A small RNA moves us one step closer to generating new body parts
Wouldn’t it be great to be able to grow new body parts as and when you needed them? In 2012 a scientist named Yamanaka discovered a method of using four factors to convert, or ‘reprogram’, adult skin cells into cells which resemble embryonic stem cells, called induced pluripotent stem (iPS) cells. By putting them in the right environment, iPS cells should have the ability to change into any type of cell you need. This finding was considered a breakthrough in regenerative medicine as these cells could be used to grow new body parts, replacing the need for donor organ transplants. However, things have not been this straight forward.
The challenge for using iPS cells for medical applications is caused by the low efficiency of reprogramming. Also, the molecular mechanisms that determine how these cells become stem cells remain unknown. Recently, scientists from the University of California have identified a small RNA called microRNA-135b which can enhance the efficiency of reprogramming mouse skin cells into iPS cells. MicroRNA-135b is thought to affect the extracellular matrix (ECM) of cells. The ECM is a complex structure which surrounds the surface of cells. It provides structure to cells but also contains receptors used in cell-to-cell communication. For example, skin cells receive signals from neighbouring skin cells telling them to stay as skin and not to change into another type of cell. In order to become fully reprogrammed iPS cells, they need to be able to ignore signals from their neighbouring skin cells.
Scientists have found that microRNA-135b reduces the level of certain proteins in the ECM. One protein named Wisp1 is involved in relaying signals from neighbouring cells. When this protein is artificially removed from cells that have been treated with the four factors, the efficiency of turning them into iPS cells is increased three-fold. Removing this protein is thought to reduce the signals cells receive from neighbouring skin cells telling them to stay as skin cells which compete with internal signals telling them to become iPS cells. Therefore, microRNA-135b could be used to reduce the level of Wisp1 in order to push cells into becoming iPS cells. This research provides significant progress in investigating the effect of extracellular events on the production of iPS cells, hopefully moving us one step closer to generating new body parts.
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