circPLOD2 knockdown suppresses endometriosis progression via the miR-216a-5p/ZEB1 axis.

The present study aimed to identify the role of circPLOD2 in endometriosis and its underlying mechanisms. We determined circPLOD2 and miR-216a-5p expression in ectopic endometrial (EC) and eutopic endometrial (EU) samples as well as in endometrial samples from uterine fibroids of ectopic patients (EN) and embryonic stem cells (ESCs) using qRT-PCR. The association between circPLOD2 and miR-216a-5p or miR-216a-5p and zinc finger E-box binding homeobox 1 (ZEB1) expression was analyzed using Starbase, TargetScan, and dual-luciferase reporter gene assays. Cell viability, apoptosis, and migration and invasion were assessed using MTT, flow cytometry, and transwell assays, respectively. In addition, qRT-PCR and western blotting was used to measure circPLOD2, miR-216a-5p, E-cadherin, N-cadherin, and ZEB1 expression. circPLOD2 was upregulated and miR-216a-5p was downregulated in EC samples compared with that in EU samples. Similar trends were observed in ESCs. circPLOD2 interacted and negatively regulated miR-216a-5p expression in EC-ESCs. circPLOD2-siRNA significantly inhibited EC-ESC growth; promoted cellular apoptosis; and inhibited EC-ESC migration, invasion, and epithelial-mesenchymal transition; these effects could be reversed following miR-216a-5p inhibitor transfection. miR-216a-5p directly targeted and negatively regulated ZEB1 expression in EC-ESCs. In conclusion, circPLOD2 promotes the proliferation, migration, and invasion of EC-ESCs and inhibits their apoptosis by targeting miR-216a-5p. These findings indicate potential therapeutic targets for endometriosis.