Making a Heart Beat

While it takes forever to make that special someone's heart beat just for you, scientists have been able to do something like that in a lab. Researchers at Johns Hopkins report that they have been able to grow human nerve cells that can partner with heart muscle cells and stimulate them to throb, to beat.

The study, published in the journal Cell Stem Cell, details how the heart-thumping nerve cells— specifically sympathetic nerve cells— were derived from induced pluripotent stem (iPS) cells that, in turn, were made from human skin cells. This means scientists will be able to grow nerve cells in the lab. But not just normal nerve cells, those that replicate particular patients' diseases.

This ability to replicate diseased cells comes into play from the fact that many promising drugs fail in clinical trials because of nervous system side effects, including increased blood pressure. With this research, scientists would be better able to predict which drugs will negatively affect the functioning of our vital organs by simply testing them on lab-grown cells.


To create the cells, the group used both human embryonic stem cells and iPS cells, training them to glow green if certain master genes were activated, thus indicating that they were sympathetic nerve cells already. They then searched for the proper combination of chemicals that takes the stem cells through different phases of maturation.

The team then grew the nerve cells with heart muscle cells from three different sources: newborn mice, mouse embryonic stem cells, and human iPS cells. They then stimulated the nerve cells to see whether they would in turn cause the heart muscle to contract.

"The key question in the stem cell field is, 'how can we make mature cells of every kind in the body?'" says team leader Gabsang Lee, Ph.D., D.V.M. "Now we can check sympathetic nerve cells off the list, although we will keep studying their maturation process to figure out what molecular changes are caused by their connection to heart cells."

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