New research says studying both adult and embryonic stem cells can benefit medical science, but banning the study of either type could harm studies of the other.

Researchers from the University of Michigan, Stanford University and the Mayo Clinic in Rochester, Minn. recently investigated whether the increased number of studies with a certain type of adult stem cell has changed the overall course of research in the field.

The researchers analyzed more than 2,000 scientific papers and found adult stem cells are not replacing human embryonic stems cells in the laboratory. Instead, the two cell types have proven to be complementary and any disruption of federal funding, they say, would negatively impact stem cell research overall.

"This is an important study that systematically examines the co-authorship networks of stem cell research articles and uses those to understand the interactions between two complementary areas of research," says Julia Lane, program director for Science of Science & Innovation Policy at the National Science Foundation (NSF), which funded the study.

"It is particularly interesting because it uses new analytical techniques to advance our understanding of how the implementation of policy in one area can affect scientific research in another area."

The research appears in the June 9 journal Cell.

"The incentives to use both types of cell in comparative studies are high," says Jason Owen-Smith, a sociologist at University of Michigan. He notes the science behind adult stem cells that can be "reprogrammed," called human induced pluripotent stem cells (hiPSCs), is still in its infancy, having become widely available in 2007.

"As a result, induced pluripotent stem cells do not offer an easy solution to the difficult ethical questions surrounding embryonic stem cell research," he says.

Pluripotent stem cells are those capable of differentiating into any type of tissue, hence the attractiveness of embryonic stem cells, or hESCs, also called ES cells, which are also pluripotent.

The researchers examined stem cell research papers published between 1998 and 2010. They found the proportion of papers using human adult and human embryonic stem cells together is growing faster than those using adult stem cells alone.

In 2008, only 15 or 5.1 percent of all papers examined in the study reported using adult stem cells, and only three of those papers combined the use of human adult and human embryonic stem cells. By 2010, some 161 of 574 or 28 percent of papers reported on studies of both cell technologies, and 62.1 percent of those papers paired adult and embryonic cell lines.

Because use of the two cell types has become so intertwined, any federal policy that would deny funding for embryonic stem cell research "would derail work with a nascent and exciting technology," says Owen-Smith.

If federal funding stops for human embryonic stem cell research, it would have a serious negative impact on adult stem cell research, says Stanford University bioethicist Christopher Scott, one of the paper's co-authors. "We may never be able to choose between iPS and ES cell research because we don't know which type of cell will be best for eventual therapies."

"The whole point with science policy is to have a more scientific basis to understand the impacts of policy decisions on science if and when those decisions are made," says Lane

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