In Search of Mouse Models for Exfoliation Syndrome

Topics:

Glaucoma

Rare and Inherited CNS and Eye Disorders

Rare Disease

Retinal Degeneration and Inherited Retinal Disease

Retinal Ganglion Cell Pathology

The Optic Nerve, its Neurons and Diseases

Publication

American Journal of Ophthalmology (Nov 01, 2024) In Search of Mouse Models for Exfoliation Syndrome

Kuchtey RW, Insignares S, Yang TS, Kuchtey J

DOI: 10.1016/j.ajo.2024.06.015 >>

This study investigates a new mouse model for exfoliation syndrome (XFS), a systemic connective tissue disorder that can lead to glaucoma. Researchers created double mutant mice lacking the LOXL1 gene and with a mutation in the FBN1 gene, both of which are involved in elastic fiber formation. These mice exhibited reduced visual acuity, altered eye structure, and systemic abnormalities related to elastic fiber defects, such as pelvic organ prolapse and cardiovascular issues. While intraocular pressure was not elevated at 16 weeks, the mice showed signs of early retinal ganglion cell dysfunction. The OptoDrum was used to measure visual acuity in the mice by assessing their optomotor response to rotating striped patterns, allowing researchers to determine their visual threshold.

Purpose: Exfoliation syndrome (XFS) is a systemic connective tissue disorder with elusive pathophysiology. We hypothesize that a mouse model with elastic fiber defects caused by lack of lysyl oxidase like 1 (LOXL1 encoded by Loxl1), combined with microfibril deficiency due to Fbn1 mutation (encoding fibrillin-1, Fbn1C1041G/+) will display ocular and systemic phenotypes of XFS. Methods: Loxl1-/- was crossed with Fbn1C1041G/+ to create double mutant (dbm) mice. Intraocular pressure (IOP), visual acuity (VA), electroretinogram (ERG), and biometry were characterized in 4 genotypes (wt, Fbn1C1041G/+, Loxl1-/-, dbm) at 16 weeks of age. Optic nerve (ON) area was measured by ImageJ, and axon counting was achieved by AxonJ. Deep whole-body phenotyping was performed in wt and dbm mice. Two-tailed Student t test was used for statistical analysis. Results: There was no difference in IOP between the 4 genotypes. VA was significantly reduced only in dbm mice. The majority of biometric parameters showed significant differences in all 3 mutant genotypes compared with wt, and dbm had exacerbated anomalies compared with single mutants. Dbm mice showed reduced retinal function and significantly enlarged ON area compared with wt. Dbm mice exhibited severe systemic phenotypes related to abnormal elastic fibers, such as pelvic organ prolapse and cardiovascular and pulmonary abnormalities. Conclusions: Ocular and systemic findings in dbm mice support functional overlap between fibrillin-1 and LOXL1, 2 prominent components of exfoliation material. Although no elevated IOP or reduction of axon numbers was detected in dbm mice at 16 weeks of age, their reduced retinal function and enlarged ON area indicate early retinal ganglion cell dysfunction. Dbm mice also provide insight on the link between XFS and systemic diseases in humans. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.