The Microglial Cells and the Arthritis-induced Hyperalgesia in the TMJ of Rats

Objectives: This study aims to evaluate the expression and activity of microglial cells of the trigeminal subnucleus caudalis (Vc) in the development of persistent inflammatory hyperalgesia induced by arthritis in the TMJ of rats.
Methods: Methods: Male Wistar rats were sensitized subcutaneously with an injection of Methylated Bovine Serum Albumin (mBSA, 500μg) in an emulsion containing phosphate buffered saline (PBS) and Freund's Complete Adjuvant. mBSA dissolved in Freund's Incomplete Adjuvant was injected in different sites in the back of the rat 7 and 14 days after the first immunization. Twenty-one days after the initial injection, TMJ-arthritis was induced in the animals immunized by intra-articular injection of an mBSA (10mg / TMJ / week) during 3 weeks. After 24 hours, 7 and 14 days after the last mBSA intra-articular injection, the animals were terminally anesthetized and their Vc was collected to biochemical analysis to measure the release of Fraktalkine (FKN) and Catepsin S (CatS) (ELISA), and expression of the migroglial cells (CD11b/c), p38MAPK, FKN receptor (CX3CR1) and ATP receptor (P2X7) (Western Blot).
Results: The release of CatS and FKN showed significantly higher on day 14 when compared to the control group (p<0.05: ANOVA, Bonferroni’s test), the FKN also showed significantly higher on day 7 compared to the control (p<0.05: ANOVA, Bonferroni’s test). Both the expression of CD11b/c and the CX3CR1 showed no significant difference between the treated and control groups. However, the expression of P2X7 showed increased at day 7 and 14 when compared to the control groups.
Conclusions: Peripheral injuries result of albumin-induced arthritis in the TMJ are able to promote changes in microglia cells trigeminal subnucleus caudalis sustained by persistent release of Cathepsin S and Fractalkine associated with the increase of the expression of P2X7 receptor.