Does Cerebrospinal Fluid Communicate with the Eye?

Abstract

Purpose: It has been suggested that a pressure gradient at the level of the lamina cribrosa between intraocular pressure and cerebrospinal fluid (CSF) may contribute to optic nerve damage in glaucoma. Any relationship between CSF and the eye is largely unknown. The purpose of this study is to determine whether CSF communicates with the eye.

Methods: All procedures adhered to the ARVO Statement for the Use of Animals. 11 mice (male 129SVE) were anesthetized with isoflurane and positioned in a stereotaxic frame (Kopf Instruments, Tujunga, CA). In 7 mice, 3 μL of a fluorescent nanoparticle tracer, Quantum Dot 655 (QD; Invitrogen, Eugene, OR) was injected into the CSF of the cisterna magna through a suboccipital incision using stereotaxic technique. In controls (n=4) quantum dots were applied to the dura mater and not injected into CSF. Tracer-loaded CSF movement was visualized by in vivo hyperspectral imaging of the head and neck region (Maestro; CRi, Woburn, MA) at 20 and 40 minutes and 1, 2 and 6 hours after injection. Mice were sacrificed 6 hours after injection, whole head tissue blocks were fixed in paraformaldehyde, and frozen sections were scanned by hyperspectral imaging, using unmixing algorithms to separate signal from background (Maestro 2.4 Imaging Software). All sections containing eyes were also imaged with fluorescence microscopy.

Results: Hyperspectral analysis of head sections showed tracer in one or both eyes of 5 of 7 mice, 6 hours following injection into CSF. Quantum dots were detected in sclera, choroid and retinal tissues by fluorescence microscopy. In vivo imaging detected tracer in submandibular lymph nodes in all mice (n=7) after injection into CSF. Control mice (n=4) showed no signal in the eye or submandibular nodes.

Conclusions: There appears to be a communication between the CSF and eye in the mouse. Further studies are needed to elucidate the specific pathways involved and whether this communication is bidirectional. A better understanding of the relationship between these two compartments may help to understand optic nerve injury at the level of lamina cribrosa in glaucoma.

Keywords: 551 imaging/image analysis: non-clinical • 599 microscopy: light/fluorescence/immunohistochemistry • 607 nanotechnology