Abstract
Migration of medial smooth muscle cells (mSMC) into the intima is one of pivotal phenomena in atherogenesis. It is crucial for the migration of mSMC to be released from the extracellular matrix surrounding them by proteases. We have identified that the migrating cells after balloon injury express elastase II mRNA by in situ hybridization.
Endothelial cells, some mSMC and adventitial fibroblasts of the carotid artery and aorta in intact rats expressed elastase II mRNA. After balloon injury, the number of mSMC expressing elastase II mRNA increased obviously, in a biphasic pattern with peaks at 12 hours and 3 days after the injury. BrdU-labeled mSMC and the migrating cells expressed strongly elastase II mRNA. Internal elastic laminae adjacent to the migrating cells which expressed elastase II mRNA were ruptured. Under a transmission electron microscope, the migrating cells were characterized by a synthetic phenotype. Elastic fibers and collagen fibers in the media were reduced resulting in decreased c ntact plaques of mSMC with elastic fibers. This study suggested that elastase synthesized by mSMCs plays an important role in neointima formation after balloon-injury.
