CSF FROM PROGRESSIVE-MS PATIENTS STIMULATES MICROGLIAL ACTIVATION PATHWAYS IN VIVO AND IN VITRO (P5.334)

OBJECTIVE: To investigate the effect of MS cerebrospinal fluid (CSF) on microglial activation in vivo and in vitro. BACKGROUND: Microglia are resident immune cells in the CNS that act as macrophages when activated by injury or disease. This activation is a characteristic of inflammatory diseases like multiple sclerosis (MS) in which two main phenotypes occur: classically activated pro-inflammatory M1 and alternatively activated anti-inflammatory M2. However, the exact role of M1/M2 cells in MS is not fully understood. DESIGN/METHODS: We investigated the effects of cerebroventricular injections of CSF derived from untreated and treated primary and secondary progressive MS patients, and control individuals on microglial activation. C57BL/6J mice (n=3 per patient) were injected biweekly through a cannula implanted into the third ventricle for 4 weeks. Animals were sacrificed 5 days post-CSF injections and microglia/macrophages were extracted using a Percoll gradient for FACS analysis. In order to assess M1 and M2 polarization, BV-2 cells (a murine microglial cell line) were treated with patient CSF for 7 days and analyzed via FACS. RESULTS: Compared to mice injected with control CSF, animals injected with either primary or secondary progressive MS CSF displayed a significant upregulation of CD11b+/CD45high macrophages. Remarkably, CSF derived from progressive MS patients who were clinically stable following therapy had greatly diminished capacity to activate macrophages compared to the paired untreated samples. In addition, CSF treatment polarized BV2 cells into M1/M2 macrophages with the latter phenotype were found to be significantly upregulated in the progressive MS groups compared to controls. CONCLUSIONS: Our preliminary evidence suggests the existence of intrinsic differences related to microglial activation between progressive MS and non-MS patients. Future studies will aim to pinpoint the specific factors in the progressive MS milieu responsible for the observed microglia polarization toward M2 phenotype. Disclosure: Dr. McDermott has nothing to disclose. Dr. Jian has nothing to disclose. Dr. Huang has nothing to disclose. Dr. Cristofanilli has nothing to disclose. Dr. Sadiq has nothing to disclose.