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Hydrogel Aids Stem Cells Repair Heart Functions

EKG graphic

(PublicDomainPictures, Pixabay)

25 September 2015. Tissue engineers and medical researchers at Johns Hopkins University developed a gel material that holds and supports the work of stem cells in repairing heart damage in lab animals. The team led by cardiologist Marie Roselle Abraham and medical materials scientist Jennifer Elisseeff published its findings earlier this month in the journal Biomaterials (paid subscription required).

The Johns Hopkins team in Baltimore is looking for a better way to apply the therapeutic effects stem cells for repairing damaged heart tissue. Because of the heart’s continuous beating, simply injecting stem cells into the heart’s wall pushes all but a few stem cells out into the lungs before they can stick to the wall and grow into new tissue. And, say the authors, applying larger quantities of stem cells by itself does not solve the problem, since metabolism of stem cells slows and the cells soon die without attaching to live cells and tissue for support.

“If we could inject fewer cells soon after heart attacks and coax them to proliferate following transplantation,” says Abraham in a university statement, “we could limit scar formation and be more successful with re-growing new heart muscle.”

The researchers designed a hydrogel material to address this problem. Hydrogels are networks of material that contain primarily water, but maintain enough substance to form into 3-D gelatinous structures. The body naturally forms some materials, such as vitreous humor in the eyes and cartilage, containing protein hydrogels.

The team infused the hydrogel with blood serum, part of the liquid component in blood rich in proteins, as well as hyaluronic acid, also found naturally in the body, mainly in eyes and joints, but also in the heart. The combination of serum and hyaluronic acid provided the nurturing environment to support quantities of stem cells, in a gel material that could stick to heart tissue.

In tests with lab cultures, the researchers found nearly all of the stem cells — both adult and embryonic — contained in the gel survived and proliferated. In addition, the stem cells encased in the hydrogel produced more growth factor proteins associated with heart tissue repair than comparable stem cells left on their own.

In tests with lab rats, a much higher percentage of stem cells delivered in the hydrogel (73%) were retained in the rats’ hearts after one hour, than for stem cells delivered in a solution (12%). Over a seven-day period, the number of stem cells in rat hearts delivered with hydrogel increased, as the stem cells proliferated, while the number of stem cells delivered in a solution declined.

Further tests on lab rats induced with heart attack damage show hearts treated with the stem-cell hydrogel improved their pumping efficiency in the left ventricle, where blood is pumped out through the aorta to most of the body, compared to stem cells injected in a liquid solution. After four weeks, pumping efficiency improved by 15 percent in rats receiving stem cells in the hydrogel, compared to 8 percent for those injected with stem cells in a solution. Hydrogel recipients also showed improved heart function and more blood vessel growth.

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