With their ability to help repair damaged muscle, stem cells have shown promise as tools for rebuilding the body's organs, but their potential is yet to be fully realized – especially when it comes to the heart. Part of this is because only a small percentage of stem cells injected actually survive the process, but a newly developed liquid could make life a little easier for freshly transplanted cells. Researchers have found that encapsulating them in a sticky hydrogel gives them the ability to not only survive, but multiply and improve the injured heart's ability to pump blood.
According to Maria Roselle Abraham, assistant professor of medicine at the Johns Hopkins University School of Medicine, most of the stem cells that are injected are repelled by the heart beat which pushes them into the lungs before they can attach to the organ wall. Furthermore, the metabolism of stem cells slows down once they are prepared for injection, a process that involves moving them from the culture flasks and into a solution, causing them to die within a few hours if they aren't attached to tissue.
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Researchers are exploring different ways to overcome the limitations of stem cell treatments, such as injecting exosomes, tiny communication modules secreted by the cells, rather than the cells themselves, or even taking a more scattergun approach and injecting as many as one billion of them. But the research team led by Abraham believes that a more precise method is the best way forward.
"If we could inject fewer cells soon after heart attacks and coax them to proliferate following transplantation," Abraham explains, "we could limit scar formation and be more successful with re-growing new heart muscle."
Her team has developed a hydrogel designed to better preserve the metabolism, functions and well-being of the stem cells while they are injected. This meant combining serum, a protein-rich liquid in the blood that carries everything needed for cell survival, with hyaluronic acid, a molecule found in the matrix surrounding cells that is already present in the heart.
Lab testing showed that adult and embryonic stem cells contained in the hydrogel survived at a rate of close to 100 percent, and over several days went on to proliferate. Another promising finding was that these cells displayed a higher production of growth factors that drive heart muscle repair than regular stem cells.
Injecting the cell-loaded hydrogel into living rat hearts saw about 73 percent of the stem cells survive, compared to only 12 percent of cells injected with the regular solution. Over the following week, the hydrogel-based cells multiplied while the others declined in number. As for heart function, the team found that the hydrogel cells boosted the pumping efficiency of the left ventricle by 15 percent over the four weeks following injection, compared to eight percent with the regular cells. Interestingly, the team even reports that injections of the hydrogel alone improved heart function and boosted the amount of blood vessels in the area of the heart attack.
The research was published in the journal Biomaterials.
Source: John Hopkins Medicine