Hopkins team is using rats to make heart cells

Research marks a step toward treatments for human diseases

Human heart muscle cells can be created in the lab, but researchers have been unable to grow the immature cells to the point where they could be useful.

It’s a conundrum that’s stumped researchers in regenerative medicine.

“You cannot really use them for regeneration. You cannot even use them for disease models,” said Dr. Chulan Kwon, a professor at the Johns Hopkins University School of Medicine.

But Kwon said he’s discovered a solution for the problem in an unlikely place — newborn rats — and he published a study about his research last month in the journal Cell Reports.

When immature human heart cells are injected into baby rats, they match the rodents’ rapid growth cycle and develop fully. These rats act as living incubators, said Dr. David Kass, a Hopkins professor, cardiologist and co-author of the study.

“The biological environment gives you whatever the magic juice is,” Kass said. “There were a lot of people looking for this magic juice.”

Researchers at the University of Washington, Harvard and Stanford universities and beyond have been working to solve this puzzle fundamental to regenerative medicine.

“Laboratories throughout the world are working on this,” said Dr. Richard Lee, a Harvard professor of stem cell and regenerative biology. “We are all very excited that we can make heart cells, but they’re heart cells like an infant’s heart cells. We want to make heart cells like our patients, who are mostly adults.”

Lee said his research team is working to unravel the conditions that stimulate cells to mature inside the body. He praised the Hopkins discovery. “It’s a very nice step forward,” Lee said. Dr. Charles Murry at the University of Washington also has tried to grow the cells to maturity.

“We tried a whole lot of things that didn’t work,” he said. “Sort of like Edison and the light bulb.”

Murry has seen some positive signs when feeding the cells fat instead of sugar.

“But we haven’t seen anything that works as well as putting them back into their natural environment, which is back into a heart,” he said.

Soon after the late 1990s, when researchers isolated embryonic stem cells, people in the field wondered if the process could be used to grow heart muscles in the lab and someday repair the lasting damage from heart attacks and disease. Researchers in 2007 developed methods to modify skin cells to behave as stem cells, and, about five years later, Murry’s research team at the University of Washington developed techniques to activate these modified skin cells into early forms of heart muscle cells.

From there researchers have worked to