Expressions of PDGF-B and collagen type III in the remodeling of experimental saccular aneurysm in rats

The essential etiologic factors of intracranial berry aneurysm may be the hemodynamic stress on the arterial wall. Vascular remodeling triggered by abnormal hemodynamic stress on the blood vessels may play an important role in the formation, development and rupture of intracranial aneurysms. However, the specific causative mechanisms associated with this remain elusive. In this study, we look for the possible mechanism of platelet-derived growth factor B (PDGF-B) on the pathogenesis of saccular aneurysms in rats. Direct microsurgical destruction of the arterial intima and internal elastic lamina at the bifurcation of the carotid artery was performed in 30 rats to induce saccular aneurysms and the contralateral carotid arteries were ligated in half of them. After 4-5 months, the size of the aneurysms was determined. The expressions of PDGF-B and collagen type III on the walls of the normal carotid arteries and the saccular aneurysms were determined by in situ hybridization and immunohistochemistry. Saccular aneurysms could be induced immediately by destroying the intima and internal elastic lamina at the bifurcation of the carotid artery in rats. Saccular aneurysms grew significantly due to the hemodynamic stress in 4-5 months, and much bigger after the ligation of the contralateral carotid artery which enhanced the hemodynamic stress. There was no PDGF-B expression on the walls of the normal carotid arteries in rats, but it was expressed on the aneurysmal walls and more distinctly with the growth of the saccular aneurysms. However, there was collagen type III expression on the media of the normal carotid artery, but its expression decreased on the aneurysmal walls and further reduced with the growth of the saccular aneurysms. So, PDGF-B may induce the expression of MMP for the degradation of collagen type III on the wall of the saccular aneurysms. This may be one of the important mechanisms on the pathogenesis of the saccular aneurysm.