Glutaraldehyde-Fixed Bioprosthetic Heart Valve Conduits Calcify and Fail From Xenograft Rejection

TLDR

Glutaraldehyde fixation reduces but does not eliminate antigenicity of bioprosthetic valves, so rejection with dystrophic calcification may cause early failure, especially in young, immunocompetent patients. The study aimed to determine whether glutaraldehyde‑fixed xenograft valves undergo rejection and whether this correlates with calcification. Young rats received 20‑day transplants of fresh or 48‑hour glutaraldehyde‑fixed ascending aortas/valves from syngeneic rats or xenogeneic guinea pigs, with a steroid‑treated xenogeneic subgroup; inflammation was blindly scored and T‑cell/macrophage infiltration and IgG levels quantified. Glutaraldehyde‑fixed xenografts exhibited over threefold valve inflammation, tenfold T‑cell/macrophage infiltration, and threefold antibody rise compared to controls; adventitial inflammation was doubled; steroids reduced inflammation and antibody; media/adventitia inflammation and macrophage infiltration predicted calcification, confirming cellular/humoral rejection drives secondary calcification.

Abstract

Glutaraldehyde fixation (G-F) decreases but likely does not eliminate the antigenicity of bioprosthetic heart valves. Rejection (with secondary dystrophic calcification) may be why G-F xenograft valves fail, especially in young patients, who are more immunocompetent than the elderly. Therefore, we sought to determine whether rejection of G-F xenograft occurs and to correlate this with graft calcification.Ascending aortas/valves (from rats [syngeneic] or guinea pigs [xenogeneic]) were transplanted (fresh or after 48 hour of G-F) into the infrarenal aortas of young rat recipients for 20 days. A xenogeneic group was also treated with steroids until graft harvest. The valves and media/adventitia were scored blindly for inflammation (0 to 4). Percent graft infiltration by T cells/macrophages was determined (immunohistochemistry), and rat IgG ELISAs were performed. There was >3 times more valve inflammation, >10 times more valve T-cell/macrophage infiltrate, and >3 times antibody rise in the G-F xenogeneic groups compared with the fresh syngeneic or the G-F syngeneic groups (P<0.05). There was >2 times more adventitial inflammation and T-cell/macrophage infiltrate in the xenogeneic groups (P<0.05). Steroid treatment decreased inflammation and antibody rise in the xenogeneic groups (P<0.05). Correlation analysis revealed media/adventitia inflammation (P=0.02) and percent macrophage (P=0.01) infiltration to be predictors of calcification.G-F xenografts have cellular/humoral rejection and calcify secondarily.