New Technology Directly Reprograms Skin Fibroblasts for a New Role

Penn study has implications for new skin disease treatments

Tuesday, 16 December 2014

Dermal fibroblasts are directly reprogrammed to

pigmented melanocytes by three transcription

factors (SOX10, MITF and PAX3).

Credit: Ruifeng Yang, Perelman School of

Medicine, University of Pennsylvania. 

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 tumourigenicity."

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 tumours.

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 foetal 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.

Source: University of Pennsylvania School of Medicine

Contact: Karen Kreeger

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ZenMaster

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For more on stem cells and cloning, go to CellNEWS at

http://cellnews-blog.blogspot.com/

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'Master Switch' for Myelination in Human Brain Stem Cells is Identified

Finding is key to developing MS treatments using stem cells

Tuesday, 01 July 2014

The identification of the transcription factor,

SOX10, in human brain cells, brings researchers

closer to the goal of treating multiple sclerosis

(MS) by transplanting into patients the brain cells

that make myelin. Credit: Jing Wang. 

Scientists at the University at Buffalo have identified the single transcription factor or "master switch" that initiates the critical myelination process in the brain. The research will be published online in Proceedings of the National Academy of Sciences (PNAS) on June 30.

The identification of this factor, SOX10, in human brain cells, brings researchers closer to the goal of treating multiple sclerosis (MS) by transplanting into patients the brain cells that make myelin.

"Now that we have identified SOX10 as an initiator of myelination, we can work on developing a viral or pharmaceutical approach to inducing it in MS patients," says Fraser Sim, PhD, senior author on the paper and assistant professor in the UB Department of Pharmacology and Toxicology in the School of Medicine and Biomedical Sciences.

"If we could create a small molecule drug that would switch on SOX10, that would be therapeutically important," he adds.

Stem cell therapy is seen as having dramatic potential for treating MS, but there are key obstacles, especially the length of time it takes for progenitor cells to turn into oligodendrocytes, the brain's myelin-making cells.

Using currently available methods, Sim explains, it can take as long as a year to generate a sufficient number of human oligodendrocyte cells to treat a single MS patient.

That's partly because there are so many steps: the skin or blood cell must be turned into induced pluripotent stem cells, which can differentiate into any other type of cell and from which neural progenitor cells can be produced. Those progenitor cells then must undergo differentiation to oligodendrocyte progenitors that are capable of ultimately producing the oligodendrocytes.

"Ideally, we'd like to get directly to oligodendrocyte progenitors," says Sim.

"The new results are a stepping stone to the overall goal of being able to take a patient's skin cells or blood cells and create from them oligodendrocyte progenitors," he says.

Using foetal (not embryonic) brain stem cells, the UB researchers searched for transcription factors that are absent in neural progenitor cells and switched on in oligodendrocyte progenitor cells.

While neural progenitor cells are capable of producing myelin, they do so very poorly and can cause undesirable outcomes in patients, so the only candidate for transplantation is the oligodendrocyte progenitor.

"The ideal cell to transplant is the oligodendrocyte progenitor cell," Sim says.

"The question was, could we use one of these transcription factors to turn the neural progenitor cell into an oligodendrocyte progenitor cell?"

To find out, they looked at different characteristics, such as mRNA expression, protein and whole gene expression and functional studies.

"We narrowed it down to a short list of 10 transcription factors that were made exclusively by oligodendrocyte progenitor cells," says Sim.

"Among all 10 factors that we studied, only SOX10 was able to make the switch from neural progenitor to oligodendrocyte progenitor cell," says Sim.

In addition, the UB researchers found that SOX10 could expedite the transformation from oligodendrocyte progenitor cell to differentiation as an oligodendrocyte, the myelin-producing cell and the ultimate treatment goal for MS.

"SOX10 facilitates both steps," says Sim.

That's tantalizing, he says, because one of the biggest problems with MS is that cells get stuck in the step between the oligodendrocyte progenitor cell and the oligodendrocyte.

"In MS, first the immune system attacks the brain, but the brain is unable to repair itself effectively," explains Sim.

"If we could boost the regeneration step by facilitating formation of oligodendrocytes from progenitor cells, then we might be able to keep patients in the relapsing remitting stage of MS, a far less burdensome stage of disease than the later, progressive stage."

Sim is also an investigator with other scientists at UB and the University of Rochester on the $12.1 million New York State Stem Cell Science award led by SUNY Upstate Medical Center. The research will test the safety and effectiveness of implanting stem cells that can reproduce myelin into the central nervous system of MS patients.

Source: University at Buffalo 

Contact: Ellen Goldbaum

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ZenMaster

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For more on stem cells and cloning, go to CellNEWS at

http://cellnews-blog.blogspot.com/

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