Glial Cell: A Potential Target for Cellular and Drug Based Therapy in Various CNS Diseases

Glial cells are integrated part of neurovascular unit of blood brain barrier (BBB). They undergo mitosis and mainly classified as astrocytes, oligodendrocytes, microglia, ependymal cells and nerve glial antigen 2 cells. Being a most versatile glial cell, astrocytes provide structural support to neurons, maintain brain homeostasis, take part in neuronal communication, and perform some housekeeping functions. Oligodendrocytes myelinate the neuronal axons for proper transmission of nerve impulse and microglia are brain immune cells. Multiple sclerosis is a prototype glia mediated disease that manifests demyelination. Fingolimod is already being marketed for this disease, while guanabenz and ibudilast are facing clinical trials. Many researches revealed the role of glial cells in Alzheimer's disease, in which riluzole (a glutamate modulator already in market for amyotrophic lateral sclerosis-ALS) was found to be effective. Q-cells® are glial cell-based therapeutic agent to treat ALS that only produce astrocytes and oligodendrocytes, when transplanted in vivo. hIL13-PE is a gene based therapeutic agent that has been smartly designed for the treatment of glioma. Although for CNS diseases, drugs are available, still it is not easy to extract satisfactory therapeutic effect of most of the drugs due to the presence of BBB. This barrier can be overcome by implanting a drug reservoir in brain parenchyma (wafer), by judicious selection of drug delivery system (nanoparticulate system), or by using an alternative route of administration (intranasal route). This review revolves around cellular and drug based modulation of glial cells to achieve maximum therapeutic benefit for some of the CNS diseases.