Adventitial cells do not contribute to neointimal mass after balloon angioplasty of the rat common carotid artery

Background-Previous studies suggest that the migration of adventitial cells into the neointima after balloon angioplasty might have an important role in vascular lesion formation. The current experiments were designed to study the migration of adventitial cells in response to mechanical injury of the rat carotid artery. Methods and Results-Adventitial cells were stained in situ with PKH26, a fluorescent dye, after balloon angioplasty of the rat common carotid artery. Animals were killed at different time points, and tissue sections were examined under light and fluorescence microscopy. PKH26-labeled cells were detected exclusively in the adventitia. No labeled cells were present in the media or the neointima at any time point examined. A highly cellular neoadventitial layer composed of myofibroblasts exhibited an extensive proliferative response 3 days after injury over the entire adventitial circumference. Conclusions-Despite the prominent role that adventitial myofibroblasts seem to have in the postangioplasty remodeling process, they do not migrate to the medial or intimal layers in the rat carotid artery angioplasty model.