Endothelin-converting enzyme expression in the neointima after percutaneous coronary intervention

Smooth muscle cells (SMCs) are the major cellular component of neointimal tissues after percutaneous coronary intervension (PCI). Endothelin-1 (ET-1) is a powerful vasoconstrictor and has a mitogenic effect on SMCs. Endothelin-converting enzyme (ECE) is a key enzyme in the process of ET-1 generation. However, the expression of ECE in association with post-PCI repair processes has not been reported. Thirteen coronary sites after PCI obtained at autopsy and 6 atherectomy specimens obtained from restenotic sites were investigated. Frozen sections were stained with antibodies against ECE, SMCs, macrophages, and endothelial cells. The immunoreactivity of ECE was quantified using computer-aided planimetry. At the early stage after PCI, most neointimal SMCs expressed ECE. The ECE-positive cell area was significantly (p<0.005) larger in the sites within 3 months after PCI than in the sites from 6 months onward. In atherectomy specimens, neointimal SMCs showed distinct ECE positivity. These findings suggest that ECE is upregulated in the neointima at early stages after PCI injury. ECE may be one of the mediators in the repair processes after PCI in humans.