To conduct the study, the researchers collected a supply of human stem cells from what is generally regarded as debris from the process of banking human red blood. (After blood is collected from volunteers, it is separated into white and red blood cells, and the white blood cells are usually thrown away.) The scientists collected white blood cells and then searched for those cells that express a protein (CD34+) that is known to be associated with stem cells. They then isolated cells with the CD34+ marker from the white cells.
To test whether peripheral blood stem cells could regenerate tissue, the research team used two groups of mice that were engineered not to have an immune system, so that they would not reject human cells. One group of mice was given an artificially induced heart attack, and then immediately treated with an injection of the human stem cells. The other mice, with healthy hearts, also received the stem cell therapy.
The researchers found that in mice with an injured heart, new cardiac muscle cells (myocytes) had developed at the edge of damaged tissue, and several layers of new blood vessel tissue (endothelial and smooth muscle cells) had also grown. Little evidence of such repair was found in the mice with healthy hearts, says Yeh.
"We've shown that CD34+-associated cells can actually transform into three different cells used by the heart, and that tissue damage is critical to this process," he says.
Several sources for regenerative stem cells have been suggested, such as bone marrow, cord blood and embryonic cells, but this study "demonstrates that adult blood stem cell
'"/>
Contact: Laura Sussman
lsussman@mdanderson.org
713-745-2457
University of Texas M. D. Anderson Cancer Center
20-Oct-2003