Using Photosynthetic Microbes to Oxygenate Ischemic Tissue

Ischemic injuries, in which insufficient oxygen is delivered to tissues, can occur in numerous ways, but heart attacks are among the most common, evident, and dangerous. A sizable branch of the research community works on ways to efficiently and quickly provide oxygen to the impacted tissues so as to reduce the long-term damage and speed recovery. At the end of this road lie permanent enhancements such as respirocyte nanomachinery that will provide hours of supplemental oxygen for all tissues, but for now researchers are still working on the first potential advances in emergency oxygen supplementation, such as the example noted here.

The use of photosynthetic microorganisms to provide much needed oxygen to damaged heart tissue could be a feasible approach to treating heart attacks. Recent research describes the injection of the cyanobacterium Synechococcus elongatus into ischemic heart muscles of live rats, where, in response to light exposure, the microbes produced oxygen and improved organ function. Photosynthetic organisms capture energy from sunlight and use it to convert carbon dioxide and water into carbohydrates for growth. The process creates a surplus of oxygen, which the organisms simply expel into the atmosphere, much to the delight of aerobic organisms such as humans. “One day I was thinking: what is the fundamental problem with a heart attack? It’s the absence of oxygen being delivered to the heart muscle. And, what in nature makes oxygen for us every single minute? Plants.”

“Cardiologists are always thinking about how to deliver more blood to ischemic heart tissue. But, if oxygen is the critical component, what if you could take a plant, or the photosynthetic mechanism of a plant, and put it right next to a heart cell?” To investigate this unusual idea, researchers took an equally unusual approach. “We started grinding up kale and spinach to isolate the chloroplasts and put them with heart cells.” But the results of these experiments were disappointing. “What we found is that chloroplasts do not like being outside of a plant cell. They’re not very stable.”

So, the team instead tried the photosynthetic unicellular microorganism S. elongatus. “We put them with heart cells in a dish and we found that they could live together and, when we shone light on them, they could produce oxygen.” The team then tested the idea in live rats. They gave the animals heart attacks and then injected their hearts with S. elongatus and exposed the hearts to light. After just 10 minutes, oxygen in the bacteria-containing and light-exposed hearts had risen approximately 25-fold compared with just a 3-fold rise in oxygen in bacteria-containing hearts kept in darkness. And by 45 minutes, left ventricle pressure and cardiac output had improved, suggesting increased heart contractility. The microbes also provided long-term improvements to heart function. Four weeks after rats were subjected to temporary cardiac ischemia (60 minutes) – during which the animals were, or were not, injected with S. elongatus and exposed to light – analyses of heart function revealed that recipients of the microbe treatment had significantly improved contractility compared with controls.




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