Song et al. 2025 — Lanosterol-synthase mRNA delivery in rat cataract models
TL;DR
Song et al. packaged 5-methoxyuridine-modified messenger RNA encoding human lanosterol synthase (hLSS) in pB-UC18 lipid nanoparticles and injected it into rat eyes. Intracameral (anterior-chamber) delivery produced lens-enriched firefly-luciferase reporter expression through the last measured time point (48 hours), while hLSS protein and increased lens lanosterol were assessed only 24 hours after a separate hLSS-mRNA injection. The intervention suppressed cataract development in a selenite experiment that began treatment before induction and reduced already-visible opacity over eight days in a galactose experiment.1 This was transient, injected mRNA protein-replacement research—not a topical eye drop, direct lanosterol dosing, genome editing, durable gene replacement, or human evidence. gap/needs-human-replication gap/needs-replication
Formulation and ocular delivery
The paper’s term “aromatized lipid nanoparticles” refers to nanoparticles containing the aromatic-scaffold ionizable lipid pB-UC18; it does not mean aerosolized or fragrance-related material. The optimized formulation combined pB-UC18, DOPE helper lipid, and DMG-PEG2k. Its reported hydrodynamic diameter was 173 ± 6 nm.1
Three-week-old Wistar rats received 1.5 µL containing 300 ng of firefly-luciferase mRNA per eye by intravitreal, subconjunctival, intracameral, or subretinal injection. Each route began with four rats: two were killed for ex-vivo imaging after the four-hour scan, while two were followed at 26 and 48 hours and then killed for ex-vivo imaging. All routes produced ocular signal at four hours. Intracameral signal peaked at 26 hours and remained above background at 48 hours, with the ex-vivo ocular signal arising predominantly from the lens; intravitreal and subretinal dosing produced more hepatic off-target signal than intracameral or subconjunctival dosing. The “more than seven-fold” result was a four-hour reporter-luminescence delivery comparison between same-dose pB-UC18 and SM-102 comparator nanoparticles after intracameral injection (the 200-ng groups used n=4 rats), not a seven-fold improvement in hLSS abundance, lanosterol, cataract grade, or vision.1
Expression compartment and duration
A single 300-ng intracameral hLSS-mRNA dose increased LSS immunofluorescence at 24 hours. Signal was not confined to the lens: it was prominent in the corneal stroma, corneal endothelium, choroid, lens epithelium, and lens cortex, with little signal in the lens nucleus. In separate non-cataract experiments, lens lanosterol was higher 24 hours after dosing in three- and eight-week-old rats (biological replicates: 3-week untreated n=3 and treated n=3; 8-week untreated n=2 and treated n=3). The study did not establish the duration of hLSS expression or lanosterol elevation beyond 24 hours; only the separate luciferase reporter was followed to 48 hours.1
The hLSS-protein and lanosterol measurements were made in otherwise normal rats, not concurrently in either cataract-efficacy cohort. The disease-model experiments did not biochemically quantify crystallin aggregation or demonstrate that lanosterol mediated the efficacy. Histology and representative TUNEL staining were consistent with less tissue disruption and apoptosis, but the TUNEL result was not quantified and therefore supports only a possible anti-apoptotic mechanism.1
Cataract-model timing and endpoints
Selenite model: suppression, not reversal of established opacity
The selenite experiment used 20 juvenile Wistar rats: healthy n=3, untreated cataract n=6, empty-LNP n=3, and hLSS-mRNA-LNP n=8. One eye in each nanoparticle-treated rat received 200 ng intracamerally at age 14 days; systemic selenite was given at day 15, and the same eye was dosed again at days 16 and 18. The contralateral eye was untreated. Cataract stage was scored by slit lamp at day 25, and lenses were photographed and examined by H&E staining and transmission electron microscopy at day 27. Treated eyes in the hLSS-mRNA group had lower cataract stage and fewer histologic/ultrastructural abnormalities than their untreated fellow eyes; empty nanoparticles did not show the same effect.1
Because the first hLSS-mRNA dose preceded selenite exposure, this experiment tested prevention or suppression of cataract development, despite the Methods heading calling it “reversal.” It did not show reversal of an already-established selenite cataract.1
