Up-regulated p75NTR neurotrophin receptor on glial cells in MS plaques

To investigate the expression of the neurotrophin receptor p75(NTR) On glial cells within MS plaques. Background: In recent studies on the pathogenesis of MS white matter plaques, we found large populations of inflammatory and resident glial cells, including oligodendrocytes undergoing cell death, and identified increased expression of Fas receptor and ligand death pathway signaling molecules on the same glial cell types. In another study, the p75(NTR) was shown to induce apoptotic death of maturing oligodendrocytes when exposed to NGF in vitro. Methods: We used immunohistochemistry and in situ reverse-transcription PCR to detect p75(NTR) expression on inflammatory and resident glial cells in MS plaques and used TUNEL staining for fragmented DNA to detect cell death. Results: Upregulated p75(NTR) messenger RNA and protein were demonstrated in both oligodendrocytes and microglia/macrophages in MS plaques but not in control white matter. However, only a fraction of p75(NTR) expressing oligodendrocytes was also stained by TUNEL. Conclusions: Glial cell expression of p75(NTR) receptor is up-regulated during MS plaque formation. The exact role of this receptor in glial cell death and/or survival in MS remains to be elucidated.