Sarcomere analysis in human cardiomyocytes by computing radial frequency spectra

In cardiomyocytes, the basic contractile unit are sarcomeres, which are organized in a regular manner facilitating their function. Here, we present a new computational approach to assess the functional properties of sarcomeres at the nanoscale level in human cardiac cells, induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). We combined our analysis to different types of high-resolution imaging data, structured illumination microscopy (SIM), stimulated emission depletion (STED) microscopy-based imaging, as well as confocal microscopy data. We show that the radially averaged magnitude spectrum (RAMS) revealed sarcomere properties in a human cardiomyocyte model, iPSC-CMs, and compared our RAMS-based analysis to a real-space approach based on manually selected regions of interest. Moreover, we found the RAMS method suitable to quantify molecular differences of sarcomeres such as present in severe cardiac diseases, such as dilated cardiomyopathy (DCM). Defects in the sarcomere organization that occur in the presence of inherited DCM mutations in sarcomere proteins were efficiently recapitulated by our analysis. This new approach may facilitate streamlined analysis of molecular disease-specific phenotypic imaging data of cardiac cells, aiding our deeper understanding of the molecular basis of cardiac diseases.