Faculty, Staff and Student Publications

Language

English

Publication Date

1-1-2025

Journal

Theranostics

DOI

10.7150/thno.111807

PMID

40963925

PMCID

PMC12439270

PubMedCentral® Posted Date

8-11-2025

PubMedCentral® Full Text Version

Post-print

Abstract

Rationale: MicroRNA-204 (miR-204) is one of the most abundant miRNA species in the retinal pigment epithelium (RPE) and RPE-derived extracellular vesicles (EVs). Knockout (KO) of miR-204 leads to dysfunction and degeneration of both the RPE and the retina. In addition to previously reported retinal pathologies, we observed the accumulation of lipid-laden subretinal microglia in miR-204 KO mice. This study aimed to identify potential molecular targets of miR-204 involved in microglia lipid processing and to determine whether RPE-derived EVs can improve the function of miR-204-deficient retinal microglia.

Methods: Lipid accumulation in microglia was detected by staining with LipidTox, a fluorescent dye specific for neutral lipids, followed by either flow cytometry analysis or direct visualization on RPE/choroid flat mounts. MiRNA database and target prediction tools, such as miRWalk and TargetScan, were used to search for potential target genes of miR-204 in microglia. The identified target mRNA was validated with a miRNA reporter assay. RPE EVs were prepared from ex vivo cultured mice eye cups and administered via retro-orbital injection in miR-204 knockout (KO) mice. RPE integrity was assessed by ERG c-wave measurement.

Results: KO of miR-204 resulted in the accumulation of neutral lipids in subretinal microglia. MiR-204 targeted the TGF-β receptor 2 gene in microglia. TGF-β markedly suppressed the expression of genes related to microglia lipid clearance. Eyes injected with RPE-derived EVs showed improved ERG c-wave responses compared to the fellow eyes injected with saline.

Conclusions: This study supports that TGF-β/TGF-β receptor 2 regulates microglia lipid metabolism primarily by suppressing lipid clearance. By modulating TGF-β signaling, miR-204 in RPE-derived EVs likely enhances the lipid metabolic activities of subretinal microglia, which are crucial for the structural integrity and proper function of the outer retina and RPE. RPE-derived EVs and their delivery of miRNAs represent a potential therapeutic approach for treating retinal diseases, such as age-related macular degeneration, which involve dysregulated lipid metabolism in subretinal microglia.

Keywords

MicroRNAs, Animals, Microglia, Mice, Mice, Knockout, Retinal Pigment Epithelium, Lipid Metabolism, Extracellular Vesicles, Retina, Mice, RPE

Published Open-Access

yes

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