Multi-faceted effects of mesenchymal stem cells (MSCs) determined by immune microenvironment and their implications on MSC/biomaterial-based inflammatory disease therapy

•MSCs have multifunction which is determined by local immune environment.•Adequate immune environment can direct MSCs into a reparative phenotype.•Over-active inflammatory milieu can direct MSCs into a pro-inflammation extreme.•Multi-faceted effect of MSCs is vital for cell/biomaterial-based therapy strategies.