**Abstract**

The well-known reparative properties of mesenchymal stem cells (MSCs) make them an attractive source for cell-based therapy. In vitro and in vivo studies support an anti-inflammatory role of MSCs by directly targeting immune cells or via the secretion of immunomodulatory factors. MSCs have been isolated from several human normal tissues, even from pathological biopsies and blood samples; in these cases, MSCs displayed peculiar characteristics, suggesting a phenotype transition into a pathological state. Indeed, MSCs derived from inflamed tissues acquired a pro-inflammatory behaviour. In this view, MSCs may be crucial players of many pathways involved in human diseases, especially during the inflammatory cascade. The present chapter will minutely describe the basic biology of human MSCs derived from normal and pathological arteries, focusing on their dual nature as cellular switchers of the inflammatory setting. We will also discuss the emerging role of miRNAs in regulating MSC functions and their potential use as alternative strategies to manipulate MSC efficacy.

**Keywords:** mesenchymal stem cells (MSCs), immunomodulation, inflammatory process, phenotype switching, vascular wall
