Physiomimetic culture of mesenchymal stromal cells affects macrophage activity in a paracrine manner

Rationale: Mesenchymal stromal cells (MSC)-based therapies for inflammatory diseases rely mainly on the paracrine ability to modulate different cell populations involved in the advance of the disease, such as macrophages. These immune cells possess a broad spectrum of inflammatory responses. Previous data have shown that the MSC secretome influences macrophage phenotype and functional capacities. Furthermore, preconditioning MSC with physiomimetic cues from the extracellular matrix (ECM) have shown to improve their repairing actions upon transplantation which could be exploited to boost their terapeutic efficacy. Aim: To assess the macrophage activity exerted by the secretome from physiomimetically-cultured lung MSC (LMSC). Methods: LMSC from human donors were cultured on in-house developed devices that enable lung-mimetic strain. Medium from LMSC cultured in either lung ECM scaffolds and in lung ECM hydrogels whilst subjected to cyclic stretch, and on tissue culture plates. Human monocytes were differentiated to macrophages by adding PMA and polarized to M1 and M2 phenotypes by adding LPS or IL-4 plus IL-10, respectively. M0, M1 and M2 macrophages were exposed to the medium of LMSC from the different culture conditions and analysed for typical surface markers by flow cytometry and their secretome content. Results: Secretome of LMSC subjected to stretch in lung scaffolds elicited changes in the gene expression of IL-10 compared to the static conditions. On the other hand, hydrogel conditions induced changes in IL-6 secreted by macrophages. Conclusion: Mechanical features of the lung ECM orchestrate key on LMSC, hence providing new insights into preconditioning of MSC for therapy.