Scientists explore using photosynthesis to help damaged hearts

June 15, 2017, Stanford University
Credit: Sweetaholic

In the ongoing hunt to find better treatments for heart disease, the top cause of death globally, new research from Stanford shows promising results using an unusual strategy: photosynthetic bacteria and light.

Researchers found that by injecting a type of bacteria into the hearts of anesthestized rats with , then using light to trigger photosynthesis, they were able to increase the flow of oxygen and improve heart function, according to a study published today in Science Advances.

"The beauty of it is that it's a recycling system," said Joseph Woo, MD, chair of cardiothoracic surgery at Stanford and senior author of the study. "You deliver the bacteria, they take up , and with energy from the light, they form oxygen."

The genesis of this somewhat mind-boggling concept sprang from scientists searching for new ways to deliver oxygen to the heart when blood flow is restricted, Woo said. This condition, known as cardiac ischemia, is most often caused by .

"We thought there is an interesting relationship in nature," he said. "In nature, humans exhale carbon dioxide and plants convert it back to oxygen. During a heart attack, the muscle is still trying to pump. There's carbon dioxide but no oxygen. We wondered if there were any way to use plant cells and put them next to heart cells to produce oxygen from the carbon dioxide."

Researchers first tried grinding up spinach and kale and combining each with heart cells in a dish, but the chloroplasts—the photosynthetic organs—of those plants weren't stable enough to survive outside of the plant cell.

"So we kept looking around," Woo said. Next, they tried photosynthetic bacteria, referred to as cyanobacteria, or blue-green algae, since it has a more rugged structure necessary for living in water. They repeated the same tests to see whether these had the ability to survive with in a dish.

"It was a little bit pie-in-the-sky," Woo said. "But it worked really well."

The next round of experiments involved injecting the cyanobacteria into the beating hearts of anesthetized rats with cardiac ischemia. They then compared the of rats with their hearts exposed to light (for less than 20 minutes) to those who were kept in the dark.

"The group that received the bacteria plus light had more and the heart worked better," Woo said. The bacteria dissipated within 24 hours, but the improved cardiac function continued for at least four weeks, he said.

"This is still very preliminary," Woo said.

The researchers plan to investigate how to apply this concept to humans and how to deliver a light source to the human heart. They are also examining the potential of using artificial chloroplasts to eliminate the need for bacteria.

Explore further: Low-oxygen environment leads to heart regeneration in mice, research shows

More information: An innovative biologic system for photon-powered myocardium in the ischemic heart Science Advances. DOI: 10.1126/sciadv.1603078

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2 / 5 (2) Jun 18, 2017
It would be very cool if this "Iron Man" tech could work, but introducing bacteria into the sterile heart would be problematic at best because bacteria within the vessel walls gum up the works, literally. Inside the muscle, diminishes light, diminishing performance. Putting the light in the heart is no problem. thanks to LEDs. O2 is a waste product of cyanobacteria, but selection for its production might increase yields and be useful elsewhere, like in mines, space travel, or even aqualungs. If selection could be automated?
Adding shocks to the blood would allow release of more O2 and gas exchange locally and might be a brighter prospect, so to speak.
1 / 5 (2) Jun 18, 2017
Providing O2 producing cyanobacteria within a capsule, perhaps with the light in it, that could transport CO2 in and O2 out, while keeping the bacteria within the device could work on a pace maker or even inserted into anoxic muscle. Perhaps an O2 producing paint for pacemakers with a low power LED? LED's are so low power that they might be made to work off current of injury or even the QRS shocks inside the heart. Selection for less light more O2 of the bacteria might improve quality. There are dyes which light up on small voltages, too, mixing such a dye with bacteria in the paint for a pacemaker or electrode might work, too?
1 / 5 (2) Jun 18, 2017
There are also radioactive luminous paints that might provide a light source, too. Many many variables, many many dead ends. Experiment!

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