantation and CTA could further minimize the need of immunosuppression and optimize functional outcomes. This will enable wider application of such treatment options for patients in need of complex reconstructive surgery for congenital deformities or devastating injuries that are not amenable to standard methods of repair.

Achievements and challenges in composite tissue allotransplantation

Overall, more than 60 hand/forearm/arm transplantations and 16 face transplantations have been performed in the past 12 years. In the European experience summarized here, three grafts have been lost in response to a vascular thrombosis (n = 1), rejection and incompliance with immunosuppression (n = 1) and death (n = 1). The overall functional and esthetic outcome is very satisfactory, but serious side effects and complications related to immunosuppression are challenges hindering progress in this field. The high levels of immunosuppression, skin rejection, nerve regeneration, donor legislation and the acceptance level need to be addressed to promote growth of this promising new field in transplantation and reconstructive surgery.

Immunologic aspects and rejection in solid organ versus reconstructive transplantation

The immunosuppressive medications developed over the past 3 decades have paved the way for solid organ transplantation to become the treatment of choice for end-stage organ failure. At the end of the century, composite tissue transplantation in humans was performed with success using the same immunosuppressive medications and therapeutic principles. A decade later, experience from >100 cases of reconstructive transplantation have increased the knowledge, changed the view, and affected the therapeutic principles in this novel field. We herein portray the evolution of this novel type of transplant with particular reference to immunologic aspects, particularly differences between reconstructive and solid organ transplantation.

Anti-αβ-T-cell receptor antibodies in the setting of laryngeal transplantation

Inhibiting T-cell activation is critically important to the induction of transplantation tolerance. Monoclonal antibodies directed against the αβ-T-cell receptor have been shown to cause selective immunodepletion of this T-cell population and can provide long-term allograft acceptance. This article discusses the role of this promising immunosuppressive agent in scientific research and clinical utilization. Specifically, the article focuses on its efficacy and mechanism of tolerance induction in solid tissue and composite tissue allograft transplantation with a particular focus on laryngeal transplantation.

Myeloablative irradiation, granulocyte-colony stimulating factor, and FK506 can induce macrochimerism and prolong the survival of experimental extremity allografts

BACKGROUND

A key component of composite tissue allografts is the vascularized limb/bone marrow because of its capacity to reconstitute the marrow cavity of the recipient. The efficacy of a new protocol that uses total body irradiation (TBI), granulocyte colony-stimulation factor (G-CSF), and FK506 to induce high level bone marrow chimerism was evaluated with particular reference to the dose requirement and toxicity of TBI.

MATERIALS AND METHODS

In total, 82 whole-limb allotransplants from LacZ transgenic rats to LEW rats were performed. TBI was administered just prior to transplantation with various doses ranging from 100 to 1500 R (almost equal to 1-15 Gy). G-CSF was given for 4 d, while FK506 was used for 28 d. The level of chimerism was evaluated by semiquantitative polymerase chain reaction (PCR).

RESULTS

The survival of limb allografts in recipients that were pretreated with a myeloablative TBI dose of >1000 R was prolonged to more than 1 y. Recipients pretreated with <500 R showed no prolongation of limb graft survival. A majority of long-term survivors showed chronic, nonlethal graft-versus-host disease (GVHD). PCR analysis revealed a high level of intra-bone marrow chimerism in the recipient, thus demonstrating successful induction of macrochimerism.

CONCLUSION

Vascularized limb/bone marrow graft is a proven method for supplying donor cells to the bone marrow of irradiated recipients. A new protocol involving pretransplant myeloablative TBI with >1000 R followed by treatment with G-CSF and FK506 was found to induce a high level of chimerism and significantly prolong the survival of limb allografts without causing lethal GVHD.

Prolonged survival of experimental extremity allografts: a new protocol with total body irradiation, granulocyte-colony stimulation factor, and FK506

The induction of a high-level of chimerism (macrochimerism) may be the most reliable strategy for achieving donor-specific tolerance. The purpose of this study was to evaluate the efficacy of a new protocol using total-body irradiation (TBI) and granulocyte-colony stimulation factor (G-CSF) to induce high-level chimerism following rat whole-limb allotransplantation. In this study, we investigated whether the timing of TBI influenced the period of graft survival. In total, 50 whole-limb allotransplants from LacZ transgenic rats to LEW rats were performed. TBI was performed at days 0 and 14, and G-CSF was given for 4 days after TBI. FK506 was given for 28 days after transplant. Nontreated limb allografts were rejected after 4.2 days. The survival time was prolonged to 64 days in the FK506 monotherapy group. In the group receiving TBI at day 14, limb allograft survival was significantly prolonged to 81 days. In the group receiving TBI at day 0, 26% of recipients died but in the surviving recipients the grafts survived for longer than 1 year without lethal graft-versus-host disease (GVHD). Polymerase chain reaction (PCR) analysis revealed a high level of intrabone marrow chimerism in the recipient, thus demonstrating successful induction of macrochimerism. A new protocol of pretransplant TBI followed by treatment with G-CSF and FK506 was found to induce a high level of chimerism and to significantly prolong the survival of limb allografts in recipients without lethal GVHD.