The National Institutes of Health may temporarily resume funding for research involving human embryonic stem cells, an appeals court ruled Thursday — though uncertainty over the future of the field remains, scientists said.

The United States Court of Appeals for the District of Columbia issued a one-page order that blocked a prohibition — set in place last month, to the shock of many scientists — against federal funding for the controversial research. A three-judge panel asked parties in the lawsuit to supply additional information by Sept. 20. After that, it will decide whether to keep its order in place until the case is resolved in the trial court.

The judges noted that their ruling should not be taken as a sign that they are likely to side with the Department of Health and Human Services, which invests more than $30 billion in biomedical research annually through the NIH.

At issue is whether a federal law prohibits the government from using taxpayer dollars to pay for experiments involving human embryonic stem cells, which are made by dismantling days-old embryos. The law, known as the Dickey-Wicker Amendment, explicitly forbids funding for “research in which a human embryo or embryos are destroyed.”

But the Department of Health and Human Services has argued that creating human embryonic stem cells is not the same as using them as tools to study genetic diseases or grow replacement tissues that could treat patients with diabetes, Parkinson’s disease or spinal cord injuries. The NIH has never paid for the creation of the stem cell lines themselves.

Last year, however, opponents of human embryonic stem cell research sued the government and argued that the distinction was meaningless. On Aug. 23, U.S. District Judge Royce C. Lamberth agreed — and surprised the NIH by telling the agency it could no longer fund some of the experiments it considers most promising.

“We are pleased with the court’s interim ruling, which will allow this important, life-saving research to continue while we present further arguments to the court in the weeks to come,” said NIH Director Francis Collins.

Scientists also welcomed Thursday’s development but said questions remained about their prospects for getting the long-term grants they needed to keep their laboratories afloat.

Dr. Anthony Blau, co-director of the University of Washington Institute for Stem Cell and Regenerative Medicine in Seattle, said he had been planning to hire a new lab member to help study cancer with embryonic stem cells. But with the funding situation still in flux, he is holding off.

Thursday’s ruling “doesn’t remove the uncertainty of this whole climate around human stem cell research,” he said. “You certainly don’t want to make a commitment to hire someone and find out in a few weeks, or a few months, that you can no longer pay their salary.”

At the University of Michigan Center for Stem Cell Biology in Ann Arbor, Director Sean Morrison learned Thursday — the day the temporary ban was lifted — that a substantial NIH training grant involving dozens of professors was canceled because he and another researcher do some work with human embryonic stem cells.

The training grant had nothing to do with stem cells, and its termination illustrates “how nuts this whole thing is,” he said. Morrison said he had no idea whether Thursday’s order will cause NIH to reconsider.

Dr. James Sherley, a senior scientist at the Boston Biomedical Research Institute and one of the plaintiffs in the case, said he was not concerned by the legal development.

“This is sort of routine court business,” he said. “It hasn’t really impacted the way we’re feeling about the case.”

In their suit, Sherley and Theresa Deisher of AVM Biotechnology in Seattle argue that the funding policy harms them because it hurts their chances of winning lucrative NIH grants for their own research using adult stem cells.

However, Collins has pointed out that scientists working with adult stem cells are not in direct competition for NIH funding with those who study embryonic stem cells. All 50,000 funding proposals sent to the agency each year compete with one another, with no particular amount earmarked for stem cells, he said.

In any event, Sherley was awarded a $425,500 grant from the NIH this fiscal year to purchase a high-tech cell-analyzing machine for use with his stem cell research and other projects at his institute, according to NIH records.

Deisher, the other plaintiff, has never applied for funding from the biomedical research agency, according to court filings.

karen.kaplan@latimes.com

amina.khan@latimes.com