Dose‐dependent effect of mesenchymal stromal cells co‐grafted with dopaminergic neurons in a Parkinson's disease rat model

A major limiting factor for cell therapy in Parkinson's disease is the poor survival and reinnervation capacity of grafted dopaminergic neurons, independently of the cell source. Mesenchymal stromal cells (MSCs) have high capability to regulate the local environment through the release of trophic, antiapoptotic and immunomodulatory factors. In this work, we investigated whether co‐grafting of MSCs could improve the survival and reinnervation ability of dopaminergic precursors transplanted in animal models of Parkinson's disease. Rats with total unilateral dopaminergic denervation were grafted with a cell suspension of rat dopaminergic precursors (500,000 cells) with or without a high (200,000 cells) or low (25,000 cells) number of MSCs. Eight weeks after grafting, rats were tested for motor behaviour and sacrificed for histological analysis. Our results showed that the survival of dopaminergic neurons and graft‐derived striatal dopaminergic innervation was higher in rats that received co‐grafts containing a low number of MSCs than in non‐co‐grafted controls. However, the survival of dopaminergic neurons and graft‐derived dopaminergic reinnervation was lower in rats receiving co‐grafts with high number of MSCs than in non‐co‐grafted controls. In conclusion, co‐grafting with MSCs or MSCs‐derived products may constitute a useful strategy to improve dopaminergic graft survival and function. However, a tight control of MSCs density or levels of MSCs‐derived products is necessary.