Deoxyribozyme-mediated knockdown of xylosyltransferase-1 mRNA promotes axon growth in the adult rat spinal cord

Abstract

In the injured spinal cord, proteoglycans (PGs) within scar tissue obstruct axon growth through their glycosaminoglycan (GAG)-side chains. The formation of GAG-side chains (glycosylation) is catalysed by xylosyltransferase-1 (XT-1). Here, we knocked down XT-1 mRNA using a tailored deoxyribozyme (DNAXTas) and hypothesized that this would decrease the amount of glycosylated PGs and, consequently, promote axon growth in the adult rat spinal cord. A continuous 2-week delivery of DNAXTas near the rostral border of a peripheral nerve graft bridging the transected dorsal columns in the thoracic spinal cord resulted in an 81% decrease in XT-1 mRNA, an average of 1.4-fold reduction in GAG-side chains of chondroitin sulphate or heparan sulphate-PGs and 2.2-fold reduction in neurocan and brevican core proteins in scar tissue. Additionally, compared to control deoxyribozyme, the DNAXTas treatment resulted in a 9-fold increase in length and a 4-fold increase in density of ascending axons growing through the nerve graft and scar tissue present at the rostral spinal cord. Together our data showed that treatment with a deoxyribozyme against XT-1 mRNA decreased the amount of glycosylated PGs and promoted axon growth through scar tissue in the injured spinal cord. The deoxyribozyme approach may become a contributing factor in spinal cord repair strategies.

A Sativex®‐like combination of phytocannabinoids as a disease‐modifying therapy in a viral model of multiple sclerosis

“…CSPG side chain synthesis is initiated by the addition of xylose to a serine moiety of the core protein, a step carried out by XT-I, among other enzymes (Gris et al, 2007). Significantly, the up-regulation of XT-I expression in stimulated astrocytes was dampened by Sativex, which could impair CSPG synthesis and thereby provide a permissive environment for regeneration in accordance with previous studies in which XT-I targeting promotes neurite outgrowth (Hurtado et al, 2008).…”

Sialidase, Chondroitinase ABC, and Combination Therapy after Spinal Cord Contusion Injury

“…This concept has been validated in mechanism-based pre-clinical SCI injury models. [3][4][5][6][7][8] Among axon regeneration inhibitor-targeted experimental therapies, two bacterial enzymes have emerged as potential drugs to treat SCI. Chondroitinase ABC (ChABC) cleaves inhibitory CSPGs, 9 and sialidase cleaves sialoglycan receptors for MAG.…”

Long term study of deoxyribozyme administration to XT-1 mRNA promotes corticospinal tract regeneration and improves behavioral outcome after spinal cord injury

“…After 7 days we observed regenerating axons, which passed the lesion site and grew into the caudal tissue. In subsequent experiments we focused on endogenous severed axons, either traced sensory axons (Hurtado et al, 2008) or labeled motor and sensory axons (Oudega et al, 2012). In these more challenging studies a treatment period of the DNAXT-1as, which started immediately and continued for 14 days with either local or systemic administration, was tested.…”

“…This so called deoxyribozyme to XT-1 mRNA (DNAXT-1as) has proven in vitro (Grimpe et al, 2005) and in diverse SCI models (Oudega et al, 2012;Hurtado et al, 2008) to be a safe and reliable candidate for therapeutic strategies of spinal cord repair. Striking was the result that toxicological and pathological investigation in a single blinded study were without any side effects (Oudega et al, 2012).…”