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

Journal of neuropathology and experimental neurology (2008-08-22)
Elizabeth Gray, Taya Louise Thomas, Samar Betmouni, Neil Scolding, Seth Love
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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Sigma-Aldrich
Total Protein Kit, Micro