Priming mesenchymal stromal cells with neurotrophic factors boosts the neuro-regenerative potential of their secretome.

Endoplasmic reticulum (ER) stress-mediated accumulation of misfolded protein is one of the causes involved in the onset of several neurodegenerative diseases (ND). Under physiological conditions, ER stress activates the unfolded protein response (UPR) that repairs the misfolded proteins. However, if the ER stress becomes chronic, the UPR fails to repair the misfolded proteins leading to disease conditions such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, etc. Most in vitro systems are based on the infliction of acute ER stress on the target cells, which kills them, and thus, are not physiologically relevant models, as their neuro-regeneration is not possible. Here, we have developed a physiologically relevant in vitro model system, wherein we exposed Neuro-2a cells to an ER stress inducer which significantly affected their neuro-regenesis without killing them. These dysfunctional cells were then used to assess the effect of secretome (conditioned medium, CM) derived from mesenchymal stromal cells (MSCs) primed or not with neurotrophic factors. We found that priming of MSCs with neurotrophic factors enhances their neuroprotective potential. We demonstrate that when primed CM is given either as a single dose or in multiple doses, it restores neuro-regenesis and protects the stressed Neuro-2a cells from cell death. More importantly, the restoration of neuro-regenesis by primed CM is significantly higher as compared with the naive CM. These results clearly underscore the importance of priming the MSCs with neurotrophic factors for developing more effective therapeutic strategies to combat ND.