Cold ischemic injury and donor-recipient MHC disparity significantly increase post-transplant cardiac graft coronary arteriosclerosis

Introduction: The effects of cold ischemic preservation and degree of donor-recipient histoincompatibility on graft coronary arteriosclerosis(GCA)were examined using a rat heterotopic cardiac transplant model. Methods: Three donor-recipient rat strain combinations were utilized. Lewis-F344 rats which vary slightly in class I Major Histocompatibility (MHC) Loci genes, ACI-Lewis which vary significantly in MHC class I and II genes, and Lewis-Lewis (control), donor-recipient strain combinations were subjected to varying lengths of cold ischemic preservation prior to transplantation(0, 4, and 24h in University-of-Wisconsin solution at 4’C).There were 9 rats per group.Grafts were harvested at 90 days post-op. and sections of the epicardial arteries were examined (H&E and van Gieson elastin stains).Intimal area ratio (IAR = intimal area/area within internal elastic lamina), intimal thickness score (ITS-based on % luminal compromise, perimeter of involvement), and rejection score (RS) were determined for each specimen using computerized image morphometry. Results: IAR, ITS and RS were significantly higher at 24hrs vs. 0hrs (p ∗ . IAR (hr) LEW-LEW (%) LEW-F344 ∗ (%) LEW-ACI ∗ (%) 0 0.38 ± 0.15 0.33 ± 0.16 0.57 ± 0.16 4 0.34 ± 0.11 0.42 ± 0.21 0.72 ± 0.29 24 0.41 ± 0.18 0.63 ± 0.14 ITS (hr) 0 0.36 ± 1.00 0.67 ± 0.84 2.00 ± 1.40 4 0.14 ± 0.29 0.82 ± 0.94 2.80 ± 2.10 24 0.91 ± 0.91 1.90 ± 0.87 RS (hr) 0 0.11 ± .33 3.30 ± 0.89 3.10 ± 1.4 4 0.56 ± .88 3.80 ± 0.71 5.00 ± 0.0 24 1.10 ± 1.4 4.50 ± 0.53 4.40 ± .71 ∗ p Conclusions: GCA is significantly increased by greater MHC disparity and longer cold ischemic times. GCA may be caused by an Immune-mediated antigen dependent vasculopathy secondary to histoincompatability. In the control group, longer cold ischemic times did not have a significant effect on GCA, suggesting that better histocompatibility may mitigate the adverse effects of longer ischemic times.