Human Mesenchymal Stromal Cell-Derived Extracellular Vesicles Improve Liver Regeneration After Ischemia Reperfusion Injury in Mice.

Hepatic ischemia reperfusion injury (IRI) remains a major obstacle in liver resection and transplantation surgery, especially in diseased organs. Human mesenchymal stromal cells (MSCs) are reported to acutely alleviate hepatic IRI in mice by releasing bioactive membrane-enclosed extracellular vesicles (EVs), but the long-term effects of MSC-derived EV on hepatic IRI are unknown. Given the considerable differentiation capacity of fibroblasts (FBs) during wound healing and their morphological similarities with MSC, the present study aimed to investigate the potential of these two cell types and their cell-derived EV in attenuating liver damage after IRI. EVs were isolated and purified from the supernatant of MSC and FB cultures and, subsequently, characterized by electron microscopy, nanoparticle tracking analysis, and western blot. Liver injury and organ regeneration in a murine in vivo model of IRI were assessed by serum transaminase levels, histopathology, and immunohistochemistry. Changes in expression of inflammation-associated genes within liver tissue were evaluated by reverse transcriptase quantitative polymerase chain reaction. MSC, MSC-derived EV, FB, and FB-derived EV were systemically administered before hepatic IRI. We found that MSC and MSC-derived EV decreased serum transaminase levels, reduced hepatic necrosis, increased the amount of Ki67-positive hepatocytes, and repressed the transcription of inflammation-associated genes. Although they had no impact on organ damage, FB and FB-derived EV showed some regenerative potential in the late phase of hepatic IRI. Compared to FB, MSC and their derived EV had a stronger potential to attenuate liver damage and improve organ regeneration after hepatic IRI. These results suggest that the key therapeutic factors are located within EV.