Clusterin regulates vascular smooth muscle cell nodule formation and migration

Vascular smooth muscle cells (VSMC) are the principal cellular component of the blood vessel wall where they exist in a differentiated state to mainta in vascular tone. However, VSMC are not terminally differentiated and can b e induced to dediffentiate, proliferate, and migrate. In fact, smooth muscl e cell migration from the vascular wall into the lumen of the vessel is a c entral feature of occlusive vascular pathologies including atherosclerosis and intimal hyperplasia. In vitro, in the presence of an extracellular matr ix, cultured vascular smooth muscle cells can migrate and invade the underl ying gelatinous matrix, form multicellular nodular aggregations, and secret e the glycoprotein clusterin. Nodular cultures appear to mimic some of the properties of differentiated VSMC, in vivo. Here, to test the hypothesis th at clusterin functions to modulate the formation of VSMC nodules and to fac ilitate cell migration a clusterin negative VSMC clone, SM-CLU13AS (Moulson and Millis, 1999, J Cell Physiol 180:355), was transiently transfected wit h plasmid pRcCMVCLU that contains the full-length porcine clusterin cDNA se quence under control of the CMV promoter The transiently transfected VSMC c ulture expressed and secreted clusterin and formed nodules. To determine if clusterin regulates VSMC migration we used modified Boyden chamber assays. Clusterin, at 10 mug/ml, clearly promotes VSMC migration. In addition, a 1 5 amino acid synthetic peptide, representing aminoacids 118-132 [KQTCMKFYA- RVCRSG] of the mature clusterin polypeptide, inhibits VSMC attachment to ge latinous substrate. Finally, clusterin appears to have a role in regulating endogenous clusterin expression in the clusterin negative clone. These res ults clearly establish that clusterin has functional role in VSMC nodule fo rmation and support the conclusion that clusterin is a critical component o f smooth muscle eel I phenotypic modulation, J. Cell. Physiol. 186:210-279, 2001. (C) 2001 Wiley-Liss, Inc.