SarcOptiM for ImageJ: high-frequency online sarcomere length computing on stimulated cardiomyocytes

Abstract

Pasqualin C, Gannier F, Yu A, Malécot CO, Bredeloux P, Maupoil V. SarcOptiM for ImageJ: high-frequency online sarcomere length computing on stimulated cardiomyocytes. Am J Physiol Cell Physiol 311: C277-C283, 2016. First published June 22, 2016; doi:10.1152/ajpcell.00094.2016.-Accurate measurement of cardiomyocyte contraction is a critical issue for scientists working on cardiac physiology and physiopathology of diseases implying contraction impairment. Cardiomyocytes contraction can be quantified by measuring sarcomere length, but few tools are available for this, and none is freely distributed. We developed a plug-in (SarcOptiM) for the ImageJ/Fiji image analysis platform developed by the National Institutes of Health. SarcOptiM computes sarcomere length via fast Fourier transform analysis of video frames captured or displayed in ImageJ and thus is not tied to a dedicated video camera. It can work in real time or offline, the latter overcoming rotating motion or displacement-related artifacts. SarcOptiM includes a simulator and video generator of cardiomyocyte contraction. Acquisition parameters, such as pixel size and camera frame rate, were tested with both experimental recordings of rat ventricular cardiomyocytes and synthetic videos. It is freely distributed, and its source code is available. It works under Windows, Mac, or Linux operating systems. The camera speed is the limiting factor, since the algorithm can compute online sarcomere shortening at frame rates Ͼ10 kHz. In conclusion, SarcOptiM is a free and validated user-friendly tool for studying cardiomyocyte contraction in all species, including human. cardiomyocyte contractility; sarcomere dynamic; video analysis; ImageJ plug-in; fast Fourier transform ISOLATED CARDIOMYOCYTE (CM) contractions can be recorded and measured with two main methods: cell shortening and sarcomere shortening. The latter is probably the most common and reliable technique used to characterize isolated CM contractile performance, because it does not depend on cell shape and size (4). Sarcomere shortening technique has applications in different research fields, including cardiovascular physiology, pathophysiology such as heart failure, pharmacology, and toxicology (2, 3, 6 -8, 11).Under transmission light microscopy, striated muscle cell sarcomeres show a transverse pattern due to the alternation of light (isotropic; I) and dark (anisotropic; A) bands, corresponding to the very regular organization of thin filaments of actin associated with regulatory proteins, such as tropomyosin and troponin (I band) and thick filaments of myosin (A band). These bands have a profile that can be assimilated to a sinusoidal curve. The frequency of this sinusoid, which represents the distance between the dark bands of the myosin filaments and, therefore, the sarcomere length (SL), can be extracted from Fourier spectrum analysis of the CM image.

Hierarchical and stage-specific regulation of murine cardiomyocyte maturation by serum response factor

“…Isolated CMs were paced at 1 Hz. Bright-field images were acquired and then analyzed using SarcOptiM 18 . In violin plots, white circles show the medians, box limits indicate the 25th and 75th percentiles, whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles, and polygons represent density estimates of data and extend to extreme values.…”

Monitoring contractility in single cardiomyocytes and whole hearts with bio-integrated microlasers

“…In adult cardiomyocytes, sarcomere length measurements were performed using DIC videos recorded at 100 fps by using the ImageJ plugin SarcOptiM. 39 Briefly, a fast Fourier transformation algorithm is used to extract the regular spacing in a line profile plotted along the longitudinal axis of the cell. Adult cardiomyocytes were electrically paced at 1 Hz with Platinum wire bath electrodes by applying 8 ms square voltage pulses with a maximum electric field of 30 V/cm.…”

Mitochondrial division inhibitor 1 (mdivi‐1) increases oxidative capacity and contractile stress generated by engineered skeletal muscle

“…Qualitatively, we observed a shift in the peak-to-peak distance of the traces due to mdivi-1 treatment ( Figure 5B). Next, we used a FFT-based method 48 to calculate the average sarcomere length from 12 consecutive sarcomeres per myotube ( Figure 5C). Sarcomere length was calculated as 2.67 ± 0.03, 2.74 ± 0.03, and 2.79 ± 0.03 in the DMSO control, 10 μM mdivi-1, and 25 μM mdivi-1 groups, respectively, with n = 35 myotubes per condition ( Figure 5D).…”