Galactose model: short-window reversal of visible opacity
Rats received intraperitoneal D-galactose from ages 31–54 days, and visible cortical vesicles or radial opacity were present at day 54 before the first ocular treatment. Both eyes then received 300 ng of hLSS mRNA or empty nanoparticles intracamerally at days 54, 58, and 62. Slit-lamp images were acquired at treatment day 0 and four and eight days later; tissues were collected at age 69 days. The prespecified quantitative endpoint was lens opacity area normalized to total lens area. Sample units were lenses: healthy n=8, untreated cataract n=8, empty-LNP n=8, and hLSS-mRNA-LNP n=9. Relative opacity diminished over eight days only in the hLSS-mRNA group; H&E sections showed less fiber swelling, and representative TUNEL images showed less staining. One healthy-group rat died during anesthetized slit-lamp examination at the eight-day time point.1
This experiment supports partial reversal/remission of an existing acute galactose-induced opacity over eight days. It did not measure visual acuity, refractive quality, contrast sensitivity, or other functional vision endpoints.1
Safety and study-quality limits
The formal in-vivo safety window was only 24 hours after a single 300-ng intracameral dose in seven-week-old male Wistar rats. Slit-lamp examination found no reported eyelid irritation, redness, corneal opacity, or edema beyond corneal puncture marks; H&E sections showed no apparent changes in the eye, heart, liver, spleen, lung, or kidney; and routine blood, liver, and kidney measures showed no statistically significant differences (n=4 rats per plotted group in Supplementary Fig. 5). These observations do not establish chronic, repeated-dose, immunologic, retinal-function, or large-animal ocular safety. gap/long-term-unknown1
The reporting summary states that samples and animals were randomly allocated, no formal sample-size calculation was used, and investigators were not blinded. Sex was not considered in the overall study design. Four authors were named as inventors on a patent application covering the delivery platform and cataract treatment.1
Interpretation
The data demonstrate that an intracamerally injected mRNA formulation can transiently produce protein in and around the rat lens and can improve morphologic opacity endpoints in two acute juvenile-rat models. The study does not establish that topical lanosterol or an mRNA eye drop can cross the cornea, nor that either approach can reverse decades-old human nuclear, cortical, or posterior-subcapsular cataract. Intracameral administration punctures the cornea and requires ophthalmic procedural skill.1
The payload encoded an enzyme and was translated transiently in the cytoplasm. No nuclease, guide RNA, DNA donor, genomic edit, or genomic integration was used or measured; describing this treatment as genome editing would therefore be incorrect.1
Extrapolation to humans
| Dimension | Status | Notes |
|---|---|---|
| Pathway conserved in humans? | yes | The payload encoded human LSS, but expression and lanosterol elevation were tested only in rats. |
| Phenotype conserved in humans? | partial | Acute juvenile-rat selenite and galactose cataracts do not reproduce the decades-long biology or all subtypes of human age-related cataract. |
| Replicated in humans? | no | No human exposure was reported. |
Supersession check
PubMed and Europe PMC searches through 2026-08-18 found no later replication, correction, retraction, non-human-primate study, or human trial of hLSS-mRNA nanoparticles for cataract. Four papers citing this article in Europe PMC were reviews or addressed other RNA/LNP indications; none superseded its efficacy or safety findings.
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Footnotes
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Song R, Lin Y, Zhang M, Liu Z, Zhang R, Zhao J, Li B · doi:10.1038/s41467-025-63553-5 · PMID 41006301 · PMC12474983 · randomized allocation reported; investigators not blinded · therapeutic efficacy: n=20 rats (selenite) and n=33 lenses (galactose) · model: juvenile Wistar rats with chemically induced cataracts; intracameral hLSS-mRNA pB-UC18 lipid nanoparticles ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13