Light sheet microscopy traces deadly heart waves
Light sheet microscopy image: calcium release (green) in a heart cell [NHLI/MacLeod et al]
Novel light sheet microscopy has been applied to heart cells to trace calcium waves that can cause arrhythmia.
Rising levels of calcium in heart muscle cells cause contraction of the muscle, helping to regulate the beating of the heart.
The rise in calcium levels is usually uniform, but sometimes a spontaneous release of calcium from isolated regions of the cells creates a wave of calcium that causes arrhythmia, irregular heart-beating that accounts for some 50 percent of deaths in patients with heart failure.
Exactly how and why calcium waves originate has been difficult to study with conventional microscopy techniques.
But now, physicists from Imperial College London have collaborated with scientists from Imperial’s National Heart and Lung Institute (NHLI) to shine new light onto the problem.
Using high speed oblique plane microscopy (OPM), researchers reveal the calcium waves originate from healthy parts of heart muscle cells, and not degraded regions as expected.
OPM is a form of light sheet microscopy that uses a single high numerical aperture microscope objective for both fluorescence excitation and collection and allows video-rate 3D imaging of features at the sub-cellular scale.
To capture the calcium waves, the researchers developed an OPM system that included two sCMOS cameras to investigate single heart muscle cells isolated from a rat model of heart failure.
As the researchers points out, within heart muscle cells, structures in the cell membrane called transverse tubules or t-tubules help to regulate calcium release. In patients with heart failure, the structure of t-tubules is degraded.
The researchers had speculated that these faulty structures were the origin of calcium waves, but microscopy data indicated calcium waves were more frequent from regions of the cell where the normal t-tubule structure was preserved.
“We thought more calcium waves would be produced from regions of deranged t-tubules, but we were surprised to find the opposite appears to be true,” highlights Dr Ken MacLeod from NHLI.
“However, this was only a small-scale study to test the technique," he adds. "We still expect the derangement of t-tubules plays a role in the poor function of failing cells, and hopefully with more research we should be able to see what’s going on in greater detail."
The researchers are now developing their OPM technique further and hope to also use the method to study signalling in neurons and in rapid 3D imaging of large arrays of samples, for, say, drug screening.
Research is published in Journal of Biophotonics