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In vitro endothelialization of bioprosthetic heart valves
1Department of Cardiac Surgery Grosshadern Medical Center, University of Munich, Germany.
Background And Aims Of The Study:
The main disadvantage of xenograft bioprosthetic heart valves is limited durability due to tissue degeneration.
Methods:
To study possible alternatives to conventional bioprosthetic heart valves, glutaraldehyde preserved porcine aortic valve leaflets were precoated with fibronectin-heparin and acidic fibroblast growth factor (aFGF) to enhance cell proliferation. Furthermore, different methods of storage and preservation (1.0% benzoic acid, 1.0% sorbic acid, 0.05% and 0.5% dialdehyde starch) were compared to conventional preservation procedures. Valve leaflets were lined with adult human saphenous vein endothelial cells (1.0 x 10(4) AHSVEC/cm2). The different methods of preservation were compared to leaflets precoated additionally with 1.0 microgram/cm2 aFGF protein, derived from gene manipulated bacteria. Endothelial growth kinetics were studied and verified by an increase of activation following 3H-thymidine incorporation, while the maintained metabolic cell activity was demonstrated by prostacyclin (PGI2) release measurements. In subsequent experiments in vivo degeneration and mineralization were determined by subcutaneous implantation in rats for up to 40 days.
Results:
Our results favored alternatively treated valve leaflets; endothelial cells grew to persistent monolayers in six to 12 days in contrast to conventional processed leaflets where no endothelial cell growth was possible. Atomic absorption spectroscopic assessment of subdermal valve implants showed significantly lower contents of calcium, magnesium and phosphate in alternatively treated leaflets. Furthermore, precoating of alternatively preserved valve leaflets with aFGF protein and endothelial cells improved in vitro and in vivo results significantly.
Conclusions:
Our study shows that endothelial cell growth as well as significantly reduced in vivo degeneration and mineralization of valve leaflets may be feasible if bioprosthetic heart valves are processed according to alternative, non-toxic conservation procedures and are precoated with angiogenic growth factor protein.