【英语时差8,16】用普通人的细胞制造干细胞（在线收听）

 Making Stem Cells From Ordinary Adult Cells Most cells in our bodies are unipotent, that is they stay the same throughout their lives. For example, once a skin cell, always a skin cell–they never start turning into brain cells. The exception is stem cells. As a fertilized egg starts to divide and grow into a complete organism, the cells in this developing ball of embryo are known as pluripotent stem cells. As these cells divide, they change, or “differentiate,” into muscle, lung, or any other kind of cell needed to build a body. This amazing trait is what makes embryonic stem cell research so important. For example, pluripotent stem cells might potentially be used to make new treatments or cures by replacing diseased cells with new ones grown from stem cells. But despite their potential for good, embryonic stem cell research has sparked intense political controversy. But in 2007, scientists made a revolutionary breakthrough. Three different groups simultaneously announced that they had converted unipotent, mature skin cells back into an undifferentiated state. In other words, they had created cells that behaved like embryonic stem cells without using any embryo derived materials. These new cells, dubbed “induced pluripotent stem cells” or IPS’s could then be converted into a variety of different cell types, such as pancreas, muscle or brain cells. The IPS’s were created by inserting certain genes into the DNA of the adult cells. The inserted genes turn on cellular signals that allow the cell to change into new cell types. This breakthrough brings us closer to exciting possibilities such as custom designed treatments, drugs or tissue transplant using stem cells made from the patient’s own cells.