Three Phases of Vascular Smooth Muscle Cells in Cerebral Aneurysms: Early Hyperproliferative, Intermediate Dedifferentiated & Late Hypoproliferative

Vascular smooth muscles play a vital role in the growth and propagation of cerebral aneurysms. These highly dynamic cells, characterized by a high degree of plasticity, show structural and functional modifications in response to external environmental influences. Following sustained endothelial injury, vascular smooth muscles avail a new functional capability characterized by proinflammatory, and promatrix remodeling abilities, losing the normal contractile and synthetic ability. Switching of differentiated vascular smooth muscle cells into undifferentiated inflammatory vascular smooth muscle cells followed by eventual apoptosis decreases the production of collagen, a vital component of the structural matrix, rendering the vessel wall less responsive to cyclical hemodynamic pressure swings and more susceptible to aneurysmal dilatation and rupture. The goal of this review is to understand the structural and functional modifications that vascular smooth muscle cells undergo during the natural course of cerebral aneurysm formation with a particular focus on the contributory molecular mechanisms