Heterotopic limb allotransplantation model to study skin rejection in the rat

Current rodent models for investigation of limb allotransplantation typically utilize orthotopic whole-limb transplantation, a morbid and time-consuming procedure. Our objective was to design a less morbid rat model to explore the immunological obstacles of limb transplantation, and particularly skin. Twenty lower hindlimbs from 10 donors were transplanted into a heterotopic subcutaneous position into 20 animals (10 isogeneic and 10 allogeneic). Each group was further subdivided to include animals with (n = 5) and without (n = 5) a skin paddle for observation of cutaneous signs of rejection. All grafts in the isogeneic group survived for 100 days, i.e., the endpoint of the study. Allogeneic transplants rejected their allografts at a mean of 12.8 days (with skin) and 20.6 days (without). Our heterotopic limb transplantation model takes less time and is less stressful to the animals, while allowing for early observation of graft skin rejection, when compared to orthotopic whole-limb transplantation.