The secretome of mesenchymal stromal cells: Role of extracellular vesicles in immunomodulation.

Mesenchymal stromal cells (MSCs) inhibit natural killer cell proliferation and activity, suppress T lymphocyte proliferation, dendritic cells maturation and B lymphocyte proliferation and activation. Moreover, MSCs may induce regulatory T cells. Several factors released from MSCs have been implicated in their immune-modulatory properties. These include soluble factors such as interleukins 6 and 10, prostaglandin E2, hepatocyte growth factor, indoleamine 2,3-dioxygenase, nitric oxide, transforming growth factor β1, human leukocyte antigen and extracellular vesicles. These vesicles released from cells have been characterized as a new mechanism of cell-to-cell communication and emerged as mediators of the MSC-immune-modulatory effects. In this review we focused our attention on the extracellular vesicles as paracrine mediators of MSC immune-modulation.