Increased Expression of Oxidative Stress in Proliferated Vascular Smooth Muscle Cells in Early Stage of Human Restenosis After Coronary Angioplasty

A large body of evidence indicates that oxidative stress has been implicated in the development of restenosis formation after angioplasty in experimental animal models and clinical studies. However, the mechanism by which cells remove oxidative stress as a mediator of restenosis formation in vascular response to balloon-injury remains unclear and data concerning human tissue is lacking. This study was designed to clarify the role of oxidative stress in the process of neointimal hyperplasia formation of human restenosis lesions after coronary angioplasty. We allocated 122 neointimal hyperplasias obtained by directional coronary atherectomy (DCA) from 115 consecutive patients with restenosis into four groups, according to the time interval until restenosis formation after angioplasty. Cellular and matrix components of neointimal hyperplasia were immunohistologically studied among the groups. To gauge proliferative activity of cellular components, active proliferating cells were identified using antibody to proliferating cell nuclear antigen (PCNA) and positive cells were determined by double-label immunocytochemistry with a-actin, CD-68, leukocyte common antigen, Factor VIII and XIII, respectively. To characterize the potential role of oxidative stress in the process of neointimal hyperplasia, we also assessed the effect of 4-hydroxy-2-nonenal (HNE), a component of oxidatively modified lipids, on cellular components of restenosis. Consequently, the subject materials for this study consisted of 7 specimens at 0 to 1 month, 42 at 2 to 3 months, 57 at 4 to 6 months and 16 at 7 to 12 months after angioplasty. Neointimal hyperplasia could be histologically categorized into four morphological types of neointimal vascular smooth muscle cells (VSMCs). Predominant granulative type with large round nuclei of VSMCs and inflammatory cells was observed in 4 (57.1%) of the 7 specimens resected at 0 to 1 month after angioplasty. Granulative and mildly edematous type with medium-sized round nuclei of VSMCs and matrix deposits was found in 18 (42.9%) of the 42 specimens resected at 2 to 3 months. Out of 57 specimens resected at 4 to 6 months, markedly myxoedematous type with stellate-shape nuclei of VSMCs and more profound matrix deposits was predominantly found in as many as 39 (68.4%) lesions than that in other phases. In contrast, at 7 to 12 months, finely collagenized type with atrophic nuclei of VSMCs was detected in 10 (62.5%) of 16 specimens. The mean PCNA (12.6±4.9%) index of VSMCs in the neointima at 0 to 1 month was significantly greater than that at 2 to 3 month (6.7±2.1%) and 4 to 6 month (0.4±0.2%) after angioplasty (p>0.001). Moreover, the large nuclei of VSMCs in the predominant granulative type were strongly positive for HNE immunostaining compared with those of stellate VSMCs in the late phase of myxoedematous type neointima (9.3% vs. 0.1%, p<0.001). In conclusion, these data suggest that oxidative stress could play a pivotal role in proliferation of synthetic VSMCs, which has potential to produce extracellular matrix in development of restenosis early after angioplasty.