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What do humanized mice have to do with fetal tissue research?

That question took center stage at a hearing Thursday before two House subcommittees considering alternatives to the controversial practice of using fetal tissue for research. Since the 1930s, scientists have used fetal tissue in the US, obtained through elective abortions in medical research and experimental therapies. And this research has been supported by the federal government since the 1950s.

During the hearing, debate focused on the merits and value of two different types of humanized mice: One requires fetal tissue; the other does not. Humanized mice, which possess human cells, DNA tissues or immune systems, are used in some biomedical research.

According to the scientist whose humanized mouse research was debated between the two sides, some truth can be found on both sides of the aisle.

What’s the issue with human fetal tissue?

In September, the Department of Health and Human Services canceled a contract with a fetal tissue procurement company due to concerns that the company was not meeting regulations. Subsequently, the agency initiated an audit of human fetal tissue acquisitions and a review to understand whether adequate alternatives exist to the use of human fetal tissue in Health and Human Services-funded research.

However, those opposed to abortion have sought, for decades, to prohibit using federal funds to support research using human fetal tissue, while those in the research world support its use.

Generally, fetal tissue is used to develop cells that “mimic many of the properties that they have in a living body, and therefore can be used as a model for researchers,” according to a 2015 Congressional Research Service report. The National Institutes of Health spends about $100 million a year on research involving human fetal tissue, government data shows.

Not only has the federal government funded fetal tissue research for more than seven decades with procurement governed by an “extensive regulatory framework,” but fetal tissue research has a “long history of support from both sides of the aisle,” said Judy Chu, the Democratic representative from California who sits on the Steering and Policy Committee, during the hearing. Only today do anti-abortion “extremists” threaten the use of fetal tissue in research.

Of the three scientists who presented testimony to the committee, Dr. Tara Sander Lee, a molecular and cell biologist and an associate scholar with the Charlotte Lozier Institute and Dr. David Prentice, an advisory board member for the Midwest Stem Cell Therapy Center argued that several ethical alternatives to human fetal tissue are currently available to researchers – including donated human tissues, bone marrow as well as stem cells and their derivatives.

Dr. Sally Temple, a board member and former president with the International Society for Stem Cell Research, which promotes dissemination of ideas and information related to stem cells, said “the alternatives mentioned may be useful at times but cannot fully replace fetal tissue.” She noted that fetal tissue, being at a different developmental stage, has “unique properties” that donated neonatal tissue lacks and therefore “the consensus of our field” is that fetal tissue is “essential” for biomedical research.

Discussion landed on humanized mice when Temple argued that the humanized mouse model created using human fetal tissue, has made advances in HIV research possible. Lee and Prentice said a new humanized mouse model created using non-fetal human tissue sources might serve as an adequate substitute.

Not so fast, said Matt Brown, an assistant scientist in the department of surgery at the University of Wisconsin at Madison, one of the creators of the new humanized mice created without fetal tissue. “I’m caught in the middle of this,” Brown told CNN after the hearing, which he did not participate in or attend.

Though he’s excited to develop an alternative humanized mouse model, he said more rigorous scientific testing is needed to understand the types of research it can be used for and its value. So it’s too early to suggest his alternative model could replace the fetal tissue model, he said, though he speculates his humanized mouse could be better, in some cases, than the current standard.

“It’s a very nuanced discussion,” Brown said. “If they go ahead and ban this – you know, black and white, let’s ban it all – there will be so many unintended side effects,” he said. “They could do so much damage if they ban this the wrong way; it could set science back years and hurt patients, too.”

At the same time, he believes scientists “should listen to people’s concerns – people feel very strongly about [human fetal tissue]. And no scientist wants to use this unless they have to [based on the science],” he said. “Scientists should pursue alternatives when they are available.”

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The hearing drew stark lines in the sand between the two sides, yet middle ground does exist, as suggested by a close listen to arguments. For example, Temple admitted some research that previously relied on fetal tissue is now done in alternative ways, while Prentice noted that the funding of historic cell lines originally derived from aborted fetuses is not in question. And, seemingly thinking aloud, Mark Meadows, the Republican representative from North Carolina who chaired the hearing, suggested the possibility of continued federal funding to support ongoing fetal tissue research, with new projects funded only if they used alternatives.

In a statement to the committees, Brown expressed modest hopes. He simply wished for a “constructive dialogue” regarding scientists’ need to access tissue, including fetal tissue, to advance the “cutting edge research we are undertaking with the goal of alleviating patient suffering worldwide.”