The Rat Femoral Arteriovenous Fistula Model: Increased Expression of Matrix Metalloproteinase-2 and -9 at the Venous Stenosis

Purpose: To determine whether a femoral arteriovenous (AV) fistula model in a rat was feasible and whether there is increased expression of matrix metalloproteinase (MMP)-2 and -9 and the tissue inhibitors of MMPs (TIMPs) at the venous stenosis of the fistula. Materials and Methods: Fifteen male Sprague-Harley rats weighing 353 g ± 26 underwent creation of an AV fistula between the left femoral artery and ipsilateral femoral vein, with the contralateral femoral vessels serving as controls. The animals were euthanized at day 14 (n = 5) and day 28 (n = 10) after fistula creation. Zymography and Western blot analysis for TIMP-1 and TIMP-2 were performed at the venous stenosis and in control vessels. Hematoxylin and eosin, Verhoeff-van Gieson, Masson trichrome, and α-smooth muscle staining were performed at the stenosis and in controls at day 28 in four animals. The intima/media ratio was determined at day 28. Results: By day 14, pro-MMP-2 measurements were 8.13 ± 1.06 at the venous stenosis and 4.1 ± 1.33 in controls (P < .05). By day 28, they had increased to 18.95 ± 4.8 at the stenosis and 12.11 ± 4.84 in controls (P < .05). By day 14, active MMP-2 measurements were 7.38 ± 1.25 at the stenosis and 2.31 ± 1.04 in controls (P < .05). By day 28, they had increased to 12.12 ± 3.45 at the stenosis and 9.26 ± 3.97 in controls (P < .05). By day 28, pro-MMP-9 measurements were 11.77 ± 4.71 at the stenosis and 7.78 ± 3.49 in controls (P < .05), with no difference at day 14. There was no difference in expression of TIMP-1 and TIMP-2. The average intima/media ratio of the stenosis increased by 28% versus controls, and the neointima was composed of primarily α-smooth muscle actin-positive cells. Conclusions: A rat femoral AV fistula model was created with venous stenosis formation characterized by thickened neointima composed of α-smooth muscle actin-positive cells compared with controls. At the venous stenosis, there was increased expression of pro-MMP-2 and active MMP-2 by days 14 and 28, with significantly increased expression of pro-MMP-9 by day 28.