J Reconstr Microsurg 2006; 22 - A005
DOI: 10.1055/s-2006-955125

A Modified Model with Allogeneic Hindlimb Osteomyocutaaneous Flap for the Study of Composite Tissue Allotransplantation in Rats

Wei-Chao Huang 1, 2, Warren C Breidenbach 1, 2, Hong Xu 1, 2, Yiming Huang 1, 2, Fu-Chan Wei 1, 2, Suzanne T Ildstad 1, 2
  • 1Christine Kleinert Institute for Hand and Microsurgery, Chang Gung Memorial Hospital, Louisville, Kentucky, USA
  • 2Institute for Cellular Therapeutics, University of Louisville, Louisville, Kentucky, USA

Composite tissue allotransplantation (CTA) could benefit millions with large tissue defects, including hand transplantations for lost limbs. However, the toxicity of the immunosuppressive agents required to prevent rejection has limited the widespread application of this approach. Mixed chimerism established by bone marrow transplantation can induce donor-specific tolerance for CTA. The authors reported the use of a novel rat model for hindlimb osteoemyocutaneous flap transplantation to evaluate for donor-specific tolerance to CTA.

Male (6- to 8-weeks-old) ACl (RT1Aa) and 6- to 10-weeks old) Wistar Furth (WF, RT1Au) rats weighing between 150 and 300 g were used. The chimeric rats were prepared with a nonmyeloablative approach for BMT. Recipient WF rats wee injected with anti-alpha-beta-TCR monoclonal antibody (R73)(mAb) 3 days before BMT (day − 3), conditioned with 400 cGy total treated with tacrolimus (1 mg/kg/day) intraperitoneally (IP) body irradiation (TBI) one day before BMT (day − 1), and from days 0 to 10, as well as one dose of 5 mg antilymphocyte serum (ALS) IP ten days after BMT (day 10). The recipient rats were transplanted with 100 million T-cell depleted ACl BM cells on day 0. Experimental groups were Group 1 (n = 6), syngeneic orthotopic hindlimb transplantation; Group 2 (n = 6), allogeneic orthotopic hindlimb allotransplantation; Group 3 (n = 6), allogeneic orthotopic hindlimb allotransplantation with the imunosuppression protocol; Group 4 (n = 7), allogeneic orthotopic hindlimb allotransplantation in the chimeric rats; Group 5 (n = 8), allogeneic hindlimb osteomyocutaneous flap allotransplantation in the chimeric rats.

The osteomyocutaneous flap offered a number of significant advantages over complete limb transplantation. The hindlimb flap was harvested after skeletonizing the deep femoral vessels. The hindlimb was tailored to the osteomyocutaneous flap with the preservation of a 3 × 2-cm skin paddle in the lower posterior limb. The average operative time, including flap harvesting, in Group 4 was 137.4 min, compared to Group 5 which was 95.6 min. The average ischemia time in Group 4 was 72.3 min, and in Group 5 was 55.5 min. The authors found that the surgical model of orthotopic complete hindlimb transplantation was associated with a high perioperative mortality approaching 85.7%. In striking contrast, there was an overall operative success rate of 62% in the rats receiving the hindlimb osteomyocutaneous flap. Notably, all chimeras accepted the donor-specific osteomyocutaneous flaps without requiring immunosuppression.

The results demonstrate that the hindlimb osteomyocutaneous flap is an ideal surgical model for evaluating acceptance of CTA and that chimerism induces tolerance and drug-free acceptance of CTA.