LINC02099 Promotes Retinal Extracellular Matrix Deposition in Diabetic Mice Via the miRNA-214-3p/CTSS Axis

Retinal fibrosis, a hallmark of proliferative diabetic retinopathy (PDR), contributes to retinal detachment and irreversible vision loss. This research aimed to explore the roles and regulatory mechanisms of long noncoding RNA (lncRNA) LINC02099 in extracellular matrix (ECM) deposition in the retina, an essential process in retinal fibrosis associated with PDR. A lncRNA microarray analysis was conducted to identify differentially expressed lncRNAs in vitreous specimens from patients with PDR. An in vitro high-glucose (HG) (25 mM) model was established in Müller cells, while an in vivo diabetic mouse model was generated via intraperitoneal streptozotocin injection. Real-time quantitative PCR was utilized to detect the expression of lncRNAs, microRNAs, and target gene mRNAs. Western blotting and immunofluorescence staining were utilized to evaluate ECM deposition. The competitive endogenous RNA network involving LINC02099, miRNA-214-3p, and its target gene was analyzed using fluorescence in situ hybridization and dual-luciferase reporter assays. Additionally, scotopic electroretinography was performed to assess visual function in the treated mice. LINC02099 was the most highly expressed lncRNA in vitreous samples from patients with PDR. Overexpression of LINC02099 exacerbated HG-induced upregulation of fibronectin, collagen I, and collagen IV in Müller cells, while LINC02099 knockdown produced the opposite effect. Mechanistically, LINC02099 was found to directly interact with miR-214-3p. Introduction of a miR-214-3p mimic significantly suppressed HG-induced expression of fibronectin, collagen I, and collagen IV. Cathepsin S (CTSS) was identified as a direct target of miR-214-3p, and its knockdown attenuated HG-induced expression of these ECM components. Furthermore, LINC02099 knockdown reduced the expression levels of fibronectin, collagen I, and collagen IV by downregulating CTSS expression under HG conditions, a process that was significantly reversed by inhibition of miR-214-3p. Finally, in vivo experiments confirmed that LINC02099 overexpression aggravated ECM deposition in the retinas of diabetic mice via the miR-214-3p/CTSS axis. This study establishes the LINC02099/miRNA-214-3p/CTSS axis as a novel regulatory mechanism in PDR-associated retinal ECM expression. Targeting this pathway may provide new therapeutic strategies for managing PDR and enhancing outcomes for patients with advanced diabetic retinopathy.