Human embryonic stem cells (hESCs) have the remarkable ability to turn into any type of cell in the body. For this reason, these cells give basic researchers an ideal model for studying early human development and advancing regenerative medicine. Typically, scientists grow hESCs in the laboratory by culturing them on a layer of mouse cells that prevents the hESCs from changing into other cell types too soon. Although stem cell therapy is still years away, scientists have searched for a way to get rid of this step because it poses a risk of contamination from animal cells.
New results from two basic researchers working independently may solve this problem. One of the two researchers who originally discovered hESCs, James Thomson, V.M.D., Ph.D., of the WiCell Research Institute in Madison, Wisconsin, discovered that adding a human protein, basic fibroblast growth factor, to a stripped-down version of cell-culture broth kept the hESCs in an undifferentiated state. It did this, he found, by stopping molecular signals that provoke the cells to mature into other cell types. Thomson also learned that by using his method, mouse cells were no longer needed. In related work, Ali Hemmati-Brivanlou, Ph.D., of the Rockefeller University in New York City discovered that turning on the production of yet another human growth factor also helped to maintain the human stem cells’ clean slate and did not require mouse cells either.
The findings are a critical step forward in the quest to understand the basic biology of hESCs. What’s more, by simplifying the procedure for growing hESCs in the absence of animal cells, the researchers pave the way for future scientists aiming to develop stem-cell therapies to replace diseased or injured cells.
