Purchase this article with an account.
Andrew Want, Stephanie Gillespie, J Mario Wolosin, Robert Ritch, Audrey Bernstein; Impaired Lysosomal and Mitochondrial Function in Exfoliation Glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1695.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
In the eye, exfoliation syndrome (XFS) is characterized by the aggregation of disorganized microfibrils (exfoliation material, XFM). Deposition of XFM and pigment in the aqueous outflow pathway leads to chronic intraocular pressure elevation leading in turn to glaucoma. Similar to other age-related diseases in which protein aggregates cause disease, we hypothesize that lysosomal and mitochondrial dysfunction contributes to the formation of XFM aggregates.
Tenon fibroblasts (TFs) were explanted from tissue discards obtained from older, age-matched XFS and primary open-angle glaucoma (POAG) patients who underwent trabeculectomy surgery and from young healthy donors who underwent strabismus surgery. Experiments were performed in supplemented serum-free media on collagen or in 1% FBS-containing media. Cell size and mitochondrial membrane potential (MMPT, JC1 dye) were quantified by flow cytometry. Lysosomes and microtubules were immunodetected with Lamp-1 and β-tubulin antibody, respectively. Culturing TFs in media with stabilized vitamin C for 1 month generated self-synthesizing 3D gels.
Normally, under conditions of nutrient deprivation, lysosomes become peri-nuclear, where they fuse with autophagosomes, clearing the cells of waste. In XFS TFs compared to POAG TFs and healthy TFs, lysosomes did not relocalize in response to changes in nutrient conditions, suggesting that lysosomal degradation is impaired in these cells (Figure 1). In 3D culture, XFS TFs demonstrated a disorganized morphology with elevated expression of XFM-containing proteins LOXL1 and Fibulin-5. Consistent with impaired lysosomal degradation a) the percent of cells displaying depolarized mitochondria was 10x higher in XFS than in POAG TFs (26 % vs. 2%, p < 0.01) and b) the build up of intracellular organelles led to a 1.7-fold increase in XFS cell size.
Our findings suggest that lysosomes and mitochondria are compromised in XFS TFs, leading to a toxic environment. This may lead to reduced degradation and increased secretion of XFM aggregates.
This PDF is available to Subscribers Only