Placental extracellular vesicles stimulate intestinal re-growth after massive small bowel resection in a rat model

Extracellular vesicles (EVs) are released by most cells, including stem cells, into the extracellular environment and regulate cell function and tissue regeneration through cell-cell communication. The EVs derived from human placenta have a crucial role in regulating the maternal immune response for a successful pregnancy outcome. The purpose of the current study was to evaluate the effects of human villous trophoblasts (HVT)-derived EVs on structural intestinal adaptation, cell proliferation and apoptosis in a rat model of short bowel syndrome (SBS). HVT-EVs were isolated from cell media after 24 and 48 h of starvation (medium without serum) by subsequent centrifugation and ultracentrifugation (UC). HVT-EV protein content were screened by protein array. Male Sprague-Dawley rats were divided into four experimental groups: sham rats underwent bowel transection and re-anastomosis, sham-EV rats underwent bowel transection and re-anastomosis and were treated with HVT-EVs given intraperitoneally (IP) at a dose of 200ug/200ul once daily from postoperative day 3 through 14, SBS rats underwent a 75% small bowel resection and anastomosis, and SBS-EV rats underwent similar bowel resection and were likewise treated with HVT-EVs. Parameters of intestinal adaptation, enterocyte proliferation and enterocyte apoptosis were determined on postoperative day 15. Apoptosis/inflammatory-related protein levels were determined by ELISA (TNF-α) and immunohistochemistry (caspase-3). SBS rats demonstrated a significant increase in jejunal and ileal bowel (400%) and mucosal (250%) weight, jejunal (18%) and ileal (13%) villus height, ileal crypt depth (17%), cell proliferation rates in jejunum (45%) and ileum (54%) and concomitant increase in cell apoptosis in jejunum (400%) and ileum (500%) compared to sham animals. Treatment of SBS rats with HVT-EVs which contain proangiogenic proteins such as angiogenin and angiopoietin-1 resulted in additional increase in jejunal bowel weight (39%), ileal mucosal weight (25%), ileal villus height (23%) and jejunal crypt depth (14%) compared to SBS-nontreated animals. Enhanced adaptation in SBS-EVs rats was achieved by a mild increase in cell proliferation and a significant decrease in cell apoptosis rates (four-fold decrease in jejunum and ten-fold decrease in ileum) vs SBS-nontreated animals. Inhibited cell apoptosis in this group was accompanied by decrease in TNF-α and caspase-3 expression. In conclusion, in a rat model of SBS, parenteral HVT-EVs stimulate structural intestinal adaptation. Increased cell proliferation and decreased cell death via apoptosis (probably by the intrinsic pathway) appears to be responsible for the increased cell mass.