Pathologic Shear and Elongation Rates Do Not Cause Cleavage of Von Willebrand Factor by ADAMTS13 in a Purified System

Maria Bortot; Alireza Sharifi; Katrina Ashworth; Faye Walker; Allaura Cox; Katherine Ruegg; Nathan Clendenen; Keith B Neeves; David Bark Jr; Jorge Di Paola

doi:10.1007/s12195-020-00631-2

Pathologic Shear and Elongation Rates Do Not Cause Cleavage of Von Willebrand Factor by ADAMTS13 in a Purified System

Cell Mol Bioeng. 2020 Jul 17;13(4):379-390. doi: 10.1007/s12195-020-00631-2. eCollection 2020 Aug.

Authors

Maria Bortot^#^{1

2}, Alireza Sharifi^#³, Katrina Ashworth¹, Faye Walker¹, Allaura Cox¹, Katherine Ruegg⁴, Nathan Clendenen⁵, Keith B Neeves^{1

2}, David Bark Jr^{1

3

6}, Jorge Di Paola⁷

Affiliations

¹ Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA.
² Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA.
³ Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523 USA.
⁴ Hemophilia Center, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA.
⁵ Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA.
⁶ School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523 USA.
⁷ Department of Pediatrics, Washington University in St. Louis, 660 S. Euclid Avenue, Campus Box 8208, 5th floor MPRB, St. Louis, MO 63110 USA.

^# Contributed equally.

Abstract

Introduction: Pathological flows in patients with severe aortic stenosis are associated with acquired von Willebrand syndrome. This syndrome is characterized by excessive cleavage of von Willebrand factor by its main protease, A Disintegrin and Metalloproteinase with a Thrombospondin Type 1 Motif, Member 13 (ADAMTS13) leading to decreased VWF function and mucocutaneous bleeding. Aortic valve replacement and correction of the flow behavior to physiological levels reverses the syndrome, supporting the association between pathological flow and acquired von Willebrand syndrome. We investigated the effects of shear and elongational rates on von Willebrand factor cleavage in the presence of ADAMTS13.

Methods: We identified acquired von Willebrand syndrome in five patients with severe aortic stenosis. Doppler echography values from these patients were used to develop three computational fluid dynamic (CFD) aortic valve models (normal, mild and severe stenosis). Shear, elongational rates and exposure times identified in the CFD simulations were used as parameters for the design of microfluidic devices to test the effects of pathologic shear and elongational rates on the structure and function of von Willebrand factor.

Results: The shear rates (0-10,000s^-1), elongational rates (0-1000 s^-1) and exposure times (1-180 ms) tested in our microfluidic designs mimicked the flow features identified in patients with aortic stenosis. The shear and elongational rates tested in vitro did not lead to excessive cleavage or decreased function of von Willebrand factor in the presence of the protease.

Conclusions: High shear and elongational rates in the presence of ADAMTS13 are not sufficient for excessive cleavage of von Willebrand Factor.

Keywords: Acquired von Willebrand syndrome; Aortic stenosis; Elongational flow; Non-surgical bleeding; Reynolds number; Shear rate.

Abstract

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