Until recently, available microscopes were too slow to capture a beating heart in 3D. Now, a team from the Max Planck Institute has developed a high-speed, selective plane illumination microscope that manages to do just that. By gently illuminating the fish heart with a thin light sheet and observing the emitted fluorescence with a fast and sensitive camera the researchers have achieved fast, non-invasive imaging of labelled heart tissue. The process involves taking multiple movies, each covering individual planes of the heart (movie stacks), then using the correlations between the individual planes to generate a synchronised, dynamic 3D image of the beating heart.
The team also obtained static high-resolution reconstructions by briefly stopping the heart with optogenetics. These renderings allow researchers to further follow characteristic structures of the heart throughout the cardiac cycle. For instance, they now can clearly observe cardiac contractions or the distance between endo- and myocardium throughout the heartbeat. Non-periodic phenomena such as irregularly beating hearts and the flow of blood cells are resolved by high-speed volume scanning using a liquid lens.
By manipulating the exposure time and magnification of the images, better resolution could be achieved and fine details such as sarcomeres and filamentous actin could also be resolved. Finally, they then also went on to resolve non-periodic phenomena by high-speed volume scanning with a liquid lens. For the first time, it has become possible to also image diseased hearts that exhibit arrhythmia, exciting news for cardiologists.
The team has developed a fantastic array of tools to image the heart in vivo, ranging from static to ultra-high-speed images. Their work offers potentially revolutionary insights into the cellular structure of the beating heart and are set to further improve knowledge of congenital heart defects.