RPE pseudopods maintain photoreceptor outer segment renewal despite subretinal space expansion in Adam9 knockout mice

Area of Science:

• Ophthalmology
• Cell Biology
• Retinal Physiology

Background:

• Photoreceptor outer segments require constant renewal, involving membrane addition and RPE ingestion.
• Close apposition between photoreceptors and RPE is thought essential for this renewal.
• Subretinal space expansion in retinal diseases doesn't always immediately impair photoreceptor function.

Purpose of the Study:

• To investigate outer segment function and renewal in Adam9 knockout mice with expanded subretinal space.
• To determine if photoreceptor-RPE separation impacts photoreceptor light response sensitivity and outer segment renewal rates.
• To explore the mechanism maintaining photoreceptor function despite RPE separation.

Main Methods:

• Analysis of photoreceptor outer segment function and renewal in Adam9 knockout mice.
• Assessment of light-response sensitivity in photoreceptors.
• Evaluation of outer segment renewal rates and RPE morphology.

Main Results:

• Adam9 knockout mice exhibit significant subretinal space expansion.
• Photoreceptor light-response sensitivity remained unaffected by the separation.
• Outer segment renewal proceeded at a normal rate, facilitated by RPE pseudopods.
• Photoreceptor degeneration was not observed prior to the onset of these findings.

Conclusions:

• RPE pseudopod formation is a key mechanism for maintaining outer segment renewal across an enlarged subretinal space.
• This pseudopod-mediated renewal may explain preserved photoreceptor function in retinal diseases with RPE separation.
• Findings offer insights into conditions like vitelliform macular dystrophy and age-related macular degeneration.