Neuronal activity regulates remyelination via glutamate signalling to oligodendrocyte progenitors.

Myelin regeneration can occur spontaneously in demyelinating diseases such as multiple sclerosis (MS). However, the underlying mechanisms and causes of its frequent failure remain incompletely understood. Here we show, using an in-vivo remyelination model, that demyelinated axons are electrically active and generate de novo synapses with recruited oligodendrocyte progenitor cells (OPCs), which, early after lesion induction, sense neuronal activity by expressing AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid)/kainate receptors. Blocking neuronal activity, axonal vesicular release or AMPA receptors in demyelinated lesions results in reduced remyelination. In the absence of neuronal activity there is a ∼6-fold increase in OPC number within the lesions and a reduced proportion of differentiated oligodendrocytes. These findings reveal that neuronal activity and release of glutamate instruct OPCs to differentiate into new myelinating oligodendrocytes that recover lost function. Co-localization of OPCs with the presynaptic protein VGluT2 in MS lesions implies that this mechanism may provide novel targets to therapeutically enhance remyelination.This work was supported by the Medical Research Council (R.T.K, R.J.M.F and H.O.B.G. G0701476; K.V. and R.T.K 1233560), Wellcome Trust (R.T.K. and K.A.E. 091543/Z/10/Z), Marie Curie training programme Axregen EC FP7 ITN (I.L. and R.T.K 214003), and core support grant from the Wellcome Trust and MRC to the Wellcome Trust – Medical Research Council Cambridge Stem Cell Institute.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/ncomms951

Cryptorchidism

The term cryptorchidism refers to the condition of abnormal testicular descent (TD). In this situation the testis is â\u80\u9chiddenâ\u80\u9d and it cannot be identified in its normal position that is inside the scrotum. In fact the term â\u80\u9ccryptorchidismâ\u80\u9d literally means â\u80\u9chidden testicleâ\u80\u9d and is often used interchangeably with the term â\u80\u9cundescended testicleâ\u80\u9d. A normal testicular function is guaranteed by its full descent into the scrotum. Undescended testes carry the risk of malignant transformation and loss of fertility. It is thus mandatory to recognize this condition in order to plan the surgical correction