Toshihiko Isaji

Eph-B4 regulates adaptive venous remodeling to improve arteriovenous fistula patency

Low rates of arteriovenous fistula (AVF) maturation prevent optimal fistula use for hemodialysis; however, the mechanism of venous remodeling in the fistula environment is not well understood. We hypothesized that the embryonic venous determinant Eph-B4 mediates AVF maturation. In human AVF and a mouse aortocaval fistula model, Eph-B4 protein expression increased in the fistula vein; expression of the arterial determinant Ephrin-B2 also increased. Stimulation of Eph-B-mediated signaling with Ephrin-B2/Fc showed improved fistula patency with less wall thickness. Mutagenesis studies showed that tyrosine-774 is critical for Eph-B4 signaling and administration of inactive Eph-B4-Y774F increased fistula wall thickness. Akt1 expression also increased in AVF; Akt1 knockout mice showed reduced fistula diameter and wall thickness. In Akt1 knockout mice, stimulation of Eph-B signaling with Ephrin-B2/Fc showed no effect on remodeling. These results show that AVF maturation is associated with acquisition of dual arteriovenous identity; increased Eph-B activity improves AVF patency. Inhibition of Akt1 function abolishes Eph-B-mediated venous remodeling suggesting that Eph-B4 regulates AVF venous adaptation through an Akt1-mediated mechanism.

Polyester vascular patches acquire arterial or venous identity depending on their environment

Polyester is commonly used in vascular surgery for patch angioplasty and grafts. We hypothesized that polyester patches heal by infiltration of arterial or venous progenitor cells depending on the site of implantation. Polyester patches were implanted into the Wistar rat aorta or inferior vena cava and explanted on day 7 or 30. Neointima that formed on polyester patches was thicker in the venous environment compared to the amount that formed on patches in the arterial environment. Venous patches had more cell proliferation and greater numbers of VCAM-positive and CD68-positive cells, whereas arterial patches had greater numbers of vimentin-positive and alpha-actin-positive cells. Although there were similar numbers of endothelial progenitor cells in the neointimal endothelium, cells in the arterial patch were Ephrin-B2- and notch-4-positive while those in the venous patch were Eph-B4- and COUP-TFII-positive. Venous patches treated with an arteriovenous fistula had decreased neointimal thickness; neointimal endothelial cells expressed Ephrin-B2 and notch-4 in addition to Eph-B4 and COUP-TFII. Polyester patches in the venous environment acquire venous identity, whereas patches in the arterial environment acquire arterial identity; patches in the fistula environment acquire dual arterial-venous identity. These data suggest that synthetic patches heal by acquisition of identity of their environment.

Improving the Outcome of Vein Grafts: Should Vascular Surgeons Turn Veins into Arteries?

Autogenous vein grafts remain the gold standard conduit for arterial bypass, particularly for the treatment of critical limb ischemia. Vein graft adaptation to the arterial environment, i.e., adequate dilation and wall thickening, contributes to the superior performance of vein grafts. However, abnormal venous wall remodeling with excessive neointimal hyperplasia commonly causes vein graft failure. Since the PREVENT trials failed to improve vein graft outcomes, new strategies focus on the adaptive response of the venous endothelial cells to the post-surgical arterial environment. Eph-B4, the determinant of venous endothelium during embryonic development, remains expressed and functional in adult venous tissue. After surgery, vein grafts lose their venous identity, with loss of Eph-B4 expression; however, arterial identity is not gained, consistent with loss of all vessel identity. In mouse vein grafts, stimulation of venous Eph-B4 signaling promotes retention of venous identity in endothelial cells and is associated with vein graft walls that are not thickened. Eph-B4 regulates downstream signaling pathways of relevance to vascular biology, including caveolin-1, Akt, and endothelial nitric oxide synthase (eNOS). Regulation of the Eph-B4 signaling pathway may be a novel therapeutic target to prevent vein graft failure.

Stem cell therapy for diabetic foot ulcers: a review of preclinical and clinical research

BackgroundDiabetic foot ulcer (DFU) is a severe complication of diabetes, preceding most diabetes-related amputations. DFUs require over US

The Mouse Aortocaval Fistula Model with Intraluminal Drug Delivery

9 billion for yearly treatment and are now a global public health issue. DFU occurs in the setting of ischemia, infection, neuropathy, and metabolic disorders that result in poor wound healing and poor treatment options. Recently, stem cell therapy has emerged as a new interventional strategy to treat DFU and appears to be safe and effective in both preclinical and clinical trials. However, variability in the stem cell type and origin, route and protocol for administration, and concomitant use of angioplasty confound easy interpretation and generalization of the results.MethodsThe PubMed, Google Scholar, and EMBASE databases were searched and 89 preclinical and clinical studies were selected for analysis.ResultsThere was divergence between preclinical and clinical studies regarding stem cell type, origin, and delivery techniques. There was heterogeneous preclinical and clinical study design and few randomized clinical trials. Granulocyte-colony stimulating factor was employed in some studies but with differing protocols. Concomitant performance of angioplasty with stem cell therapy showed increased efficiency compared to either therapy alone.ConclusionsStem cell therapy is an effective treatment for diabetic foot ulcers and is currently used as an alternative to amputation for some patients without other options for revascularization. Concordance between preclinical and clinical studies may help design future randomized clinical trials.

PC236. Cav-1 Regulates EphB4-Mediated Arteriovenous Fistula Maturation

The arteriovenous fistula (AVF) is the most common type of vascular access currently used for hemodialysis, but long-term outcomes remain poor in many patients; understanding the basic mechanisms of venous remodeling within the fistula environment is critical to improve our understanding of AVF maturation. In this chapter, we describe a method to create a murine aortocaval fistula that allows intraluminal drug delivery. This model reliably recapitulates human AVF maturation and therefore is a good consideration to study venous remodeling.

