Toll-like receptor 3-stimulation and aggregate-formation synergistically enhances anti-inflammatory activity of feline mesenchymal stem cells.

Importance: Mesenchymal stem cells (MSCs) used to treat inflammatory diseases in humans show improved clinical outcomes compared to other treatments. On the other hand, feline MSCs have limited therapeutic effects because of their low bioactivity. Successful clinical treatment requires enhancing the anti-inflammatory ability of feline adipose-derived MSCs (fAdMSCs).

Objective: To enhance the anti-inflammatory activity of fAdMSCs.

Methods: fAdMSCs were treated with the toll-like receptor 3 (TLR3) ligand poly (I:C) and aggregated. Indoleamine 2,3-dioxygenase-1 (IDO-1) expression and kynurenine production were measured to evaluate the anti-inflammatory activity. Anti-inflammatory effects were assessed by culturing fAdMSCs with rat macrophages and transplanting them into the kidney capsules of rats.

Results: IDO-1 expression and kynurenine production in fAdMSCs were increased significantly by a poly (I:C) treatment and enhanced using a basic fibroblast growth factor (bFGF) treatment. The level of fAdMSC aggregation increased IDO-1 expression significantly compared to the monolayer. These effects were enhanced by pretreatment with bFGF and poly (I:C). The bFGF and poly (I:C)-pretreated fAdMSC aggregates suppressed tumor necrosis factor-α expression in rat macrophages. During transplantation, the pretreated fAdMSC aggregates avoided leakage, survived in aggregate form, and induced anti-inflammatory macrophages.

Conclusions and relevance: TLR3-stimulated, bFGF-pretreated fAdMSC aggregates increase the anti-inflammatory activity significantly, providing a potential therapeutic approach for inflammatory diseases in felines.