ENDOTHELIALIZATION OF CARDIAC-VALVE BIOPROSTHESES

The main disadvantage of implanted xenograft valves used in cardiac su rgery is their poor clinical long-term result, due to early tissue deg eneration. In order to improve the performance of such glutaraldehyde fixed bioprostheses, a biological coating with viable endothelial cell s was suggested. Therefore, glutaraldehyde preserved bovine pericard p atches, as well as commercially available xenograft valves, were lined using human venous endothelial cells or microvascular cells from the subcutaneous fat tissue. Before cells were transplanted into their new environment, grafts were treated with an amino acid solution in order to neutralize the cytotoxic effect of free aldehydes, and precoated w ith fibronectin-heparin and basic fibroblast growth factor (bFGF) or e ndothelial cell growth supplement (ECGS) in order to enhance cell prol iferation. Coated specimens were kept in culture conditions for a furt her seven days. Proliferation of transplanted cells was verified by an increase of activation following H-3-thymidine incorporation, while t he maintained metabolic cell activity was demonstrated via Prostacycli ne (PGI(2)) measurement. Morphology was evaluated by means of scanning electron microscopy (SEM). As evaluated by the beta-Counter, 7 ng/ml bFGF (288,727 +/- 39,668 counts on day 4) substantially enhanced cell proliferation after seeding, opposed to the stimulation with 30,000 ng /ml ECGS (91,924 +/- 1129 counts on day 4), (p<0.001). The PGI(2) rele ase of transplanted cells was stimulated with 25 mu M Na arachidonic a cid by the factor 2.6 +/- 0.3 and inhibited with 5 mM acetylsalecylic acid by the factor 0.7 +/- 0.2 on day 4 when compared with the basic l evel. After seven days of cultivation, SEM observation revealed that s pecimens stimulated with bFGF showed areas of confluent coated leaflet s with an even distribution of cell layer. We therefore conclude that proliferation of transplanted cells is most favorable when stimulated with bFGF and that a special treatment of GA preserved cardiac valve b ioprostheses allows a vital biological coating with human endothelial cells.