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James Thomson, pictured here in 2001 in his Primate Center lab. Source: Jeff Miller/UW-Madison Communications.
MADISON, Wis. University of Wisconsin anatomy professor James Thomson
attempted to separate hype from reality on Friday in the controversial field of stem cell research, which in some cases uses tissue from human embryos. The pioneer in stem cell research spoke to about 200 at the UW Memorial Union as part of the Plato discussion series for retired people.
Acknowledging the fierce political debate around the issue of destroying embryos for the purpose of research, Thomson noted that there are still some fundamental reasons why embryonic stem cells, as well as stem cells taken from adults, are needed for research breakthroughs in the next decade. Since 1998, when Thomson reported the first cultivation of embryonic stem cells in the journal Science
, the medical world and media have hailed the discovery as revolutionary.
But pro-life advocates denounce the research as unethical, since it involves the use of human tissue. Thomson noted that in his federally funded research program, only extra embryos from in-vitro fertilization programs that would otherwise be destroyed were used. President Bush in 2001 announced a compromise for federally funded programs that allowed the government to pay for research, but only with cell lines created before that date. Thomson said those existing 12 lines are not enough to support important research goals.
Examining the options
Adult stem cells, currently under no restriction, are limited for research purposes because they cannot be reproduced in the lab indefinitely as embryonic stem cells can. Researchers study these cells, which bodies use to repair themselves, but have so far been unable to use them to treat many diseases.
Thomson also noted limitations with using animal stem cells. Using the mouse is a bad model [in embryonic stem cell research] for many reasons, he said. For example, the mouse does not use a corpus luteum in reproduction, a major failing for replicating human reproduction processes.
Another problem with adult stem cells is that heart cells dont divide in the laboratory, and healthy heart tissue is difficult to access. Growing embryonic stem cells for the purpose of developing heart tissue gives scientists a way to study what goes wrong with healthy tissue when blood flow is blocked, as in the case of heart disease, he said.
The limited number of existing cell lines also poses problems for drug trials, Thomson said. The 12 lines available represent a small pool of genes, which is a problem when testing for drug reactions in people who do not share these genes. Having more genetically diverse stem cells available would reveal more drug reactions at an earlier stage for a larger population, he said.
Recent media attention in the political arena has centered around the potential of using stem cell research to treat various diseases, such as diabetes and Parkinsons disease.
Both Republicans and Democrats have expressed support for using stem cells to treat these diseases by growing replacement organs through the use of undifferentiated embryonic stem cells that are made to develop into organ tissue. This work, Thomson says, is less likely to proceed in the near future.
There are significant safety issues with transplanting tissue from the lab into humans, he noted. Although growing pancreatic tissue from beta cells in the lab is relatively easy to do, the safety issues revolve around understanding how these lab tissues will develop after they are transplanted into a human, he said. We dont understand how they might grow into a cancer, for example, which is a theoretical worry. In addition, the lines developed before 2001 may be of questionable quality, he said.
Instead, he said that basic science has to be conducted to understand why pancreatic tissue is killed by a diabetics immune system in the first place. When science answers these fundamental questions, Thomson predicts a new focus on using embryonic stem cells for growing replacement organs.
Stem cell research in Thomsons lab within this decade will focus on basic science questions such as how cells live and die, important for answering how disease affects living cells, and why stem cells differentiate into organs, significant in finding out how to reprogram cells to form tissue on demand.
Christine Javid is a Madison-based freelance writer for the Wisconsin Technology Network and can be reached at firstname.lastname@example.org