CSF Exosome Transcriptomic Analysis in Acute Spinal Cord Injury: A Prospective Pilot Study Transcriptomic Analysis

Introduction: Exosomes are nanosized vesicles involved in transport of protein and RNA between cells. In acute spinal cord injury (aSCI), exosomes target pathways involving inflammation, apoptosis, angiogenesis and microglial migration, which make them a promising avenue for therapeutic intervention. In this pilot study, we use next-generation sequencing to evaluate CSF exosome transcriptomes (miRNA, lncRNA, and mRNA) during the acute phase of SCI to identify inflammatory pathway modulators and pathways known to promote secondary injury. We additionally assess exosomes as biomarkers for injury severity and recovery.

Methods: CSF was obtained from prospectively enrolled patients with aSCI on days 1-5 postinjury. Exosomes were extracted from CSF and lysed to isolate RNA for quantification and qualification. Next-generation sequencing was used to analyze miRNA profiles. Differential expression analysis (DE) identified valuable miRNAs. Integrative bioinformatics were used to analyze miRNA-mediated regulation of pathways and function of target genes. Neurologic impairment was defined by the ASIA Impairment Scale (AIS) grade at presentation and 3 months postinjury.

Results: Twenty aSCI patients (9 AIS A, 6 AIS B, and 5 AIS C) were included. DE found 19 valuable miRNAs between complete and incomplete SCI, including 11 down-regulated genes and 8 up-regulated genes. At 3 months follow-up, 65% of patients showed neurologic improvement. DE between patients with and without AIS conversion identified 13 valuable miRNA (7 down-regulated and 6 up-regulated). Targets of up-regulated genes in patients with AIS conversion were most enriched in pathways suppressing apoptosis and promoting cell differentiation. Down-regulated gene targets were most enriched in pro-inflammatory pathways, cell-matrix adhesion, and cell migration.

Conclusion : This is the first study characterizing the transcriptional changes that occur in CSF exosomal miRNA expression after aSCI. We additionally identified specific genes and target pathways associated with clinical improvement. Further research is needed to better delineate these pathways and the therapeutic potential of exosomal miRNA in SCI.