Lentiviral-mediated targeted transgene expression in dorsal spinal cord glia: tool for the study of glial cell implication in mechanisms underlying chronic pain development.

Activated glial cells in the dorsal spinal cord take an important part in the development of pain after peripheral nerve injury. Our understanding of mechanisms involved in functional changes of spinal glia remains incomplete. Excepting drugs that completely disrupt glial function, pharmacological studies fail to target glia and to modify locally its function in order to really discriminate the role of neuronal versus glial cells in chronic pain. We developed an intraspinal gene transfer approach using pseudotyped lentiviral-derived vector targeting highly preferentially glial cells. Single microinjection of vector expressing EGFP under a CMV promoter control (LV-EGFP) allowed vector diffusion along a rostro-caudal axis but strictly restricted to the grey matter of the ipsilateral dorsal spinal cord. EGFP transgene was mainly expressed in astrocytes and microglial cells whereas less than 9% of cells containing EGFP were neurons. Notably, LV-EGFP administration and EGFP overexpression in glial cells did neither modify glial activity, nor alter animal's nociceptive or locomotor behaviors. Targeted modulation of the expression of gene of interest in glial cells, closely restricted to a particular region of the spinal cord, may thus represent an interesting approach to refine the understanding of mechanisms by which spinal glial cells participate in pain processing.