Elevated matrix metalloproteinase-9 and degradation of perineuronal nets in cerebrocortical multiple sclerosis plaques.

MS Laboratories, Burden Centre, University of Bristol Institute of Clinical Neurosciences, Frenchay Hospital, Bristol, UK.
Journal of Neuropathology and Experimental Neurology (Impact Factor: 4.35). 10/2008; 67(9):888-99. DOI: 10.1097/NEN.0b013e318183d003
Source: PubMed

ABSTRACT Matrix metalloproteinases (MMPs) degrade extracellular matrix; MMP activity, particularly of MMP-9, is elevated in the white matter in multiple sclerosis (MS) patients. The cerebral cortical extracellular matrix includes perineuronal nets (PNs) that surround parvalbumin-positive neurons (PV-positive neurons) and are important for their function. We measured active and total MMP-9 levels in postmortem homogenates of demyelinated and nondemyelinated cerebral cortical regions from 9MS and 7 control cases and assessed Wisteria floribunda agglutin (WFA)-positive PNs in paraffin sections from 15 MS and 6 controls and PV-positive neurons in sections from 26 MS and 6 controls. Active MMP-9 levels were higher in demyelinated than in nondemyelinated or control cortex (p < 0.05). The area fraction positive for WFA was lower in demyelinated than nondemyelinated MS or control cortex; the latter difference was significant (p < 0.05). Most PV-positive neurons in demyelinated but not intact cortex lackeda PN, and some showed perikaryal phosphorylated neurofilament protein accumulation. Loss of WFA-labeled PNs was not associated with reduced PV-positive neurons numbers. Thus, elevated MMP-9 in cortical plaques is associated with loss of PNs; PV-positive neurons are preserved but show abnormal neurofilament accumulations. Matrix metalloproteinase-mediated degradation of PNs in cortical plaques may, therefore, contribute to neuronal dysfunction and degeneration in MS patients.

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