Background: Crosstalk between pro-inflammatory cytokines and platelet-derived growth factor (PDGF) regulates smooth-muscle-cell proliferation in cardiac-allograft arteriosclerosis. In this study, we tested the effect of STI 571, a novel orally active protein tyrosine kinase (PTK) inhibitor selective for PDGF receptor (PDGF-R) on transplant and accelerated arteriosclerosis in hypercholesterolemic rabbits.
Methods: Cardiac allografts were transplanted heterotopically from Dutch Belted to New Zealand White rabbits. A 0.5% cholesterol diet was begun 4 days before transplantation. Recipients received STI 571 5 mg/kg per day or vehicle intraperitoneally throughout the study period of 6 weeks. Cyclosporine A was given as background immunosuppression.
Results: In cardiac allografts of vehicle-treated rabbits, 76.2+/-2.1% of medium-sized arteries were affected by intimal thickening, and the percentage of arterial occlusion was 45.0+/-5.0%. Treatment with STI 571 reduced the incidence of affected medium-sized arteries to 41.2+/-8.1% (P <0.05) and the arterial occlusion to 27.6+/-5.0% ( P<0.05). In addition, we observed that STI 571 treatment reduced intimal lesion formation in proximal ascending aorta of transplanted hearts from 72.3+/-19.9 to 12.7+/-1.9 microm ( P<0.05). Our results also show that STI 571 significantly inhibited accelerated arteriosclerosis in medium-sized arteries of recipients' own hearts.
Conclusions: The results of the present study suggest that PDGF-R activation may regulate the development of transplant and accelerated arteriosclerosis in hypercholesterolemic rabbits. Thus, PTK inhibitors may provide new strategies for prevention of these fibroproliferative vascular disorders.