Mouse Stem Cells Form Heart Muscle

A new Harvard study may open the possibility of using human stem cells to regenerate diseased or damaged hearts.

Led by Medical School Professor Kenneth R. Chien ’73, the project—published in today’s issue of Science—was a collaborative effort of scientists at the Harvard Stem Cell Institute, Massachusetts General Hospital, and Harvard’s School of Engineering and Applied Sciences.

The team used a mouse cardiac stem cell to develop a functioning, intact strip of mouse heart muscle, raising the possibility that such cardiac stem cells can have regenerative capacity if manipulated appropriately.

Chien—the director of the Cardiovascular Research Center at Harvard-affiliate MGH—said that technology developed by SEAS Professor Kevin Kit Parker was integral to the team’s discovery.

“[Parker] created an imprint like Saran Wrap, and when cells are put on top of it, they can be forced into a pattern,” Chien said. “We take cells we have isolated to form strips of functioning muscle. It’s like a Band-Aid for the heart, and cells line up just the way you want them to.”

Chien said this is the first time someone has been able to make a functional muscle in a mature conformation by facilitating the transition from a pluripotent embryonic stem cell—a cell that has the capacity to differentiate into any other cell type—to heart tissue.

Ibrahim J. Domian, the first author on the paper and an HMS instructor, said color receptors were used to tag heart cells in a genetically-modified mouse embryo. This color-coding approach was used to identify and purify a rare daughter cell of a master heart stem cell that the researchers then used to make a an actual working heart muscle cell.

Beneath the film that Parker developed, cells can grow, and when they bunch up, scientists can measure and observe the cells’ transition from a mere collection of cells to actual muscle tissue.

Domian added that while the researchers only used mice for this study, their next step will be to generalize the results to humans.

Despite his team’s findings, Chien said he is “still in the early days” of his research.

His ultimate goal is to create a three-dimensional muscle, instead of just a two-dimensional set of cells. These cells would behave as fully functional cardiac and vascular cells, which could then be used to repair damaged hearts.