Abstract: OBJECTIVE To investigate the impact of sepsis serum exosomes on the function of intestinal mucosal microvascular endothelial cells and the underlying mechanisms in sepsis-associated intestinal mucosal microcirculatory dysfunction. METHODS A total of 10 mice models were developed through the cecal ligation and puncture (CLP) method, with a sham surgery group serving as the control. Serum exosomes were isolated from both the sham surgery and sepsis groups by ultracentrifugation. Transmission electron microscopy, nanoparticle tracking analysis and protein immunoblotting were adopted for comprehensive identification. Exosomes from sepsis serum labeled with the fluorescent dye PKH-67 were co-cultured with intestinal mucosal microvascular endothelial cells, and their uptake by endothelial cells was observed by confocal microscopy. The cells were randomly divided into the following groups: control group, sham surgery exosome group, sepsis exosome group, sham surgery exosome-depleted serum group and sepsis exosome-depleted serum group. Each group was subjected to continuous intervention. Cell proliferation activity, migration ability, apoptosis rate and cell cycle distribution were detected through CCK-8, Transwell and flow cytometry, respectively. RESULTS Vesicles with a typical saucer-shaped double-layer membrane structure were isolated, with a peak particle size of approximately 131 nm and a high expression of CD63 and HSP70 proteins, consistent with the characteristics of exosomes. PKH-67-labeled exosomes were effectively internalized by endothelial cells. Compared with the control group and the sham surgery exosome group, the sepsis exosome group showed lower cell proliferation activity and migration number (both P<0.05), a higher apoptosis rate (P<0.05) and a higher proportion of cells in the G0/G1 phase (P<0.05). The aforementioned effects in the exosome-depleted serum groups were weaker than those in the corresponding exosome groups. CONCLUSION Serum exosomes from mice with sepsis are taken up by intestinal mucosal microvascular endothelial cells and lead to endothelial dysfunction by inhibiting proliferation and migration, inducing G0/G1 phase arrest and promoting apoptosis.