Tissue plasminogen activator gene expression in multiple sclerosis brain tissue.

Recent studies have implicated tissue-type plasminogen activator (tPA) in neurodegeneration. We studied multiple sclerosis (MS) brain tissue for tPA gene and protein expression in comparison with reference tissue, by in situ hybridisation and immunohistochemistry. MS is characterised by demyelination in the central nervous system. In this study, neuronal cell bodies in MS brain showed high expression of tPA mRNA and protein, while in reference brains, staining for protein and mRNA expression were very low in neurons and mostly restricted to blood vessel walls. In MS, there was an additional staining of mononuclear cells within perivascular cuffs and foamy macrophages within demyelinating plaques. In view of evidence that the final process of demyelination in MS is thought to be enzyme-mediated, our work suggests the involvement of tPA and by inference plasmin, in the demyelinating process. Blocking tPA or plasmin activity may be a potentially beneficial therapeutic approach in MS.