Inhibitory effect of methylene blue-induced photooxidation on intimal thickening of vein graft

Background. We have previously speculated that methylene blue-induced photooxidation of adventitial surface for 5 minutes can completely inhibit the intimal and medial growth of surgically prepared saphenous vein in vitro. In this study, inhibitory effect of methylene blue-induced photooxidation on intimal thickening of vein graft in vivo was investigated. Methods. Jugular vein grafts were photooxidized in 0.01% methylene blue solution for 5 minutes, and interposed into arterial circulation for 4 weeks in rabbits. Vein grafts were studied by morphometry and immunohistochemistry. Results. The intimal thickening of photooxidized vein grafts were suppressed significantly compared with those in the nonphotooxidized group. Proliferated cell nuclear antigen (PCNA) index (total PCNA-positive cells/total cell count × 100%) of vein graft was significantly higher in the nonphotooxidized group than those in the photooxidized group. Conclusions. Methylene blue-induced photooxidation is effective in the inhibition of intimal thickening of vein graft interposed in the arterial circulation for 4 weeks in vivo.