Jan. 31, 2011
Scientists with the Scripps Research Institute have directly converted adult mouse skin cells into beating heart cells, without using any stem cell intermediate, and without the laborious process of generating embryonic-like stem cells. Using a reprogramming process similar to that for induced pluripotent stem (iPS) cells, they were able to directly produce "spontaneously contracting patches" of heart cells in the lab. The research is published online in Nature Cell Biology.
The group used the same four genes ("Yamanaka factors") often used to make iPS cells, but switched off the gene activity after a few days, before the cells had a chance to become iPS cells. Then they stimulated the cells with factors to direct them into becoming cardiac-type cells.
According to Dr. Sheng Ding, senior author of the study:
In 11 days, we went from skin cells to beating heart cells in a dish. It was phenomenal to see.
"This work represents a new paradigm in stem cell reprogramming. We hope it helps overcome major safety and other technical hurdles currently associated with some types of stem cell therapies."
The worrisome type of stem cells is pluripotent stem cells, i.e., embryonic stem cells, which have a propensity to grow out of control and form tumors.
Back in 2009, similar story titles (converting skin to beating heart cells) appeared when a group used skin cells to make human iPS cells (pluripotent, embryonic-like stem cells), then turned those iPS cells into cardiomyoctyes in culture. But because of the embryonic-like nature of iPS cells, their practical application for patient transplant is in doubt. When pluripotent cells are injected in mice, they cause cancer-like growths.
Direct reprogramming, going from one cell type to another without forming a pluripotent stem cell, offers a way around the practical problems of pluripotent stem cells. Several other groups have shown the possibility of direct reprogramming to form various tissue types.
Meanwhile, adult stem cells have already successfully treated patients with chronic heart failure.