RhoA, RhoB, RhoC, Rac1, Cdc42, and Tc10 mRNA levels in spinal cord, sensory ganglia, and corticospinal tract neurons and long‐lasting specific changes following spinal cord injury

Abstract

Inhibition of RhoA has been shown to enhance axonal regeneration following spinal cord injury. Here we mapped mRNA expression patterns of RhoA, B, and C, Rac1, Cdc42, and Tc10 in spinal cord, sensory ganglia, and sensorimotor cortex in uninjured rats, and following spinal cord injury or sham laminectomy. In the intact spinal cord, neurons displayed high levels of Rac1, Cdc42, and Tc10 mRNA hybridization signal. GFAP-immunoreactive astrocytes expressed primarily RhoB and Rac1, while oligodendrocyte-like cells expressed RhoA, Rac1, and Cdc42. Injury caused profound, long-lasting upregulation of RhoA, Rac1, Cdc42, and Tc10 mRNA in the spinal cord, while RhoB was modestly increased and RhoC did not change. GFAP-immunoreactive reactive astrocytes exhibited a dramatic increase of RhoA mRNA expression along with increases of Rac1 and Cdc42. Injury also led to elevation of RhoA, Cdc42, and Tc10 in neurons and modest increases of RhoA, Rac1, and Tc10 in oligodendrocyte-like cells. Laminectomy caused similar, but less pronounced alterations of investigated mRNA species. In dorsal root ganglia neuronal RhoA, Rac1, Cdc42, and Tc10 mRNA levels were increased similarly by spinal cord injury and sham surgery. The CST pyramidal cells expressed Tc10 mRNA and the CST itself was Tc10-immunoreactive. Tc10-immunoreactivity disappeared distal to injury. We conclude that there are gene-specific patterns of expression of the six different Rho-GTPases in normal spinal cord and dorsal root ganglia, and that specific changes of temporal and spatial expression patterns occur in response to spinal cord injury, suggesting different roles of these GTPases in the cellular sequelae of CNS injury.