A research article set for online publication in this week's edition of Nature journal calls into question whether reprogramming adult cells into stem cells actually results in stem cells identical to their embryonic cousins.
Induced pluripotent stem cells (iPS cells) were first generated in 2006 by Japanese scientist Shinya Yamanaka. The development of iPS cells has enabled scientists to conduct regenerative medicine research using stem cells without the ethical problems associated with embryonically derived stem cells. Dr. Yamanaka's lab revealed that with sequential expression of only a few genes, specialized cells could turn back the clock in both shape and gene expression profile, essentially regaining a stem cell state. Once reprogrammed, a new cocktail of gene products could be added or induced endogenously, redirecting cells toward a completely new fate. In just a few years since their development, research on iPS cells has grown exponentially, with both scientists and physicians hoping one day they would be utilized to grow all kinds of new tissues as treatment for a myriad of diseases. And while experts in both fields continue to hold on to that promise, a new research article from Dr. Joseph Ecker's lab at the Salk Institute in La Jolla, California has slammed the brakes on the previously rapid-moving field.
Though iPS cells have a DNA code identical to their embryonic parents they hope to mimic, a second "code" called the epigenome – DNA-associated proteins and alterations that affect gene expression without changing the DNA sequence itself – is actually different from embryonic stem cells (ES cells), according to research from Dr. Ecker's lab. Ecker and his lab members analyzed DNA methylation – a common form of epigenetic change – across the genome of multiple cell lines. The group of researchers discovered that iPS cell methylation patterns near the caps and centers of chromosomes differed from true ES cells. Most importantly, the DNA methylation patterns in the iPS cells resembled the patterns from the specialized cell type they were derived from. This could restrict the types of tissues iPS cells are capable of differentiating into.
The field of iPS research is still very trendy, but the latest findings from Dr. Ecker's lab may start to cool down the buzz.
Lister, R. et al. (2011). Nature. [access required]
Source: Nature News
