All members of the families of the neuroglia have the ability to adopt a reactive state (>gliosis> in general, >astrogliosis> >oligodendrogliosis> and >microgliosis> in its specific form) face to situations where importantly is modified homeostasis of the nervous tissue and / or normal functional dynamics of neurons and their accompanying neuroglial cells (trauma, neurotoxicity, infections, neurodegenerative processes). In this reactive state, neuroglial cells become >new cells with new functions> because a significant change of their cellular functions occurs, mainly by the expression of new genes. Thus they become major players on the different stage of the new SN pathological situations. Activation of neuroglia cells is initially beneficial, aiming to solve the pathological changes, but it can turn detrimental to nerve tissue. Also, in recent years, it has been found that also the lack of reactive responses or the existence of >maladaptative responses> of the different neuroglial cells as well as the involution or regression of these cells, are important sources of nervous pathology. Studies of these different types of reactive glial cells have significantly expanded the knowledge we had about the pathogenesis of diseases of the SN. Moreover, many studies are revealing that they may be important to define new therapeutic drug targets or create new cell therapies to control the progress of the >pathogenic cascades>, through activating neuroprotection-neurorepair and/or inhibiting the neurotoxicity-neurodegeneration.

Peer Reviewed