Crucial role of IL1beta and C3a in the in vitro-response of multipotent mesenchymal stromal cells to inflammatory mediators of polytrauma.

Multipotent mesenchymal stromal cells (MSC) exert immune-modulatory effects and support tissue regeneration in various local trauma models. In case of a polytrauma, high amounts of danger-associated molecular patterns are released, leading to a systemic increase of inflammatory mediators. The influence of such a complex inflammatory microenvironment on human MSC is mainly unknown so far. Therefore, we investigated the effects of a defined serum-free polytrauma "cocktail" containing IL beta, IL6, IL8 and the anaphylatoxins C3a and C5a, in concentrations corresponding to those measured in the blood of polytrauma patients, on human MSC in vitro. The polytrauma cocktail induced directed migration of MSC with C3a representing its major soluble chemoattractive agent. Furthermore, the polytrauma cocktail and IL1beta upregulated the expression of MMP1 indicating a potential role of IL1beta to enhance MSC migration in the tissue context. COX2, PTGES and TSG6 were also found to be upregulated upon stimulation with the polytrauma cocktail or IL1beta, but not through other single factors of the polytrauma cocktail in pathophysiologically relevant concentrations. An RNA expression array of 84 inflammation-related genes revealed that both the polytrauma cocktail and IL1beta induced C3, CSF1, TLR3 and various chemokines without major qualitative or quantitative differences. These results indicate that IL1beta is a crucial mediator of the polytrauma cocktail in terms of immune-modulation and MMP1 expression. Thus, upon encountering the primary sterile, inflammatory milieu of a polytrauma, endogenous or systemically transfused MSC might be able to migrate to sites of injury, secrete TSG6 and PGE2 and to influence macrophage biology as observed in local trauma models.