Investigating the Role of a Specific Chondroitin Sulfate Motif in Neuroinflammation and Regeneration

The extracellular matrix (ECM) provides a supportive framework for neurons and glia in the healthy central nervous system (CNS). However, extensive ECM remodeling occurs after CNS insult or injury, and in neuroinflammation. Upregulation and deposition of growth-inhibitory ECM components results in failures in neuronal generation and resolution of harmful inflammation. Chondroitin sulfate proteoglycans (CSPGs), which consist of chondroitin sulfate (CS) polysaccharide chains attached to a core proteoglycan, have been identified as the predominant inhibitory component of this dysregulated ECM, impeding critical repair processes and contributing to prolonged inflammation. Furthermore, CSPGs exert their inhibitory and immunomodulatory effects through their polysaccharide side chains. These CS chains undergo further modification by the addition of sulfate groups, giving rise to various sulfation patterns, or motifs. Recognition of these motifs by protein ligands and cell-surface receptors enable CSPGs to modulate the activity of downstream signaling pathways and regulate neuronal growth and immune processes. Thus, understanding the structure-function relationships of CS glycosaminoglycans (GAGs) will enable development of strategies to promote neuroregeneration and repair after injury and in neurodegenerative diseases. Current strategies to target CSPGs and CS GAGs broadly act on all sulfation patterns. This has limited efforts to decode the biological functions of individual sulfation motifs. Herein, we describe our efforts to comprehensively examine the shifts in the CS sulfation composition profile following spinal cord contusion injury. We develop a novel single-chain variable fragment (scFv) selective for the disulfated CS-E motif, and demonstrate its ability to rescue CSPG-mediated inhibition of neurite outgrowth on primary cortical neurons. Furthermore, we provide the first evidence that the CS-E sulfation motif directly modulates the activity of microglia, and that 4-O-sulfated CS exacerbates pro-inflammatory immune cell activation and conversion of T cells to a pathogenic phenotype in the experimental autoimmune encephalomyelitis (EAE) model of neuroinflammation. Together, our results contribute toward a greater understanding of the role of ECM components in disease processes and provide insights into the role of specific CS sulfation motifs in neuroinflammation and regeneration.