Quantifying lamella dynamics of cultured cells by SACED, a new computer-assisted motion analysis

Formation of lamellipodia and the retraction of ruffles are essential activ ities during motility and migration of eukaryotic cells. We have developed a computer-assisted stroboscopic method for the continuous observation of c ell dynamics (stroboscopic analysis of cell dynamics, SACED) that allows on e. to analyze changes in lamellipodia protrusion and ruffle retraction with high resolution in space and time. To demonstrate the potential of this me thod we analyzed keratinocytes in culture, unstimulated or stimulated with epidermal growth factor (EGF), which is known to induce cell motility and m igration. Keratinocytes stimulated with EGF exhibited a 2.6-fold increase i n their migration velocity, which coincided with enhanced ruffle retraction velocity (144%) and increased ruffle frequency (135%) compared to control cells. We also recorded an enhanced frequency of lamellipodia (135%), where as the velocity of lamellipodia protrusion remained unchanged. These result s on ruffle and lamellipodia dynamics in epidermal cells show that SACED is at least equal to established methods in terms of accuracy. SACED is, howe ver, advantageous concerning resolution in time and therefore allows one to analyze the activity of lamellipodia and ruffles in as yet unknown detail. Moreover, SACED offers two opportunities that render this technique superi or to established methods: First, several parameters relevant to cell motil ity can be analyzed simultaneously. Second, a large number of cells can con veniently be examined, which facilitates the compilation of statistically s ignificant data. (C) 1999 Academic Press.