Impaired Integrin β3 Delays Endothelial Cell Regeneration and Contributes to Arteriovenous Graft Failure in Mice

Abstract

Objective Neointima formation is associated with stenosis and subsequent thrombosis in arteriovenous grafts (AVG). A role of integrin β3 in the neointima formation of AVGs remains poorly understood. Approach and Results In integrin β3−/− mice, we found significantly accelerated occlusion of AVGs compared to the wild type mice. This is caused by the development of neointima and lack of endothelial regeneration. The latter is a direct consequence of impaired functions of circulating angiogenic cells (CACs) and platelets in integrin β3−/− mice. Evidence suggests the involvement of platelet regulating CAC homing to and differentiation at graft sites via TGF-β1 and Notch signaling pathway. First, CACs deficient of integrin β3 impaired adhesion activity toward exposed subendothelium. Second, platelets from integrin β3−/− mice failed to sufficiently stimulate CACs to differentiate into mature endothelial cells. Finally, we found that TGF-β1 level was increased in platelets from integrin β3−/− mice and resulted in enhanced Notch1 activation in CACs in AVGs. These results demonstrate that integrin β3 is critical for endothelial cell homing and differentiation. The increased TGF-β1 and Notch1 signaling mediates integrin β3−/−-induced AVG occlusion. This accelerated occlusion of AVGs was reversed in integrin β3−/− mice transplanted with the bone marrow from WT mice. Conclusion Our results suggest that boosting integrin β3 function in the endothelial cells and platelets could prevent neointima and thrombosis in AVGs.

Integrin β3 Mediates the Endothelial-to-Mesenchymal Transition via the Notch Pathway

“…These results showed that the ECs of AVFs from ESRD patients express the mesenchymal cell marker, SMA-α. We also reported that integrin β3 expression was located in the endothelium and neointima of arteriovenous grafts from patients [10]. Double staining of SMA-α and integrin β3 in AVFs from mice and patients confirmed that SMA-α and integrin β3 were located in the endothelium and the neointima (Fig.…”

“…Circulating endothelial progenitor cells deficient in integrin β3 show impaired adhesion activity toward exposed subendothelium, fail to differentiate into mature ECs, and promote neointimal formation at arteriovenous graft sites [10]. However, integrin αvβ3 arginine-glycine-aspartic acid (RGD) antagonists have been used to reduce neointimal hyperplasia, mainly by blocking VSMC accumulation [19].…”

“…The former is primarily expressed on platelets, whereas the latter is found in ECs and selective inflammatory cells. Our previous report showed that integrin β3 is expressed in both circulating endothelial progenitor cells and in platelets, influencing EC regeneration and blocking neointimal formation in arteriovenous grafts in mice [10]. However, whether integrin β3 influences the EndMT in neointimal hyperplasia remains unknown.…”

Notch Signaling in Endothelial Cells: Is It the Therapeutic Target for Vascular Neointimal Hyperplasia?

“…Recent studies support the emerging concept that Notch signaling is also involved in the development of neointimal hyperplasia. The increased Notch-1 signaling mediates neointimal formation in integrin β3(−/−)-induced arteriovenous graft occlusion through impairing EC regeneration [ 19 ]. Dll-4-mediated Notch activation promotes VSMC proliferation and migration in vein graft lesions and leads to vein graft failure [ 20 , 21 ].…”

“…As shown in Figure 2 , Notch activation suppresses EC proliferation, regeneration and promotes neointimal formation ( Figure 2 A). In integrin β3 knockout mice, the increased Notch-1 signaling inhibits circulating angiogenic cells’ (CACs) homing and differentiation, delays endothelial regeneration and promotes neointimal formation at the sites of arteriovenous grafts [ 19 ]. It is also reported that endothelial progenitor cells’ (EPCs) activity is greater in Notch-1(+/−) EPCs than in wild type (WT) EPCs, and subsequently, transplantation of Notch-1(+/−) bone marrow accelerates endothelial recovery after arterial injury in WT mice.…”