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Reprogramming of nerve cells into stem cells disseminates Leprosy

Reprogramming of nerve cells into stem cells disseminates Leprosy

In an article entitled, “Reprogramming Adult Schwann Cells () to Stem Cell-like Cells by Leprosy Bacilli Promotes Dissemination of Infection,” published on 17th January 2013 issue of Cell (152:51–67), the lead author Toshihiro Masaki with four other associates from four research groups have  reported  that the bacterium Mycobacterium leprae (responsible for leprosy) spread infection by hijacking specialized cells in the adult nervous system, reprogram them into a stem cell-like state and convert them to muscle-like cells. In this study, they first isolated Schwann cells from adult mice, grew them in Petri dishes and infected them with Mycobacterium leprae. They found that the bacterium gradually turns off the genes that give Schwann cells their characteristic properties and then activates another set of genes that transforms them into something resembling neural crest stem cells, which are only present in the embryo and migrate from the developing nervous system along various routes to form a wide variety of tissues including muscle, bone, cartilage, and the Schwann cells and sensory neurons of the peripheral nerves. The researchers also found that the reprogrammed stem cells secrete chemokines (small signaling proteins that attract immune cells called macrophages). When infected stem cells were injected into mice, they recruited macrophages to the infection site, which then take up the bacteria and accumulate to form areas of inflammation called granulomas. The bacteria-laden macrophages are then released from the granulomas, thus providing another way for the disease to spread further. Moreover, Leprosy can be treated with multi-drug therapy, but diagnosis usually follows the appearance of symptoms. The presence of stem cells or the proteins they synthesize could be an early marker for the disease, which may enable clinicians to reach a diagnosis before any symptoms present themselves. The new findings could also pave the way for a safe method of producing stem cells for researching neurodegenerative diseases and developing treatments for them. The discovery that cells taken from just about any part of the human body can be induced to revert to stem cells with the ability to re-differentiate into any other cell type raised hopes, until it was subsequently found that these so-called pluripotent stem cells harbor genetic defects and can cause tumors when transplanted. [Summarized by Samsad Razzaque, a graduate student from BMB, DU]

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