THE CELLULAR ORIGIN OF LYSOSOMAL ENZYMES IN THE PLAQUE IN MULTIPLE SCLEROSIS: A COMBINED HISTOLOGICAL AND BIOCHEMICAL STUDY

Abstract

Using a combined biochemical and histological approach certain conclusions can be drawn as to the origin of the increase in lysosomal enzymes in white matter from (human) MS brains. There is a gradient of lysosomal enzyme activity, plaque > periplaque > macroscopically normal white matter, which appears to be independent of the developmental stage of the plaque. The most consistent change in cellular composition within and around all plaques is a marked astrocytosis. The increases in lysosomal enzymes can mainly be attributed to reactive astrocytes; macrophages and cells of the perivascular infiltrate making only a limited contribution. Only 1 of enzyme tested was significantly elevated in histologically normal white matter, i.e., n-acetyl-.beta.-D-glucosaminidase. Since this enzyme appears to be a particularly sensitive marker for astrocytes this may be indicative of proliferation of astrocytes in so-called normal white matter.