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Images of calcium signalling provides insights into blood vessel disease

A laser spinning disk system with a high-speed, ultrasensitive digital camera has allowed US researchers to capture the first pictures of intercellular calcium signalling in blood vessel walls.

Calcium signalling between the cells that line blood vessels and surrounding smooth muscle is critical for blood flow and pressure regulation. This study will therefore provide insights into blood vessel disease.

The researchers, led by Professor Mark Nelson from the University of Vermont and Professor Michael Kotlikoff from Cornell University, used an Andor Technology Revolution XD microscopy system with iXonEM+ 897 back-illuminated EMCCD camera to detect calcium signals, or 'sparks', released from inositol 1,4,5-trisphosphate receptors (IP3Rs) in arterial interior wall cells (endothelium). Local calcium signals from IP3Rs of this type have never been observed.

Nelson attributes the team's success to the Andor laser confocal system and a new tissue model developed by Kotiloff's team. The tissue expressed a calcium biosensor (GCaMP2) exclusively in its endothelium allowing calcium signalling between endothelium and smooth muscle cells to be more easily observed. When calcium concentrations increased, the endothelial cells fluoresced.

Acquiring at 15-30fps with Andor iQ software, the team was able to record stationary calcium signals, which they named calcium pulsars because they had a frequency similar to celestial pulsars, and they occur near 'black' holes in the internal elastic lamina (IEL). The IEL separates the endothelial and the surrounding smooth muscle cells in the arterial wall.

According to Nelson: 'The signals are hard to pick out unless you know what you're looking for and have a good camera that is fast enough. The calcium events last for less than half a second. They also occur in a very small volume so you have to have both the spatial and temporal resolution to see them.' The Andor system has exceptional sensitivity, critical for imaging the very small signals that control the function of living cells.


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