Quantification of cardiomyocyte contraction based on image correlation analysis

Quantification of cardiomyocyte contraction is usually obtained by measuring globally cell shortening from the displacement of cell extremities. We developed a correlation‐based optical flow method, which correlates the whole‐cell temporal pattern with a precise quantification of the intracellular strain wave at the sarcomeres level. A two‐dimensional image correlation analysis of cardiomyocytes phase‐contrast images was developed to extract local cell deformations from videomicroscopy time‐lapse sequences. Test images, synthesized from known intensity displacement fields, were first used to validate the method. Intracellular strain fields were then computed from videomicroscopy time‐lapse sequences of single adult and neonatal cardiomyocytes. The propagation of the sarcomeres contraction–relaxation wave during cell contraction has been successfully quantified. The time‐varying patterns of intracellular displacement were obtained accurately, even when cardiomyocyte bending occurred in pace with contraction. Interestingly, the characterization of the successive 2D displacement fields show a direct quantification of the variation with time of intracellular strains anywhere in the cell. The proposed method enables a quantitative analysis of cardiomyocyte contraction without requiring wave tracking with the use of fluorescent calcium probes. Thus, our algorithmic approach provides a fast and efficient tool for analyzing the correlation between global cell dynamical behavior and mechanosensitive intracellular processes. © 2008 International Society for Advancement of Cytometry