Mitochondrial Dysfunction in Exfoliation Glaucoma

Abstract

Purpose : Exfoliation syndrome (XFS) is an age-related systemic disease characterized by the deposition of large aggregated fibrillar material in the anterior segment of the eye. These aggregates are a major risk factor for the development of exfoliation glaucoma (XFG), a secondary open-angle glaucoma, accounting for up to 50% of cases. Growing evidence suggests that XFS is a complex multifactorial late-onset disease with altered cellular processes such as increased protein aggregation, impaired protein degradation, and cellular stress. This study investigated whether mitochondrial homeostasis and dynamics are altered in XFG patient-derived primary cells.

Methods : Control Primary human Tenon Capsule tissue was obtained from retinal surgeries and explanted to expand no Glaucoma control tenon fibroblast (NG TFs). Tissue was also obtained from Exfoliation patients undergoing glaucoma surgery or dislocated IOL repair and explanted to expand XFG tenon fibroblasts (XFG TFs). The Seahorse XFe96 analyzer was used to measure the oxygen consumption rate for evaluating mitochondrial bioenergetics. The mitochondrial reactive oxygen species (ROS) was measured using live cell microscopy. Proteomic analysis was performed using LC-MS/MS. Cellular apoptosis was measured by flow cytometry. Mitochondrial ultrastructure (area, shape, cristae) was analyzed using transmission electron microscopy.

Results : Compared with NG TFs, the bioenergetics profiles of TFs from XFG patients showed reduced maximal respiration (p=0.0307), spare respiratory capacity (p=0.0456), and ATP production (p=0.0460). The XFG TFs exhibited a 5-fold increased mitochondrial ROS (p=0.0001) but did not induce cellular apoptosis. Mitochondria in XFG TFs were smaller (p=0.0004), had abnormal cristae, and fused to autophagosome-like vesicles. The mitochondrial protein homeostasis is altered with a 3.9-fold increase of antioxidant SOD2 in the XFG TFs. Treatment with Mitophagy inducers Urolithin A (p=0.0027) or nicotinamide riboside (p=0.0001) significantly reduced ROS in XFG TFs, whereas the effect was non-significant in NG TFs.

Conclusions : Our study provides evidence that mitochondria are dysfunctional in XFG patients. Alterations in mitochondrial bioenergetics, mitochondrial homeostasis, and mitochondrial morphological impairment may play a vital role in XFG pathogenesis. Treating with mitophagy enhancers is a promising therapeutic to improve cell health in XFG.

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