Up‐regulation of MMP‐8 and MMP‐9 activity in the BALB/c mouse spinal cord correlates with the severity of experimental autoimmune encephalomyelitis

SUMMARY Induction of EAE can be inhibited or repressed by administration of soluble metalloproteinase inhibitors. We studied the matrix metalloproteinase (MMP) and their tissue inhibitor (TIMP) expression pattern in experimental autoimmune encephalomyelitis (EAE) of the resistant Th2 prone BALB/c mouse, where the disease can be induced with ultrasound‐emulsified antigen/adjuvant (son‐ag), but not with conventional technique (syr‐ag). We found highly elevated expression of MMP‐8 (neutrophil collagenase) mRNA and protein in diseased son‐ag challenged mice, colocalizing to neutrophil infiltrates found in brain and extensively in the spinal cord submeningeal space. MMP‐8 expression has not been found previously in sensitive mouse strains. The infiltrates stained positive also for MMP‐9 protein, and brain homogenates from corresponding mice showed MMP‐9 activity during overt disease (days 12–16 post‐immunization). TIMP‐1 gene expression could be detected in CNS samples from diseased son‐ag challenged mice but not in syr‐ag or control mice, and the TIMP‐1 protein colocalized with GFAP‐staining. In contrast, in syr‐ag mice both TIMP‐2 and TIMP‐3 gene expression in the spinal cords was elevated. The results show that sonication, but not extrusion, creates an adjuvant formula potent in activating the matrix metalloproteinase cascade similar to sensitive mouse strains, strongly implicating their role in EAE induction in this Th2 prone strain. The study provides the basis for establishment of MMP‐specific therapy in this model.