President GEMpath, Inc. Longmont, Colorado, United States
Gliosis in the central nervous system (CNS [brain and/or spinal cord]) is a common non-neoplastic reaction in nonclinical studies. Gliosis typically presents as enlargement and/or proliferation of astrocytes and/or microglia and can develop in rodents and non-rodents as a spontaneous finding or following test article exposure (whether delivered centrally or systemically). Several patterns of CNS gliosis may be encountered in nonclinical species. First, gliosis may occur as variably sized, randomly scattered foci in the absence of visible damage to neural parenchyma. Second, gliosis may accompany test article-related or procedure-associated injury such as degeneration / necrosis of neurons, neuronal processes, or myelin. Finally, gliosis may develop in combination with inflammation (i.e., leukocyte accumulation causing parenchymal damage) or neoplasm formation. When interpreting CNS gliosis, adversity is shown by test article-related parenchymal injury (e.g., degeneration, necrosis, inflammation) and not the mere existence of a glial reaction. If obvious structural damage to the CNS parenchyma is lacking, gliosis as a standalone CNS finding typically should be viewed as a non-adverse reaction to local alterations in microenvironmental conditions rather than as evidence of neurotoxicity.
