New Modification of the Oldest Flap in Rats to Increase Antigenicity of Transplanted Skin: The Extended Groin Flap Model

Abstract

Tolerance to composite tissue allograft may allow for widespread clinical use of reconstructive allotransplantation. However, the skin component of composite tissue allograft poses an intractable barrier towards achieving this goal: skin is the most antigenic tissue due to rich representation of immunocompetent cells. Moreover, the immunologic response may increase in proportion to the size of skin. In order to precisely evaluate this correlation in experimental studies, a new skin transplant model with a large skin component will be necessary. In the present study, the authors investigated an extended groin (EG) flap transplant model in rats to test its feasibility in two groups: an anatomic study group and an experimental transplant group. In the former group, EG flaps were elevated on superficial epigastric vessels. The EG skin islands of all flaps were shown to be viable at postoperative day 21. In the latter group, isograft transplantations were performed between Lewis rats (RT11), while allograft transplantations were performed between LBN (RT 1+n) donors and Lewis (RT11) recipients. All EG transplants were viable post-transplant day 200 under cyclosporine A monotherapy protocol. In addition, microangiography of the transplant demonstrated that the entire skin island was supplied by the pedicle of the superficial epigastric vessels (SEV). Moreover, studies with India ink demonstrated dye uptake in all flap components, and histological examination demonstrated the viability of flap tissue. Chimerism level was detected below 1 % at post-transplant day 7. Starting from post-transplant day 21, total chimerism began to increase (0.94 % of RT1n cells), and improved during the follow-up period: at 100 days post-transplant it was assessed at 1.25 % of RT1n cells. EG transplant involves fairly uncomplicated surgery, with a short operation time. These cumulative advantages suggest that it may serve as a new experimental model with a large skin component, and may also be used to ascertain the immunologic differences in the recipient body.