Hypoxia macrophage-derived exosomal miR-26b-5p targeting PTEN promotes the development of keloids

Background Hypoxia is the typical characteristic of keloids. The development of keloids is closely related to the abnormal phenotypic transition of macrophages. However, the role of exosomal microRNAs (miRNAs) derived from hypoxic macrophages in keloids remains unclear. This study aimed to explore the role of hypoxic macrophage-derived exosomes (HMDE) in the occurrence and development of keloids and identify the critical miRNA.Methods The expression of CD206+ M2 macrophage in keloids and normal skin tissues was examined through immunofluorescence. The polarization of macrophages under a hypoxia environment was detected through flow cytometry. The internalization of macrophage-derived exosomes in human keloid fibroblasts (HKFs) was detected using a confocal microscope. miRNA sequencing was used to explore the differentially expressed miRNAs in exosomes derived from the normoxic and hypoxic macrophage. Subsequently, the dual-luciferase reporter assay verified that phosphatase and tension homolog (PTEN) was miR-26b-5p's target. The biological function of macrophage-derived exosomes, miR-26b-5p and PTEN were detected using the CCK-8, wound-healing and Transwell assays. Western blot assay was used to confirm the miR-26b-5p's underlying mechanisms and PTEN-PI3K/AKT pathway.Results We demonstrated that M2-type macrophages were enriched in keloids and that hypoxia treatment could polarize macrophages toward M2-type. Compared with normoxic macrophages-derived exosomes (NMDE), HMDE promote the proliferation, migration and invasion of HKFs. A total of 38 differential miRNAs (18 upregulated and 20 downregulated) were found between the NMDE and HMDE. miR-26b-5p was enriched in HMDE, which could be transmitted to HKFs. According to the results of the functional assay, exosomal miR-26b-5p produced by macrophages facilitated HKFs' migration, invasion and proliferation via the PTEN-PI3K/AKT pathway.Conclusions The highly expressed miR-26b-5p in HMDE promotes the development of keloids via the PTEN-PI3K/AKT pathway. Graphical Abstract