AKT is a unique downstream mediator of TLR signaling in human mesenchymal stem cells 2927

Abstract Description Mesenchymal stem cells (MSCs) are being extensively studied in clinical trials for different medical conditions. Understanding the mechanism of MSC therapy is valuable for its clinical application. Activation of TLR signaling pathways in MSCs can modulate their therapeutic effects, including differentiation, migration, and immunomodulatory properties. TLR signaling triggers a cascade of molecular events. We hypothesize that activation of the downstream mediators by TLR is important for the therapeutical function of MSCs. To test this hypothesis, human MSCs were stimulated with a panel of TLR agonists. Activation of the downstream signaling proteins were quantified by measuring phosphoproteins with a magnetic bead multiplex assay. We found that phosphorylation of AKT was the most dominant signaling protein among the tested in all MSCs treated by 10 TLR agonists. The findings were confirmed by Western blotting analyses. TLR4 agonist LPS stimulated more cytokine production and inhibiting AKT suppressed the cytokine production, suggesting the importance of AKT in mediating MSCs’ immunomodulatory function. Further research demonstrated that LPS suppressed AKT activation in a short time range but exogenous H2S rescues the AKT activation. In conclusion, AKT activation is important to TLR signaling in MSCs. Our work suggests that activating AKT by TLR may promote the survival of transplanted MSCs. Future work will focus on studying TLR signaling in MSCs using an in vivo animal model. Funding Sources This research was supported in part by the George H. Clowes Memorial Research Career Development Award (TAM), the Riley Children’s Foundation (TAM), the Gerber Foundation (TAM), National Institutes of Health R01HD105301 (TAM), the Department of Surgery at the Indiana University School of Medicine. Topic Categories Transplantation Immunology (TRAN)