Pericellular interphotoreceptor matrix dictates outer retina critical surface tension

Area of Science:

• Ophthalmology
• Biophysics
• Materials Science

Background:

• Retinal detachments create new pathological surfaces between the neural retina and retinal-pigmented epithelium (RPE).
• The physicochemical properties of these surfaces are poorly understood, limiting knowledge of detachment formation, reattachment optimization, and prevention.
• Lack of information on the biophysical consequences of retina-RPE separation hinders progress.

Purpose of the Study:

• To determine the molecular properties of the pathological interface surfaces in retinal detachments.
• To investigate the biophysical characteristics of the detached bovine retina's outer surface.
• To identify the molecular components responsible for the surface properties of detached retinas.

Main Methods:

• Contact angle goniometry was used to measure the critical surface tension of the outer retinal surface, isolated insoluble interphotoreceptor matrix (IPM), and purified interphotoreceptor retinoid binding protein (IRBP).
• Multiple attenuated internal reflectance infrared (MAIR-IR) spectroscopy characterized the molecular composition of the retinal surface.
• Ellipsometry, light microscopy, immunohistochemistry, and electron microscopy were employed for structural and spectroscopic analysis.

Main Results:

• The critical surface tension of the detached bovine retina was found to be 24 mN/m, similar to isolated insoluble IPM and lower than IRBP.
• MAIR-IR spectroscopy penetration depth was calibrated to 0.2 μm using barium-stearate films.
• Ultrastructural and spectroscopic analyses indicated that a pericellular IPM coating the outer retinal surface is primarily responsible for its surface properties.

Conclusions:

• The surface properties of detached retinas are dictated by the pericellular interphotoreceptor matrix (IPM) covering the outer segment tips.
• These findings provide crucial biophysical insights into the molecular basis of retinal detachment.
• Understanding these surface properties is essential for developing strategies to optimize retinal reattachment and prevent detachment progression.