Alginate Biomaterial Evades Immune System To Enhance Stem Cell Therapy

Researchers at Rice University and Baylor College of Medicine have developed an immuno-evasive alginate biomaterial hydrogel that can enhance stem cell therapy after myocardial infarction. Stem cells delivered to the heart within the biomaterial survive in greater numbers and for a longer period than cells delivered alone, resulting in a significant enhancement in healing.

Stem cells hold huge promise as regenerative therapeutics, but they also demand specific requirements for successful use. One of the most important is their ability to stay and survive at the site of delivery. Simply injecting these cells into a tissue in a simple saline solution, particularly an inflamed and hypoxic tissue such as the post-infarct myocardium, leads to a significant proportion of the cells being rapidly dispersed and dying, greatly limiting their therapeutic potential. This is a particular issue for donor cells that are implanted into someone else, as they are recognized as foreign by the immune system and destroyed.

To address this, researchers have been developing a variety of biomaterial carriers to encapsulate cells, and protect them in the body. This latest biomaterial is an alginate hydrogel, which contains agents to suppress the local immune response, meaning that the body does not recognize the gel as foreign and does not attack it. Alginate is a polysaccharide that occurs naturally in seaweed. The encapsulated stem cells are shielded and are intended to release healing paracrine factors over time, helping to repair nearby damaged heart tissue.

“Initially, researchers had hoped that stem cells would become heart cells, but that has not appeared to be the case,” said Ravi Ghanta, a researcher involved in the study. “Rather, the cells release healing factors that enable repair and reduce the extent of the injury. By utilizing this shielded therapy approach, we aimed to improve this benefit by keeping them alive longer and in greater numbers.”

The biomaterial can be delivered minimally invasively in the form of tiny capsules loaded with stem cells. Each capsule is only 1.5 mm in size and contains approximately 30,000 cells. “We can deliver the capsules through a catheter port system, and that’s how we imagine they would be administered in a human patient,” said Omid Veiseh, another researcher involved in the study. “You could insert a catheter to the area outside of the heart and inject through the catheter using minimally invasive, image-guided techniques.”

So far, the researchers have tested the biomaterial in an animal model and found that alginate hydrogel cell delivery resulted in a 2.5-fold increase in heart healing compared with cells delivered alone, suggesting that the material has significant clinical potential.

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