Wavelet analysis reveals heterogeneous time-dependent oscillations of individual mitochondria.

Mitochondrial inner membrane potential oscillations in cardiac myocytes synchronize under oxidative or metabolic stress, leading to synchronized whole cell oscillations. Gaining information about the temporal properties of individual mitochondrial oscillators is essential to comprehend the network's intrinsic spatiotemporal organization. We have developed methods to detect individual mitochondrial tetramethylrhodamine ethyl ester fluorescence oscillations and assess their dynamical properties using wavelet analysis. We demonstrate that these advanced signal processing tools can provide quantitative spatiotemporal information about intermitochondrial coupling. We have found that the mean frequency of selected groups of continuously oscillating mitochondria was 16.49 ± 1.04 mHz, whereas the mean frequency in the normalized mean global wavelet spectrum was 22.84 ± 1.80 mHz (n = 9 myocytes). In conclusion, this novel methodology will help shed new light on the dynamical properties of the mitochondrial network on the verge of synchronization.