Sifting through all that monkey business
by David Kent
Yesterday, a landmark paper emerged from Cell which reported two major findings to the scientific community:
- Primate embryonic stem cells cannot generate chimeras, and
- Aggregation and injection of multiple early-stage four-cell primate embryos (not embryonic stem cells) can form chimeras.
Together these findings underscore a fundamental difference between rodent and primate embryonic stem cell lines and show that generating primate chimeras is possible.
As you might expect, this article was heavily publicized (e.g.: The Guardian, The National Post, and the BBC) but it seems that all of the reports focus on the generation of a monkey chimera and not on the more challenging question for scientists that results from not being able to do this from embryonic stem cells. Much of our understanding about embryonic stem cells comes from studies in lower order animal models (frog, mouse, sheep, etc.) and scientists sometimes tacitly assume that this process operates similarly in humans. This not only has major implications for our understanding of early development, but also substantially impacts the struggle to bring stem cell derived therapies and treatments into the clinic.
Indeed, for a more sober reporting of this research paper, one must read the accompanying preview in Cell by Alan Trounson and Uta Greishammer or read the recent review article by Jenny Nichols and Austin Smith, which concludes that human “embryonic” stem cell lines in labs are not as similar to mouse embryonic stem cells as the scientific community would like them to be:
“Although these pluripotent human cell lines are widely used for academic and pharmaceutical research, they tend to be somewhat restricted in their differentiation capacity and are generally more difficult to manipulate than are mouse ES cells.”
Overall, at the risk of sounding like a broken record, stem cell progress, and the progress of the scientific community at large, needs to be viewed with cautious optimism, and therapies from the basic science need to be derived and approved from a substantial evidence base. I fear that unrealistic public expectations and media hype could quickly lead to scientists cutting corners in order to satisfy demand.