0412 GMT February 25, 2020
The findings offer a potential first step to a new way to heal human hearts after heart attacks as well, Physorg said.
The experiments build on the idea that although stem cells have shown enormous promise in repairing organs after injury, using them in the heart itself has not yielded the expected results because very few of the transplanted cells survive in the heart, said M. Roselle Abraham, an assistant professor of medicine at the Johns Hopkins University School of Medicine. When the heart beats, she explained, it pushes cells injected into the heart wall out into the lungs before they get a chance to attach to the wall.
Additionally, when stem cells move from the culture flasks they are grown in and into a solution for injection in the heart, their metabolism slows, causing them to die in several hours unless they are given the opportunity to attach to tissue.
Researchers have tried to improve stem cell retention in the heart by injecting millions, only to have a mere 10-to-20 percent stick around an hour after injection, Abraham said. And even then, she added, a large number of these cells die within 24 hours due to a sluggish metabolism.
"If we could inject fewer cells soon after heart attacks and coax them to proliferate following transplantation, we could limit scar formation and be more successful with re-growing new heart muscle," Abraham explained.
In an effort to counter these difficulties, Abraham and her team developed a hydrogel that combines serum, a protein-filled component of blood that contains everything cells need to survive, with hyaluronic acid, a molecule already present in the heart and in the matrix that surrounds and supports cells.
By mixing these two components, the researchers created a sticky gel that functioned as a synthetic stem cell niche: It encapsulated stem cells while nurturing them and rapidly restored their metabolism.
Tests in petri dishes showed that both adult and embryonic stem cells encapsulated in this material not only survived at levels near 100 percent but thrived for days and proliferated. When the cell-gel combination was injected into living rat hearts, about 73 percent of the cells were retained in the hearts after an hour, compared with 12 percent of cells suspended in a solution.