Lipid extraction attenuates the calcific degeneration of bovine pericardium used in cardiac valve bioprostheses.

Bovine pericardial bioprostheses frequently fail due to dystrophic calcification. Since (a) recent studies indicate that membrane-associated complexed acidic phospholipids play an important role in the process of both physiologic and pathologic calcification, and (b) cytoplasmic organelles and plasma membrane of interstitial cells seem to serve as initial sites of calcific degeneration of bioprosthetic bovine pericardial tissue, this investigation was undertaken to evaluate whether, and if so, to what extent, the mineralization of valve tissue could be attenuated by previous lipid extraction. Pretreatment of glutaraldehyde-preserved bovine pericardium with acidified sulphuric ether (pH 3.0-4.0) attenuated calcification significantly: 28 days after subcutaneous implantation in young rats the degree of mineral deposition was approximately equal to typical 7 days implants in this model. The mechanism of this beneficial effect is suggested to be due to partial extraction of tissue phospholipids, as demonstrated by electron microscopy, thus reducing the number of available sites for deposition of hydroxyapatite crystals. In addition, and importantly, the present results indicate that any attempt to reduce cardiac valve bioprosthesis mineralization will have to take into account the role of lipids and, particularly, the membranous phospholipids in the calcification mechanism.