Pseudoexfoliation syndrome: The critical role of the extracellular matrix in pathogenesis and treatment

Pseudoexfoliative Syndrome in Cataract Surgery-A Quality Register Study and Health Economic Analysis in the Split-Dalmatia County, Croatia

PURPOSE

To investigate the impact of pseudoexfoliation (PEX) syndrome on intraoperative phacoemulsification (PHACO) parameters and assess the economic cost of PHACO surgery for cataracts in patients with and without PEX syndrome.

METHODS

This was a retrospective quality register study on 5889 patients (6236 eyes) who underwent PHACO cataract surgery in the Eye Clinic, Clinical Hospital Centre Split, Croatia, over a 7-year period (May 2015 to December 2022), in accordance with the Guidelines of the Helsinki Declaration and approval from the Research Ethics Committee of the University Hospital Centre Split, Croatia. Inclusion criteria were patients with either presenile or senile cataract or cataract related to PEX syndrome who undertook PHACO procedure by the same experienced surgeon using the same PHACO device (Infiniti Vision System, Alcon Laboratories, Inc., Fort Worth, TX, USA). Eyes were categorized according to PEX presence- (PEX group) or absence (Group without PEX). The following recorded data about intraoperative PHACO parameters were collected: Cumulative Dissipated Energy (CDE), Ultrasound total time, PHACO time, torsional time, aspiration time, estimated fluid used, and duration of the surgical procedure. In the economic analysis, all PHACO parameters were considered, with a specific focus on the duration of the surgical procedure, costs associated with additional medical materials and devices, complications during surgery, and surgery procedure Diagnosis-Related Group (DRG) codes.

RESULTS

A total of 4535 cases were eligible for inclusion in the study, 278 (6.13%) were diagnosed with PEX and 4257 (93.87%) had no PEX. Significantly higher PHACO parameters were observed in the PEX group. Similarly, a statistically significant increase in the values of all PHACO parameters was observed with the increase in nuclear lens density. Intraoperative complications were more frequent in the PEX group. Zonular weakness requiring the use of a capsular tension ring (CTR) and posterior capsular rupture occurred 30 and 13 times more often, respectively, in the PEX group. The expected cost of the PHACO procedure was found to be 1.4 times higher in patients with PEX, compared to those without PEX, for all types of nuclear cataract.

CONCLUSIONS

All PHACO parameters are significantly higher in patients with PEX. The costs associated with PHACO surgery for cataracts are greater for patients with PEX and are not covered by the present DRG codes, which highlights the need to accordingly adjust the DRGs for PHACO procedures in PEX patients, in order to maintain the quality of healthcare provided for these vulnerable patients.

Association between pseudoexfoliation and Alzheimer's disease-related brain atrophy

BACKGROUND/AIMS

Pseudoexfoliation (PEX) syndrome is an age-related disorder characterized by the accumulation of extracellular material in the anterior eye segment. PEX pathogenesis is not fully understood, but amyloid which accumulates in the brain of patients with Alzheimer's disease (AD) is a PEX component. PEX deposition shares features with amyloid aggregation in AD, and brain atrophy is a common AD feature, with β-amyloid accumulation among contributing factors. This study investigated whether PEX syndrome is associated with AD-related brain atrophy.

METHODS

We reviewed the medical records of patients diagnosed with PEX at the Veterans Health Service Medical Center between January 2015 and August 2021. This retrospective cohort study included 48 patients with PEX and 48 healthy age- and sex-matched controls. Patients with PEX were divided into two groups: with and without glaucoma. The main outcome measure was brain atrophy, using a visual rating scale, and AD incidence. Brain atrophy was measured using the Scheltens scale for medial temporal atrophy, the posterior cortical atrophy scale for parietal atrophy, and the Pasquier scale for global cortical atrophy.

RESULTS

The percentage of participants with medial temporal atrophy was 56.3% in the PEX group and 35.4% in the control group. The global cortical atrophy and parietal atrophy scores were significantly higher in the PEX group (P<0.05), whereas the PEX and PEX glaucoma groups showed no difference. Among the 96 participants, 16 and 5 participants in the PEX and control groups, respectively, were diagnosed with dementia. Patients with PEX glaucoma tended to have lower Mini-Mental State Examination scores, indicating impaired cognitive function, than those without glaucoma.

