EFFECT OF CRYOPRESERVATION AND HISTOCOMPATIBILITY ON TYPE-I PROCOLLAGEN GENE-EXPRESSION IN AORTIC-VALVE GRAFTS

Background: Allograft valves are excellent substitutes for diseased or absent valves but undergo primary tissue degeneration. Fibroblast via bility may determine resistance to valve deterioration. This study eva luated gene expression for procollagen by valve grafts and studied the effects of cryopreservation and histocompatibility on this property, Methods and results: Fresh and cryopreserved rat aortic valves were im planted heterotopically into syngeneic or allogeneic recipients. Nonvi able, cryothermally injured valves were used as negative controls, The grafts and native aortic roots were excised 3 days after implantation , Northern hybridization with a human procollagen alpha(1)(I) compleme ntary DNA probe was used to assess the expression of type I procollage n mRNA, The content of procollagen mRNA relative to 18S ribosomal RNA was evaluated by means of scanning densitometry, In situ hybridization was used to locate the areas of procollagen mRNA expression in the gr afts. Both fresh and cryopreserved grafts exhibited greater expression than the native valve, This increase in expression was observed in bo th syngeneic and allogeneic grafts, but not in the negative control gr oup, In situ hybridization showed a strong signal for procollagen in t he aortic wall and a weak signal in the leaflet and myocardium in the viable grafts and in native tissues, Conclusions: Regardless of preser vation or allogenicity, fibroblast viability in aortic valve grafts pe rsists after implantation, Increased gene expression for procollagen s uggests a capacity for repair and regeneration.