hsa_circ_0099682 exacerbates the development of diabetic retinopathy by promoting pathological neoangiogenesis via the miR-125b-5p/HNRNPU axis

Objective

Diabetic retinopathy (DR) is a leading cause of vision loss, driven by hyperglycemia-induced human retinal microvascular endothelial cell (HRMEC) dysfunction, mitochondrial impairment, oxidative stress, inflammation, and aberrant angiogenesis. Circular RNAs (circRNAs) have emerged as critical regulators in various ocular pathologies, yet their contributions to DR remain unclear. This study identified and characterized hsa_circ_0099682, derived from the alpha motif domain-containing protein 1B (ANKS1B) gene, and investigated its role and molecular mechanism in high glucose (HG)-induced HRMEC injury.

Methods

Hsa_circ_0099682 was validated as a genuine circRNA through bioinformatic analyses (circPrism, circBank), RNase R digestion, actinomycin D treatment, and PCR with divergent/convergent primers. HG-exposed HRMECs were transfected with siRNAs targeting hsa_circ_0099682, miR-125b-5p inhibitors, or heterogeneous nuclear ribonucleoprotein U (HNRNPU) overexpression constructs. Mitochondrial function was assessed by reactive oxygen species (ROS) measurement and JC-1 staining for mitochondrial membrane potential. Inflammatory and oxidative stress markers (interleukin [IL]-6, IL-1β, superoxide dismutase [SOD], and malondialdehyde [MDA]) were quantified by enzyme-linked immunosorbent assay (ELISA) and commercial kits. Apoptosis and tube formation assays evaluated cell survival and angiogenic potential. Luciferase reporter and RNA immunoprecipitation assays confirmed ceRNA interactions. streptozotocin-induced DR rats were treated with AAV-shRNA to silence hsa_circ_0099682. Hematoxylin and eosin staining, immunofluorescence, ELISA, and Western blot analyses were performed to assess retinal structure, inflammation, oxidative stress, and angiogenic markers.

Results

Hsa_circ_0099682 showed stable circular configuration and abundant cytoplasmic localization. In HG-stressed HRMECs, hsa_circ_0099682 knockdown reduced ROS accumulation, preserved mitochondrial membrane potential, diminished IL-6 and IL-1β secretion, enhanced antioxidant capacity, lowered apoptosis, and suppressed tube-forming ability. Mechanistically, hsa_circ_0099682 functioned as a sponge for miR-125b-5p, thereby relieving miR-125b-5p-mediated repression of HNRNPU. Inhibiting miR-125b-5p or overexpressing HNRNPU reversed the protective effects of hsa_circ_0099682 knockdown. In DR rats, silencing hsa_circ_0099682 improved retinal structural integrity, mitigated inflammation and oxidative stress, and restored balance in angiogenesis-related protein expression.

Conclusion

Hsa_circ_0099682 accelerates DR progression by suppressing miR-125b-5p, enhancing HNRNPU expression, and inducing mitochondrial dysfunction, inflammation, and irregular neoangiogenesis.