Astragaloside IV - mediated endothelial progenitor cell exosomes promote autophagy and inhibit apoptosis in hyperglycemic damaged endothelial cells via miR-21/PTEN axis.

Introduction: As one of the basic components of Astragalus, Astragaloside IV (AS-IV) has a protective effect on endothelial injury caused by diabetes. AS-IV stimulated endothelial progenitor cells (EPCs) to secrete exosomes loaded with miR-21. This study aimed to investigate the effects of AS-IV-mediated EPCs exosomal miR-21 (EPC-exos-miR-21) on high glucose (HG) damaged endothelial cells.

Materials and methods: After the isolation of EPCs derived from fetal umbilical cord blood, exosomes of EPCs were obtained by differential centrifugation. The morphology of exosomes was observed by electron microscopy. The particle size distribution of exosomes was detected by Nanoparticle Tracking Analysis. Human umbilical vein endothelial cells (HUVECs) were treated with 33 mM glucose to establish an HG injury model. Flow cytometry and TUNEL assay were used to characterize the surface markers of primary EPCs and the apoptosis of HUVECs. The gene and protein expression were detected by qPCR, immunofluorescence, and Western blotting. A dual luciferase assay was used to verify the targeting relationship of miR-21 with PTEN.

Results: HG environment led to time- and dose-dependent inhibition and enhancement of autophagy and apoptosis in HUVECs. AS-IV stimulated EPCs to secrete exosomes loaded with miR-21. Exosomes secreted by EPCs pretreated with AS-IV [EPC-exo(ASIV)] promoted autophagy and inhibited apoptosis in HG-impaired HUVECs. PTEN is a target of miR-21. MiR-21 carried by EPC-exo(ASIV) repressed PTEN expression in HG-impaired HUVECs. In contrast, p-AKT, p-mTOR, p-PI3K, cleaved PARP and PARP levels were upregulated. Compared to the HG group, the expression of autophagy regulatory genes (ATG5, beclin1 and LC3) was enhanced in the EPC-exo(ASIV) group and EPC-exo(ASIV)-miR-21 mimic group. In contrast, apoptosis-positive regulatory genes (Bax, caspase-3 and caspase-9) were attenuated. Further overexpression of PTEN reversed the expression of these genes.

Conclusions: AS-IV-mediated EPC-exos-miR-21 could enhance autophagy and depress apoptosis in HG-damaged endothelial cells via the miR-21/PTEN axis.