THE first reports of the successful reprogramming of adult human cells back into so-called induced pluripotent stem (iPS) cells, which by all appearances looked and acted like embryonic stem cells, created a media stir. But the process was woefully inefficient: Only one out of 10,000 cells could be persuaded to turn back the clock. Now, a team of researchers led by Juan Carlos Izpisa Belmonte at the Salk Institute for Biological Studies, succeeded in boosting the reprogramming efficiency more than 100-fold, while cutting the time it takes in half. In fact, they repeatedly generated iPS cells from the tiny number of keratinocytes attached to a single hair plucked from a human scalp. Their method, published ahead of print in the Oct. 17, 2008 online edition of Nature Biotechnology, not only provides a practical and simple alternative for the generation of patient- and disease-specific stem cells, which had been hampered by the low efficiency of the reprogramming process, but also spares patients invasive procedures to collect suitable starting material, since the process only requires a single human hair. "Having a very efficient and practical way of generating patient-specific stem cells, which unlike human embryonic stem cells, wouldn't be rejected by the patient's immune system after transplantation brings us a step closer to the clinical application of stem cell therapy," says Belmonte, PhD., a professor in the Gene Expression Laboratory and director of the Center of Regenerative Medicine in Barcelona, Spain. Keratinocytes form the uppermost layer of skin and produce keratin, a tough protein that is the primary constituent of hair, nails and skin. They originate in the basal layer of the epidermis, from where they move up through the different layers of the epidermis and are eventually shed.                - SD