FORMATION OF MYOINTIMAL HYPERPLASIA AND CYTOKINE PRODUCTION IN EXPERIMENTAL VEIN GRAFTS

Background. The purpose of this study was to determine the correlation between progression and regression of myointimal hyperplasia (MH) and cytokine production in experimental vein grafts. Although the autolog ous vein is the best suitable bypass conduit for reconstruction of per ipheral arteries, at the end of the first year thrombosis in the coron ary and lower extremity circulation ranges from 20% to 50%. Many of th ese failures are caused by MH. Methods. In 76 inbred Lewis rats, a 1 c m long segment of inferior vena cava was inserted at the level of the abdominal aorta. The segments of inferior vena cava were obtained from syngeneic Lewis rats. In 56 animals the arterial vein graft was expla nted 3 days (n = 10), 7 days (n = 10), 4 weeks (n = 26), and 12 weeks (n = 10) after operation. In 20 animals the vein graft was explanted 4 weeks after being in the arterial system and reimplanted as iliac ven ovenous bypass in syngeneic Lewis rats. These grafts were explanted 2 weeks (n = 10) and 8 weeks (n = 10) later Grafts were analyzed by ligh t and electron microscopy, morphometric study, and histochemical analy sis an were put in an organ culture to assess cytokine production. Res ults. We observed MH formation in arterial vein grafts and MH regressi on in reimplanted vein grafts (p < 0.001). MH formation was correlated with production of platelet-derived growth factor; basic fibroblast g rowth factor interleukin-1, and tumor necrosis factor-alpha. MH regres sion was correlated with transforming growth factor-beta(1) production . Conclusions. On the basis of the results of our study, we conclude t hat MH formation in experimental vein grafts depends on production of platelet-derived growth factor basic fibroblast growth factor, interle ukin-1, and tumor necrosis factor-alpha, and MH regression depends on transforming growth factor-beta(1) production. Cytokine therapy may re present a valuable new treatment to prevent vein bypass failures cause d by MH.