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Cell migration at biointerfaces

Dr. Prabhas MogheBiointerfacial

Characterization125:583

September 18, 2006

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Outline• Importance of Cell Migration• Modes of cell migration• Cell migration and cell adhesion• Methods to quantify cell migration• Cell migration on dynamic

biointerfaces

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Significance of studying cell motility

• Cell motility is key to:– Wound healing/repair (quality and kinetics)– Tissue adhesion and turnover on implanted

materials– Cancer invasiveness/metastasis– Sorting of cells during

development/embryogenesis– White blood and immune cell functions

–

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Modes of Cell Migration - A Primer

(a)

(c)(d)

(e) (f)

(b)

(a) Random Motility: No orientation bias is exhibited with respect to S or P. (b) Topotaxis: Biased turning toward gradient direction (shown toward right) (c) Orthotaxis: Enhanced S when the cell is oriented in the gradient direction, (d): Klinotaxis: Decreased P when the cell is oriented in the gradient direction (e): Orthokinesis: S decreases with increasing stimulus concentration (f) Klinokinesis: P increases with increasing stimulus concentration

S: Cell SpeedP: Directional Persistence

Simplest Classification: Random Motility versus Chemotaxis

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Cell MigrationIndirect Methods

• Under-Agarose Assay• Membrane Infiltration Assay (Millipore/Boyden)• 3-D Conjoined Gel Assay•  Orientation Assay (Zigmond)

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Cell Migration AssaysFilter Assay

Under-Agarose Assay

Conjoined Gel Assay

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Molecular View of Cell Adhesion

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Strength of Adhesion & Receptor-Ligand Affinity

Kuo SC. Lauffenburger DA. Relationship between receptor/ligand binding affinity and adhesion strength. [Journal Article] Biophysical Journal. 65(5):2191-200, 1993 Nov.

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Relation between cell adhesion and cell migration

DiMilla et al., JCB, 1992

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Cell migration & cell adhesive strengthPalecek et al., Nature 385:537 (1997)

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3-D Cell migration

Biophys J. 2005 Aug;89(2):1389-97. Epub 2005 May 20.

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Cell Migration Analysis on Biomaterials: Direct

Methods

Biophys J. 1997 Mar;72(3):1472-80. Biophys J. 1992 Feb;61(2):306-15.

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Direct Migration Methods, Contd.

D2(t)=4μ{t−P+Pexp(−t/P)}

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Theory of Cell Migration:Indirect Assays

• Cell Population Migration is described in terms of objectivemigratory parameters, , and . These parameters do not vary withsystem size, time of incubation, etc.

= random motility coefficient (cm2/s) = chemotaxis coefficient (cm2/s-M)

• Two fundamental equations are required:- Cell transport equation (captures migration behavior)- Cell conservation equation

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Theory of Cell Migration• Cell Migration in an Isotropic Environment (Random Migration):

Jc =−μ(a).∂C∂xwhere c is the cell density and a is the concentration of soluble stimulant concentration (if any).

• Cell conservation equation:∂C∂t =−∂Jc∂x

• ∂C∂t =μ.∂

2C∂x2Overall equation:

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Solution to Cell Migration Model

time, t

Co

xSolution: If η =x/ 4μ.t

C(η) =Co.{1−erf(η)}

C(x,t)

C(η)

ηerf(η) = 2π

e−y2dy

0

η∫where

(Note, erf(0)=0; erf(∞)=1)

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Example of variation with biomaterial substrate

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10

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0 10

-10

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10

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Untreated ePTFE

Albumin-ePTFE

IgG-ePTFE

Random Motility Coefficient

[

2

/s]

FMLP Conentration [ M ]

Chang, C., Lieberman, S., and Moghe, P.V., J. Mat. Sci. Mat. Med. 11: 337 (2000)

• Human Neutrophilson ePTFE, a vascularprosthetic material,treated with differentplasma proteins, andin the presence ofthe chemoattractant,formyl-methionyl-leucyl-phenylalanine (fMLP).

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Protein interface on biomaterials shifts the directional motility of cells

Chang, C., Lieberman, S., and Moghe, P.V., J. Mat. Sci. Mat. Med. 11: 337 (2000)

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Cell migration on anisotropic substrates

• Cell migration under flow• Cell migration on oriented textured

substrates• Cell migration on substrates with

chemical, electrical, stiffness gradients.

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Analysis of Cell Motility on Biosubstrates under Flow

Rosenson-Schloss et al,J. Biomed. Mater. Res., 60:8, 2002’

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Quantitation of Cell Migration under Flow

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Cell migration on dynamic biointerfaces (ligand-nanoparticles)

Tjia and Moghe, Tissue Eng, 8: 247 (2002); Annals of Biomed. Eng, 30: 851 (2002)

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Cell motility behavior characterization as a function of ligand-microparticle density

(Tjia and Moghe, Tissue Eng., 2002)

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Cell motility behavior characterization, continued

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Mathematical description of cell motility and ligand binding (Tjia & Moghe, ABE, 2002)

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Kinetics of ligand binding and internalization within motile cells

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Cell motility correlates with matrix ligand sampling