FRIDAY, Aug. 7, 2009 (HealthDay News) -- Only two of 21 approved human embryonic stem cell lines are routinely used by researchers in the United States, says a new study.
The study found that two cell lines, known as H1 and H9, accounted for 941 of 1,217 requests, or 77 percent, placed by scientists since 1999 for human embryonic stem cell lines housed at the two largest stem cell banks in the country.
Another line, H7, was requested 111 times, and 13 other lines were requested fewer than 10 times.
The study's authors also found that H9 was discussed in 83 percent of 534 published studies from 1999 to 2008, H1 was discussed in 61 percent and H7 in 24 percent. The total is more than 100 percent because many studies used more than one cell line.
"I was surprised by the results," Christopher Scott, director of Stanford University's Program on Stem Cells in Society, said in a news release. "I never imagined that we would find that three-fourths of the requests would be for the same two cell lines."
The study appears in the Aug. 7 issue of Nature Biotechnology.
Scott and his fellow researchers said the findings raise concerns about the reauthorization process of stem cell lines under way at the U.S. National Institutes of Health. If the lines that have been in use are excluded from federal funding because of ethical considerations, they said, scientists might abandon research on them in favor of other cell lines.
However, they added, the two most-used lines might have abnormalities or other characteristics that would make them less useful than newer lines.
Future NIH policies should preserve scientists' ability to continue work on the well-studied lines while also encouraging the study of new lines expected to become eligible for federal funding, Scott said.
The U.S. National Institutes of Health has more about stem cells.