Happy International Stem Cell Awareness Day! Researchers from the New York Stem Cell Foundation are celebrating by publishing (subscription required) the first reports of human stem cell lines created through a technique called somatic cell nuclear transfer, or SCNT. Although the technique is similar to that used to clone Dolly the sheep in 1996, the resulting human embryonic stem cell lines have three copies of each gene, rather than the normal two. As a result, they can not be used for therapies. But the research is an important proof of principle that will set the stage for future work, said study co-author Scott Noggle, PhD, in a press briefing yesterday:
The goal of this research was to create patient-specific embryonic stem cells. We have shown for the first time that the human oocyte has the capacity to reprogram somatic nuclei to a pluripotent state.
To conduct the research, Noggle and Dieter Egli, PhD, used donated human eggs. They first tried removing the eggs' own haploid genomes (as reproductive cells, eggs and sperm each have one half the normal complement of genetic material) and replacing it with the nuclei of a somatic, or specialized adult, cell. They found that the resulting cell underwent only a few cell divisions before halting. When they simply added the somatic nuclei to the eggs, they had much better luck: the cell went on to form a multi-cellular structure called a blastocyst, from which Noggle and Egli successfully prepared human embryonic stem cell lines with three, rather than two, copies of each gene. Says Egli:
We are now trying a number of approaches to remove the egg genome. Although the long-term goal is to generate cells for use in therapies, we can use these cells now for several important studies, including comparing them to human iPS cells.
iPS cells are pluripotent cells created from somatic cells by using viruses or other genetic manipulation. While they, like cells derived from SCNT, can be generated from the patient they are meant to treat (and thus should not generate an immune response), researchers agree that they are not genetically identical to true embryonic stem cells and more research is needed to determine their therapeutic usefulness.
The full study requires a subscription to access. But you can read a nice review of the work in today's Nature News.
