Survival of aortic allografts containing living cells

Abstract

There is agreement among investigators that the “in vivo reaction” to the implanted allograft is complex and variably related to (1) donor age; (2) procurement and processing methods; (3) implantation position and technique; and (4) immunogenic reaction within the valve cusps (1, 2, 3). Many human and animal experiments have been performed to determine the nature of the donor and host reaction after implantation, and there is disagreement as to whether the transplanted donor cells remain viable. Our findings, as well as O’Brien’s remain opposed to those of Brian Barrett-Boyes and Ross on this issue (4, 5, 6, 7). We believe that donor cells remain viable for extended periods, and that long-term valve function is related to the presence of viable cells in the donor graft (Fig. 1). If viable donor cells are not present, then long-term function is secondary to the basic tissue integrity of the functional valve cusp and not due to repopulation by host cells. It is proven that viable fibroblasts in valve cusps can be detected histologically and by tissue culture after ex-plantation. Our data suggests that these are living donor fibroblasts, and there is limited host invasion into and onto the functional valve cusps after implantation (5, 8, 9). Morphology of both experimental and clinical valve expiants indicate that donor cell hyperplasia and host overgrowth or pannus can be advantageous or deleterious depending upon the location and intensity of collagen deposition (Fig. 2).