10Hochedlinger(2010) - medicine sad0510Hoch4p.indd 46...

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MEDICINE
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BRYAN CHRISTIE DESIGN SCIENTIFIC AMERICAN 47 KEY CONCEPTS Induced pluripotent stem cells u are mature body cells that have been made to change their identities and revert to an em- bryolike state—without the help of eggs or embryos. Rejuvenating the normal body u cells of any individual—then converting them to any of the 220 human cell types—could yield new disease treatments and custom replacement tissues. Scientists are now working u to understand how these cells are able to reverse their biologi- cal clocks and whether the new- est kind of stem cell will prove as powerful as embryonic cells. —The Editors Reprogramming cells from your own body could give them the therapeutic power of embryonic stem cells, without the political controversy BY KONRAD HOCHEDLINGER
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48 SCIENTIFIC AMERICAN May 2010 COURTESY OF HYESOO KIM AND LORENZ S TUDER Sloan-Kettering Institute cures, such as type 1 diabetes, Alzheimer’s dis- ease and Parkinson’s disease. The possibility of changing a cell’s identity just by delivering a few select genes has transformed the way scientists think about human development as well. Throughout history people have dreamed of finding a Fountain of Youth to escape the con- sequences of aging and disease, and the ability to return an adult body cell to an embryonic state would certainly appear to be as close as humanity has come to that fantasy so far. Of course, the technology is still in its infancy. Many important questions must be answered before anyone can say whether iPSCs will change the practice of medicine or even whether they will actually prove equivalent to the more controversial embryonic stem cells. Primordial Power To understand the hopes inspired by the discov- ery of iPSCs, one must return to what makes embryos so special. Current iPSC studies rely heavily on techniques and concepts developed in work with embryonic cells over the past 30 years, particularly the phenomenon of pluri- potency. Mammalian development is normally a one way-street, where cells become progres- sively more specialized and less versatile with time, a process called differentiation. Only dur- ing a brief window very early in development do all the cells within an embryo possess the ability to become any of the 220 cell types in the human body. Extracting those cells and growing them in culture gives rise to em±- bryonic stem cells. The ability of true embry- onic stem cells to indefinitely maintain their capacity to generate any tissue type defines the term “pluripotent.” Even in a late-stage embryo, stem cells have specialized to the extent that they can give rise only to specific families of cell types, such as those in muscle and bone. These cells are con- sidered “multipotent,” but they are no longer pluripotent. In an adult, all that remains of those precursors are so-called adult stem cells that replenish mature cells within a tissue. Blood stem cells continuously regenerate the 12 dif- ferent blood and immune cell types, for exam- I
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This note was uploaded on 09/15/2010 for the course BIO 346 taught by Professor Kalthoff during the Spring '07 term at University of Texas at Austin.

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10Hochedlinger(2010) - medicine sad0510Hoch4p.indd 46...

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