Exosome spray may be better able to heal damaged hearts

After someone has suffered a heart attack, non-beating scar tissue grows back in place of the damaged cardiac tissue, leaving the heart permanently weakened. A newly developed spray-on medication, however, may someday help change that.

Stem cell therapy is one of the main methods that has been suggested for regrowing cardiac tissue on damaged hearts. Unfortunately, though, it can result in problematic immune responses or uncontrollable cell growth.

Instead, scientists have looked to stem-cell-produced membranous sacs known as exosomes. These contain lipids, proteins and nucleic acids which are secreted by stem cells, and they have been shown to more safely aid in the regrowth of cardiac tissue.

Previously explored techniques for introducing them to the heart have included injecting them right into the damaged tissue, or applying them onto its surface in the form of an adhesive patch. They tend to quickly break down in the former approach, however, while the latter involves risky and invasive open-heart surgery.

Seeking a better alternative, a team led by Yafeng Zhou of China's Dushu Soochow University developed a liquid solution that combines exosomes with fibrogen, which is a protein that aids in blood clotting. That liquid was loaded into one barrel of a tiny double-barrelled syringe, the other barrel of which contained an additional clotting protein called thrombin.

In lab tests performed on rats, a spray needle on the end of the syringe was able to access the animals' hearts through a single small incision in their chest – another small incision was used to insert a mini-endoscope.