Cardiac stem cell therapy is a promising treatment for damaged hearts. However, researchers are still working on two major issues with the therapy – how to keep the stem cells in place and how to prevent rejection when the stem cells are not from the patient’s own body. A new approach may solve both of these problems.

One of the major drawbacks of cardiac stem cell therapy is simply that the cells do not stick to the injured heart tissue. Enter a thermosensitive nanogel that is liquid at room temperature but becomes a thick, sticky gel as it warms.

The nanogel, poly(N-isopropylacrylamine-co-acrylic acid), or P(NIPAM-AA) for short, had another property that made it appealing for use: in its thickened state, it had porous openings large enough for a stem cell’s healing factors to escape, but not large enough for immune cells to enter. And it could be adjusted to slowly degrade over time, giving stem cells enough time to repair a damaged heart before dissolving away.

The researchers tested the nanogel delivery system in mice and pigs with hearts damaged by a heart attack. Without the nanogel, only about one percent of injected stem cells stayed in the heart. With the gel, up to 15 percent of the stem cells stayed put. They also found that in both animal models heart function improved three to four weeks after treatment.