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April 28, 2009

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Stem cell recipe gets even simpler

Feb. 5, 2009
Courtesy Cell Press
and World Science staff

A sim­ple rec­i­pe sci­en­tists ear­li­er de­vised for mak­ing adult stem cells act like more pow­er­ful em­bry­on­ic-like stem cells may have got­ten sim­pler. A new re­port in­di­cates one chem­i­cal can con­vert stem cells from adult mice in­to the de­sired type.

Stem cells are im­ma­ture cells that haven’t yet de­vel­oped in­to spe­cif­ic types to form or­gans. A large body of med­i­cal re­search is aimed at us­ing stem cells to grow new or­gans and heal tis­sue. But there have been dif­fi­cul­ties in ob­tain­ing or pro­duc­ing stem cells with­out get­ting them from live em­bryos—which are usu­ally de­stroyed in the pro­cess, rais­ing eth­i­cal prob­lems.

The new work, published in the Feb. 6 is­sue of the re­search jour­nal Cell, in­volves con­verting cells us­ing a sub­stance called a tran­scrip­tion fac­tor, a mo­le­cule pro­duced by genes and that con­trols the ac­ti­vity of oth­er genes.

The find­ing fol­lows a 2006 re­port al­so in Cell that four in­gre­di­ents could trans­form dif­fer­en­ti­ated cells from adult mice in­to “in­duced pluripo­tent stem cells” with the char­ac­ter­is­tics typ­i­cal of em­bry­on­ic stem cells. Pluripo­tent refers to the abil­ity to dif­fer­en­ti­ate in­to most oth­er cell types. The same rec­i­pe was lat­er found to work with hu­man skin cells also.

Sub­se­quent stud­ies found the four in­gre­di­ents could some­times be pared to just two or three, said Hans Schö­ler of the Max Planck In­sti­tute for Mo­lec­u­lar Bi­o­med­i­cine in Mün­ster, Ger­ma­ny. “Now we’ve come down to just one,” he added. “It’s really quite amaz­ing.”

The find­ing sheds light on centuries-old ques­tions about what dis­tin­guishes the em­bry­on­ic stem cells that give rise to egg and sperm from oth­er body cells, Schöler said. It might al­so have im­plica­t­ions for the use of “re­pro­grammed” stem cells for re­plac­ing cells lost to dis­ease or in­ju­ry.

In the new study, Schöler and col­leagues found a tran­scrip­tion fac­tor called Oct4 suf­ficed to make stem cells from the adult mouse nerv­ous sys­tem be­come pluripo­tent. The con­verted cells, dubbed 1F iPS, can dif­fer­en­ti­ate in­to all three germ lay­ers of the body, which even­tu­ally form all tis­sues and or­gans, the re­search­ers said; when in­jected in­to mouse em­bryos, the cells al­so found their way in­to the or­gans and could be passed to the next genera­t­ion.

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A simple recipe scientists earlier devised for making adult stem cells act like more powerful embryonic-like stem cells may have gotten simpler. A new report indicates a single chemical can convert stem cells from adult mice into the desired type. Stem cells are immature cells that haven’t yet developed into specific types to form organs. A large body of medical research is aimed at using stem cells to grow new organs and heal tissue. But there have been difficulties in obtaining or producing stem cells without getting them from live embryos—which are usually destroyed in the process, raising ethical problems. The new work, in the Feb. 6 issue of the research journal Cell, focuses on converting cells using a substance called a transcription factor, a molecules produced by genes and that controls the activity of other genes. The finding follows a 2006 report also in Cell that showed that four ingredients could transform differentiated cells taken from adult mice into “induced pluripotent stem cells” with the characteristics typical of embryonic stem cells. Pluripotent refers to the ability to differentiate into most other cell types. The same recipe was later found to work with human skin cells as well. Subsequent studies found the four ingredients could sometimes be pared to just two or three, said Hans Schöler of the Max Planck Institute for Molecular Biomedicine in Germany. “Now we’ve come down to just one,” he added. “It’s really quite amazing.” The finding sheds light on centuries-old questions about what distinguishes the embryonic stem cells that give rise to egg and sperm from other body cells, Schöler said. It might also have implications for the use of “reprogrammed” stem cells for replacing cells lost to disease or injury. Schöler and colleagues found a transcription factor called Oct4 sufficed to make stem cells from the adult mouse nervous system become pluripotent. The converted cells, dubbed 1F iPS, can differentiate into all three germ layers of the body, which eventually form all tissues and organs, the group said; when injected into mouse embryos, the cells also found their way into the organs and could be passed to the next generation.