CONCLUSION

PEX is associated with brain atrophy, reflecting the risk of developing AD. Patients with PEX glaucoma may present with advanced AD stages. Our results suggest that PEX may be a predictor of AD.

Critical role of transcriptome-wide m6A methylation in the aqueous humor of patients with pseudoexfoliation glaucoma

N⁶-methyladenosine (m⁶A) modification is one of the most common types of methylation modifications in eukaryotic mRNA. However, its role in the pathogenesis of pseudoexfoliation glaucoma (PXG) has not yet been reported. To enhance understanding in this regard, we assessed the m⁶A methylome in the aqueous humor of patients with PXG. MeRIP-Seq and RNA-Seq analyses were performed to compare the m⁶A methylomes and gene expression profiles of the aqueous humor of patients with PXG with those of patients with age-related cataract (ARC). Colorimetric m⁶A quantification was performed to detect global m⁶A levels. Quantitative reverse transcription PCR confirmed the expression of m⁶A-related enzymes and mRNAs in both groups. Results showed significantly higher aqueous humor m⁶A levels in the PXG group than in the ARC group. Five m⁶A-related enzymes, including METTL3, YTHDC2, HNRNPA2B1, HNRNPC, and LRPPRC, were significantly up-regulated in PXG specimens. We also observed 9728 m⁶A-modified peaks related to 6126 gene transcripts in the PXG group, with more than 250 genes containing one m⁶A peak (hypomethylated or hypermethylated). The distribution of the m⁶A peaks was enriched in coding sequences and 3'-untranslated regions for both groups. GGAC motif structures were also significantly enriched. Bioinformatics analysis further revealed that m⁶A plays a critical role in extracellular matrix formation and histone deacetylation. Additionally, MMP14, ADAMTSL1, FN1, and HDAC1 showed significant changes in m⁶A methylation and mRNA expression in the PXG group. Therefore, m⁶A methylation may regulate extracellular matrix composition in PXG and METTL3 may be a pivotal regulator of this process. In the future, it would be necessary to investigate MMP14, ADAMTSL1, FN1, and HDAC1, which are potential target genes.

Analysis of genetically determined gene expression suggests role of inflammatory processes in exfoliation syndrome

BACKGROUND

Exfoliation syndrome (XFS) is an age-related systemic disorder characterized by excessive production and progressive accumulation of abnormal extracellular material, with pathognomonic ocular manifestations. It is the most common cause of secondary glaucoma, resulting in widespread global blindness. The largest global meta-analysis of XFS in 123,457 multi-ethnic individuals from 24 countries identified seven loci with the strongest association signal in chr15q22-25 region near LOXL1. Expression analysis have so far correlated coding and a few non-coding variants in the region with LOXL1 expression levels, but functional effects of these variants is unclear. We hypothesize that analysis of the contribution of the genetically determined component of gene expression to XFS risk can provide a powerful method to elucidate potential roles of additional genes and clarify biology that underlie XFS.

RESULTS

Transcriptomic Wide Association Studies (TWAS) using PrediXcan models trained in 48 GTEx tissues leveraging on results from the multi-ethnic and European ancestry GWAS were performed. To eliminate the possibility of false-positive results due to Linkage Disequilibrium (LD) contamination, we i) performed PrediXcan analysis in reduced models removing variants in LD with LOXL1 missense variants associated with XFS, and variants in LOXL1 models in both multiethnic and European ancestry individuals, ii) conducted conditional analysis of the significant signals in European ancestry individuals, and iii) filtered signals based on correlated gene expression, LD and shared eQTLs, iv) conducted expression validation analysis in human iris tissues. We observed twenty-eight genes in chr15q22-25 region that showed statistically significant associations, which were whittled down to ten genes after statistical validations. In experimental analysis, mRNA transcript levels for ARID3B, CD276, LOXL1, NEO1, SCAMP2, and UBL7 were significantly decreased in iris tissues from XFS patients compared to control samples. TWAS genes for XFS were significantly enriched for genes associated with inflammatory conditions. We also observed a higher incidence of XFS comorbidity with inflammatory and connective tissue diseases.

CONCLUSION

Our results implicate a role for connective tissues and inflammation pathways in the etiology of XFS. Targeting the inflammatory pathway may be a potential therapeutic option to reduce progression in XFS.