A cornerstone of several common therapies for human diseases is the surgical use of a vein as an arterial conduit. Surgeons frequently create arteriovenous fistulae (AVF), the preferred access for hemodialysis. However, the poor maturation and patency of AVF, requiring additional re-do procedures and surgery, reflects our imperfect understanding of the biology of venous remodeling that leads to successful venous adaptation to the arterial environment. This knowledge gap creates an unmet medical need for novel approaches to enhance venous adaptation and maturation, to increase successful use of venous conduits. The tyrosine kinase receptor Eph-B4 is an embryonic determinant of veins. Diminished Eph-B4 expression is associated with shear stress conditions with laminar-like flow such as occurs during vein graft adaptation in humans and mice. We present exciting new data that: 1) our innovative mouse model of AVF faithfully recapitulates human AVF maturation including the presence of disturbed shear stress and an approximately 1/3 failure rate; 2) in both humans and mice, Eph-B4 expression initially increases during AVF adaptation to the arterial environment; 3) Eph-B4 function is essential for AVF remodeling; 4) Eph-B4 tyrosine- 774 is a critical regulator of Eph-B4 phosphorylation and activation of downstream signaling in vitro; 5) manipulation of Eph-B4 function via delivery of wild type or mutant Eph-B4 in vivo alters AVF remodeling; and 6) Akt-1 knockout mice have reduced AVF remodeling and altered responses to Eph-B4 stimulation. Our data suggests that surgical placement of a vein into the arterial environment regulates Eph-B4 phosphorylation and/or expression that is critical for successful venous adaptation and AVF maturation. We hypothesize that altering Eph-B4 activity will improve venous adaptation to the arterial circulation, thereby improving AVF maturation. We will use our innovative in vivo model of AVF maturation, as well as use a bioreactor that can control and deliver hemodynamic loads to small diameter vessels and endothelial monolayers in vitro, to test our hypothesis with the following specific aims:
Aim I : Determine optimal Eph-B4 manipulation and delivery to enhance venous adaptation to the arterial environment and improve AVF maturation.
Aim II : Determine whether Akt function is a mechanism of Eph-B4-mediated AVF maturation. The work in this proposal will have lasting impact by establishing that Eph-B4 is a component of the mechanotransduction mechanism in veins. We will test our novel hypothesis that Eph-B4 activity, or lack thereof, defines venous phenotype and function. We use an innovative strategy, as well as innovative in vivo and in vitro models, to manipulate Eph-B4 signaling and optimize delivery in vivo to alter vessel identity and thereby improve AVF maturation.

Public Health Relevance

A cornerstone of several common therapies for human diseases is the surgical use of a vein as an arterial conduit, such as an arteriovenous fistula (AVF), the preferred access for hemodialysis. However, AVF fail to mature in ~20-50% of cases, and of the AVF that do mature, primary AVF failure occurs in ~35-40% in just the first year; these poor clinical results lead to patient suffering and extensive expenditure of precious healthcare dollars and other resources for additional re-do procedures and surgery. The work to be accomplished within this proposal addresses the knowledge gap in the biology of venous remodeling that has created a serious unmet medical need for novel approaches to enhance venous adaptation to the arterial environment, maturation, and successful long-term use of venous conduits.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL128406-01A1
Application #
9102364
Study Section
Bioengineering, Technology and Surgical Sciences Study Section (BTSS)
Program Officer
Lee, Albert
Project Start
2016-04-01
Project End
2020-03-31
Budget Start
2016-04-01
Budget End
2017-03-31
Support Year
1
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Yale University
Department
Surgery
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
Bai, Hualong; Lee, Jung Seok; Hu, Haidi et al. (2018) Transforming Growth Factor-?1 Inhibits Pseudoaneurysm Formation After Aortic Patch Angioplasty. Arterioscler Thromb Vasc Biol 38:195-205
Protack, Clinton D; Foster, Trenton R; Hashimoto, Takuya et al. (2017) Eph-B4 regulates adaptive venous remodeling to improve arteriovenous fistula patency. Sci Rep 7:15386
Bai, Hualong; Hu, Haidi; Guo, Jianming et al. (2017) Polyester vascular patches acquire arterial or venous identity depending on their environment. J Biomed Mater Res A 105:3422-3431
Bai, Hualong; Li, Xin; Hashimoto, Takuya et al. (2017) Patch Angioplasty in the Rat Aorta or Inferior Vena Cava. J Vis Exp :
Isaji, Toshihiko; Hashimoto, Takuya; Yamamoto, Kota et al. (2017) Improving the Outcome of Vein Grafts: Should Vascular Surgeons Turn Veins into Arteries? Ann Vasc Dis 10:8-16
Kuwahara, Go; Hashimoto, Takuya; Tsuneki, Masayuki et al. (2017) CD44 Promotes Inflammation and Extracellular Matrix Production During Arteriovenous Fistula Maturation. Arterioscler Thromb Vasc Biol 37:1147-1156
Bai, Hualong; Lee, Jung Seok; Chen, Elizabeth et al. (2017) Covalent modification of pericardial patches for sustained rapamycin delivery inhibits venous neointimal hyperplasia. Sci Rep 7:40142
Hu, Haidi; Patel, Sandeep; Hanisch, Jesse J et al. (2016) Future research directions to improve fistula maturation and reduce access failure. Semin Vasc Surg 29:153-171