CREDIT: A. BONGSO

A group at the National University of Singapore reported last week that it has successfully started a new line of human embryonic stem (hES) cells using human instead of mouse cells as "feeder" cells.

One concern about using hES cells to treat diseases is the fact that all the lines eligible for U.S. government funding have been cultured with mouse fibroblasts, which raises the possibility of contamination. Last year, researchers at Geron Corp. in Menlo Park, California, managed to keep mouse cell ingredients out of a medium that had been exposed to them. But lead Singapore investigator Ariff Bongso says his group found that the Geron recipe supported undifferentiated cell growth for only short periods.

The Singapore team thinks they've found something better: human fetal muscle cells. These cultures not only stably support existing cell lines, the researchers report in the 5 August online edition of Nature Biotechnology--they also enabled the creation of a new line, which has now undergone 50 cell divisions. "This certainly opens the way to deriving more new, safe cell lines," says Bongso.

Stem cell researcher Ronald McKay of the National Institute of Neurological Disorders and Stroke says Bongso's team has done "important" work. "[hES] cells are hard to grow, and there is a real need for methods that make them grow better," he says. Geron CEO Thomas Okarma says that Geron still thinks its own technology, which has been transferred to seven other labs, is more promising. But he says that because of the Bush Administration's decision to limit federal funding to lines created before 9 August 2001, "it's not a surprise" that the first group to derive a new line of hES cells without animal cells works "outside U.S. borders."