Since 1998, the volume of research being conducted with hES cells has expanded, primarily with private funds because of restrictions on the use of federal funds for such research. Those restrictions are both legislative and by executive order. Federal legislation forbids the use of federal funds for any research that destroys an embryo, that is, is “nontherapeutic” for the embryo. That effectively prevents any use of federal funds to derive hES cells from blastocysts. Research with established hES cell lines is further limited by presidential policy: the policy announced by President George W. Bush in 2001 restricts federal funding of research with hES cells to use of specific federally approved cell lines already in existence before August 9, 2001. The policy states further that funding is available only for research with hES cell lines that were derived before August 9, 2001 from frozen human blastocysts that remained at infertility clinics and that were (1) generated for reproductive purposes, (2) donated with informed consent, and (3) donated with no financial inducements.1 Laboratories or companies that provide cells that meet those conditions (originally thought to be roughly 60 cell lines, now thought to be about 22) could list the lines in the National Institutes of Health (NIH) Human Embryonic Stem Cell Registry. To do so they were required to submit a signed assurance that their hES cells met the criteria. Once the assurance was verified, the cell lines became available for use in federally funded hES cell research. The date of August 9, 2001, was set as the cutoff point to distance the federal government from any privately funded future use of embryos for hES cell research.

Not all the original hES cell lines thought to be available for federally funded research have been viable, nor do they exhibit sufficient genetic diversity for all research endeavors and possible future clinical use. Furthermore, the roughly 22 lines now available were grown on mouse-feeder cell layers. That does not necessarily render them inadequate for research pursuing human applications, but it does raise concerns about contamination. The presence of animal feeder cells increases the risk of transfer of animal viruses and other infectious agents to humans that receive the hES cells and in turn to many others. There is also the risk that hES cells grown with nonhuman animal products will have incorporated antigenic glycolipids into their cell surface. If hES cell research and therapy are to be thoroughly investigated, cell lines that are more genetically diverse and free of animal contaminants must be available. A first step in that direction was taken in February 2005 with the publication of a paper documenting the first successful growth of hES cell lines without mouse feeder cells, although contact with a growth supplement derived


“Notice of Criteria for Federal Funding of Research on Existing Human Embryonic Stem Cells and Establishment of NIH Human Embryonic Stem Cell Registry (Nov. 7, 2001)”, at

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