Molecular identity of arteries, veins, and lymphatics.

in registered deaths resulting from the given meteorological conditions compared with the average meteorological conditions. Results: We have found that ruptured aortic aneurysms are most common in a weather situation that occurs when the cold flow regime of a fast-moving Mediterranean cyclone passes through the Carpathian Basin. The direction of the air movement is north and northeast. Such weather conditions cause overheating in the majority of the year, but in winter it usually attenuates the temperature. In all seasons it is rainy with snow showers in the winter, with spring thunderstorms. Mostly windy, daytime heat is often periodic. We reported that change in atmospheric pressure has a greater effect than daily temperature variation. This connection is a straight proportionate relationship between increasing barometric pressure change and registered fatal aortic aneurysm cases. Conclusions: Earlier studies aimed to determine if there is a connection between aortic catastrophies and weather conditions, and had no information about the intensity of the connection. We examined the connection of ruptured aortic aneurysms and complex climate patterns, and we established a new method that provides quantitative results and is able to forecast other instantaneous events. We believe our knowledge will be useful in the prevention ruptured aortic aneurysms.

Transforming Growth Factor-β1 Inhibits Pseudoaneurysm Formation After Aortic Patch Angioplasty

Background: Arteries, veins, and lymphatic vessels are distinguished by structural differences that correspond to their different functions. Each of these vessels is also defined by specific molecular markers that persist throughout adult life; these markers are some of the molecular determinants that control the differentiation of embryonic undifferentiated cells into arteries, veins, or lymphatics. Methods: This is a review of experimental literature. Results: The Eph‐B4 receptor and its ligand, ephrin‐B2, are critical molecular determinants of vessel identity, arising on endothelial cells early in embryonic development. Eph‐B4 and ephrin‐B2 continue to be expressed on adult vessels and mark vessel identity. However, after vascular surgery, vessel identity can change and is marked by altered Eph‐B4 and ephrin‐B2 expression. Vein grafts show loss of venous identity, with less Eph‐B4 expression. Arteriovenous fistulas show gain of dual arterial‐venous identity, with both Eph‐B4 and ephrin‐B2 expression, and manipulation of Eph‐B4 improves arteriovenous fistula patency. Patches used to close arteries and veins exhibit context‐dependent gain of identity, that is, patches in the arterial environment gain arterial identity, whereas patches in the venous environment gain venous identity; these results show the importance of the host infiltrating cells in determining vascular identity after vascular surgery. Conclusions: Changes in the vessels molecular identity after vascular surgery correspond to structural changes that depend on the hosts postsurgical environment. Regulation of vascular identity and the underlying molecular mechanisms may allow new therapeutic approaches to improve vascular surgical procedures.

Stenotic lesion level did not affect outcomes of carotid endarterectomy

Objective— Pseudoaneurysms remain a significant complication after vascular procedures. We hypothesized that TGF-&bgr; (transforming growth factor-&bgr;) signaling plays a mechanistic role in the development of pseudoaneurysms. Approach and Results— Rat aortic pericardial patch angioplasty was associated with a high incidence (88%) of pseudoaneurysms at 30 days, with increased smad2 phosphorylation in small pseudoaneurysms but not in large pseudoaneurysms; TGF-&bgr;1 receptors were increased in small pseudoaneurysms and preserved in large pseudoaneurysms. Delivery of TGF-&bgr;1 via nanoparticles covalently bonded to the patch stimulated smad2 phosphorylation both in vitro and in vivo and significantly decreased pseudoaneurysm formation (6.7%). Inhibition of TGF-&bgr;1 signaling with SB431542 decreased smad2 phosphorylation both in vitro and in vivo and significantly induced pseudoaneurysm formation by day 7 (66.7%). Conclusions— Normal healing after aortic patch angioplasty is associated with increased TGF-&bgr;1 signaling, and recruitment of smad2 signaling may limit pseudoaneurysm formation; loss of TGF-&bgr;1 signaling is associated with the formation of large pseudoaneurysms. Enhancement of TGF-&bgr;1 signaling may be a potential mechanism to limit pseudoaneurysm formation after vascular intervention.

Abstract 240: TGFβ-Activated Kinase 1 is Required for Arteriovenous Fistula Maturation

Background Carotid endarterectomy is the established treatment for carotid artery stenosis, and remains the primary surgical option due to its superior outcomes compared to carotid arterial stenting. However, Japanese patients are known to have unfavorable anatomical conditions for carotid endarterectomy, with a relatively higher level of the carotid artery bifurcation than in the Western population. We investigated the outcomes of carotid endarterectomy in our institute and evaluated the procedural quality by comparing patients based on higher or lower lesion levels. Methods The clinical data of 65 patients who underwent carotid endarterectomy were collected retrospectively. The outcomes reviewed included stroke-free survival and stroke-free rate. The patients were divided into a higher group (n = 25) and a lower group (n = 40), based on lesion location in respect of the 2nd cervical vertebral level. Results There was no perioperative death and only one case of stroke in the higher group within 30 days after carotid endarterectomy. At 5 years after carotid endarterectomy, the stroke-free survival rates were 83.4% in the higher group and 87.8% in the lower group, while the stroke-free rates were 96.0% and 94.0%, respectively; there were no significant differences between groups. Conclusions Stenotic lesion level did not affect the outcome or procedural quality of carotid endarterectomy.