Human skin keratinocytes can be reprogrammed to express neuronal genes and proteins after a single treatment with decitabine.

Patient-specific cell replacement therapy is fast becoming the future of medicine, requiring safe, effective methods for reprogramming a patient's own cells. Previously, we showed that a single transient transfection with a plasmid encoding Oct4 was sufficient to reprogram human skin keratinocytes (HSKs), and that this transfection resulted in a decrease in global DNA methylation. In more recent work we showed that decreasing global DNA methylation using the U.S. Food and Drug Administration-approved cancer treatment drug decitabine was sufficient to induce expression of endogenous Oct4. Here we report that a single treatment with decitabine, followed by 5 days in a defined neuronal transformation medium, then 7 days in a neuronal maintenance medium is sufficient to convert HSKs into cells that change their morphology substantially, gain expression of neuronal markers, and lose expression of keratinocyte markers. Within 1 week of treatment the cells express mRNA for β3-tubulin and doublecortin, and at the end of 2 weeks express mRNA for NeuN, FOXP2, and NCAM1. Additionally, at the end of this protocol, neurofilament-1, nestin, synapsin, FOXP2, and GluR1 proteins are detectable by immunostaining. Thus, we demonstrate a simple method that begins the process for producing cells for cell replacement therapies without using exogenously introduced DNA.