Characterization of rat primary trigeminal satellite glial cells and associated extracellular vesicles under normal and inflammatory conditions

Satellite glial cells (SGCs) in sensory ganglia contribute to the pathogenesis of chronic pain, potentially through mediating extracellular or paracrine signaling. Recently, extracellular vesicles (EVs) in the form of exosomes have been found to play an important role in cell-cell communication. However, their release from SGCs and extent in modulating pain remain unknown. An in vitro cell platform using fresh primary SGCs was used to characterize the shed vesicles by size and proteomic profiling following activation of SGCs by lipopolysaccharide (LPS), simulating neurogenic inflammation in vivo. Results demonstrated that SGCs shed vesicles in the size range of exosomes (>150 nm) but with altered protein expression upon LPS-activation. Proteomic profiling of SGCs-shed EVs showed that a number of proteins were differentially regulated upon LPS stimulation such as junction plakoglobin and myosin 9 that are proposed as novel biomarkers of SGCs activation under inflammatory conditions. Findings from this study highlight the utility of using fresh primary SGC cultures as a model to further investigate EVs under normal and inflammatory conditions. Significance: This study demonstrated that 1. Primary SGCs express the phenotypic marker GS.2. One ng/mL LPS is sufficient to activate SGCs in vitro without any form of toxicity.3. SGCs shed a population of extracellular vesicles in the exosomal size range and the identified proteins have a potential effect on SGCs morphology upon activation by LPS.4. Myosin-9 was identified as a novel biomarker of LPS-activated fresh primary SGCs that can be applicable for inflammatory pain conditions.