Macrophages Regulate Smooth Muscle Differentiation of Mesenchymal Stem Cells via a Prostaglandin F 2α −Mediated Paracrine Mechanism

Objective— Mesenchymal stem cells are useful for vascular regeneration of injured tissues. Macrophages are involved in acute or chronic inflammatory diseases, and interleukin-1β (IL-1β), a proinflammatory cytokine, plays a key role in the activation of macrophages within injured tissues. To explore the role of macrophages on mesenchymal stem cell–mediated vascular regeneration, we examined the effects of IL-1β–activated macrophages on differentiation of human adipose tissue–derived mesenchymal stem cells (hASCs) to smooth muscle cells (SMCs) and the vascular regenerative capacity of the differentiated SMCs in a hindlimb ischemia animal model. Methods and Results— We demonstrate that IL-1β–conditioned medium from RAW 264.7 macrophages induces differentiation of human adipose tissue–derived mesenchymal stem cells to α-smooth muscle actin–positive SMCs, and the differentiated SMCs exhibited increased contractility in response to KCl and carbachol treatment. Transplantation of the differentiated SMCs attenuated severe hindlimb ischemia and promoted vascular regeneration. IL-1β treatment stimulated secretion of prostaglandin F2α from RAW 264.7 cells. Small interfering RNA–mediated silencing of the prostaglandin F2α receptor completely abrogated IL-1β conditioned medium–stimulated α-smooth muscle actin expression. Moreover, prostaglandin F2α treatment stimulated expression of α-smooth muscle actin in human adipose tissue–derived mesenchymal stem cells.Conclusion— These results suggest that IL-1β–activated macrophages promote differentiation of human adipose tissue–derived mesenchymal stem cells to SMCs through a prostaglandin F2α –mediated paracrine mechanism.