VASCULAR ENDOTHELIUM &VASCULAR ENDOTHELIUM &ITSITS FUNCTIONAL ASSESSMENTFUNCTIONAL ASSESSMENT

Upa KukongviriyapanUpa KukongviriyapanDepartment of Physiology, Faculty of MedicineDepartment of Physiology, Faculty of Medicine

Khon Kaen University, Thailand.Khon Kaen University, Thailand.

B.Sc. Experimental PathologyB.Sc. Experimental PathologyQueen Mary’s School of Medicine and Queen Mary’s School of Medicine and

DentistryDentistryThe Royal London HospitalThe Royal London Hospital

October 12, 2005October 12, 2005

Topic ContentsTopic Contents

• Structure and functions of Structure and functions of vascular endothelial cell.vascular endothelial cell.

• The endothelial dysfunction. The endothelial dysfunction. • The oxidant- stress induced The oxidant- stress induced

endothelial dysfunction.endothelial dysfunction.• How to assess endothelial How to assess endothelial

functions.functions.• SummarySummary

The Normal Vascular EndotheliumThe Normal Vascular Endothelium

• Historically viewed as a passiveHistorically viewed as a passive vascular liningvascular lining..

Vascular Endothelium Vascular Endothelium

• Many important roles to maintain vascular Many important roles to maintain vascular homeostasis:homeostasis:– Vascular tone regulationVascular tone regulation– VSMC proliferationVSMC proliferation– Inflammatory responsesInflammatory responses– HaemostasisHaemostasis

• It produces and releases vasoactive, thromb It produces and releases vasoactive, thromb oregulatory and growth factor substances. oregulatory and growth factor substances.

Tousoulis, et al., Heart 2005; 91Tousoulis, et al., Heart 2005; 91: 353-358.: 353-358.

Endothelial cell Endothelial cell functionsfunctions

• Maintaining the vascular tone: Vasodilation and Vasoconstriction

Functional targetsFunctional targets Physiological Physiological action/Mediators action/Mediators

GrowthGrowth StimulationStimulation Inhibition Inhibition PDGF, FGFPDGF, FGF NO, PGI NO, PGI22, TGF, TGF

IGF-1, ET, AIIIGF-1, ET, AII

Endothelial cell Endothelial cell functionsfunctions

InflammationInflammation ProinflammatoryProinflammatory AntiinflammatoryAntiinflammatoryAdhesion moleculesAdhesion moleculesSelectin-ESelectin-E, VCAM-1, ICAM-1, PECAM-1, VCAM-1, ICAM-1, PECAM-1

Functional targetsFunctional targets Physiological Physiological action/Mediators action/Mediators

HaemostasisHaemostasis ProthromboticProthromboticAntithromboticAntithrombotic

PAI-1PAI-1 PGIPGI22, TPA, TPA

Endothelial cell Endothelial cell functionsfunctions

Calles-Escandon and Cipolla, Endocrine Rev 2001; 22: 36-52.

• Factors affecting vascular tone and structureFactors affecting vascular tone and structure

- pathological conditions

- altered anticoagulant & anti-inflammatory properties

- impaired modulation of vascular growth & dysregulation of vascular remodeling

“ An impairment of endothelium-dependent vasorelaxation caused by a loss of NO bioactivity in the vessel wall.

Unifying model: Endothelial dysfunction Unifying model: Endothelial dysfunction to CVDto CVD

Xanthine oxidase, NADP/NADPH oxidaseuncoulpled eNOS

NO bioavailability

How can we assess the How can we assess the

endothelial function?endothelial function?

Methods for exploring endothelial function.(Guerci et al., Diabetes Metab 2001; 27: 425-434.)

Clinical Studies Supporting the Prognostic Va lue of Endothelial Vasomotor Function Testin

g.(Ganz, et al. Circulation 2003; 108: 2049-2053.)

P atients with endothelial dysfunction had a far greater incidence - of adverse cardiovascular events in follow up compared wit

h patients with preserved endothelial function.

Key points for evaluating Key points for evaluating ED. ED.

Tousoulis D, et al., Heart 2005; 91Tousoulis D, et al., Heart 2005; 91: 353-358.: 353-358.

Evaluating Endothelial Function in Evaluating Endothelial Function in HumansHumans

Non-invasive techniquesNon-invasive techniques

• High resolution ultrasonography: Assessment High resolution ultrasonography: Assessment of flow-mediated dilatation (FMD).of flow-mediated dilatation (FMD).

• Strain-gauge plethysmography: Evaluation ofStrain-gauge plethysmography: Evaluation offorearm blood flow (FBF).forearm blood flow (FBF).

