Global histone modifications predict the outcome of glaucoma surgery

Abstract

PurposeConjunctival and subconjunctival fibrosis at the surgical site influences the outcome of glaucoma surgery. Since glaucoma surgery initiates a cascade of events that leads to up‐ or downregulation of various genes and the subsequent release of cytokines and growth factors, we analyzed global histone modifications at the site of glaucoma surgery and their relationship with the outcome of glaucoma surgery.Methods44 patients who were scheduled to undergo glaucoma surgery were enrolled in this study. A 4 × 4 mm section of Tenon's tissue with overlying conjunctiva was cut from the eye at the margin of the incision. Primary rabbit anti‐histone antibodies were applied in humidified chamber at the following dilutions: H3 K9 K14 K18 K23 K27Ac at 1:200, H4 K5 K8 K12 K16Ac at 1:200, H3 K4diMe at 1:800 (Abcam), and H4 R3diMe at 1:25 (Millipore). The sections were counterstained with Harris's haematoxylin, dehydrated, and mounted.ResultsUsing histochemical staining, we determined the number of cells that were positive for histone acetylation and demethylation of histones H3 and H4. The patients were divided into high‐ and low‐acetylated or ‐methylated groups accordingly. The low‐acetylation group for H3 K9 K14 K18 K23 K27 and H4 K5 K8 K12 K16 had poorer surgical outcomes based on Kaplan‐Meier plots. The preoperative intraocular pressure was significantly related to acetylation of both H3 K9 K14 K18 K23 K27 and H4 K5 K8 K12 K16 in univariate and multivariate regression analyses.ConclusionsOur findings suggest global histone modifications in the conjunctival and subconjunctival tissues predict glaucoma surgery outcomes. A low acetylation status indicated a poor prognosis for glaucoma surgery. Prognostication using histone modifications might have implications for epigenetic therapy to improve glaucoma surgery outcomes.