Quantifying cell-matrix adhesion dynamics in living cells using interference reflection microscopy.

Focal adhesions and podosomes are integrin-mediated cell-substratum contacts that can be visualized using interference reflection microscopy (IRM). Here, we have developed automated image-processing procedures to quantify adhesion turnover from IRM images of live cells. Using time sequences of images, we produce adhesion maps that reveal the spatial changes of adhesions and contain additional information on the time sequence of these changes. Such maps were used to characterize focal adhesion dynamics in mouse embryo fibroblasts lacking one or both alleles of the vinculin gene. Loss of vinculin expression resulted in increased assembly, disassembly and/or in increased translocation of focal adhesions, suggesting that vinculin is important for stabilizing focal adhesions. This method is also useful for studying the rapid dynamics of podosomes as observed in primary mouse dendritic cells.