PATTERNS OF SPONTANEOUS MOTILITY IN VIDEOMICROGRAPHS OF HUMAN EPIDERMAL-KERATINOCYTES (HEK)

The subject of our observations was the spontaneous behaviour of norma l and transfected human epidermal keratinocytes. Cell movements were r ecorded on video micrographs and analyzed by a mathematical approach, using new methods of image processing and statistical correlation anal ysis. Protrusive activity of single lamellae was examined using one-di mensional analysis of phase-contrast image sequences along section lin es transversal to the cell edge. This method revealed high periodicity and correlation in the motility patterns of lamellae and ruffles. Two -dimensional correlation analysis of automatically digitized cell outl ines was applied to detect spatiotemporal patterns and coordination of lamellar extension and retraction. Most cells showed regularly altern ating pulsations of lamellar protrusions. In some extreme cases, exten sion waves rotating around the cell periphery were observed. The resul ts were compared with computer simulations of two simple models for la mellar dynamics and shape deformation, based on few assumptions about chemical kinetics of F-actin and cytomechanical properties of the acti n network, neglecting regulatory effects of actin-associated proteins or extracellular stimulations. The simulation results reproduced the m ain dynamical features of the observed real cells, indicating the poss ibility that the basic universal mechanism for lateral coordination of lamellipodial protrusion is the interplay between hydrostatic pressur e and viscocontractile tension in the cortical F-actin - plasma membra ne complex.