Mesenchymal Stem Cells Pretreated with <em>Lactobacillus plantarum </em>Supernatant Attenuate Depressive‐like Behavior via Inhibition of NLRP3‐Mediated Neuroinflammation: An Ex Vivo, In Vivo, and In Silico Studies

Mesenchymal stem cells (MSCs)-based therapy has received considerable research atten-tion for its anti-inflammatory properties in depressive-like behavior, but poor MSC sur-vival and immunogenicity after transplantation limit their therapeutic effectiveness. This study evaluated pretreated bone marrow-derived MSCs (BM-MSCs) with lactobacillus plantarum supernatant (L.PS) in an animal model of chronic restraint stress (CRS)-induced depressive-like behavior. BM-MSCs were pretreated with 15 μM of fluoxetine or 10 10 µl/ml of L.PS for 24 hours. Thirty-six adults male Wistar rats were divided into six groups: CTRL, CRS, CRS+PBS, CRS+MSCs, CRS+Flx/MSCs, and CRS+L.PS/MSCs groups. The open field test (OPT), Morris water maze (MWM), forced swimming test (FST), body weight, and blood glucose levels were measured. After sacri-fice, the hippocampal tissues underwent histopathological analysis. Additionally, hip-pocampal mRNA levels of NF-κB and pro-inflammatory cytokines (IL-1β, IL-6, IL-18, and TNF-α) were measured using real-time PCR, while ELISA measured protein levels of these cytokines and serum corticosterone. A bioinformatic analysis, including pro-tein-protein interaction (PPI) network, enrichment, and correlation analysis related to depression was performed. Pre-treatment of MSCs with L.PS significantly improved de-pressive-like behavior (p &lt; 0.05) by enhancing MSCs neuroprotection via downregulating NF-κB and pro-inflammatory cytokines. An in-silico analysis also highlighted the im-portance of evaluating and targeting this pathway. In conclusion, we found that L.PS pretreated MSCs significantly improve CRS-induced depressive-like behavior, which can be partly attributed to the inhibition of NLRP3-mediated neuroinflammation.