| Objective To make diabetic rat vascular stenosis model.To explore the neointimal formation, the proliferation of vascular smooth muscle cells (VSMC) in neointima, the expression of matrix metalloproteinases (MMPs) and the expression of insulin-like growth factor-1 (IGF-1) in vascular wall in diabetic Wister rats after carotid balloon injury. To investigate the effects of doxycycline on the neointimal formation and to supply the theoretic evidence of for prevention and treatment of restenosis after angioplasty.Methods One hundred healthy male Wistar rat, 200~275g weight, after 1 week's observe, were injected into celiac with 60mg/kg streptozotocin (STZ). Rats whose blood glucose levels were above 16.7mmol/L were taken as diabetic rats after 72 h. All rats were anesthesized with 3% pentobarbital sodium (25mg/kg). The distal left common carotid artery of all animals exposed through a midline wound in the neck. The left common carotid artery was denuded of endothelium by the intraluminal passage of 2 F balloon catheter introduced through the external carotid artery following a 0.014 inch guide wire. The balloon catheter was passed three times with the balloon dilated sufficiently with saline to generate slight resistence. The dilation of balloon also caused the expansion of the carotid itself. The external carotid was ligated after removel of the balloon catheter and the wound closed. The completeness of denudation was conformed by optical microscope and scanning elcctron microscopy on perfusion- fixed specimens. After balloon injury, the rats were randomly divided into two groups: diabetic group (n=24) and group (n=24). Doxycycline 30mg/kg.d was injected into stomach in doxycycline group, and equal capacity of nornal saline injected into stomach in control group. Four rats in eachgroup were killed 24 hours, 4 days, 1 weeks and 2 weeks after balloon injury, all survival rats (8 rats in control group and 8 rats in doxycycline group) were killed 4 weeks after the operation, and common carotid arteries and other samples needed were taken. Blood glucose, lipid, cholesterol. The area surrounded by internal elastic lamina (IEL), area of neointima and vascular lumen, the intimal hyperplasia index, the percentage of lumen stenosis, and the index of lumen stenosis were measured with VIDAS image system. The specimens of common carotid artery tissue was dyed by means of immunohistochemistry to detect PCNA , MMPs and IGF-1 stained positive cells in injured artery wall. The specimens were perfusion-fixed for electron microscopy examination. Tissue total mRNA was abstracted from lOOmg common carotid artery with Trizol reagent, and RT-PCR was performed to observe the expression of MMPs and IGF-1.Results The morphological change were markedly, and VSMC were taken on synthetical phenotype in two groups, and were much severe in doxycycline group. Compared with control group, in doxycycline group the amount of PCNA stained positive cells were increased (PO.01) at 1 week, the IEL was larger (P<0.01),the neointimal area (P<0.01), the intimal hyperplasia index (PO.01) and percentage(P<0.01) were smaller, the vascular lumen area and the lumen stenosis index were larger(PO.Ol) at 4 week, and the expression of MMPs and IGF-1 were decreased respectively at 24h, 4 day, 1 week, 2 week, and the expression level of IGF-1 was persistently reduced till 4 week post balloon injury in injured artery wall (allpO.Ol).Conclusions ?The diabetic rat vascular stenosis model can successfully be made by balloon injury, and the process was easy and practical. ?The reason of the neointimal formation and vascular stenosis was mainly caused by proliferation and migration of VSMC. ?Doxycycline can inhibit VSMC proliferation and prevent the neointimal formation after angioplasty, and the effects of doxycycline maybe mediated by inhibiting the expression of MMPs and IGF-1.
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