During this webinar Dr. Éric Thorin, a leading expert in the effects of shear stress in the vasculature, explains key concepts in setting up a system for the purpose of examining flow-mediated responses in isolated blood vessels. The webinar sponsor, Living Systems Instrumentation, has been supplying tools for in vitro studies of cardiovascular function for over 20 years. Viewers will gain an understanding of how to setup and utilize a pressure arteriograph capable of simultaneous control of intravascular pressure and intraluminal flow. Background information: The physiological significance and effects of flow on controlling and coordinating vascular function are well-appreciated. However, flow-mediated regulation of vascular function is a complex and difficult mechanism to study experimentally. Care must be taken to select appropriate instrumentation to allow for precise control of intravascular pressure and intraluminal flow, while minimizing artifacts introduced by the small size of glass cannulae. With proper simultaneous control of intravascular pressure and intraluminal flow, the researcher will be able to explore such responses as flow-mediated dilation, flow-induced constriction and other physiological responses that depend upon shear stress in the vasculature. About Our Presenter: Dr. Éric Thorin has a long-standing interest in the study and mechanisms of ageing related to the vascular endothelium. His laboratory has developed several approaches to investigate the functional consequences of ageing combined with risk factors for cardiovascular diseases (CVD) on the evolution of a reversible endothelial dysfunction to an irreversible vascular disease. His main areas of research include the study of the cerebrovascular and peripheral vascular dysfunction in the mouse model of human dyslipidemia and atherosclerosis, the molecular mechanisms leading to endothelial cell senescence and the impact of risk factors for CVD in patients with obesity, diabetes and coronary artery disease.

1. Studying Flow Mediated Responses
in Isolated Vasculature
Éric Thorin, PhD
Professor of Surgery,
Université de
Montréal
Gerry Herrera, PhD
President,
Living Systems
Instrumentation

2. InsideScientific is an online educational environment
designed for life science researchers. Our goal is to aid in
the sharing and distribution of scientific information
regarding innovative technologies, protocols, research
tools and laboratory services.

3. Studying Flow Mediated Responses
in Isolated Vasculature
Copyright 2016 Living Systems Instrumentation and InsideScientific. All Rights Reserved.
Gerry Herrera, PhD
President,
Living Systems Instrumentation

4. To learn how to
mount an arteriole
on pipets, please
refer to the
previous Webinar:
Getting Started
with In-Vitro
Blood Vessel
Research

5. Perfused Resistance Vessels
Advanced Application:
Vascular reactivity can be studied under
conditions of constant or variable
intraluminal flow (shear stress)

6. Anatomy of a Pressurized Arteriograph System
Constant Pressure
& Flow
• Key components include a pressure
source, vessel chamber, means for
temperature control, and data
acquisition hardware/software
• Distal end of vessel remains open
• In addition to the basic items for
regulating intravascular pressure,
you will also need a pump to control
intraluminal solution flow and a way
to monitor pressure on both sides of
the cannulated vessel

7. Studying Flow-Mediated Responses
in Isolated Vasculature
Copyright 2016 E. Thorin, Living Systems Instrumentation and InsideScientific. All Rights Reserved.
Éric Thorin, PhD Professor of Surgery,
Université de Montréal

8. 1. Required equipment
2. How to setup and calibrate instrumentation
3. Best practices, including how to minimize cannulae
resistance
4. Sample experimental protocols and applications
What are we going to cover today?

9. There are
two types of
equipment…
Mechanic & Automatic

10. 1. Pipettes with
equal
diameter
2. Two
reservoirs
3. Pressure
transducers
Kuo, Davis & Chilian.
Am J Physiol 1990;
259(28): 1063-1070.
Mechanic
Air bubbles

11. Automatic
1. Pipettes with
equal
diameter.
2. Pressure
Servo
3. Flow pump

12. Endothelium-dependent, flow-induced dilation of
isolated coronary arterioles
Kuo, Davis & Chilian. Am J Physiol 1990;259(28):1063-1070.
• Increasing
pressure gradient
leads to an
increase in flow
• Increase in flow
stimulates the
endothelium
• The endothelium
releases dilatory
factors
• This leads to a
dilation

13. Ex vivo, when using the arteriograph, it is better to express
the flow rates that you impose to the arterioles as shear
stress values. It will help others to compare their own results
to your results
An increase in flow increases shear stress

