Hypoxic pretreatment of adipose-derived stem cell exosomes improved cognition by delivery of circ-Epc1 and shifting microglial M1/M2 polarization in an Alzheimer’s disease mice model

Alzheimer’s disease (AD) is the most common dementia in the world. Increasing evidence has shown that exosomes from hypoxic pretreated adipose-derived stem cells (ADSCs) could be an effective cognitive function therapeutic in AD-associated pathophysiology. However, their role and regulatory mechanism remain largely unknown. High-throughput sequencing was used to identify differentially expressed circRNAs from ADSCs or hypoxia pretreated ADSC exosomes. Luciferase reporter assays and RT-qPCR were used to investigate the relationships between circ-Epc1, miR-770-3p, and TREM2. APP/PS1 double transgenic AD model mice were then used to study therapeutic effects regarding circ-Epc1 in ADSC exosomes. BV2 cells were used to show the regulatory relationships between circ-Epc1, miR-770-3p, and TREM2 and to show how these interactions modulated phenotypic transformations and inflammatory cytokine expressions in microglia. The results showed that exosomes from hypoxia pretreated ADSCs had a good therapeutic effect on improving cognitive functions by decreasing neuronal damage in the hippocampus. High-throughput sequencing showed that circ-Epc1 played an important role in hypoxia-pretreated ADSC exosomes regarding their ability to improve cognitive functions. Luciferase reporter assays showed that TREM2 and miR-770-3p were downstream targets of circ-Epc1. Overexpressing miR-770-3p or downregulating TREM2 reversed the effects of circ-Epc1 on M2 microglia during lipopolysaccharide treatment. In vivo experiments showed that circ-Epc1-containing ADSC exosomes increased the therapeutic effect of exosomes by improving cognitive function, decreasing neuronal damage, and shifting hippocampal microglia from the M1 polarization to the M2 polarization stages. Taken together, the data show that hypoxic pretreatment of ADSC exosomes improved cognition by delivery of circ-Epc1 and by shifting microglial M1/M2 polarization in an AD mouse model.