The oligodendrocyte precursor cell in health and disease

Adult oligodendrocyte precursor cells (OPCs) make up around 5-8% of the gli al cell population in the CNS. Their function in the undamaged CNS is large ly unknown, but their processes are in contact with nodes of Ranvier and sy napses, suggesting a regulatory role at these structures. The cells divide slowly, and constitute similar to 70% of cells labelled following a pulse i njection of bromodeoxyuridine. In the injured CNS the cells form a reactive glial population that undergoes hypertrophy and mitosis, probably driven b y a variety of growth factors and cytokines. In response to demyelination t hey divide and are thought to differentiate to provide new oligodendrocytes to replace those that have been lost. However, remyelination fails during the later stages of multiple sclerosis, and it is not clear whether this is as a result of a depletion of adult OPCs, inhibition within the glial scar , or damage to the axons that prevents myelination,Adult OPCs are also acti vated and proliferate following other forms of CNS damage, such as mechanic al injury, excitotoxicity and viral infection,The cells produce several of the chondroitin sulphate proteoglycans that might inhibit axon regeneration .