A laser-induced mouse model with long-term intraocular pressure elevation.

Hongmin Yun,Joel S Schuman,Kira L Lathrop,Ming Sun,Enzhi Yang,Valeria Fu,Donna B Stolz,Larry Kagemann,Yiqin Du,Bang V Bui

doi:10.1371/journal.pone.0107446

Hongmin Yun, Joel S Schuman + Show 8 more

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https://doi.org/10.1371/journal.pone.0107446

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Abstract

PurposeTo develop and characterize a mouse model with intraocular pressure (IOP) elevation after laser photocoagulation on the trabecular meshwork (TM), which may serve as a model to investigate the potential of stem cell-based therapies for glaucoma.MethodsIOP was measured in 281 adult C57BL/6 mice to determine normal IOP range. IOP elevation was induced unilaterally in 50 adult mice, by targeting the TM through the limbus with a 532-nm diode laser. IOP was measured up to 24 weeks post-treatment. The optic nerve damage was detected by electroretinography and assessed by semiautomatic counting of optic nerve axons. Effects of laser treatment on the TM were evaluated by histology, immunofluorescence staining, optical coherence tomography (OCT) and transmission electron microscopy (TEM).ResultsThe average IOP of C57BL/6 mice was 14.5±2.6 mmHg (Mean ±SD). After laser treatment, IOP averaged above 20 mmHg throughout the follow-up period of 24 weeks. At 24 weeks, 57% of treated eyes had elevated IOP with the mean IOP of 22.5±2.5 mmHg (Mean ±SED). The difference of average axon count (59.0%) between laser treated and untreated eyes was statistically significant. Photopic negative response (PhNR) by electroretinography was significantly decreased. CD45+ inflammatory cells invaded the TM within 1 week. The expression of SPARC was increased in the TM from 1 to 12 weeks. Histology showed the anterior chamber angle open after laser treatment. OCT indicated that most of the eyes with laser treatment had no synechia in the anterior chamber angles. TEM demonstrated disorganized and compacted extracellular matrix in the TM.ConclusionsAn experimental murine ocular hypertension model with an open angle and optic nerve axon loss was produced with laser photocoagulation, which could be used to investigate stem cell-based therapies for restoration of the outflow pathway integrity for ocular hypertension or glaucoma.

Highlights

Glaucoma is a major cause of blindness throughout the world and the second leading cause of irreversible blindness in the USA [1,2]
The intraocular pressure (IOP) of both eyes are normally distributed (Fig 1) (p = 0.4735, D’Agostino-Pearson normality test) with 20 mmHg as the top 97.5th percentile and 20.3 mmHg as the top 99.5th percentile of normal IOP range in C57BL/6 mice
Laser Photocoagulation to the Trabecular meshwork (TM) Induces IOP Elevation The IOP changes between laser-treated and untreated control eyes at different post-treatment time points are shown in Table 2 and Fig 2

Summary

Introduction

Glaucoma is a major cause of blindness throughout the world and the second leading cause of irreversible blindness in the USA [1,2]. The IOP is regulated primarily by a fluid resistance to the aqueous humor outflow [4]. The juxtacanalicular connective tissue (JCT) and Schlemm’s canal endothelial cells are generally believed to be the major sites of resistance to the aqueous outflow, and the primary determinants of IOP [5,6,7]. Trabecular meshwork (TM) cells are believed to have a major role in regulation of the aqueous outflow. TM cells modulate the permeability of Schlemm’s canal endothelial cells in vitro via paracrine signaling [8,9,10,11], and keep the aqueous outflow channels patent via phagocytic activities [12,13].

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