MORPHOLOGIC STUDY OF HOMOGRAFT VALVES BEFORE AND AFTER CRYOPRESERVATION AND AFTER SHORT-TERM IMPLANTATION IN PATIENTS

Cryopreserved heart valve homografts have been implanted in patients f or the past 15 years, but controversies still exist on the survival of donor cells, matrix maintenance, and possible rejection by the host. Therefore a full morphologic study (histology, immunohistochemistry, t ransmission electron microscopy, and cuprolinic blue-TEM for glycosami noglycans [GAG]) of short-term implanted uninfected grafts was done us ing unimplanted Valves as the reference. Unimplanted tissues consisted of 5 fresh and 11 cryopreserved valves. Eight implants were recovered at reoperation (4) or autopsy (4), 4 from the right and 4 from the le ft ventricular outflow tract. The implantation time was 2 hours to 30 days. For unimplanted valves we found a partial preservation of the en dothelium, the presence of dendritic Langerhans cells (Lc) and macroph ages, and no significant damage to fibroblasts, collagen framework, an d GAG pattern, except when the tissues had been ischemic for a long ti me. Explanted cusps exhibited (i) early disappearance of endothelium a nd Lc; (ii) nonspecific low-grade inflammatory cell infiltration, most ly of monocytoid type; (iii) viable degree of devitalization of fibrob lasts with persistence of viable cells in some areas in most cusps; an d (iv) fair preservation of collagen framework and GAGs. A is likely t hat, in view of the good graft preservation at implantation, humoral r ejection is responsible for the earlier destruction of the endothelium and dendritic cells and the delayed devitalization of the fibroblasts and that preservation of the collagen framework and other intercellul ar matrix components (glycosaminoglycans) should guarantee longterm gr aft function. (C) 1997 by Elsevier Science Inc.