Expression of lumican in thickened intima and smooth muscle cells in human coronary atherosclerosis.

Lumican is a member of a small leucine-rich proteoglycan family. Members of this family play an important role in cell migration and proliferation during embryonic development, tissue repair, and tumor growth. Lumican is reported to be overexpressed during the wound-healing process in the cornea and ischemic and reperfused heart. Recently, we found that lumican mRNA and its protein are expressed in cultured vascular smooth muscle cells (VSMCs) from the rat aorta. However, the expression and role of lumican in human atherosclerotic tissues are not clearly elucidated. In the present study, we aimed to clarify whether lumican is expressed in VSMCs and its localization in human coronary atherosclerotic tissues. The lumican protein and its mRNA were expressed in a small number of VSMCs in the media of normal coronary artery, but the lumican protein was not localized in the medial stroma. In contrast, the lumican protein and its mRNA were expressed in most of VSMCs that migrated into the thickened intima, but not in infiltrating foamy macrophages. The lumican protein was prominently localized in the thickened intimal stroma. The lumican protein and its mRNA were also expressed in VSMCs in the inner layer of the media and its protein was localized in medial stromal tissues. These findings indicate that the lumican protein is mainly synthesized by intimal and medial VSMCs in coronary atherosclerosis and that lumican contributes to collagen fibrillogenesis of coronary atherosclerosis.