Tolerance to limb tissue allografts between swine matched for major histocompatibility complex antigens.

Transplantation of limb tissue allografts would greatly expand the realm of reconstructive surgery. However, the toxicity of chronic immunosuppression has adversely tilted the risk-benefit balance for clinical transplant. In this study, a procedure was sought to achieve host tolerance to limb tissue allografts through matching of the major histocompatibility complex (MHC) antigens between donor and host swine using only a 12-day course of cyclosporine. Massachusetts General Hospital (MGH) miniature swine were used as a large animal model with defined MHC, and musculoskeletal grafts from the donor hind limb were transplanted heterotopically to the recipient femoral vessels. Allografts from MHC-mismatched donors treated with cyclosporine (n = 4) were rejected in less than 6 weeks by gross inspection and histologic sections. Allografts from MHC-matched, minor antigen mismatched donors not treated with cyclosporine (n = 4) were rejected between 9 and 12 weeks. Allografts from similarly matched donors treated with 12 days of cyclosporine (n = 7) showed no evidence of rejection until sacrifice between 25 and 47 weeks. Thus allograft tolerance was achieved between MHC-matched swine using a limited course of cyclosporine. Demonstration of limb tissue allograft survival in a large animal model without long-term immunosuppression represents an important step toward clinical transplantation.

Arthroscopic repair of triangular fibrocartilage complex injuries.

The triangular fibrocartilage complex is a functionally and anatomically intricate group of structures located at the ulnar aspect of the wrist. Injury to this structure affects the biomechanics of the wrist and makes functional restoration difficult. This article reviews the anatomy, biomechanics, diagnosis, and arthroscopic treatment of triangular fibrocartilage complex injuries.

Using intact nerve to bridge peripheral nerve defects: an alternative to the use of nerve grafts.

This preliminary study was conducted to determine whether a regenerating peripheral nerve in a rat model can use the epineurium of an intact nerve to bridge a nerve gap defect. To create the intact nerve bridge a 1-cm segment of the peroneal nerve is resected leaving a gap defect. The proximal and distal peroneal nerve stumps are sutured 1-cm apart, in an end-to-side fashion, to the epineurium of the intact tibial nerve. The following experimental groups were used (n = 12): group A, immediate primary repair of resected segment; group B, intact nerve bridge technique; group C, nerve autograft; and group D, gap in situ control. Evaluation 12 weeks after surgery included measurement of the tibialis anterior muscle contraction force, axonal counting, wet weight of the tibialis anterior muscle, and histologic examination. The results of this animal study support 3 main conclusions: regenerating axons can use the epineurium of an intact nerve to bridge a gap in nerve continuity; when using functional recovery to assess regeneration, there is no significant difference between standard nerve autografts and the intact nerve bridge technique; and based on histologic examination, the intact nerve bridge technique does not injure the intact tibial nerve used to bridge the gap defect. Taken together, the results of this preliminary animal study suggest that the intact nerve bridge technique may be a potential alternative to standard nerve autografts in appropriate circumstances. Further investigation in a higher animal model is warranted before considering clinical application of the intact nerve bridge technique.

Injection of allogeneic bone marrow cells into the portal vein of swine in utero.

The ability to safely manipulate the immune system of the developing fetus carries the hope of effective treatment strategies for certain congenital disorders that can be diagnosed during gestation. One possible intervention is the induction of specific transplantation tolerance to an adult donor who could provide tissue after birth without the need for immunosuppression. Although the introduction of allogeneic stem cells to a developing immune system has been shown to result in hematopoietic chimerism, donor-specific transplantation tolerance has not been demonstrated in a large animal model. In previous reports of in utero stem-cell transplantation, the cells were injected into the fetus by an intraperitoneal route. We sought to improve upon this technique of cell transplantation by developing a method for the safe delivery of allogeneic stem cells directly into the hepatic circulation of fetal swine. In the second phase of our study, we determined if adult allogeneic bone marrow cells delivered to the fetus by this intravascular route could result in result in hematopoietic chimerism and donor-specific transplantation tolerance. A method of successful intravascular injection was designed in which a laparotomy was performed on a sow at midgestation (50-55 days) to administer 1 cc of inoculum into the portal vein of each fetus using transuterine ultrasound guidance and a 25-gauge spinal needle. In one sow, 10 piglets were injected with saline to test safety, and 8 piglets were born. For transplantation of stem cells to the fetuses, donor bone marrow was harvested from a genetically defined miniature swine. In one sow the marrow was injected without T-cell depletion resulting in abortion. In the third sow, the marrow was depleted of T-cells to less than 0.01% using magnetic beads conjugated to anti-CD3 monoclonal antibodies. No chimerism was detected in these offspring. Only in the fourth sow where the T-cell depletion was reduced to about 1% of the cells in the inoculum did one animal demonstrate chimerism. This piglet showed reproducible blood chimerism (0.95% donor cells) detected by flow cytometry measurement of monoclonal antibodies to the donor MHC. In addition, this animal demonstrated hyporesponsiveness to donor lymphocytes in an MLR assay while reacting strongly to third-party stimulator cells. A split-thickness skin graft from the donor was accepted, and a third-party graft was rapidly rejected.

Skin allograft survival following intrathymic injection of donor bone marrow.

BACKGROUND: Success has been reported using intrathymic injection in the preconditioning regimen to induce allograft tolerance. Although long-term stable tolerance has been achieved in numerous rodent vascularized solid organ allograft models, tolerance to skin transplants has only been achieved across minor antigenic or concordant species disparities. This study sought to induce tolerance across an allogeneic barrier in a rat model with a major genetic disparity. MATERIALS AND METHODS: Lewis rats were injected intrathymically with 1 x 10(8) Brown-Norway (BN) bone marrow cells and intraperitoneally with 1.0 cc of rabbit anti-rat anti-lymphocyte serum (ALS). Twenty-one days later, BN skin grafts were placed on the injected animals. Control groups were included to isolate the effect of technique, thymic manipulation, strain specificity, and ALS. RESULTS: Animals receiving both intrathymic bone marrow cells and ALS had a skin graft median survival time of 24 days versus 8 days for the control group (P = 0.003). Groups receiving anti-lymphocyte serum alone or intrathymic bone marrow cell injection alone exhibited no skin graft survival prolongation. Mixed lymphocyte reactions revealed normal responsiveness of tolerant animal lymphocytes to donor strain lymphocytes. CONCLUSION: This protocol utilizing the intrathymic injection of donor bone marrow cells along with short-term immunosuppression with anti-lymphocyte serum produced markedly prolonged survival of skin allografts transplanted across a major histocompatibility barrier. Although tolerance was incomplete, significant prolongation has not previously been reported in genetic disparities of this degree. These results suggest that the application of this technique for central immune modulation may be beneficial for allograft tolerance induction and deserves further study in large animals models.

Minimal connectivity between six month neostriatal transplants and the host substantia nigra.

The present study sought to determine if axonal connectivity is established between 6-month-old neostriatal transplants and the host substantia nigra. Cell suspensions of fetal neostriatum were transplanted into the adult rat neostriatum lesioned previously by kainic acid. Horseradish peroxidase injections into the ipsilateral ventral midbrain labelled the lesion site and the intact neostriatum extensively, but no appreciable anterograde or retrograde label was found within the graft. These results demonstrate a paucity of connectivity between neostriatal grafts and the host brain at a time when other investigators have described transplant-mediated recovery of function.