A size-matching heterotopic aortic valve implantation model in the rat

Background. Structural failure of cardiac valve allografts may be related t o technical factors such as size mismatch, resulting in early intimal proli feration and fibrosis or immunological reactions against the transplanted v alves, featuring lymphocytic infiltration. Objective, To develop a heterotopic aortic valve implantation model in the rat to study the immunological factors leading to graft failure in the sett ing of a technical adaptation for size mismatch. Methods. Syngeneic (WAG-WAG or DA-DA) and allogeneic (WAG-BN or WAG-DA) rat strain combinations were used to study the effect of the allogeneic respon se on valve properties. An end-to-side anastomosis was made between the U-s haped aortic root graft and the recipient's abdominal aorta to resolve the problems of size matching. Results. No animals suffered from ischemic or neurological complications du ring the study period. One hundred percent survival and patency of the aort ic grafts were achieved at the end of a 21-day observation period. In the s yngeneic group 9 of 10 valves were still competent when assessed during ret rograde injection. In contrast, 2 of 10 allogeneic valve grafts were compet ent on postoperative Day 21, Microscopic evaluation revealed no fibrosis or intimal thickening in the syngeneic valve grafts while the allogeneic valv e grafts demonstrated rejection-like morphology, Conclusion. The absence of fibrosis and intimal thickening in the syngeneic transplanted valve grafts indicates that this implantation model is not in fluenced by nonimmunological-based structural changes. Therefore, this new model enables us to study the association between donor-directed immune res ponses and allograft degeneration in a technically unbiased manner. (C) 199 9 Academic Press.