Transthyretin-induced increase in circ_0007411 represses neovascularization of human retinal microvascular endothelial cells in hyperglycemia via the miR-548m/PTPN12/SKP1/EGFR pathway

BACKGROUND: To investigate the mechanism of transthyretin (TTR) induced high expression of circ_0007411 and its parent gene, protein tyrosine phosphatase nonreceptor type 12 (PTPN12) in human retinal microvascular endothelial cells (hRECs) cultivated under high glucose condition. METHODS: The levels of PTPN12, circ_0007411, miR-548m, S-phase kinase associated protein 1 (SKP1) and epidermal growth factor receptor (EGFR) were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The direct interaction between circ_0007411/PTPN12 and miR-548m was investigated via Dual-luciferase reporter assay. The physiological characterization of hRECs was investigated through Cell Counting Kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU) labelling, Transwell, flow cytometry (FCM), wound healing, and tube formation assays. Co-immunoprecipitation (Co-IP) was used to detect the interaction between PTPN12 and SKP1. The function of PTPN12 against diabetic retinopathy (DR) was studied in streptozotocin (STZ) induced DR C57BL/6 mice. RESULTS: The levels of circ_0007411 was increased in hRECs in hyperglycemia with the induction of TTR. The overexpressed circ_0007411 could significantly enhance the level of PTPN12 and repress that of miR-548m, and it could enhance apoptosis and prohibit the proliferation, migration, and tube formation of hRECs. miR-548m mimics enhanced the proliferation, migration, and tube formation of hRECs by reducing the expression level of PTPN12 and promoting that of EGFR, whereas circ_0007411 rescued it. The direct binding of PTPN12 and SKP1 was confirmed by Co-IP. Additionally, the anti-neovascularization function of PTPN12 was confirmed in a STZ-induced mouse model of DR. CONCLUSIONS: In hyperglycemia, the TTR-induced increase in circ_0007411 could repress retinal neovascularization via the miR-548m/PTPN12/SKP1/EGFR pathway.