Transcriptome of dorsal root ganglia caudal to a spinal cord injury with modulated behavioral activity

Spinal cord injury (SCI) is a devastating clinical condition resulting in significant disabilities for affected individuals. Apart from local injury within the spinal cord, SCI patients develop a myriad of complications characterized by multi-organ dysfunction. Some of the dysfunctions are directly related to the disrupted integrity of sensory afferents from DRGs, which signal to both the spinal cord and peripheral organs. Some classes of DRG neurons undergo axonal sprouting both peripherally and centrally after spinal cord injury. Such physiological and anatomical re-organization of afferent axons after SCI contributes to both adaptive and maladaptive plasticity, which may be modulated by activity/exercise. In this study, we collected comprehensive gene expression data in whole dorsal root ganglia (DRGs) throughout the levels below the injury comparing the effects of SCI with and without activity/exercise. Overall design: Rats were subjected to a single level laminectomy at T2 vertebrae before receiving a complete transection injury or moderately-severe contusion injury (25 g-cm SCI) at the T2 spinal cord level using the NYU Impactor (W.Young, Rutgers University, Newark, NJ). After four days of recovery, all animals were housed two per cage in tiny cage (7.5” x 8.5” x 8”) as opposed to standard cage (22” x 12.5” x 8”) to restrict their motion for the duration of the study. The subjects were then randomized in to one of four groups: 1) Contusion SCI + swimming (SWIM), 2) Contusion SCI + shallow water walking (SWW), 3) Contusion SCI, un-exercised, 4) Complete Transection, un-exercised and 5) un-injured and un-exercised control group. Swimming and shallow water walking as exercise intervention, began 2.5 weeks post injury in T2 contused group and was conducted 5 days a week for 10 weeks. Animals were sacrificed at 13.5 weeks post-injury for contusion SCI+Exercise, at 11.5 weeks post-injury for contusion SCI alone, and 8.5 weeks post-injury for transection SCI. DRGs from T11-L4 levels were retrieved from both sides of the spinal column of each animal and total RNA was extracted for Illumina NextSeq RNA sequencing.