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Treating Heart Attacks With Photosynthetic Bacteria

S u m m a r y :
Photosynthetic bacteria protect the heart from damage caused by a heart attack, suggest new findings published in the journal Science Advances.

Saving hearts (lives) with photosynthetic bacteria

Heart disease claims thousands of lives throughout the year. Researchers are always trying to find better treatment methods to undo the damage done by heart attacks and related conditions. The new study boasts of an unconventional way to tackle this problem: using photosynthetic bacteria (more specifically, cyanobacteria) to restore the heart’s health.

Bringing the tree to the heart

A lack of oxygen in heart cells and muscle is extremely damaging, and can even be fatal to the cells. This is what happens during heart attacks: a reduced bloodflow to the heart (this can be the result of blocked arteries) will inevitably lead to a decreased oxygen supply. But, what if we could insert an oxygen-producing organism into the heart? Because, if you can’t take the heart to an oxygen source, how about bringing the oxygen directly to the heart? This is what the researchers of the new study aimed for. Stanford cardiovascular surgeon Joseph Woo wanted to find a way to feed the starved heart tissues with oxygen while the obstruction in the blocked blood vessels was being removed to restore bloodflow. “Why not bring the tree to your heart?”, thought Woo. So, he considered using cyanobacteria as a way for the heart to have its own oxygen supply on a temporary basis.

Following a heart attack, a rat’s heart is kept beating thanks to cyanobacteria injected into it to provide it with oxygen. Photo credits: Department of cardiothoracic surgery/stanford university school of medicine.

A previous failed attempt with plants

Before actually using the bacteria, the researchers had attempted to do the same thing with kale and spinach: they grinded the plants to harvest chloroplasts, the organelles that carry out photosynthesis, and thus crucial for the production of oxygen. However, the chloroplasts did not survive outside the cells. This is why the team eventually used the photosynthetic bacteria; the latter were first tested on heart cells in a lab dish before being used in rats.

The rat heart cells (red) grown in laboratory are kept alive by photosynthetic bacteria (cyanobacteria) which supply them with oxygen. Photo credits: J.E. Cohen et al/ Science Advances 2017.

The cyanobacteria, Synechococcus elongatus, is not uncommon to the world of research: it has previously been used by other scientists to make biofuels, but this is the first time that its use has been introduced for a medical purpose.

Injecting cyanobacteria into rats

Woo and his team stopped the bloodflow in a part of the rat hearts to starve them of oxygen. 15 minutes later, they injected cyanobacteria in some of the rats while others were fed with a saline solution as a control. The bacteria-based method proved to be fruitful as the findings show that it mitigated the harm caused by heart attacks: the oxygen levels increased to three times the ones measured immediately after the heart attack. Of course, as expected, the saline-treated rats had barely any increase in oxygen.

Light vs darkness

When the researchers exposed the hearts to light, the rats with the bacteria had 25 times more oxygen than they did after the heart attack. Four weeks down the road, the rats with the cyanobacteia displayed less heart damage than those treated with saline. Furthermore, the hearts were beating strongly, with a 30% higher bloodflow registered in rats with bacteria exposed to light than those with bacteria left in the dark.

Can this be done for humans?

Woo explains that the additional bloodflow generated by using the bacteria might be the difference between life and death for some patients. Still, this method, though promising, would be difficult to reproduce in humans. Firstly, injecting cyanobacteria in human hearts is risky, even if the organism is harmless and, despite the fact that it was removed from the rats bodies within 24 hours. Furthermore, exposing human hearts to light remains a challenge.

“It will be next to impossible to open the chest to light,” says a cardiovascular scientist from Boston’s Massachusetts General Hospital, Matthias Nahrendorf. “A day on the beach won’t do the trick.”

Bring the sun to the heart?

Woo and his colleagues are trying to bypass this obstacle by engineering devices to shine light through bones and tissues into the heart.

A scientific feat!

Nevertheless, these findings constitute a real scientific breakthrough. A fellow researcher from Washington University, Himadri Pakrasi, not involved in the study, describes the research as “science fiction”, but that it is “fantastic if it works”. Another scientist, Susan Golden from the University of California, comments that it is “outrageous in a good way”, and that the idea is “really fresh”.


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