Papers of the Week

Mechanisms underlying neuropathic pain (NP) are complex with multiple genes, their interactions, environmental and epigenetic factors being implicated. Transcriptional changes in the trigeminal (TG) and dorsal root (DRG) ganglia have been implicated in the development and maintenance of NP. Despite efforts to unravel molecular mechanisms of NP, many remain unknown. Also, most of the studies focused on the spinal system. Although the spinal and trigeminal systems share some of the molecular mechanisms, differences exist. We used RNA-sequencing technology to identify differentially expressed genes (DEGs) in the TG and DRG at baseline and 3 time-points following the infraorbital or sciatic nerve injuries, respectively. Pathway analysis and comparison analysis were performed to identify differentially expressed pathways. Additionally, upstream regulator effects were investigated in the two systems. DEG (differentially expressed genes) analyses identified 3,225 genes to be differentially expressed between TG and DRG in naïve animals, 1,828 genes four days post injury, 5,644 at day 8 and 9,777 DEGs at 21 days post injury. Comparison of top enriched canonical pathways revealed that a number of signaling pathway was significantly inhibited in the TG and activated in the DRG at 21 days post injury. Finally, CORT upstream regulator was predicted to be inhibited in the TG while expression levels of CSF1 upstream regulator were significantly elevated in the DRG at 21 days post injury. This study provides a basis for further in-depth studies investigating transcriptional changes, pathways, and upstream regulation in TG and DRG in rats exposed to peripheral nerve injuries.