An original method to quantify mitochondria movement in cultured cardiomyocytes

We studied in confocal microscopy non-beating cells from the HL-1 cardiac cell line. Using a fluorescent dye, mitochondria appeared as a dense tubular network, in permanent fusion, fission and displacement. To quantify these movements in response to pharmacological stimuli, we needed a method only based on their position. Time-lapse recording was performed in physiological medium. Every image was first converted into binary images by ultimate erosion or skeletonization. Then a distance map was created by attributing to every point a grey level equal to the distance from the skeleton. In a third step, the following binary image was laid over the distance image, by pixel to pixel multiplication. The pixel value below the binary objects indicated the distance ran between the two images. The method is fast and accurate, and can be scaled in absolute values. The average velocity lies in the range obtained by other methods