Periodate-mediated glycosaminoglycan stabilization in bioprosthetic heart valves

Bioprosthetic heart valves (BPHVs) derived from glutaraldehyde-crosslinked porcine aortic valves are frequently used in heart valve replacement surgeries. However, the majority of bioprostheses fail clinically because of calcification and degeneration. We have recently shown that glycosaminoglycan (GAG) loss may be in part responsible for degeneration of glutaraldehyde-crosslinked bioprostheses. In the present studies, we used a mild reaction of periodate-mediated crosslinking to stabilize glycosaminoglycans in the bioprosthetic tissue. We demonstrate the feasibility of periodate reaction by crosslinking major components of extracellular matrix of bioprosthetic heart valve tissue, namely type I collagen and hyaluronic acid (HA). Uronic acid assay of periodate-fixed HA-collagen matrices showed 48% of HA disaccharides were bound to collagen. Furthermore, we show that such reactions are also feasible to fix glycosaminoglycans present in the middle spongiosa layer of bioprosthetic heart valves. The periodate reactions were compatible with conventional glutaraldehyde crosslinking and showed adequate stabilization of extracellular matrix as demonstrated by thermal denaturation temperature and collagenase assays. Moreover, uronic acid assays of periodate-fixed BPHV cusps showed 36% reduction in the amount of unbound GAG disaccharides as compared with glutaraldehyde-crosslinked cusps. We also demonstrate that calcification of BPHV cusps was significantly reduced in the periodate-fixed group as compared with the glutaraldehyde-fixed group in 21-day rat subdermal calcification studies (periodate-fixed tissue Ca 72.01 +/- 5.97 microg/mg, glutaraldehyde-fixed tissue Ca 107.25 +/- 6.56 microg/mg). We conclude that periodate-mediated GAG fixation could reduce structural degeneration of BPHVs and may therefore increase the useful lifetime of these devices.