ACIDIC GLYCOPROTEINS ACCUMULATE IN CALCIFIED AREAS OF BIOPROSTHETIC TISSUE

Background and nim of the study: This study was performed to evaluate the role of collagen fibrils, cellular elements and matrix proteins in calcification of glutaraldehyde (GA)-fixed bioprosthetic material. Me thods: Lyoplant(R) (lyophilized bovine pericardium, type I collagen) w as processed according to three protocols. DF-group (double fixation): after conventional fixation in GA (0.5% for 72 h; storage 0.25%) Lyop lant was implanted subcutaneously into rats for 5 days. Specimens were explanted and re-fixed (conventional fixation), followed by autologou s or homologous reimplantation in rats for 21 or 63 days. CF-group (co nventional fixation): Lyoplant patches were conventionally fixed (as D F-group), kept in 0.9% saline for one week, and then autologously and homologously reimplanted. GF-group (high-concentration GA): Lyoplant p atches were processed (as GF-group) but 0.5% GA was used for tissue st orage. Explanted specimens were studied by light microscopic histochem istry; calcium contents were measured by atomic absorption spectroscop y. Results: Severe calcification occurred in the DF-group without diff erences between autologous and homologous reimplantation. In CF-and GF -groups, calcification was negligible, but immunologic response agains t homologous implants was accompanied by increased calcium content. Hi stologic characterization of matrix material in calcified areas reveal ed oxyphilic glycoproteins, identified as sialoglycans. Conclusions: M odification of extracellular matrix by GA is assumed as essential to c ause calcification of bioprosthetic material. Calcium deposition and a ccumulation of sialoglycans are simultaneous events. A specific role o f this glycoprotein for calcification has to be considered.