Calcification of Rat Valve Allografts

Scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDS) have been used to quantify calcium deposition in bioprosthetic valves. To further characterize the calcification process as it pertains to allograft valve tissue, two models of tissue valve implantation were used. The first model used subcutaneous implantation of glutaraldehyde-preserved allogeneic aortic and pulmonary valve leaflets. The second model used syngeneic or allogeneic fresh aortic valve grafts implanted heterotopically into the abdominal aorta of recipient rats. Reference light microscopy was used to select sections for SEM and EDS. In the subcutaneous model, calcium content in both the pulmonary and aortic valves increased up to three weeks, followed by a plateau. The pulmonary leaflets showed greater calcium content than aortic leaflets. In the heterotopic implantation study, calcification occurred to a significantly greater degree in the allogeneic than in the syngeneic valves. This technique may be useful in analyzing the factors that contribute to deterioration of bioprosthetic and allograft valves

Effect of Immunological Differences on Rat Aortic Valve Allograft Calcification

Calcification may be a cause of allograft valve degeneration. To determine whether immunological differences between donor and recipient affect the degree of calcification that occurs, adult Lewis rats received aortic valve allografts transplanted heterotopically into the abdominal aorta. All valves were transplanted immediately after harvest. The valves were not exposed to antibiotics or albumin before insertion. Valve donors were of the Lewis (syngeneic), F344 (weakly allogeneic, RT1 compatible, non-RT1 incompatible), LBN F1 (moderately allogeneic, one haaplotype identical, one haplotype incompatible at the RT1 and non-RT1 loci), and Brown Norway (strongly allogeneic, RT1 and non-RT1 incompatible) strains. Valves were harvested 3–12 weeks following transplantation. Scanning electron microscopy and energy dispersion x-ray microanalysis were performed on one leaflet of each valve to evaluate calcium content. Calcium content expressed in counts (mean ± standard error) according to donor strain were: Lewis, 1642 ± 233; F344, 4853 ± 1412; LBN F1, 4714 ± 823; and Brown Norway, 4358 ± 835. Significant differences (p < 0.05) existed between valves from Lewis donors and those from each other strain. No differences among the other strains were statistically significant. It is concluded that syngeneic valve allografts calcify less than allogeneic grafts. However, the degree of allogenicity did not influence the magnitude of calcification.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72976/1/j.1540-8191.1992.tb00776.x.pd