Protein adsorption of calcified and noncalcified valvular bioprostheses after human implantation

Background. The incidence of calcification of porcine valve bioprostheses shows important, and as yet unexplained, variations. Previous studies by others showed that osteopontin and osteocalcin are expressed in calcified porcine valve bioprostheses. However, no study has yet explored other proteins that could also be involved. Methods. Twelve porcine valve bioprostheses were retrieved from 12 patients and were separated into two groups. Group 1 (n = 6) had early calcification after 4 to 9 years (mean, 6 +/- 2.3 years). The mean age of the patients at the time of implantation was 46 +/- 9 years. Group 2 (n = 6) had no calcification after 8 to 14 years (mean, 12 +/- 2.8 years). The mean age was 47 +/- 13.4 years. These valves were analyzed by electrophoresis, and the bands were quantified by densitometry. Results. A 14-kd protein showed a 50% increase in the calcified group. A 31-kd protein found in the calcified group was not detected in the noncalcified group. Three other proteins (45, 39, and 28 kd) showed reduced adsorption in the calcified group. Conclusions. Important differences were found in the proteins adsorbed in calcified and noncalcified bioprostheses after implantation in patients. Besides osteopontin and osteocalcin, several other proteins may play a role in the process of calcification of valvular bioprostheses. (C) 2001 by The Society of Thoracic Surgeons.