Chimerism studies as an approach for the induction of tolerance to extremity allografts

Lessons learned from the first quadruple extremity transplantation in the world

BACKGROUND

Limb transplantation is emerging as a promising area of surgery and is an indispensable alternative for prosthetic rehabilitation of amputees, the severity of which is increasing because of combat-related injuries. Successful unilateral and bilateral limb transplantations have already been performed before this operation.

METHODS

We performed the first ever quadruple limb transplantation in February 2012. The limbs procured from a 40-year-old man heart-beating donor were transplanted to a 27-year-old male patient who was a quadruple amputee for the last 14 years because of an electrical injury.

RESULTS

To shorten the ischemic period to a minimum, 3 separate microsurgery teams worked simultaneously. All extremities were reperfused within 8 hours of procurement, and the operation lasted for 12 hours. Metabolic load was managed by hemodialysis. One hour after the completion of the operation, cardiac arrest developed, resuscitation of which necessitated median sternotomy and temporary partial cardiopulmonary support. Despite the removal of the transplanted limbs and all efforts including continuous hemodialysis, plasmapheresis, and extracorporeal membrane oxygenation, the patient died on the fourth day after transplantation in a clinical condition of severe systemic inflammation.

CONCLUSIONS

The problems we faced were difficulty of vascular access for invasive monitoring and fluid replacement, and the severe systemic inflammation effects of which could not be dealt with, despite aggressive supportive treatment. We hope that our experience will enlighten the surgeons who are willing to extend the limits of limb transplantation and serve the success of future operations.

Would you be a face transplant donor? A survey of the Turkish population about face allotransplantation

With the technical advancement in face allotransplantation, we decided to survey the Turkish population to gain perspective into their thoughts and reactions toward face transplantation. A questionnaire was given to 1000 volunteers, regarding data about demographics, educational status, religious, and behavioral preferences. Their attitudes about donating their faces, knowledge about the pros and cons of this procedure, and personal desire for face transplantation if needed were inquired.The results of the survey demonstrated that knowing more about the procedure increases its acceptance but even so, the majority would rather undergo multiple operations with self-tissues before getting a facial transplantation (FT). When the risks of immunosuppression were exposed, less people agreed to FT, thinking it was not worth the risks.The cultural, ethnical, religious, and social background of different societies may influence the way FT is perceived and accepted. As this procedure is thought to challenge many ethical, physiological, and social points of views, we believe that it is important for a surgical team to have insight into their population's perception and general thoughts concerning the issue.

Immunomodulatory effects of pre-irradiated extremity allograft in the rodent model

Allogeneic human hand transplantation requires combination immunotherapy to maintain viability. Immunosuppression will be lifelong, with doses as high or higher than those required for solid organ allotransplantation. The risks associated with lifelong immunosuppression are unacceptable, particularly for younger transplant patients. It therefore becomes imperative to explore ways to reduce or eliminate the requirement for immunosuppression. Reconstructive surgery should consider, to a large extent, graft pre-treatment as a strategy for the transplantation of vascularised limb tissue allografts with reduced requirement for immunosuppression. In the clinical setting of composite tissue allograft (CTA), the graft is always procured from a cadaveric donor. Therefore, only a short time is available between harvesting the graft from the donor and transplanting into the recipient. This period provides the only opportunity to manipulate the CTA. Quite a few studies, however, have so far investigated donor pre-treatment and pre-transplant modification of the extremity allograft. Work from our group and others has demonstrated that removal of allogeneic bone marrow in the limb graft by irradiation and its rapid reconstitution with recipient marrow cells can significantly prolong the survival of limb allografts in the absence of immunosuppression. In the current work, we review these studies and discuss the immunomodulatory effects on the extremity allograft.

Bone marrow transplantation combined with mesenchymal stem cells induces immune tolerance without cytotoxic conditioning

BACKGROUND

Transplantation of allogeneic donor bone marrow (BM) into sufficiently conditioned recipients is an effective approach to induce immune tolerance as assessed by mixed chimerism. However, this approach is hampered by the lack of feasible protocols devoid of cytoreductive conditioning. We investigated whether mixed chimerism could be established by intra-bone marrow-bone marrow transplantation (IBM-BMT) combined with bone marrow-derived mesenchymal stem cells (BMSCs) treatment without additional cytoreductive conditioning.

MATERIALS AND METHODS

The recipient mice (C57BL/6) accepted BMSCs from donor mice (Balb/c) through daily tail vein injection for 4 d followed by IBM-BMT immediately. Full-thickness skin grafts from donor mice as well as from the third party mice (ICR) were transplanted to the dorsum of the recipient mice after the combined IBM-BMT with BMSCs treatment. The immune tolerance was assessed by the survival time of skin allografts. The establishment of mixed chimerism and cytokine expression profile in recipient peripheral blood were determined by flow cytometry and enzyme-linked immunosorbent assay, respectively.

RESULTS

IBM-BMT combined with BMSCs treatment led to stable mixed chimerism and donor-specific skin graft tolerance. The flow cytometry analysis revealed that recipient mice developed 20%-25% chimerism levels among the myeloid lineage. The skin allografts survived more than 1 y and the hair re-grew normally on the grafts. Cytokine profile showed that IBM-BMT combined with BMSCs treatment prolonged humoral tolerance in recipient chimeras.

CONCLUSIONS

Our results demonstrate that donor specific immune tolerance can be effectively induced by IBM-BMT combined with BMSCs treatment without any additional cytoreductive recipient treatment. This approach provides a promising allograft transplantation strategy when the donor bone marrow is available.

The new immunosuppressant PLNPK prolongs allograft survival in mice

The pentapeptide PLNPK (Pro-Leu-Asn-Pro-Lys) is extracted from the spleen. Preliminary studies have shown that PLNPK could inhibit T lymphocyte transformation and antibody production. In the present study, we detected the inhibitory effect of PLNPK on one-way mixed leukocyte reaction (MLR) in vitro and observed the effect of PLNPK on the duration of allograft survival in mouse models of skin or cardiac transplantation. Pathological damage and T cell infiltration of the grafts were also detected. Results showed that PLNPK could significantly inhibit T lymphocyte proliferation, with an optimized inhibition of 40%. Also PLNPK could significantly prolong the mean survival time of skin allograft and cardiac allograft, producing survival rates of 42% and 38.7%, respectively. PLNPK at a dose of 200 μg/kg/d or 100 μg/kg/d could significantly suppress ConA-induced T cell proliferation and T cell IL-2 secretion in transplant recipient mice, compared to the saline group (P<0.05). This information suggests that PLNPK can effectively antagonize transplant rejection, possibly by reducing IL-2 secretion by T cells and inhibiting T cell proliferation and activation.

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.