Functional Changes Within the Rod Inner Segment Ellipsoid in Wildtype Mice: An Optical Coherence Tomography and...

Area of Science:

• Retinal biology
• Mitochondrial function
• Ophthalmology

Background:

• Mitochondria are crucial for the high energy demands of photoreceptor cells.
• Understanding mitochondria distribution is key to understanding retinal energy metabolism.
• Rod inner segment ellipsoid zone (ISez) shape may reflect mitochondrial status.

Purpose of the Study:

• To investigate if changing energy needs alter mitochondria distribution within the rod inner segment ellipsoid.
• To explore the potential of optical coherence tomography (OCT) to assess mitochondrial distribution noninvasively.

Main Methods:

• Used optical coherence tomography (OCT) to measure the ISez profile shape in mice (B6J and S6) under different light conditions (simulating varying energy demands).
• Quantified ISez aspect ratio, external limiting membrane-retinal pigment epithelium (ELM-RPE) thickness, and hyporeflective band intensity.
• Examined spatial distribution of rod ellipsoid mitochondria using electron microscopy.

Main Results:

• In B6J mice, darkness (higher energy demand) increased ISez aspect ratio and altered mitochondria distribution.
• S6 mice showed higher baseline ISez aspect ratio and less change in mitochondria distribution between light and dark conditions compared to B6J mice.
• OCT-derived ISez shape correlated with mitochondria distribution and bioenergy status.

Conclusions:

• Rod mitochondria activity in mice can potentially be evaluated noninvasively using the ISez profile shape.
• ISez shape is a novel OCT index that complements existing OCT biomarkers for retinal energy status.
• This approach may offer new insights into retinal diseases associated with mitochondrial dysfunction.