Role of glial cells in itch

Chronic itch is a prevalent medical condition with a large negative impact on the quality of life of affected individuals and a burden to healthcare systems. Persistent itch accompanies a diverse range of conditions, including both dermatological (e.g., psoriasis, atopic dermatitis, and lichen planus) and non-dermatological conditions (e.g., chronic renal disease, chronic hepatobiliary conditions, diabetes mellitus, hypothyroidism, and some malignancies). Severe and abnormal itch responses, such as sensitization for itch and the itch-scratch vicious cycle are often present and lead to exacerbation of the conditions. The mechanisms underlying chronic itch are only partially understood and consequently, treatments remain sub-optimal. Therefore, attempts are ongoing to further reveal chronic itch pathogenesis and enhance the efficiency of treatments by providing possibilities for mechanism-based therapies. Current evidence highlights the important role of both neuronal and non-neuronal cells in chronic itch. This presentation will focus on recent findings on the role of glial cells in itch. Both central and peripheral glial cells have attracted scientific attention and accordingly the involvement of astrocytes, microglia, satellite glial cells, and Schwann cells has been reported. Patterns and timing of activation of glial cells in itch are however different. For example, evidence shows that microglia may contribute to the early phase of itch, while astrocytes are involved in the chronic or maintenance phase of itch. Glial modulation, therefore, has become an active research area for targeting itch. Examples of potentials and challenges of glial modulation will be presented and future perspectives will be outlined.