Ultrastructural changes in re-endothelialized and non-endothelialized rabbit aortic neo-intima following re-injury with a balloon catheter.

The response by normal rabbit aortas to the removal of the endothelium with a balloon catheter, was compared to the response to the removal of regenerated endothelium from rabbit aortas that had been previously de-endothelialized. De-endothelialization results in the formation of a neo-intima. Thrombus formation following a second balloon catheter injury was compared among injured neo-intima that had been re-endothelialized, non-re-endothelialized neo-intima, and the subendothelium of normal vessels following a single injury. Rabbit aortas were examined by scanning electron microscopy of full circumference segments of the aorta and by transmission electron microscopy. Thirty minutes after a single de-endothelialization injury with a balloon catheter the luminal surface is covered by a monolayer of platelets adhering to the subendothelial connective tissues. Two weeks later there is neo-intimal formation and endothelial regeneration around branch vessel orifices. The remainder of the luminal surface is composed of smooth muscle cells (SMC). A balloon catheter injury to a vessel injured 2 weeks previously results in fibrin formation and platelet-fibrin microthrombi on the aortic intimal surface. The response of the aortic wall to re-injury does not seem to be related to the prior existence of endothelium. Both single and repeated injuries result in a distribution of formed elements which may depend, in part, on haemodynamic factors.