Cell replication induces in-stent lesion growth in rabbit carotid artery with preexisting intimal hyperplasia

This study examined the responses of rabbit carotid artery with a preexisting intimal lesion, to stent implantation and balloon dilation. Rabbit carotid arteries were injured with a Fogarty catheter, and 28 days later the same arteries were subjected to implantation of a Palmaz-Schatz stent or balloon dilation angioplasty. Intimal size was significantly increased after stent implantation and balloon dilation, and no significant difference was detected between the two procedures. After stent implantation, replicating intimal cells were increased mainly in the inner intima, and the increase of cell replication was prolonged until day 28. In contrast, a significant increase of intimal cell replication was detected only at 2 days after balloon dilation. Intimal cell number after stent implantation was significantly higher than that after balloon dilation from day 7. Abundant leukocytes adhered to the luminal surface until 14 days after stent implantation, and significant infiltration of macrophages was observed in the mid-intima. Activation of proteases was prolonged, and obvious accumulation of proteoglycans was detected after stent implantation as compared with balloon dilation. These findings suggest that, an increase in cell replication is critical in the development of in-stent restenosis, and that inflammatory responses represent a unique property after stent implantation.