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 stud y the migration of adventitial cells in response to mechanical injury of th e rat carotid artery. Methods and Results-Adventitial cells were stained in situ with PKH26, a fl uorescent dye, after balloon angioplasty of the rat common carotid artery. Animals were killed at different time points, and tissue sections were exam ined under light and fluorescence microscopy. PKH26-labeled cells were dete cted exclusively in the adventitia. No labeled cells were present in the me dia or the neointima at any time point examined. A highly cellular neoadven titial layer composed of myofibroblasts exhibited an extensive proliferativ e 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.