Seeing inside the heart at an unprecedented scale
A team of researchers in Canada and India has developed a novel method to image the whole mouse heart wall at a spatial resolution that is three orders of magnitude finer than that seen till now, revealing entirely new, previously unknown cardiac fiber systems within it.
In a paper published today and featured on the cover of The EMBO Journal, Professor Kaleem Siddiqi of the School of Computer Science at McGill and Professor Minhaj Sirajuddin of the Institute for Stem Cell Science and Regenerative Medicine in Bengaluru, India, describe their discovery. Applying computer vision techniques to 3D confocal microscopy, the team reconstructed cardiomyocyte arrangements in the heart wall at a fine spatial scale and recovered distinct geometries that, up to now, have never been observed.
Cardiomyocytes are densely packed in the mammalian heart wall and drive it to contract and pump blood. Their arrangement is known to be intimately linked with electrical and mechanical function in the heart.
Nearly all other models of cardiomyocytes in mammals are at the millimeter scale and describe fibers arranged in a smooth helical pattern as a ‘helicoid.’ But when the researchers used their new methods to recover cardiomyocyte orientation at the micron scale – a thousand times smaller – in addition to this helical arrangement their technique revealed previously unknown fiber systems that are geometrically distinct and run in thin bands in the direction of the long-axis.
“We think these new fiber systems may play a unique functional role in the heart,” Siddiqi said. “Understanding them in the context of both healthy and diseased states opens many exciting challenges and directions for future work.”
The joint first authors of the article are Tabish Syed, a doctoral student at McGill when the work was conducted, and Drisya Dileep, a doctoral student at inStem.