A Novel Rat Model of Carotid Artery Stenting for the Understanding of Restenosis in Metabolic Diseases

Abstract

The effects of risk modifiers such as diabetes, obesity and hypertension on vascular healing after stent deployment are largely unknown, because of a lack of an appropriate animal model to study. Since many inbred strains of rats expressing these phenotypes are available, we validated a carotid artery model of in-stent restenosis in the rat. A detailed histomorphometric analysis was performed on 2-cell Multi-Link^TM stents (1.5 × 5 mm) deployed in the common carotid artery of male Wistar rats. Early focal thrombus formation around stent struts with adherent leukocytes was evident by day 3. The number of ED-1-positive macrophages was maximal by day 7 and declined markedly thereafter. Neointimal cell proliferation peaked by day 7 (19.3 ± 6.9) and progressively decreased to <2% by day 60. By day 14, neointimal area was significantly increased (0.39 ± 0.03 vs. 0.18 ± 0.05 mm² at day 7, p = 0.003) characterized by an enhanced number of α-actin-positive smooth muscle cells surrounded by extracellular matrix rich in versican and hyaluronan. At day 28, neointimal area was maximal accompanied by an appreciable decrease in the staining intensity for hyaluronan and versican. By day 60, neointimal area decreased significantly (0.28 ± 0.04 vs. 0.45 ± 0.07 mm² at day 28, p = 0.04) independent of a change in cell density. This regression phase was accompanied by a marked increase in elastin fibrils and collagen type I. In summary, vascular healing following carotid artery stenting in the rat parallels that of larger animals; however, it is accelerated relative to humans.

Increased In-Stent Stenosis in ApoE Knockout Mice

“…We have developed and validated a model which fulfils these criteria but also provides the advantage of investigating the role of key genes through transgenic and knockout technology. Importantly, the time course of neointimal hyperplasia in the present study is similar to that found in rat, [15][16][17] rabbit, 18 -20 and pig models. 13,[21][22][23] In the present study, 1 day after stenting the luminal surface showed a predominance of surface-adherent leukocytes and platelets.…”

Versican Degradation and Vascular Disease

“…Furthermore, it would enable the physician to treat the population of patients (up to 30%) who actually develop a problem with stenosis or restenosis. Of particular interest from the perspective of this review, a consistent feature of acute intimal hyperplasia is the increased content of versican (Nikkari et al 1994, Finn et al 2002, Kenagy et al 2005, Chung et al 2002, Farb et al 2004. Therefore, understanding the mechanisms of intimal regression and the role of versican in this process is of great interest.…”

“…Like angioplasty, stent placement also initially stimulates intimal hyperplasia in animal models and human arteries. Intimal atrophy occurs spontaneously in stented arteries after 6 months in humans (Asakura et al 1998) and 2 months in rats (Finn et al 2002, Langeveld et al 2004. At these late times during regression, the extracellular matrix (ECM) shows a relative loss of versican and a gain of collagen compared to earlier times (Chung et al 2002, Finn et al 2002, Langeveld et al 2004, Farb et al 2004.…”

“…At late times, SMCs proliferate near the endothelial cells of the lumen (Berceli et al 2002, Inoue et al 2002. Finally, the neointima formed has a versican-rich matrix (Inoue et al 2002, Finn et al 2002.…”

“…Recent reviews have focused on the role of versican generally and, more specifically, in vascular disease (Wight 2002, Wight andMerrilees 2004). For example, synthesis and deposition of versican in the extracellular matrix are acutely increased in the neointima after arterial injury caused by angioplasty, stents, or grafting (Nikkari et al 1994, Finn et al 2002, Kenagy et al 2005, Chung et al 2002, Farb et al 2004, Wight et al 1997, Matsuura et al 1996. In addition, there is selective accumulation of versican at the plaque thrombus interface in eroded human atherosclerotic plaques, suggesting a role for this proteoglycan in thrombosis ).…”