The synergistic effect of hypercholesterolemia and mechanical injury on intimal hyperplasia.

In an attempt to clarify data obtained from animal models of intimal hyperplasia, we used New Zealand white rabbits, a standardized balloon catheter injury model, and a 0.25% cholesterol supplemented diet. The effects of mechanical injury and hypercholesterolemia separately and combined were determined at the carotid and iliac positions at 12 weeks. En-face planimetry of lesioned intima and measurement of transverse intima-to-media thickness were taken as indices of intimal hyperplasia. No animals received antiplatelet agents or postoperative anticoagulation and all vessels remained patent. Neither procedure alone resulted in statistically significant lesion increase. However, combinations of injury and cholesterol resulted in statistically significant and synergistic lesion enhancement. The quantitative data, coupled with distinctive features noted on scanning electron microscopy and transmission electron microscopy, showed separate and synergistic effects of mechanical injury and cholesterol diet on intimal lesions in this model. Additionally, these effects must be considered in evaluation of animal models of intimal hyperplasia and atherosclerosis. Furthermore, this may help dissect mechanisms of failed revascularizations.