Stem Cells Help Regenerate Tissue Damaged From Heart Attack

The work, led by Drs. Margaret Goodell and Karen Hirschi, is the latest in the fast-moving field of stem cell research, which focuses on the ever-versatile cells that can transform themselves into various tissues. Study results are published in the June 1 issue of The Journal of Clinical Investigation.

Goodell, Hirschi and their research team found that stem cells taken from the bone marrow of an adult mouse and transplanted into the bone marrow of another adult mouse had the capability to transform into blood vessels and cardiac muscle, contributing to the restoration of tissue that had been damaged from a heart attack.

"The body's natural response to injury is to repair itself," Goodell said. "By letting the cells move into the blood stream, we've shown that the transformation of the bone marrow stem cells into blood vessels and heart tissue is part of a naturally occurring process."

The natural repair process, however, is overwhelmed after severe injuries, like those caused by a heart attack, and is not sufficient to completely restore the heart tissue. The scientists are working to enhance that process.

For the research, Goodell and Hirschi, assistant professors in the Center for Cell and Gene Therapy and the department of pediatrics at Baylor, and their team extracted stem cells from the bone marrow of the mouse. The cells were "purified," using a cell sorter, and a technique designed by Goodell to isolate certain types of stem cells one by one.

Those cells were tagged with a blue marker so they could be easily identified and transplanted into the bone marrow of another mouse.

To induce a non-fatal heart attack, Dr. Mark Entman, a professor of medicine at Baylor and scientific director of The DeBakey Heart Center at Baylor and The Methodist Hospital, created a blockage by temporarily tying off the coronary artery of the mouse with the new stem cells.

The researchers then waited two weeks for the tissue to repair. Upon examining the heart, they found marked stem cells in both the blood vessels and cardiac muscle. Marked stem cells were not found in the hearts of healthy mice with normal hearts, even though they had been injected with the marked stem cells as well.

""We believe that the cells can contribute to the regeneration of tissue, but are not sufficient to fully repair a heart at this point. If we can improve upon this process, it could be a promising addition to current therapy," Goodell said.

This approach distinguishes these findings from similar studies. Use of the blood stream eliminates the risks of open-heart surgery, which is necessary to inject stem cells directly into the heart, and infections.

More than a million Americans suffer heart attacks each year. Although medications can minimize damage, they don't repair the dead tissue and prevent complications that often arise such as scarring that can cripple the heart.

"Ultimately, we want to develop targeted therapy, taking the patient's own stem cells to repair damaged tissue, preventing rejection. But first, we need to understand the mechanism –- how stem cells turn into heart or vessel cells -- and improve on that to make it more efficient. We want to direct that development," Goodell said.

Study co-authors were Kathyjo A. Jackson, Susan M. Majka, Hongyu Wang, Jennifer Pocius, Craig J. Hartley, Mark W. Majesky, Mark L. Entman, and Lloyd H. Michael.