Inhibition of Local Macrophage Growth Ameliorates Focal Inflammation and Suppresses Atherosclerosis.

Objective Macrophages play a central role in various stages of atherosclerotic plaque formation and progression. The local macrophages reportedly proliferate during atherosclerosis, but the pathophysiological significance of macrophage proliferation in this context remains unclear. Here, we investigated the involvement of local macrophage proliferation during atherosclerosis formation and progression using transgenic mice, in which macrophage proliferation was specifically suppressed. Approach and Results Inhibition of macrophage proliferation was achieved by inducing the expression of cyclin-dependent kinase inhibitor 1B, also known as p27(kip), under the regulation of a scavenger receptor promoter/enhancer. The macrophage-specific human p27(kip) Tg mice were subsequently crossed with apolipoprotein E-deficient mice for the atherosclerotic plaque study. Results showed that a reduced number of local macrophages resulted in marked suppression of atherosclerotic plaque formation and inflammatory response in the plaque. Moreover, fewer local macrophages in macrophage-specific human p27(kip) Tg mice helped stabilize the plaque, as evidenced by a reduced necrotic core area, increased collagenous extracellular matrix, and thickened fibrous cap. Conclusions These results provide direct evidence of the involvement of local macrophage proliferation in formation and progression of atherosclerotic plaques and plaque stability. Thus, control of macrophage proliferation might represent a therapeutic target for treating atherosclerotic diseases.