Dynamics of RBCs with altered mechanicalproperties in shear flow. Towards a clinical

marker for sickle cell disease

Emmanuèle Helfer

Aix Marseille Univ, CNRS, CINaM, Marseille, France

Sickle cell disease: 1st genetic disease in the world

Hemoglobin polymerizationCell stiffening

- Dehydration- Deoxygenation

Mutation in Hemoglobin: HbSS

Partially reversible

Malaria atlas project

4.5 million people, 300 000 births/year

Life expectancy in developed countriesof the order of 40 years

Palliative care

Efforts only on systematic prevention

Decrease in RBC deformability

Clogging of small blood vessels

Vital prognosis: acute chest syndrome

Sequelae: stroke, bone necrosis

Unpredictable, very painful

Vaso-occlusive crisis

RBC mechanical marker sensitive to the imminence of a crisis?

Vaso-occlusive crises

Top view

8

µm

Sectional view

2

µm

Lipidmembrane

2Dcytoskeleton Elastic

shear modulus

Cytoplasmicviscosity

Hb solution

Aspectratio

Red blood cell deformability

Volume loss

Swelling

Need for a marker sensitive to these parameters

The mechanics of RBCs controls their motion under shear flow

γ.

.γ

Tank-Treading

Rolling

Tumbling

g.

gc

.

Bottom views

Y

Z

X

Flow chamber

Goldsmith and Marlow, 1972Fischer et al., Science 1978Abkarian et al., PRL, 2007Dupire et al., PNAS, 2012

The mechanics of RBCs controls their motion under shear flow

Y

Z

X

Flow chamber

γ.

.γ

Tank-Treading

Rolling

Tumbling

g.

gc

.

« broad spectrum » markerrelated to RBC deformability

Another marker?

Detection of RBC type of motion under shear flow

HbAA Healthy

HbSS Sickle

population of at least 250 cells

Shear rate (s-1)

fTT

Fraction of TT RBCs as function of shear rate

Shear rate: 10 s -1

Healthy Sickle Thalassemia

fTT

Fraction of TT RBCs SCD and thalassemia

Healthy

Sickle

Sickle

Healthy

d = 1,085

d = 1,092

d = 1,101

d = 1,122

d = 1,107

SickleHealthy

Volume reduction0.51 0.60.75

The fraction of TT RBCs is related to cell hydration and density

TT fraction during the course of a vaso-occlusive crisis

day after hospitalization

f TT

Sequence of two crises

crisis 11crisis

10Pre-crisis

decrease

European patent applicationEP 18305914.6

Clinical trial from sept. 2018

fTT trend evolution during vaso-occlusive crises

The fraction of tanktreading RBCs is

sensitive to genetic diseases that affect RBC deformability a perfect candidate for predicting vaso-occlusive crises in

SCD

Low cost device that can be installed at the patient’s bedside

Other applications: in-vitro test for drug evaluation…

Conclusion

Acknowledgments

• Scott ATWELL

• Alexander HORNUNG

• Maxime SAHUN

• Anne CHARRIER

• Annie VIALLAT

Marseille Medical Genetics

Aix-Marseille Université, INSERM

CINaM

Aix-Marseille Université, CNRS

• Catherine BADENS

THANK YOU FOR YOUR ATTENTION!

A*MIDEX project (n° ANR-11-IDEX-00001-02)

CNRS Pre-maturation