Cannabidiol/tetrahydrocannabinol-enrich extract decreases neuroinflammation and improves locomotor outcome following spinal cord injury.

Neuroinflammation is one of the main players in lesion expansion and locomotor deficits after spinal cord injury (SCI), thus treatments to control the inflammatory process emerge as novel therapeutic strategies. In this context, the anti-inflammatory effects of tetrahydrocannabinol (THC) and cannabidiol (CBD), the main phytocannabinoids of Cannabis sativa, are increasingly recognized. The aim of this work was to investigate the effects of a standardized Cannabis sativa extract (CSE), which is mainly composed by THC/CBD in equimolar concentration, on neuroinflammation, secondary damage and locomotor outcome after SCI in rats. After acute SCI, CSE therapy increased the number of non-inflammatory (arginase-1 positive) microglial cells in the epicenter of the lesion and decreased the number of pro-inflammatory ones (arginase-1 negative) in the epicenter and in the rostral and caudal regions of the lesion. CSE also reduced the number of reactive astrocytes in the grey matter of the rostral and caudal regions. These results are consistent with the downregulation of mRNAs of inflammatory mediators (IL-1β, TNFα, IL-6, C3) and the upregulation of anti-inflammatory markers (ARG-1, MRC). In the chronic phase, CSE treatment prevented cyst expansion and also increased the volume of spared grey and white matter. Regarding locomotor outcome, CSE-treated rats showed better locomotor scores (open field test), higher latency to fall (Rotarod test) and lower number of hindlimb foot misplacements (horizontal ladder walking test) than untreated injured rats. These results suggest that this standardized CSE offers a promising perspective for reducing acute neuroinflammation and promoting functional recovery after SCI.