'Master molecule' may improve stem cell treatment of heart attacks

Johns Hopkins researchers have discovered that a single protein molecule may hold the key to turning cardiac stem cells into blood vessels or muscle tissue, a finding that may lead to better ways to treat heart attack patients.

Human heart tissue does not heal well after a heart attack, instead forming debilitating scars. For reasons not completely understood, however, stem cells can assist in this repair process by turning into the cells that make up healthy heart tissue, including heart muscle and blood vessels. Recently, doctors elsewhere have reported promising early results in the use of cardiac stem cells to curb the formation of unhealthy scar tissue after a heart attack. But the discovery of a "master molecule" that guides the destiny of these stem cells could result in even more effective treatments for heart patients, the Johns Hopkins researchers say.

In a study published in the June 5 online edition of the journal Science Signaling, the team reported that tinkering with a protein molecule called p190RhoGAP shaped the development of cardiac stem cells, prodding them to become the building blocks for either blood vessels or heart muscle. The team members said that by altering levels of this protein, they were able to affect the future of these stem cells.

"In biology, finding a central regulator like this is like finding a pot of gold," said Andre Levchenko, a biomedical engineering professor and member of the Johns Hopkins Institute for Cell Engineering, who supervised the research effort.

The lead author of the journal article, Kshitiz, a postdoctoral fellow who uses only his first name, said, "Our findings greatly enhance our understanding of stem cell biology and suggest innovative new ways to control the behavior of cardiac stem cells before and after they are transplanted into a patient. This discovery could significantly change the way stem cell therapy is administered in heart patients."

Earlier this year, a medical team at Cedars-Sinai Medical Center in Los Angeles reported initial success in reducing scar tissue in heart attack patients after harvesting some of the patient's own cardiac stem cells, growing more of these cells in a lab and transfusing them back into the patient.

Using the stem cells from the patient's own heart prevented the rejection problems that often occur when tissue is transplanted from another person.

Levchenko's team wanted to figure out what, at the molecular level, causes the stem cells to change into helpful heart tissue. If they could solve this mystery, the researchers hoped the cardiac stem cell technique used by the Los Angeles doctors could be altered to yield even better results.

During their research, the Johns Hopkins team members wondered whether changing the surface where the harvested stem cells grew would affect the cells' development. The researchers were surprised to find that growing the cells on a surface whose rigidity resembled that of heart tissue caused the stem cells to grow faster and to form blood vessels. A cell population boom occurred far less often in the stem cells grown in the glass or plastic dishes typically used in biology labs. This result also suggested why formation of cardiac scar tissue, a structure with very different rigidity, can inhibit stem cells naturally residing there from regenerating the heart.