Vessel size-dependent expression of intermediate-sized filaments, calponin, and h-caldesmon in smooth muscle cells of human coronary arteries.

The arterial media is composed of a heterogeneous population of smooth muscle cells (SMCs). Recently, the properties of SMCs were observed to be heterogeneous not only among individual cells but also among arteries of the same vascular bed. To test the hypothesis that a site-specific heterogeneity exists in the SMCs of human coronary arteries, we examined the expression of desmin, vimentin, calponin, and high-molecular-weight (h-) caldesmon in arteries of various sizes. Specimens of arteries were obtained at autopsy from 12 patients: 6 adults (67 +/- 4 years old); 3 younger adults (26 +/- 2 years old); and 3 neonates. The size of the arteries was estimated by the number of SMC layers of the media. The expression was compared in SMCs of large arteries (>10 layers in adults, >5 layers in neonates), medium-sized arteries (5-10 layers in adults, 3-5 SMC layers in neonates), and small arteries (<3 layers). In adults, the percentage of arteries positive for desmin was lower in the small (17% +/- 3%) and medium-sized arteries (44% +/- 12%) than in the large arteries (94% +/- 6%) (P < 0.01). The percentage of arteries positive for calponin was also lower in the small (18% +/- 2%) and medium-sized arteries (66% +/- 5%) than in the large arteries (100%) (P < 0.01). The percentage for vimentin and h-caldesmon did not differ among large, medium-sized, and small arteries. These observations in adults were similar to those in younger adults or neonates. The phenotypes of medial SMCs are vessel size-dependent in human coronary arteries. This finding should be important for understanding the site-specific characteristics of vascular function in the regulation of myocardial perfusion or those of vascular responses to environmental changes.