Alterations in anterior lens capsule structure and LTBP-2 expression in primary angle-closure glaucoma

Abstract

Objective: This study investigated the role of latent-transforming growth factor β-binding protein 2 (LTBP-2) in primary angle-closure glaucoma (PACG) by analysing its expression and the ultrastructure of the anterior lens capsule in PACG patients with age-related cataract (ARC).

Methods: Tissue samples of the anterior lens capsule were collected from patients undergoing cataract phacoemulsification surgery. Patients in the experimental group were diagnosed with primary angle-closure (PAC) combined with ARC (PAC+ARC) and PACG combined with ARC (PACG+ARC). The control group consisted of patients with only ARC. The techniques used included scanning electron microscopy, real-time fluorescence quantitative polymerase chain reaction (RT-qPCR), western blotting and immunofluorescence.

Results: Ultrastructural analysis revealed disordered connections in PAC+ARC, loose connections in PACG+ARC and well-ordered connections in ARC. RT-qPCR and western blotting showed significantly lower LTBP-2 mRNA and protein expression in PAC+ARC and PACG+ARC than in ARC, with PAC+ARC having the lowest levels. Immunofluorescence confirmed these findings, showing varying LTBP-2 fluorescence intensities across groups.

Conclusion: The study identified ultrastructural changes in the anterior lens capsules in PACG accompanied by reduced LTBP-2 expression, especially in PAC+ARC patients. This suggests a potential role for LTBP-2 in PACG development, warranting further investigation.

Keywords: Glaucoma.

Figure 1. Scanning electron microscopy at ×5000 magnification. The image on the left shows an enlarged view of the area highlighted by the black box on the right. ARC, age-related cataract; PAC, primary angle-closure; PACG, primary angle-closure glaucoma.

Figure 2. Relative mRNA expression levels of LTBP-2 in the anterior lens capsule in each group (*p<0.01, ****p<0.0001). Data are presented as mean±SD. ARC, age-related cataract; LTBP-2, latent-transforming growth factor β-binding protein 2; PAC, primary angle-closure; PACG, primary angle-closure glaucoma.

Figure 3. Analysis of LTBP-2 protein expression in the human anterior lens capsule ((A) depiction of LTBP-2 and β-actin protein bands; (B) quantitative representation of LTBP-2 protein levels across different groups. ‘*’ denotes a significance level of p<0. 05.). ARC, age-related cataract; LTBP-2, latent-transforming growth factor β-binding protein 2; PAC, primary angle-closure; PACG, primary angle-closure glaucoma.

Figure 4. Immunofluorescence staining and quantitative analysis of LTBP-2 in the human anterior lens capsule. (A) Immunofluorescence staining for LTBP-2 (grey) and DAPI nuclear staining (blue) in human anterior lens capsule sections at ×400 magnification. () Quantitative analysis of LTBP-2 fluorescence intensity. Data are presented as mean±SD. *P<0.05, **p<0.01, ***p<0.001. ARC, age-related cataract; DAPI, 4′,6-diamidino-2-phenylindole; LTBP-2, latent-transforming growth factor β-binding protein 2; PAC, primary angle-closure; PACG, primary angle-closure glaucoma.