To figure out how CBSCs might behave in the heart in the first place, Houser's team, led by Temple graduate student Jason Duran, began by collecting the cells from mouse tibias. The particular mice used had been engineered with green fluorescent protein (GFP), which meant that the CBSCs carried a green marker to allow for their later identification. The cells were then expanded in petri dishes in the laboratory before being injected directly into the hearts of non-GFP mice that had suffered heart attacks. Some mice received cardiac stem cells instead of CBSCs.
In the following weeks, as the team monitored the progress of the mice, they found that the youthfulness of the CBSCs had prevailed. The cells had triggered the growth of new blood vessels in the injured tissue, and six weeks after injection, they had differentiated, or matured, into heart muscle cells. While generally smaller than native heart cells, the new cells had the same functional capabilities, and overall they had improved survival and heart function. Similar improvements were not observed in the subset of mice treated with cardiac stem cells. Nor was there evidence in those mice that the cardiac cells had undergone differentiation.
The findings challenge the general assumption that cardiac stem cells, because they reside in the heart, are the cells most capable of repairing damaged heart tissue. For that reason, according to Houser, the new paper likely will be controversial.
"What we did generates as many questions as it does answers," he said. "Cell therapy attempts to repopulate the heart with new heart cells. But which cells should be used, and when they should be put into the heart are among many unanswered questions."
To address at least some of those questions, Houser's team plans next to
|Contact: Jeremy Walter|
Temple University Health System