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[Healing process of high porous EPTFE graft wrapped in the omental pedicle flap--experimental study of portal vein replacement].

This study investigates the healing process of high porous EPTFE graft wrapped in the omental pedicle flap. One way to provide good pseudointima is to use grafts with more porosity which allows increased cell infiltration into the inner capsule, and it is facilitated more by using grafts wrapped in the omental pedicle flap. We implanted two kinds of grafts at the portal veins of mongrel dogs. They are 60 microns fibril length EPTFE grafts, one with its outer surface covered by fluoridized rubber. (F-EPTFE graft), and the other without the covering (EPTFE graft). Grafts were extirpated and examined the implanted grafts at 1, 2, and 4 weeks after the implantation. We were seen on both grafts the developments of organization at the inner capsules, mainly from the anastomotic lines toward the midportion of the grafts. In addition, some developments of organization from outer side to inner side of the capsules were also seen. Light microscopy demonstrated endothelial lining at parts of insides of both grafts after 4 weeks with Factor-VIII staining. EPTFE grafts showed more developments of organization than F-EPTFE grafts and the degree of organization correlated with the degree of cell infiltration into the graft wall. The thickest pseudointima was found with the F-EPTFE grafts examined two weeks after the implantation. These results suggest that the cell infiltration into the graft wall facilitates the organization of inner capsules. We also investigated the expression of TGF-beta, which was potent cytokine that promote fibrosis by enhancing the synthesis of extracellular matrix components. The immunohistochemical staining of TGF-beta positively stained vessels, vascular endothelial cells, macrophages, and spindle cells. Northern blot analysis suggested that TGF-beta was induced in the course of graft healing, and it promoted the production of extracellular matrix components.