Bcl-2-expressing oligodendrocytes in multiple sclerosis lesions

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system leading to selective destruction of myelin sheaths and/or oligodendrocytes. The immunological mechanisms responsible for myelin destruction and the primary target of the immune response have not yet been identified. Prior studies have reported a variable degree of oligodendrocyte preservation in actively demyelinating lesions. We have previously demonstrated that oligodendrocyte survival is heterogenous and varies between individual MS patients. Bcl-2 belongs to the group of apoptosis-associated proteins that protects cells from cell death. The purpose of the present study was to determine whether bcl-2 expression is associated with oligodendrocyte preservation observed in some early MS lesions. Double immunocytochemistry was performed with antibodies against bcl-2 and myelin oligodendrocyte glycoprotein (MOG) to identify bcl-2-expressing oligodendrocytes within MS lesions from 43 patients. The number of bcl-2-positive oligodendrocytes was determined depending on the lesion demyelinating activity and the disease course of the patients. The number of bcl-2-expressing oligodendrocytes increased within demyelinating lesions compared to the periplaque white matter, with highest numbers in remyelinating lesions. There was a significant association between the presence of bcl-2-positive oligodendrocytes and the presence of remyelination. The highest proportion of bcl-2-positive oligodendrocytes was observed in a subgroup of patients with relapsing-remitting disease course. The expression of apoptosis-associated proteins may contribute to oligodendrocyte preservation or loss in MS lesions.