Gliosis is the proliferation of astrocytes in response to the destruction of neurons. It leads to an astrocytic scar. This process is the way in which nervous tissue, which lacks the extracellular matrix and other features of connective tissue found elsewhere in the body, can repair itself.
see Sofroniew MV, Vinters HV. Astrocytes: biology and pathology. Acta neuropathologica. 2010 Jan; 119(1):7-35.(Link to article – subscription may be required.)