Paracrine in vivo inhibitory effects of adipose tissue-derived mesenchymal stromal cells in the early stages of the acute inflammatory response

Background aims. Excessive or unresolved inflammation leads to tissue lesions. Adipose tissue derived mesenchymal stromal cells (AMSCs) have shown protective effects that may be dependent on the modulation of inflammation by secreted factors. Methods. We used the zymosan-induced mouse air pouch model at two time points (4 h and 18 h) to evaluate the in vivo effects of AMSCs and their conditioned medium (CM) on key steps of the early inflammatory response. We assessed the effects of AMSCs and CM on leukocyte migration and myeloperoxidase activity. The levels of chemokines, cytokines and eicosanoids in exudates were measured by use of enzyme-linked immunoassay or radio-immunoassay. In addition, the expression of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 (mPGES-1) was studied by use of Western blotting and the phosphorylation of p65 nuclear factor-kappa B (NF-kappa B) by immunofluorescence. Results. All inflammatory parameters were significantly reduced by CM and AMSCs to a similar extent at 4 h after zymosan injection with lower effects at 18 h. The observed inhibition of leukocyte migration was associated with reduced levels of chemokines and leukotriene B-4. Interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha and tumor necrosis factor stimulated gene 6 levels were significantly decreased. The downregulation of mPGES-1 was associated with inhibition of prostaglandin E-2 production. Our results suggest that these anti-inflammatory effects are related, in part, to the inhibition of NF-kappa B activation. Conclusions. AMSCs dampen the early process of inflammation in the zymosan-induced mouse air pouch model through paracrine mechanisms. These results support the potential utility of these cells as a source of novel treatment approaches for inflammatory pathologies.