And There Was Light

Looking in real time into heart
cells with the help of fireflies
© Elinor Griffiths

Dr Elinor Griffiths from the University of Bristol said: "Being able to see exactly what's going on in heart cells will be of great benefit to understanding heart disease."

The 'power stations' within heart cells that make energy are called mitochondria. They convert energy from food into chemical energy called adenosine triphosphate, or ATP. Under normal conditions, mitochondria are able to make ATP extremely rapidly when the heart is stressed, such as during exercise or in "fight-or-flight" mode.

However, if the cells are made to beat suddenly from rest, a situation that happens when the heart is re-started after cardiac surgery or a heart attack, the team found there is a lag phase where the supply of ATP drops before mitochondrial production starts again, potentially preventing the heart from beating properly.

The researchers made use of a protein called luciferase, which is normally found in the tails of firefly and is what causes them to light up. Using molecular biological techniques, they transferred modified forms of the luciferase DNA into heart cells. The cells could then make their own luciferase, and the modifications enabled the luciferase to be produced inside the mitochondria.

Since luciferase lights up in the presence of ATP, the amount of light, and hence the amount of ATP, could be detected using a microscope and a highly sensitive camera. Dr Griffiths explained: "The breakthrough presented by this technique could be of benefit in heart diseases where mitochondria cannot make enough ATP. When that happens the heart does not have enough energy to perform its function of pumping blood efficiently which can result in a heart attack."; Source: University of Bristol