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A fresh way to yield adult stem cells without the risk

TRANSFORMERS: Derrick Rossi and colleagues have found a new way to reprogram adult stem cells.<br/><br/>Photo by Justin Ide<br/>Harvard News OfficeIt’s a stop-the-presses kind of discovery. With colleagues, Derrick Rossi, an HMS assistant professor of pathology at the Immune Disease Institute, has devised a new way of producing induced pluripotent stem (iPS) cells. His technique, published in the November 5 issue of Cell Stem Cell, has so upended work at the Harvard Stem Cell Institute that researchers there plan to abandon other production techniques and to adopt the new method.

Researchers favor iPS cells not only because the cells can be tailored to a specific patient and a specific disease, but also because they can be derived from adult cells, skirting the need to harvest cells from embryos, a controversial source. But clinical use of iPS cells has been hampered by problems.

First, generating iPS cells has meant using viruses to introduce reprogramming factors into cellular DNA so as to nudge the cell back to a pluripotent state. Viruses, however, can trigger cancers. Rossi’s team elected to use messenger RNAs, modified to avoid triggering the cell’s normal antiviral response, to add the reprogramming factors. This use of mRNA spawned a new name: RiPS, short for RNA-iPS cells.

Second, previous methods produced extremely low numbers of usable iPS cells. Rossi’s method broke that barrier by yielding usable iPS cells in quantities that are orders of magnitude greater than current yields.

Finally, reprogramming iPS cells has involved the manipulation of growth mediums or the addition of constraining factors. Rossi’s team instead used their mRNA technology to direct the fate of the iPS into muscle cells.

“Although we developed this technology for cellular reprogramming,” says Rossi, “its utility extends far beyond that. It offers a way to get a cell to express any protein without triggering the cell’s antiviral response pathways.”

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