Stimulation Of Eph-B4 Prevents Adult Venous Remolding In Arterial Environment

Introduction:Vein graft adaptation to the arterial circulation entails many changes at the cellular or/and molecular levels, including both cell proliferation and extracellular matrix (ECM) deposition or remodeling, resulting in thickening of the vein wall, and in excessive cases, pathological neointimal hyperplasia. Eph-B4 determines mammalian venous differentiation in the embryo. However, it is thought to be a quiescent marker of adult veins. Previously conducted studies have shown that surgical transposition of a vein into the arterial environment is characterized by loss of venous identity, as indicated by the loss of Eph-B4, and intimal thickening. We used a mouse model of vein graft implantation to test the hypothesis that Eph-B4 is a critical determinant of venous wall thickness during postsurgical adaptation to the arterial environment.Methods:To establish a model of vein graft adaptation, we determined the time course of morphological and physiological changes in veins implanted into allogeneic rats. The suprahepatic inferior vena cava was transplanted from a donor rat into the infrarenal aorta of a recipient rat.24 rats were divided into two groups,12 in Control group and 12 in Intervention group. Half of the vein grafts from each group were harvested after 1 week and the remaining half of the vein grafts were harvested after 4 weeks. To stimulate Eph-B4 in surgically implanted vein grafts, the vein graft was submerged in Ephrin-B2/Fc for 20 minutes right before transplantation and Ephrin-B2/Fc was injected intraperitoneally from the day after surgical implantation and then every other day after surgical vein graft implantation until vein graft harvest. All the vein grafts were preserved in liquid nitrogen and HE staining, a-actin immunohistochemical staining and EphB4 immunofluorescence staining were performed to study the changes at cellular and molecular level. All the data were analyzed and statistically compared with the help of SPSS 12.0 software.Results:Vein graft wall thickness increased in a time dependent manner, with increased wall thickness up to 4 week after implantation. Notably, after Ephrin-B2/Fc treatment, vein grafts showed reduced wall thickness and reduced a-actin expression compared with control group vein grafts in 4 weeks. However, no significant difference in wall thickness and a-actin expression was noted in 1 week. Moreover, control group vein grafts showed diminished Eph-B4 expression and loss of venous identity in the arterial environment whereas vein grafts derived from Ephrin-B2/Fc-injected rat showed retention of Eph-B4 expression.Conclusion:Eph-B4 is not simply a passive marker of adult veins. Rather, stimulation of Eph-B4 during vein graft adaptation promotes retention of venous identity and prevents vein wall thickening. As such, it is possible that vein graft failure may be prevented by promotion and continual stimulation of venous identity. Stimulation of Eph-B4 in adult cells represents a new paradigm to treat adult diseases.