Neuroprotective effect of umbilical cord mesenchymal stem cell-derived exosomes on hippocampal neurons in mice with intracerebral hemorrhage

BACKGROUND: Exosomes derived from mesenchymal stem cells can inhibit neuroinflammation and some damage after intracerebral hemorrhage. There are few studies on the mechanism of neuroprotective effect of exosomes derived from mesenchymal stem cells on hippocampal neurons after intracerebral hemorrhage through heme oxygenase-1. OBJECTIVE: To explore the protection and mechanism of exosomes derived from umbilical cord mesenchymal stem cells on hippocampal neurons after intracerebral hemorrhage. METHODS: (1) A mouse model of intracerebral hemorrhage was established using autologous blood infusion, and then exosomes derived from umbilical cord mesenchymal stem cells were injected into the tail vein at 8 hours after intracerebral hemorrhage. Western blot assay was used to verify the expression of heme oxygenase 1, high mobility group box B1 and Toll-like receptor 4 at 24 hours, 4 and 30 days after intracerebral hemorrhage. (2) In vitro, the mouse hippocampal neuron cell (HT22 cell) intracerebral hemorrhage model was established by hemin stimulation, and cells were pretreated with exosomes derived from umbilical cord mesenchymal stem cells for 12 hours before modeling, and then the HT22 cells were stimulated by hemin for 6 hours. Heme oxygenase 1 expression was detected by western blot assay. (3) HT22 cells were transfected with lentivirus to reduce the expression of heme oxygenase 1, and then pretreated with exosomes derived from umbilical cord mesenchymal stem cells for 12 hours, stimulated with hemin for 6 hours. The expression of heme oxygenase 1 was detected by western blot assay. RESULTS AND CONCLUSION: (1) At 24 hours, 4 and 30 days after intracerebral hemorrhage, the expression of heme oxygenase 1 in the hippocampus on the injured side was significantly increased (all P < 0.05). Compared with the sham-operated group, the protein expression levels of heme oxygenase 1, high mobility group box B1 and Toll-like receptor 4 were significantly increased in the mice of the cerebral hemorrhage group on day 4 after cerebral hemorrhage (all P < 0.05). Compared with the intracerebral hemorrhage group, the protein expression levels of heme oxygenase 1, high mobility group box B1 and Toll-like receptor 4 in the intracerebral hemorrhage + exosome group were significantly decreased (all P <0.05). (2) In the in vitro cerebral hemorrhage model, compared with the control group, the expression of heme oxygenase 1 protein in HT22 cells was significantly increased in the hemin+PBS group. Compared with the hemin+PBS group, the heme oxygenase 1 protein expression was significantly decreased in HT22 cells in the hemin+exosome group (all P < 0.05). (3) After lentiviral transfection of HT22 cells to knock down the expression of heme oxygenase 1, there was no significant difference in the protein expression of heme oxygenase 1 between the knockdown heme oxygenase 1+hemin+PBS group and the knockdown heme oxygenase 1+hemin+exosome group. (4) The results showed that exosomes derived from umbilical cord mesenchymal stem cells had a neuroprotective effect on injured hippocampal neurons after intracerebral hemorrhage. The mechanism may be related to the regulation of high mobility group box B1 and Toll-like receptor 4-related inflammatory pathways through heme oxygenase 1.