A library of cell-penetrating peptides combined with lysosomal targeting signals achieved up to 4-fold selective uptake into retinal pigment epithelium cells over corneal cells, enabling targeted drug delivery for retinal diseases.
4x selective RPE uptakeSpecific cell-penetrating peptide candidates internalized into retinal pigment epithelium cells at four times the rate of corneal lens cells, demonstrating engineered cell-type selectivity
What the researchers found
Researchers developed a combinatorial library of cell-penetrating peptides (CPPs) combined with lysosomal sorting signals and tested them for cell-type specificity in retinal cells versus corneal cells. Several CPP candidates showed up to 4-fold greater internalization in ARPE19 retinal pigment epithelium cells compared to B3 corneal lens cells, demonstrating that CPPs can be engineered for cell-type selectivity rather than the non-specific uptake typically seen.
Follow-up cargo transport studies confirmed that the selected CPPs could effectively deliver payload into ARPE19 cells and target it specifically to lysosomes — the cellular organelles where storage diseases cause dysfunction and eventual blindness.
Why it matters
The eye contains many different cell types in close proximity, and diseases often affect specific ones. Lysosomal storage diseases in the retinal pigment epithelium (RPE) impair the cell's ability to clear waste, leading to RPE death and blindness. Current drug delivery methods struggle to target RPE cells specifically without affecting neighboring cell types. Demonstrating that CPPs can be engineered for 4x selective uptake into RPE cells — and can deliver cargo directly to lysosomes — opens a new approach for treating retinal diseases with precision-targeted peptide delivery.
The numbers in context
Up to 4x internalization efficiency in RPE cells vs. corneal cells · combinatorial CPP + lysosomal sorting signal library · effective lysosomal targeting confirmed in ARPE19 cells
How the study worked
A combinatorial library was created by combining different cell-penetrating peptides with lysosomal sorting signals. The library was screened on two human cell lines: ARPE19 (retinal pigment epithelium) and B3 (corneal lens cells). Internalization efficiency and cell-type selectivity were measured by comparing uptake between the two cell types. Cargo transport studies assessed whether the CPPs could deliver payload to lysosomes within ARPE19 cells.
Who was studied
ARPE19 retinal pigment epithelium cells and B3 corneal lens cells
What this study cannot tell us
This is a preprint (Research Square) that has not been peer-reviewed. All experiments used cell lines (ARPE19 and B3), not primary retinal cells or in vivo models. The 4x selectivity, while promising, may not translate to the complex multicellular environment of the living eye. No therapeutic cargo was delivered — only proof-of-concept internalization was demonstrated. The RPE cell line ARPE19 may not fully represent primary RPE cell behavior.
How to read the evidence
This study is graded as preliminary. It is a preprint (not peer-reviewed), conducted entirely in cell culture with two cell lines. No animal or human testing was performed, and no therapeutic cargo was delivered — only proof-of-concept uptake was demonstrated.
When this study was published
Posted as a preprint in 2023, this work has not yet appeared as a peer-reviewed publication. The findings should be interpreted with appropriate caution pending peer review.
The bigger picture
Retinal diseases like age-related macular degeneration and lysosomal storage disorders affecting the RPE are leading causes of blindness with limited treatment options. Drug delivery to specific cell types within the eye remains a major challenge because the eye's tight barriers and cellular diversity make precision targeting difficult. This proof-of-concept that CPPs can be rationally designed for cell-type and organelle selectivity could transform ophthalmic drug delivery. Combined with enzyme replacement therapies for lysosomal storage diseases, CPP-mediated delivery could enable treatments that currently can't reach their target cells.
Questions still open
- Will the 4x selectivity observed in cell culture hold up in the complex tissue architecture of a living eye?
- Can these CPPs deliver functional enzymes to lysosomes in RPE cells to treat lysosomal storage diseases?
- Could this approach be adapted for other retinal cell types affected by different diseases, such as photoreceptors in retinitis pigmentosa?
Common questions
What are cell-penetrating peptides?
Why is targeting lysosomes in retinal cells important?
Read the original research
Comparative transport analysis of cell penetrating peptides and Lysosomal sequences for selective tropism towards RPE cells.
Research square
Citation
Grohn, Kris; Parella, Kyle; Lumen, Ellie; Colegrove, Hanna; Bjork, Victor; Franceski, Alana; Wolfe, Aaron; Moody, Kelsey. (2023). Comparative transport analysis of cell penetrating peptides and Lysosomal sequences for selective tropism towards RPE cells.. Research square. https://doi.org/10.21203/rs.3.rs-3651531/v1