Identification of keratoconus-related phenotypes in three Ppip5k2 mouse models

Abstract

Purpose : Our previous study has identified several mutations (S419A and N843S) in the phosphatase domain of PPIP5K2 in two multiplex families affected by keratoconus (KC). It is necessary to determine how PPIP5K2 mutations contribute to KC pathogenesis. We aimed to determine the corneal phenotypes in three mouse models with Ppip5k2 mutations.

Methods : Our study included three mouse models: Ppip5k2 gene-trap mice with elevated kinase and no phosphase activities (Ppip5k2^{^}) and two knock-in mice (Ppip5k2^S419A and Ppip5k2^N843S). We measured the central corneal thickness (CCT) using Spectral Domain Optical Coherence Tomography (SD-OCT) in Ppip5k2^{+/K^} and Ppip5k2^{K^/K^} mice (n=58 eyes) and two knock-in mice, Ppip5k2^S419A/+ and Ppip5k2^S419A/S419A (n=90 eyes), and Ppip5k2^D843S/+ and Ppip5k2^D843S/D843S (n=74 eyes) at 3 and 6 months. Pachymetry maps were generated using the Mouse Corneal Analysis Program (MCAP) to process the OCT images. Slit lamp biomicroscopy was used to determine any corneal abnormalities, and lastly hematoxylin-eosin staining using corneal sections from these animals to examine morphological changes.

Results : CCT significantly decreased from 3 to 6 months in the Ppip5k2^{+/K^} and Ppip5k2^{K^/K^} mice compared to their littermate controls. No significant CCT changes were identified in the two knock-in mice compared to their wild-type littermate controls. OCT-based pachymetry maps revealed abnormally localized thinning in all three models compared to their wild-type controls. Slit lamp examinations revealed corneal abnormalities in the form of bullous keratopathy, stromal edema, stromal scarring, deep corneal neovascularization, and opacities in the heterozygous / homozygous mice of the three models in comparison with their controls. Corneal histological abnormalities such as epithelial thickening and stromal layer damage were observed in the heterozygous/homozygous mice of the three models in comparison with controls.

Conclusions : We have identified phenotypic and histological changes in the corneas of three mouse lines that could be relevant in the development of animal models of KC.

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