Background: This study was conducted to investigate the impact of the preservation method of bioprosthetic heart valve materials on calcification rates and biocompatibility of the biologic tissue.
Methods: In subcutaneous rat implants, conventionally preserved bioprosthetic heart valve material was compared with bovine pericardium that was treated with L-glutamic acid to reduce residual glutaraldehyde released from the fixed tissue. Both these methods were compared with bovine pericardium that was stabilized by a dye-mediated photooxidation reaction without glutaraldehyde. Biocompatibility of these biomaterials was tested in vitro using human endothelial cell cultures.
Results: Conventionally preserved bovine pericardium with a high amount of glutaraldehyde incorporated into the tissue resulted in severe calcification 63 days after subcutaneous implantation in rats (165.4 +/- 20 mg Ca2+/g dry weight). Postfixation treatment with L-glutamic acid, which reduces free, unbound aldehyde groups, showed a significant decrease in calcification (89.6 +/- 14 mg Ca2+/g dry weight). Glutaraldehyde-free preservation by dye-mediated photooxidation showed no calcification after 63 days of subcutaneous implantation (1.0 +/- 0.4 mg Ca2+/g dry weight). Regular endothelial cell proliferation was observed on photooxidized and L-glutamic acid-treated tissue, whereas conventionally treated tissue caused endothelial cell death.
Conclusions: This study underlines the detrimental role of glutaraldehyde in the calcification process of bioprosthetic heart valve materials and emphasizes alternative preservation methods that reduce or avoid the use of glutaraldehyde.