Biomedical engineers from Duke University in North Carolina and the biotechnology company VistaGen in San Francisco grew in the lab human heart tissue material from stem cells that could one day repair heart muscle or test new drugs. Findings of the team led by Duke professor Nenad Bursac appeared online last week in the journal Biomaterials (paid subscription required).
Bursac and colleagues started with human pluripotent embryonic stem cells, which they induced through chemical and physical stimulation to form into a single-layer of cardiomyocyte cells, then into three-dimensional or fibrous tissue. Tests of the tissue in the lab showed it was able to conduct electrical signals and contract much like normal cardiomyocytes. These conductive and muscle-emulating properties, say the researchers, were generally missing from earlier attempts to grow heart tissue from stem cells.
“This is the closest man-made approximation of native human heart tissue to date,” says Bursac. “The structural and functional properties of these 3-D tissue patches surpass all previous reports for engineered human heart muscle.”
Lab-grown tissue from a patient’s own stem cells could be used to repair heart muscle damaged by heart attacks, which would overcome problems of immune-system rejection. However, current methods would need to be speeded up to be beneficial to patients. It took a little more than a month for the team to mature the tissue in the study; Bursac believes it would take five to six weeks to produce a functioning heart patch.
Another potential application for lab-grown heart tissue is for drug screening. Three-dimensional tissue, say the researchers, would provide a more realistic testing medium than either single layers of cells or animal models. “Instead of, or along with testing drugs on animals,” says Bursac, “the ability to test on actual, functioning human tissue may be more predictive of the drugs’ effects and help determine which drugs should go on to further studies.”
VistaGen, the company collaborating with the Duke researchers, is developing a test for cardiac toxicity called CardioSafe 3D that generates a testing medium made of mature heart cells from stem cells. CardioSafe 3D, says the company, can be used to screen heart drug candidates for toxicity and other effects in the lab before engaging in expensive clinical trials.
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