To determine mechanisms responsible for the reduced calcification in short-term glutaraldehyde (Glu)-treated autologous pericardial bioprostheses, we studied the time effect of Glu on subsequent calcification and differences in calcification of autograft and xenograft implants in a rat subcutaneous implantation model. In experiment 1, four groups of bovine pericardial pieces (1 cm2) were prepared: (A) fresh bovine pericardium without Glu, (B) with 15-minute Glu, (C) with 60-minute Glu, and (D) with 120-minute Glu. Seven young male Sprague-Dawley rats were used; each received four bovine pericardial pieces from group A, B, C, or D for subcutaneous implantation. Calcium content of the implants (μg/mg dry weight) 45 days later was 4.8 ± 2.9, 29.8 ±13.6, 106.3 ±13.7, and 176.3 ± 85.5 in groups A, B, C, and D, respectively (p < 0.05 between any two groups). Experiment 2 used 8 young male Sprague-Dawley rats from different mothers. Each received five subcutaneous skin implants. The five skin implants were prepared as follows: (1) fresh self skin, (2) self skin with 30-minute Glu, (3) self skin with 48-hour Glu, (4) fresh skin of others, and (5) skin of others with 48-hour Glu. After 45 days of implantation the calcium content of the implants was 1.4 ± 1.1, 57.9 5 4, 142.7 ± 61.4, 1.5 ± 1.1, and 94.9 ± 24.1 μg/mg dry weight in groups 1, 2, 3, 4, and 5, respectively (p < 0.05 for 1 versus 2, 3, or 5; 2 versus 3, 4, or 5; 3 versus 4; and 4 versus 5). Neither self nor other skin implants without Glu fixation calcified; however, once treated with Glu calcification developed in both types of implants. In this model, the extent of calcification of bovine pericardial pieces or skin implants was solely Glu fixation time-dependent. Autologous tissues treated with Glu behave biologically like Glu-treated xenogenic tissues there was no difference between them regarding the degree of calcification that makes one preferable to the other. A short duration of Glu fixation of autologous tissue used in valve repair is important to avoid calcification.
Bibliographical noteFunding Information:
Doctor Liao acknowledges the receipt of a research fellowship from the Hearst Foundation. We thank Pablo Bon, Astolfo Leon, and Fred Wasserman for their valuable technical assistance.