High-Resolution MRI Imaging Reveals Retinochoroidal Lymphatic Drainage during the Development of Subretinal Neovascularization

Abstract

Purpose: : To demonstrate the occurrence of retinal lymphangiogenesis during the development of subretinal choroidal neovascularization and to track the drainage route of retinochoroidal lymph vessels.

Methods: : CNV was induced in adult Brown Norway rats (n=4) using a double-frequency YAG laser (532 nm; 600 mW; 0.1 sec; 50 μm; 8-12 spots/eye). A transcorneal lens extraction was performed 24 hours later to create adequate space for the subsequent intravitreal injection of magnetic nano-particles and avoid any reflux into the periocular structures. 10 days later, 10 µl of iron oxide nano particles (10-15 nm, 5 mg/ml) were injected into the vitreous cavity. Nano particles were imaged with a birdcage quadrature volume coil in an Agilent 9.4T/31cm MRI scanner for up to 30 minutes. The tract of the lymphatic drainage was determined by acquiring multiple sagittal slices of 1 or 2 mm thickness without slice-interspacing using Fast Spin-Echo Multi-Slice (FSEMS, TR=2000 ms, TE=30 ms) pulse sequence for the head and neck region. FSEMS scans were repeated every 5 to 10 min. Subsequently, animals were sacrificed and their plasma was cross-blotted with retina extracts to determine whether lymphatic drainage from the retina resulted in de novo antibody production against retinal auto-antigens. Animals that received subconjunctival magnetic particles and intravitreal PBS were used as controls.

Results: : T2-weighted images revealed lymphatic drainage from the eyes of the animals that received intravitreal magnetic nano particles after being lasered for CNV induction. In these animals,magnetic nanopatricles appeared within periocular lymphatics four minutes after intravitreal injection, and they reached to the superficial and deep cervical lymph nodes within 30 minutes. Animals that received the magnetic nano tracer into the subconjunctival space also revealed a similar lymphatic drainage pattern. Cross-blotting of the retinal proteins with the plasma of the experimental group revealed de novo antibody production against 12 retinal proteins.

Conclusions: : Lymphangiogenesis occurs along with subretinal angiogenesis in laser-induced animal model of choroidal neovascularization. Lymphatic drainage from the retina results in an antibody response to a retinal autoantigens.

Keywords: age-related macular degeneration • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • antigen presentation/processing