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Dynamics of ß₁-Integrins in Living Fibroblasts—Effect of Substratum Wettability

I. Zlatanov ^*, T. Groth  , A. Lendlein  and G. Altankov ^* 

^* Institute of Biophysics, Bulgarian Academy of Sciences, Sofia, Bulgaria; Biomedical Materials, Institute of Bioengineering, Martin-Luther University, Halle-Wittenberg, Halle, Germany; and GKSS Research Center, Institute of Chemistry, Teltow, Germany

Correspondence: Address reprint requests to G. P. Altankov, Tel.: 359-2-979-2634; E-mail: altankov{at}obzor.bio21.bas.bg.

The dynamics of integrin receptors mobility was studied in living human fibroblasts using fluorescence-labeled ß₁-integrin monoclonal antibodies. Time-lapse image series were obtained by confocal laser scanning microscopy when cells were adhering on model hydrophilic (clean glass) and hydrophobic (octadecyl-silanized; i.e., ODS) surfaces coated with fibronectin. Direct measurements showed approximately twice-higher velocity of integrins on glass compared to ODS, and these velocities varied in different zones of the cells. A kinetic model and algorithm for quantification of images was developed, and the analysis identified three receptor populations on glass: immobilized (82.76% of all), slow (4.16%), and fast (13.08%), while, on ODS, only two were identified: immobilized (83.36%) and fast (16.64%). Fast integrins in the peripheral zone of cells have maximal velocities of 0.353 ± 0.02 µm/min (n = 48, four cells) on hydrophilic and 0.218 ± 0.02 µm/min (n = 30, three cells) on hydrophobic substrata. The slow population has a velocity of 0.114 µm/min (n = 48, four cells). Further analyses show that these velocities also differ significantly in the peripheral and middle zones of cells in a substrate-dependent fashion. A well-defined circular motion of receptors around the cell center expressed mainly on hydrophobic substrata was monitored and quantified as well.