Extracellular vesicles as immune mediators in response to kidney injury

Important progress has been made on cytokine signaling in response to kidney injury in the past decade, especially cytokine signaling mediated by extracellular vesicles (EVs). For example, EVs released by injured renal tubular epithelial cells (TECs) can regulate intercellular communications and influence tissue recovery via both regulating the expression and transferring cytokines, growth factors, as well as other bioactive molecules at the site of injury. The effects of EVs on kidney tissue seem to vary depending on the sources of EVs; however, the literature data are often inconsistent. For example, in rodents EVs derived from mesenchymal stem cells (MSC-EVs) and endothelial progenitor cells (EPC-EVs) can have both beneficial and harmful effects on injured renal tissue. Caution is thus needed in the interpretation of these data as contradictory findings on EVs may not only be related to the origin of EVs, they can also be caused by the different methods used for EV isolation and the physiological and pathological states of the tissues/cells under which they were obtained. Here, we review and discuss our current understanding related to the immunomodulatory function of EVs in renal tubular repair in the hope of encouraging further investigations on mechanisms related to their antiinflammatory and reparative role to better define the therapeutic potential of EVs in renal diseases.