R11 - In situ Characterization of von Willebrand Factor Unravelling Under Continuous and Modulated Pulsatile Flow

Thursday, October 9, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Javier E. Dominguez De Leon

University of Alabama at Birmingham
Birmingham, Alabama, United States

Co-Author(s)

JS

Jay Sah

Posdoctoral Fellow, Department of Cardivascular Disease
University of Alabama at Birmingham
Birmingham, Alabama, United States
SB

Samuel C. Bartley

University of Alabama at Birmingham
Birmingham, Alabama, United States
Esraa Ismail

PhD student
Lehigh University
Bethlehem, Pennsylvania, United States
IB

Ian Berg

Postdoctoral Fellow, Division of Cardiovascular Disease
University of Alabama at Birmingham, United States
AM

Alexa Mattheyses

University of Alabama at Birmingham, United States
Xuanhong Cheng, PhD

Professor
Lehigh University
Bethlehem, Pennsylvania, United States
GG

Guruprasad A. Giridharan

Professor
University of Louisville
Not Hispanic or Latino, Kentucky, United States

Last Author(s)

PS

Palaniappan Sethu

Professor
University of Alabama at Birmingham, United States

Primary Investigator(s)

PS

Palaniappan Sethu

Professor
University of Alabama at Birmingham, United States

Introduction: : Patients supported on Continuous Flow Ventricular Assist Devices (CF-VAD) develop a condition called acquired von Willebrand Syndrome (AVWS), characterized by reduced total von Willebrand Factor (vWF) and increased cleavage by ADAMTS-13 into low molecular weight (LMW) multimers, impairing coagulation. vWF degradation is closely associated with its extensional behavior in response to shear stress. Our prior in vitro studies have characterized this behavior under continuous and modulated flow frequencies using immobilized vWF molecules; however, this behavior has not yet been validated under in situ conditions. Our objective is to evaluate and characterize vWF elongation, cleavage site exposure, and degradation under continuous and modulated pulsatile flow.

Materials and

Methods: : Primary aortic endothelial cells (HAECs) were cultured and seeded into microfluidic devices, stimulated with histamine to induce vWF release, and exposed to either continuous (95/90 mmHg pressure, constant average 12 dyne/cm2 shear stress), modulated frequency and pulse pressure conditions (20 bpm, 40 bpm, 60 bpm, 80 bpm; 10, 20, 30, and 40 mmHg pulse pressure, under physiological shear stresses) pulsatile flow. Post-processing includes immunofluorescent staining to assess vWF strand extension and A2 domain exposure, measurement of substrate in media, and Western Blotting to measure vWF degradation.

Results, Conclusions, and Discussions::

Results:
Preliminary immunofluorescence reveals a significantly greater number of elongated vWF strands under continuous flow compared to normal pulsatile flow (60 bpm). Partial elongation under pulsatile conditions was observed, marked by red arrows in Figure B, supporting the hypothesis of reduced A2 domain exposure. Figure C illustrates vWF strand lengths across flow regimes, with continuous flow resulting in more extensive elongation.

Conclusion:
Initial findings suggest that continuous flow promotes full elongation of vWF strands and greater exposure of A2 domains, facilitating cleavage by ADAMTS-13 into LMW fragments. In contrast, pulsatile flow results in only partial elongation and fewer accessible cleavage sites. Ongoing experiments aim to

Acknowledgements and/or References (Optional):: This study was supported by a research grant from the National Institute of Health (Grant # HL151663).