Automated cardiac sarcomere analysis from second harmonic generation images

Abstract

Abstract. Automatic quantification of cardiac muscle properties in tissue sections might provide important information related to different types of diseases. Second harmonic generation (SHG) imaging provides a stain-free microscopy approach to image cardiac fibers that, combined with our methodology of the automated measurement of the ultrastructure of muscle fibers, computes a reliable set of quantitative image features (sarcomere length, A-band length, thick-thin interaction length, and fiber orientation). We evaluated the performance of our methodology in computer-generated muscle fibers modeling some artifacts that are present during the image acquisition. Then, we also evaluated it by comparing it to manual measurements in SHG images from cardiac tissue of fetal and adult rabbits. The results showed a good performance of our methodology at high signal-tonoise ratio of 20 dB. We conclude that our automated measurements enable reliable characterization of cardiac fiber tissues to systematically study cardiac tissue in a wide range of conditions.

Permanent Cardiac Sarcomere Changes in a Rabbit Model of Intrauterine Growth Restriction

“…Additionally, since SHGM arises from the thick-thin filament overlap in mature and developing sarcomeres [21] , its length was calculated as the mean width of the A-band-related peak (namely in our study as thick-thin filament interaction length; TTIL). The three distinctive sarcomere distances (SL, ABL and TTIL) were measured automatically with a custom algorithm based on an optimal fitting of a parametric model of the autocorrelation function of the SHGM intensity profile in sarcomere fibers, as previously reported [22] . Briefly, the local orientation of the sarcomere fibers was estimated to perform automatically the following tracking of all the fibers within an image.…”

Structural origin of the drastic modification of second harmonic generation intensity pattern occurring in tail muscles of climax stages xenopus tadpoles

“…However the mechanism underlying 2f sarcomeric SHG-IPs is still not completely elucidated. Several mechanisms have been proposed to explain the ultrastructural origin of this 2f sarcomeric SHG-IP encompassing centrosymmetry of antiparallel myosin tails arrangement at the M-band in normal cardiac muscles (Boulesteix et al, 2004;Garcia-Canadilla et al, 2014;Plotnikov et al, 2006), disease dependent myofibrillar deformation or change of myosin orientation (Friedrich et al, 2010), proteolysis induced intra-sarcomeric misalignment of myosin thick filaments (Rouede et al, 2011) and myofibrillar misalignment (Rouede et al, 2013a). Difficulties in correlating SHG and electron microscopy (EM) images represent the major technological limitation.…”

On the interpretation of second harmonic generation intensity profiles of striated muscle

“…The first approach relies on a phenomenological profile definition such as a double Gaussian peak. 16,18 This is useful for analyzing double peaked intensity profiles observed in cardiac muscle tissue, but apart from the sarcomere length, the resulting parameter values have no direct relation to the biological structural properties of sarcomeres. The second approach is developed by Rouède et al 9 and relies on a more rigorous model based on the molecular organization of sarcomeres.…”

“…14 Various studies have recently emerged, suggesting SHG microscopy to be a valuable label-free tool to study muscular disorder. 13,15,16 However, to fully understand the effect of muscle degradation on the SHG signal, detailed knowledge of sarcomere structures and their relation to the second harmonic signal generation is necessary.…”

“…[9][10][11]17 Two SHG-based approaches have been used to quantify these striations. 9,16,18 Both methods are based on analyzing a one-dimensional intensity profile, mostly extracted from two-dimensional SHG images. The first approach relies on a phenomenological profile definition such as a double Gaussian peak.…”