Non-invasive characterization of mouse embryonic stem cell derived cardiomyocytes based on the intensity variation in digital beating video.

The interest in cardiomyocytes derived from differentiation of embryonic stem (ES) cells or induced pluripotent stem (iPS) cells is increasing due to their potential for regenerative therapeutics and as a pharmaceutical model of drug screening. Characterization of ES or iPS derived cardiomyocytes is challenging and inevitable for the intended usage of such cells. In this paper we have outlined a novel, non-invasive method for evaluating in vitro beating properties of cardiomyocytes. The method is based on the analysis of time dependent variation in the total pixel intensities in derivative images obtained from the consecutive systolic and diastolic frames from the light microscopic video recordings of beating tissue. Fast Fourier transform (FFT) yielded the frequency domains for these images. The signal to noise ratio for the analysis met the Rose criterion. We have successfully applied our method for monitoring mouse ES cell (mESC) derived cardiac muscle cells to determine the initiation of beating, organization and maturation of beating tissue, calculating the beating rhythms in terms of beating interval or frequency and the strength of beating. We have shown the successful application of our image analysis method in direct monitoring of the responses of differentiated cardiomyocytes towards caffeine hydrate, p-hydroxyphenylacetamide and calcium chloride dehydrate - respectively as positive, neutral and negative inotropic agents. This non-invasive method of characterization will be useful in studying the response of these cells to various external stimulations, such as differentiation promoting agents or treatments, as well as in preliminary drug screening in a quick and inexpensive manner without needing much expertise.