Dysregulation of neurovascular unit in the retina after optic nerve injury

PURPOSE: To investigate the changes in the neurovascular unit (NVU) of the retina in rats following optic nerve (ON) injury, and to explore the translational implications for traumatic optic neuropathy (TON). METHODS: The ON transverse quantitative traction (ONTQT) was performed to establish the model of ON and retinal injury. The rats were divided into the sham operation group (SG) and the model group (MG). At 14th day post-modeling, flash visual evoked potential (FVEP) test was performed to evaluate the visual function. Transmission electron microscopy (TEM) was used to observe the microstructure of retinal NVU. RNA binding protein with multiple splicing (RBPMS) immunofluorescence was applied to detect the survival retinal ganglion cell (RGC). The activity of astrocytes and Müller cells in retina was detected by glial fibrillary acidic protein (GFAP) immunofluorescence. The expression of tight junction proteins (Claudin-1, Claudin-5) and glial end feet markers aquaporin-4 (AQP4) and inwardly rectifying potassium channel subtype 4.1 (Kir4.1) in retinal tissue were test by western blot and Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR). RESULTS: At 14th day following ONTQT, the FVEP results exhibited the prolonged peak latency of P2 and the reduced amplitudes of N1-P1 and N2-P2. TEM showed structural changes of the basement membranes in NVU and ultrastructural abnormalities of tight junctions (TJs) after ONTQT. Besides, the expression of RBPMS in ganglion cell layer (GCL) was down-regulated and GFAP was over-expression in the injured retinal sections. The relative expressions of claudin-1and claudin-5 declined and the mRNA levels of AQP4 increased in the retina at 14 days following ONTQT. The mRNA levels of Kir4.1 was downregulated in the retina of MG. CONCLUSIONS: ONTQT can be applied in the model of ON and retina injury. The dysfunction of retinal NVU may promotes the optic degeneration in rats following ONTQT, contributing to the RGC loss and impaired visual function. These findings provide a mechanistic basis for NVU-targeted neuroprotection and identify potential clinical biomarkers for the diagnosis and treatment of TON.