Functional integrity of vascular allografts after endothelial removal

Several studies have indicated that antigen-presenting endothelial cells represent the primary initiator of acute arterial graft rejection, leading to decreased arterial patency rates. Patency rates dramatically increase upon endothelial removal (denudation) prior to orthotopic transplantation into antigenically disparate hosts. Although patent, the biomechanical and functional changes seen in these allograft vessels (ACI rats to Lewis rats) have not been described. The present investigation examined functional differences between these allograft arteries and normal rat femoral arteries. Moreover, endothelial removal may also alter function; thus, an autograft injury model (Lewis to Lewis) was employed to discern the differences between injury and rejection. The results indicate that denudation injury alone caused no change in the passive stress-strain curve, the muscle length at which stress was maximum (Lo), or in phenylephrine- or nitroglycerin-induced concentration-response curves. Similarly, concentration-response curves were not affected by allograft transplantation; however, both the passive stress-strain curve and Lo values were shifted to significantly longer lengths (0.25 and 0.20 mm, respectively), suggesting an increase in arterial plasticity but not compliance. Furthermore, allografts produced significantly weaker KCl-induced contractions than did autografts (22 vs. 66% of control values, p < 0.05). Acetylcholine maximally relaxed phenylephrine-contracted arteries in the following descending order. ACI > Lewis > autograft > allograft. In conclusion, these data suggest that vascular rejection involves subendothelial tissues, is distinct from vascular injury, and that the denudation allograft transplantation model can be employed to examine this process.