14. Where...
τ = dynes/cm2
η = viscosity (0.009 P)
Q = applied flow rate through the lumen (ml/sec)
r = lumen radius (cm)
Excel template to
calculate mean
shear stress
How to calculate shear stress?
τ = 4ηQ/πr3

15. Any change in shear stress will be
transitory and will induce a dilation.
Hence, shear stress will return to baseline.
Shear stress tends to be
constant in the body…
Langille BL, O’Donnell F, 1986. Science 231, 405–407
La Barbera, 1990. Science 249, 992-1000
Malek AM, et al, 1999. JAMA 282, 2035–2042
Bolduc et al, 2013. Am J Physiol 305, H620–H633

16. Ex vivo,
the change in flow (shear stress) is the
stimulus to induce an arterial response
1. An increase in shear stress stimulates the endothelium
2. The endothelium releases factors primarily NO, but
also, depending on the experimental conditions, EDHF,
MMPs, transglutaminase, bradykinin, etc…

17. Exception: ex vivo in diseased
animals with a dysfunctional
endothelium, a rise in flow will
dilate much less and therefore
will increase shear stress
outside the “normal” range.
Shear stress is constant in the body...
Drouin et al. Am J Physiol; 300: H1032–H1043, 2011

18. Exception: ex vivo in diseased
animals with a dysfunctional
endothelium, a rise in flow will
dilate much less and therefore
will increase shear stress
outside the “normal” range.
Shear stress is constant in the body...
Drouin et al. Am J Physiol; 300: H1032–H1043, 2011

19. Exception: ex vivo in diseased
animals with a dysfunctional
endothelium, a rise in flow will
dilate much less and therefore
will increase shear stress
outside the “normal” range.
Shear stress is constant in the body...
Drouin et al. Am J Physiol; 300: H1032–H1043, 2011

20. Exception: ex vivo in diseased
animals with a dysfunctional
endothelium, a rise in flow will
dilate much less and therefore
will increase shear stress
outside the “normal” range.
Shear stress is constant in the body...
Drouin et al. Am J Physiol; 300: H1032–H1043, 2011

21. Exception: ex vivo in diseased
animals with a dysfunctional
endothelium, a rise in flow will
dilate much less and therefore
will increase shear stress
outside the “normal” range.
Shear stress is constant in the body...
Drouin et al. Am J Physiol; 300: H1032–H1043, 2011

22. An increase in shear stress may dilate to a stable maximum
Kuo, Davis & Chilian. Am J Physiol 1990;259(28):1063-1070.
• In pig coronary arterioles,
increased flow stimulates the
endothelium that leads to a
dilation
• The dilation reaches a stable
maximum despite increasing
flow
• Removing the endothelium
eliminates the dilatory
response

23. An increase in shear stress may dilate to a maximum
and then lead to a reduction in diameter
Raignault, Bolduc, Lesage, Thorin. JCBFM 2016; Jan 28, Epub.
• In mouse cerebral arteries,
Increased flow stimulates the
endothelium that leads to a
dilation
• This dilation declines above
shear stress values higher than
10 Dyn/cm2
• Removing the endothelium
eliminates the dilatory
response

24. Different responses to a rise in shear
stress are possibly due to the following:
1. Difference in vascular bed
2. Shear stress induces the release of dilatory factors only (as in
coronary arteries of the previous example)
3. Shear stress induces the release of dilatory factors associated at
high shear stress to the release of constricting factors and/or the
inhibition of the release of dilatory factors (cerebral arteries)

25. • Make sure you have the right equipment
and that you master it
• Have two pipettes with similar diameter
• Practice, practice, practice
• Until there is a direct relationship between shear stress and diameter
Summary
Langille BL, O’Donnell F, 1986. Science 231, 405–407
La Barbera, 1990. Science 249, 992-1000
Malek AM, et al, 1999. JAMA 282, 2035–2042
Bolduc et al, 2013. Am J Physiol 305, H620–H633

26. Thank You!
Eric Thorin, PhD
eric.thorin@umontreal.ca
Gerry Herrera, PhD
info@livingsys.com
For additional information on
Pressure Arteriograph Systems,
Wire Myographs and solutions for
studying vessel function in-vitro
please visit: www.livingsys.com