The National Institutes of Health (NIH) is requesting public comment on a revision to the definition of human embryonic stem cells (hESCs) in the NIH “Guidelines for Human Stem Cell Research.”
The guidelines were initially implemented on July 7, 2009, to outline policies and procedures under which the NIH will fund stem cell research and to ensure that stem cell research funded by NIH is ethical, scientifically worthy, and conducted in accordance with applicable law.
The July guidelines define hESCs as those generated from the blastocyst; an embryonic stage reached 5 days after fertilization. According to NIH, this definition had the unintended consequence of excluding certain hESCs—such as those derived from an embryo that fails to develop to the blastocyst stage.
NIH’s proposed change to the definition in the new guidelines would allow researchers to work with cells derived from eggs at an earlier stage, meaning that they could use cell lines created from blastomeres—the cells derived after the first few divisions of the fertilized egg.
The new proposed definition will be amended as follows: “hESCs are pluripotent cells that are derived from early stage embryosm up to and including the blastocyst stage, are capable of dividing without differentiation for a prolonged period in culture, and are known to develop into cells and tissues of the three primary germ layers.”
Public comment must be entered by March 25, 2010, at the NIH stem cell information website.