Characterization of the recruitment of intimal smooth muscle cells in vascular disease

Abstract

Intimal hyperplasia occurs as a response to a variety of vascular insults and results in vascular stenosis, and organ ischemia. This process represents a fundamental component of atherosclerosis, venous graft stenonsis, and allograft arteriopathy in solid organ transplants. Smooth muscle cells (SMCs), and their associated extracellular matrix (ECM) form major components of intimal hyperplasia. We hypothesize that chemokines play a critical role in SMC migration into such intimal lesions. A number of chemokine-chemokine receptor interactions that mediate inflammatory cell recruitment have been characterized. However, the specific chemokine- chemokine receptor pathways that contribute to SMC recruitment are not known. The aims of this study are to examine the expression of C-C chemokine receptor 1 (CCR1) on medial SMCs (MSMCs), and to test its functionality in SMC recruitment. SMCs were derived from murine aortas; cultures were >95% SMC as demonstrated by the expression of smooth muscle α-actin (SMA), calponin, smooth muscle myosin heavy chain (SM-MHC). Interferon-gamma (IFN-γ) and Tumor necrosis factor- alpha (TNF-α) - stimulated MSMCs express CCR1 with a peak expression between 30 h and 48 h after cytokine stimulation. The functionality of receptors was initially demonstrated by agonist-induced calcium mobilization: the addition of CCR1 ligands, Regulated on activation, Normal T cell expressed and secreted (RANTES) and Macrophage inflammatory protein -1α (MIP-1α) to MSMCs caused an increase in intracellular Ca2+ concentration. Blockade of CCR1 by BX471, a CCR1 antagonist, inhibited the Ca2+ mobilization induced by RANTES and MIP-1α. The results suggest that up-regulation of CCR1 expression on cytokine-stimulated SMCs may facilitate recruitment into intimal lesions through endothelial-derived chemokine expression.