Infection Of Wall Shear Stress To Rat's Abdominal Aortic Caliber And Matrix Metalloproteinases-9 Expression

Objective: To observe the expression of MMP-9 and the arterial caliber change in conditions that local arterial wall sheer stress is elevated and analyse the relationship between high shear stress and arterial remodling.Methods: 48 S-D rats were divided into 4 experiment and 4 comparison groups averagely at radom, During the operation of the experiment groups, An infra-renal aortocaval fistula was construsted by needle puncture using a 22-G needle.The aorta proximal to the fistula was harvested after 1 day,7 days, 14 days and 28 days respectively,while sham operations were done in the comparison groups.The diameters of the aorta were measured after fistula made and before harvest.The internal perimeter and wall thickness were measured by computer skills.The level change of MMP-9 was observed by immunohistochemistry and computer skills.Results: The diameters and the internal perimeters were enlarged in the 1day group at the sacrifice time (p<0.05),and the value was growing with the time ;Meanwhile, wall thickness were decreased with the time. Large amount of inflammatory cells soakaged the hemal wall,and endothelial cells and internal elastic lamina were destructed with the time,Stastics of all the result showed that MMP-9 had reached the peak value in the 7days group(p<0.01) ,and remained a high level expression continually.Conclusions: when shear stress increases, the diameters of arteries increase by company of wall thickness decrease; the expression of MMP-9 up-regulates and gets a top in 7 day after operation ;the enlargement of the aorta and the decrease of wall thickness has a close relationship with the continuous expression of the MMP-9;and MMP-9 may be involved in the flow induced arterial remodling.