Stem cell researchers at the University of Miami Miller School of Medicine have made another discovery advancing the field of cardiac stem cells. Nanette H. Bishopric, M.D. (pictured), professor of medicine and director of the Cardiovascular Genetics Laboratory, has led a team of researchers in discovering a factor that can serve as a predictor of stem cell development into blood vessels, a key finding for future applications.
The heart is composed largely of rhythmically contracting muscle cells, known as cardiac myocytes, and cells that make up the inner and outer layers of blood vessels, called smooth muscle and endothelial cells. Heart cells are long-lived, but can be damaged and lost by different types of heart disease. Only recently have researchers discovered that the adult heart contains stem cells, cardiac progenitor cells (CPCs) that can differentiate into each of these three cell types, potentially repairing the damaged heart.
Because heart failure affects an estimated 5 million people in the U.S., a figure which is expected to increase 25 percent by the year 2030, there is a distinct need to develop more effective therapies. The results of this study advance the field of stem cell therapy for cardiac repair on two levels.
One key discovery of this study is that the CPCs vary greatly in their ability to differentiate into blood vessels. Some can differentiate efficiently into blood vessels while others have a more limited ability. Forming blood vessels is critically important for heart repair.
Bishopric and her team also discovered which CPCs have the most potential to develop into blood vessels. They found that those particular stem cells can be recognized both by their shape and by an enhanced capacity to make a protein called SDF-1.
“Discovering that all cardiac stem cells are not created equal changes our approach to using stem cell therapy in cardiac repair,” says Bishopric. “Our work to distinguish which are most likely to differentiate into blood vessels helps all researchers hone in on the most promising types of stem cells in cardiac repair.”
Previously, SDF-1 was thought to be a signal coming from the damaged tissue to recruit repair cells. It turns out that SDF-1 is made by the stem cells themselves and the amount varies from cell to cell, depending on unknown factors. Working with mouse models, Bishopric’s team discovered that stem cells with high levels of SDF-1 were able to generate blood vessels and form connections with blood vessels from the recipient animals, while those with low levels of SDF-1 could not.
Illustration: University of Miami Miller School of Medicine.
University of Miami Miller School of Medicine News Release (08/24/11)
Abstract (Public Library of Science ONE; 6(8) (08/24/11))