Flow-mediated dilatation (FMD)

• I s defin ed as an endotheliu- m dependent process that refl

ects the relaxation of a condui t artery when exposed to incr

eased flow and, thereby, incre ased shear stress.

• A n impaired FMD response reflects endothelial dysfuncti

on.• A temporary increase in she

ar stress can be induced by in creasing the local blood flow,

- the so called“re active hyperemia”.

• An abrupt decrease in vascular resistance mediated by the EDNO caused FMD.

Tousoulis D, et al., Heart 2005: 91: 553-558.Tousoulis D, et al., Heart 2005: 91: 553-558.

The genesis of FMDThe genesis of FMD

Moens, et al., Chest 2005; 127: 2254-2263.

Flow-mediated vasodilation (FMD)

Equipment: Ultrasonic imaging of brachial artery diameter

Measurement of vasodilation response by ultrasonic imaging of arterial diameter:

• should be equipp ed with vascular so

ftware for 2 D ima ging, color and spe ctral Doppler, an in

ternal ECG monitor and high frequen

cy vascular transducer attached to a

- high quality mainfr ame ultrasound. an

d• Noninvasive, simple, costly, widely available, need furtherNoninvasive, simple, costly, widely available, need furthervalidation.validation.

Brachial Artery Flow-Mediated Brachial Artery Flow-Mediated DilationDilation

BaselineBaseline 5 Minutes5 Minutes

Post-OcclusionPost-OcclusionBlood Pressure CuffBlood Pressure CuffOcclusion – 1 MinuteOcclusion – 1 Minute Release Release

3.1 mm 3.6 mm

Forearm blood flow (Strain-gauge plethysmography

) • Noninvasive, simple, reproducible and less Noninvasive, simple, reproducible and less

observer dependent, need further validationobserver dependent, need further validation..

• The strain-gauge is attached to the upper forearm, and connected to plethysmographic device.

..• FBF is measured by temporarily occluding the FBF is measured by temporarily occluding the

venous return (by a cuff inflated to 40 mmHg) and venous return (by a cuff inflated to 40 mmHg) and measured the slight swelling of the distal portion measured the slight swelling of the distal portion of the limb due to continued arterial inflow.of the limb due to continued arterial inflow.

• The initial rate of The initial rate of swelling represents the swelling represents the arterial inflow.arterial inflow.

• The technique evaluates The technique evaluates the percentage change the percentage change of flow from baseline to of flow from baseline to the maximum flow the maximum flow during reactive during reactive hyperaemia following a hyperaemia following a five minute ischaemia of five minute ischaemia of the forearm.the forearm.

Forearm blood flow(Strain-gauge plethysmogra phy)

Tousoulis D, et al., Heart 2005: 91: 553-558.Tousoulis D, et al., Heart 2005: 91: 553-558.

Sample window• The FBF is estimated by the gradient of the tangent to the curve

during the first cardiac cycles.• R esult of forearm flow is expressed as ml/100 ml tiss/min or the percent changes in flow.

Timetable of FMD & FBF

Tousoulis D, et al., Heart 2005; 91Tousoulis D, et al., Heart 2005; 91: 353-358.: 353-358.

Application in clinical trials

• Study design: A - cute or long term intervention tr

ials.

• Sample size: A crossover or - a parallel group de

sign study.

• Methodology: S elect most reproducible results.

• E valuating precision of the technique.

• I ndividual training in the principles and te

chnical

aspect of Doppler ultrasonography and Strain-

gauge

plethysmography.

SUMMARYSUMMARY

• Endothelial functional testing can be used as an indicator for vascular damage or vascular disease and also other diseases relating to oxidative stress conditions.

• Reversal of endothelial dysfunction protects against progression of vascular disease.

• Proposed new tests for evaluating endothelial function should be developed with optimal characteristics; – Cost-effective, reproducible and

standardization.– Ability to predict risk and relationship to

established tests of risk.– Useful as a screen for drug development.– Can identify individual patients.– Can predict a reduction in the risk of clinical

events.

SUMMARYSUMMARY

QUESTIONSQUESTIONS

• What are the main functions of the vascular What are the main functions of the vascular

endothelial cell?endothelial cell?

• What is the endothelial dysfunction? How can it What is the endothelial dysfunction? How can it

lead to the cardiovascular disease?lead to the cardiovascular disease?

• How can we evaluate the endothelial How can we evaluate the endothelial

functions?functions?

• What are the key points for evaluating the What are the key points for evaluating the

endothelial dysfunction?endothelial dysfunction?

The End For NowThe End For NowBut there is much more to But there is much more to

learn!!!!learn!!!!

Thank you!