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Updated: Nov 3, 2025
A Protocol to Evaluate and Quantify Retinal Pigmented Epithelium Pathologies in Mouse Models of Age-Related Macular Degeneration
Published on: March 10, 2023
Retinal Pigment Epithelium Remodeling in Mouse Models of Retinitis Pigmentosa
Debora Napoli1, Martina Biagioni1, Federico Billeri1,2
1CNR Neuroscience Institute, 56124 Pisa, Italy.
Abstract:
In retinitis pigmentosa (RP), one of many possible genetic mutations causes rod degeneration, followed by cone secondary death leading to blindness. Accumulating evidence indicates that rod death triggers multiple, non-cell-autonomous processes, which include oxidative stress and inflammation/immune responses, all contributing to cone demise. Inflammation relies on local microglia and recruitment of immune cells, reaching the retina through breakdowns of the inner blood retinal barrier (iBRB). Leakage in the inner retina vasculature suggests similarly altered outer BRB, formed by junctions between retinal pigment epithelium (RPE) cells, which are crucial for retinal homeostasis, immune response, and privilege. We investigated the RPE structural integrity in three models of RP (rd9, rd10, and Tvrm4 mice) by immunostaining for zonula occludens-1 (ZO-1), an essential regulatory component of tight junctions. Quantitative image analysis demonstrated discontinuities in ZO-1 profiles in all mutants, despite different degrees of photoreceptor loss. ZO-1 interruption zones corresponded to leakage of in vivo administered, fluorescent dextran through the choroid-RPE interface, demonstrating barrier dysfunction. Dexamethasone, administered to rd10 mice for rescuing cones, also rescued RPE structure. Thus, previously undetected, stereotyped abnormalities occur in the RPE of RP mice; pharmacological targeting of inflammation supports a feedback loop leading to simultaneous protection of cones and the RPE.
Insights
Retinitis pigmentosa (RP) causes retinal pigment epithelium (RPE) barrier dysfunction, leading to cone cell death. Treating inflammation in RP mouse models rescued RPE structure and protected cones.
Area of Science:
- Ophthalmology
- Neuroscience
- Cell Biology
Background:
- Retinitis pigmentosa (RP) is an inherited condition causing progressive vision loss.
- Rod photoreceptor degeneration in RP triggers secondary cone death via inflammatory processes.
- The blood-retinal barrier (BRB) integrity is critical for retinal homeostasis and immune privilege.
Purpose of the Study:
- To investigate retinal pigment epithelium (RPE) structural integrity in mouse models of retinitis pigmentosa (RP).
- To determine if RPE barrier dysfunction contributes to photoreceptor degeneration in RP.
- To evaluate the therapeutic potential of targeting inflammation for RPE and cone protection.
Main Methods:
- Utilized three mouse models of RP (rd9, rd10, Tvrm4).
- Performed immunostaining for zonula occludens-1 (ZO-1) to assess tight junction integrity in the RPE.
- Quantified ZO-1 discontinuities and assessed barrier permeability using in vivo dextran leakage assays.
- Administered dexamethasone to rd10 mice to evaluate therapeutic effects.
Main Results:
- All RP mouse models exhibited discontinuities in ZO-1 profiles, indicating RPE tight junction defects.
- ZO-1 interruptions correlated with increased RPE barrier permeability to dextran.
- Dexamethasone treatment in rd10 mice not only rescued cone photoreceptors but also restored RPE structural integrity.
- These findings reveal previously unrecognized RPE abnormalities in RP.
Conclusions:
- RP is associated with significant RPE barrier dysfunction, contributing to photoreceptor degeneration.
- Targeting inflammatory pathways can simultaneously protect both RPE and cone photoreceptors in RP.
- These findings highlight a critical feedback loop between RPE integrity and photoreceptor survival in RP pathogenesis.
