WASHINGTON -- Scientists at a laboratory affiliated with the University of Wisconsin-Madison have developed a stem cell culture medium free of animal cells and used it to derive two new human embryonic stem cell lines.
The new work, reported in the journal Nature Biotechnology, is a crucial step in stem cell research because it will allow growth of these cells without using animal products that can harbor viruses and other potential sources of problems.
''This work helps us clear some of the major hurdles for using these cells therapeutically," wrote Tenneille Ludwig, the University of Wisconsin-Madison research scientist at the WiCell Research Institute, who led work on developing the new medium.
The development comes as the push for stem cell research has been shaken by the discrediting of South Korean scientist Hwang Woo Suk's claim to have produced tailored embryonic stem cells, and as US lawmakers consider expanding funding for stem cell research.
Growing living cells outside the body generally requires providing the cells in a lab dish with the right mix of nutrients, hormones, growth factors, and blood serum.
This method often depends on animal cells, such as those obtained from mouse embryos in the case of embryonic stem cells, to keep the cells alive and thriving in the culture.
''This is the first time it has been possible for us to derive new cell lines in completely defined conditions in medium that completely lacks animal products," said James Thomson, senior author of the new study and a University of Wisconsin-Madison professor of anatomy who was the first to grow human embryonic stem cells in the lab seven years ago.
Many scientists worry that animal viruses and other agents might be taken up in the human cells and could infect human patients if those cells were to be used for therapy.
''All of the concerns about contaminating proteins in existing stem cell lines can essentially be removed using this medium," Ludwig wrote in the Nature Biotechnology paper.
The two new Wisconsin stem cell lines have survived for more than seven months in the new culture medium, but one line had an abnormal chromosome at four months and the second developed an abnormality by seven months, according the report.
This latest development in stem cell research comes at a crucial time as US lawmakers are set to debate legislation that would expand funding for stem cell lines derived after August 2001.
President Bush had allowed the use of federal funds in 2001 to study only a limited number of established stem cell lines.