Strain Differences in Mouse Models of Pentosan Polysulfate Retinopathy

Abstract

Purpose : Pentosan polysulfate sodium (PPS) is prescribed to treat bladder pain or discomfort associated with interstitial cystitis. Pearce et al. [2018] discovered that long term PPS use is associated with a maculopathy suggestive of retinal pigment epithelium (RPE) injury. We previously demonstrated that prolonged treatment with PPS causes retinal dysfunction and subtle changes to outer segment length and RPE cell morphology in the 129S2/SvPas mouse. Here we report and compare the effects of the drug on the more common C57BL/6 mouse strain.

Methods : 10 male and 10 female age-matched C57BL/6J mice were given ad libitum mouse chow, either standard or supplemented with PPS. The daily dosage of PPS was initially 500 mg/kg mouse weight, later increased to 1000 mg/kg, then finally 2000 mg/kg over 14 months. Mice regularly had retinal function assessed by electroretinography (ERG). Mice were sacrificed after being maintained for 7 months on the highest PPS dose and eyes were fixed for RPE flat-mounting. Flatmounts were stained with a-e-catenin and ZO-1 and imaged using confocal microscopy. Images were analyzed using a custom pipeline in CellProfiler.

Results : During the 7 months on the highest dose, we observed a main drug effect of reduced ERG c-wave amplitudes (p=0.02, 2-way ANOVA). We observed no significant difference in a- or b-wave amplitudes. Analysis of the RPE flatmounts showed subtle differences in RPE cell shape. RPE from PPS-treated mice had decreased mean cell solidity, form factor, and extent, as well as increased compactness (p<0.05, unpaired t-tests). RPE flatmount analysis also showed that treated mice had less a-e-catenin immunostaining at cell edges (p=0.04, unpaired t-test).

Conclusions : The C57BL/6J mouse seems to be more resistant to retinal effects of PPS treatment than 129S2/SvPas mice. The C57 phenotype may be reflective of earlier processes in the 129SV mice. For example, ERG c-wave amplitudes were reduced before a- and b-wave amplitudes in the 129SV while the only reductions we saw in the C57 mice were with c-waves. C57 mice had differences in RPE cell shape in common with the 129SV mice. C57 mice had changes in RPE a-e-catenin immunostaining, but they were decreases at the cell edges rather than increases in the intracellular space seen in 129SV mice. Future studies are aimed at discovering what accounts for these strain differences as that should be useful in determining the mechanism of drug toxicity.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.