An in situ-crosslinked hydrogel-induced chronic ocular hypertension model with characteristic neurodegeneration

Abstract

Purpose : A reliable animal model providing chronic ocular hypertension (COH) and characteristic neurodegeneration is essential to recapitulate human glaucoma and understand molecular mechanisms. This study aims to develop an experimental glaucoma model induced by a novel in situ-crosslinked hydrogel and thoroughly evaluate the effectiveness of this model.

Methods : We designed and developed a novel method of inducing persistent IOP elevation in C57BL/6J mice using an injectable hydrogel formulated by hyperbranched macromolecular poly(ethylene glycol) (HB-PEG) and thiolated hyaluronic acid (HA-SH). The hydrogel’s characteristics were first assessed to determine its mechanical strength, swelling profile and cytocompatibility. Retinal whole-mount immunostaining was used to determine retinal ganglion cell (RGC) loss and hematoxylin-eosin (HE) staining was used to measure ganglion cell complex (GCC) thickness. All experimental data were analyzed using GraphPad Prism (v9.0; GraphPad Software, CA, USA) and were presented as the mean ± standard error of the mean (SEM). A P value less than 0.05 was regarded as statistically significant.

Results : An appropriate hydrogel formulation was determined to induce chronic IOP elevation and the effectiveness of our model was thoroughly evaluated. We determined that the HB-PEG/HA-SH hydrogel generated under physiological conditions was suitable for intracameral injection. When the concentration ratio of HB-PEG and HA-SH was 1:1 (10 mg/ml each), the highest storage modulus (68 Pa) was observed (Fig. 1A) while minimal swelling (Fig. 1B) and degradation profile (Fig. 1C) was observed. Besides, HTMCs maintained high viability after co-culture with HB-PEG/HA-SH hydrogel (Fig. 1D), indicating the good cytocompatibility of the hydrogel. Injection of the hydrogel (Fig. 2A-B) induced a persistent IOP elevation over 50% above baseline (Fig. 2C), which led to progressive RGC loss (37.12 ± 2.61% and 41.62 ± 4.94% on day 28 in the central and peripheral retinal regions, mean ± SEM, P<0.001) (Fig. 2D-E) and GCC thickness reduction (10.03 ± 3.25%, mean ± SEM, P = 0.0093) (Fig. 2F-G).

Conclusions : The in-situ forming HB-PEG/HA-SH hydrogel system could be an appropriate strategy for developing a reliable experimental glaucoma model without any confounding factors. We expected this model would be conducive to the development of neuroprotective and neuroregenerative therapies.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.