A Novel DNA Enzyme Reduces Glycosaminoglycan Chains in the Glial Scar and Allows Microtransplanted Dorsal Root Ganglia Axons to Regenerate beyond Lesions in the Spinal Cord

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Abstract
CNS lesions induce production of ECM molecules that inhibit axon regeneration. One major inhibitory family is the chondroitin sulfate proteoglycans (CSPGs). Reduction of their glycosaminoglycan (GAG) chains with chondroitinase ABC leads to increased axon regeneration that does not extend well past the lesion. Chondroitinase ABC, however, is unable to completely digest the GAG chains from the protein core, leaving an inhibitory “stub” carbohydrate behind. We used a newly designed DNA enzyme, which targets the mRNA of a critical enzyme that initiates glycosylation of the protein backbone of PGs, xylosyltransferase-1. DNA enzyme administration to TGF-β-stimulated astrocytes in culture reduced specific GAG chains. The same DNA enzyme applied to the injured spinal cord led to a strong reduction of the GAG chains in the lesion penumbra and allowed axons to regenerate around the core of the lesion. Our experiments demonstrate the critical role of PGs, and particularly those in the penumbra, in causing regeneration failure in the adult spinal cord.