PHILADELPHIA  As the main component of connective tissue in    the body, fibroblasts are the most common type of cell. Taking    advantage of that ready availability, scientists from the    Perelman School of    Medicine at the University of    Pennsylvania, the Wistar Institute, Boston University    School of Medicine, and New Jersey Institute of Technology have    discovered a way to repurpose fibroblasts into functional    melanocytes, the body's pigment-producing cells. The technique    has immediate and important implications for developing new    cell-based treatments for skin diseases such as vitiligo, as    well as new screening strategies for melanoma. The work was    published this week in     Nature Communications.  
    The new technique cuts out a cellular middleman. Study senior        author Xiaowei George Xu, MD, PhD, an    associate professor of Pathology and Laboratory Medicine,    explains, "Through direct reprogramming, we do not have to go    through the pluripotent stem cell stage, but directly convert    fibroblasts to melanocytes. So these cells do not have    tumorigenicity."  
    Changing a cell from one type to another is hardly unusual.    Nature does it all the time, most notably as cells divide and    differentiate themselves into various types as an organism    grows from an embryo into a fully-functional being. With stem    cell therapies, medicine is learning how to tap into such cell    specialization for new clinical treatments. But controlling and    directing the process is challenging. It is difficult to    identify the specific transcription factors needed to create a    desired cell type. Also, the necessary process of first    changing a cell into an induced pluripotent stem cell (iPSC)    capable of differentiation, and then into the desired type, can    inadvertently create tumors.  
    Xu and his colleagues began by conducting an extensive    literature search to identify 10 specific cell transcription    factors important for melanocyte development. They then    performed a transcription factor screening assay and found    three transcription factors out of those 10 that are required    for melanocytes: SOX10, MITF, and PAX3, a combination dubbed    SMP3.  
    "We did a huge amount of work," says Xu. "We eliminated all the    combinations of the other transcription factors and found that    these three are essential."  
    The researchers first tested the SMP3 combination in mouse    embryonic fibroblasts, which then quickly displayed melanocytic    markers. Their next step used a human-derived SMP3 combination    in human fetal dermal cells, and again melanocytes    (human-induced melanocytes, or hiMels) rapidly appeared.    Further testing confirmed that these hiMels indeed functioned    as normal melanocytes, not only in cell culture but also in    whole animals, using a hair-patch assay, in which the hiMels    generated melanin pigment. The hiMels proved to be functionally    identical in every respect to normal melanocytes.  
    Xu and his colleagues anticipate using their new technique in    the treatment of a wide variety of skin diseases, particularly    those such as vitiligo for which cell-based therapies are the    best and most efficient approach.  
    The method could also provide a new way to study melanoma. By    generating melanocytes from the fibroblasts of melanoma    patients, Xu explains, "we can screen not only to find why    these patients easily develop melanoma, but possibly use their    cells to screen for small compounds that can prevent melanoma    from happening."  
    Perhaps most significantly, say the researchers, is the far    greater number of fibroblasts available in the body for    reprogramming compared to tissue-specific adult stem cells,    which makes this new technique well-suited for other cell-based    treatments.  
    The research was supported by the National Institutes of Health    (R01-AR054593, P30-AR057217)  
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Cutting Out the Cellular Middleman: New Technology Directly Reprograms Skin Fibroblasts For a New Role