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The Structural and Compositional Changes of Chondroitin Sulfate Chains in the Aged Mouse Hippocampus

The hippocampus plays important roles in learning and memory. In the hippocampus, the extracellular matrix (ECM) is known to function in synaptic plasticity. Chondroitin sulfate (CS) chain, one of the major ECM components in the brain, is a long unbranched polysaccharide consisting of repeating sulfated disaccharide units. After sugar extension, sulfation occurs at specific positions in the saccharides, and the pattern of CS sulfation influences several biological processes. The hippocampus is also known as a primary target for age-related conditions such as Alzheimerʼs disease. Still, how the CS chains differ over time in the aged mouse hippocampus is still poorly understood. In this study, we examined the immunoreactivity and disaccharide components of CS chains in young and aged mouse hippocampi. We found that the immunoreactivity for specific CS epitopes recognized by the CS56 antibody exhibited two major patterns in the hippocampus; one was in the form of patches and the other was diffused pattern, especially in the CA1 region. Furthermore, the immunofluorescence intensity of both patterns significantly decreased with aging. Correspondingly, the specific disaccharide components of CS chains (C- and D-unit) in the hippocampus significantly decreased with aging. Therefore, our study may help to understand the roles of chondroitin sulfate in the neurological decline due to aging.