Up-regulated p75(NTR) neurotrophin receptor on glial cells in MS plaques

To investigate the expression of the neurotrophin receptor p75(NTR) On glia l cells within MS plaques. Background: In recent studies on the pathogenesi s of MS white matter plaques, we found large populations of inflammatory an d resident glial cells, including oligodendrocytes undergoing cell death, a nd identified increased expression of Fas receptor and ligand death pathway signaling molecules on the same glial cell types. In another study, the p7 5(NTR) was shown to induce apoptotic death of maturing oligodendrocytes whe n exposed to NGF in vitro. Methods: We used immunohistochemistry and in sit u reverse-transcription PCR to detect p75(NTR) expression on inflammatory a nd resident glial cells in MS plaques and used TUNEL staining for fragmente d DNA to detect cell death. Results: Upregulated p75(NTR) messenger RNA and protein were demonstrated in both oligodendrocytes and microglia/macrophag es in MS plaques but not in control white matter. However, only a fraction of p75(NTR) expressing oligodendrocytes was also stained by TUNEL. Conclusi ons: Glial cell expression of p75(NTR) receptor is up-regulated during MS p laque formation. The exact role of this receptor in glial cell death and/or survival in MS remains to be elucidated.