From the Guidelines
Gliosis in multiple sclerosis (MS) is the formation of scar tissue in the central nervous system caused by the activation and proliferation of glial cells, particularly astrocytes, in response to damage, as evidenced by advanced MRI techniques such as magnetization transfer MRI and MRS 1.
Definition and Pathophysiology
Gliosis is a hallmark feature of MS lesions, where myelin and nerve fibers are damaged by the immune system, leading to the multiplication and shape change of glial cells, creating dense fibrous tissue that replaces normal neural tissue. This scarring process contributes to the characteristic plaques or sclerotic areas visible on MRI scans. The glial scars act as physical barriers that block the regrowth of axons and interfere with the ability of oligodendrocyces to form new myelin sheaths around damaged nerves.
Clinical Implevance
The extent of gliosis correlates with disease progression and disability in MS patients, as accumulated scar tissue leads to permanent neurological deficits over time. Advanced MRI techniques, such as diffusion tensor imaging (DTI) and proton magnetic resonance spectroscopy (1H MRS), can quantify the extent of gliosis and tissue damage, providing valuable information on the severity of clinical and cognitive impairment 1.
Monitoring and Treatment
Quantitative MRI techniques might enable measurement and monitoring of disease-related mechanisms that occur before the development of atrophy, which primarily occurs in the late stages of MS. Some studies have shown that certain treatments, such as alemtuzumab and laquinimod, may protect against grey matter damage and reduce the accumulation of microscopic white and grey matter damage 1. However, the actual contribution of advanced MRI techniques to clinical management has not been fully validated, especially in a longitudinal manner.
From the Research
Definition of Gliosis
Gliosis is a key feature of Multiple Sclerosis (MS), characterized by the activation of glial cells, including microglia, astrocytes, and oligodendrocytes, in response to injury or disease [(2,3,4,5)].
Role of Glial Cells in MS
Glial cells play a crucial role in the pathogenesis of MS, contributing to both tissue damage and repair [(2,4,5)]. Microglia, astrocytes, and oligodendrocytes are each promising targets for disease-altering treatment of MS 2.
Characteristics of Gliosis in MS
Gliosis in MS is associated with demyelination, inflammation, and axonal damage [(3,6,5)]. The extent of axon damage is correlated with the numbers of CD8-positive cytotoxic T cells and macrophages/microglia 3.
Pathological Features of Gliosis
The pathological features of gliosis in MS include:
- Activation of microglia, astrocytes, and oligodendrocytes [(2,4,5)]
- Formation of glial scars 4
- Demyelination and axonal degeneration [(3,6,5)]
- Chronic, tissue-restricted inflammation 5
Therapeutic Implications
Understanding the role of gliosis in MS is leading to the development of new therapeutic approaches, including therapies targeting glial cells and promoting remyelination and neuroprotection [(2,6,4,5)].