Abstract
Purpose :
Mucous membrane pemphigoid (OcMMP) is an immunobullous disease characterised by a progressive conjunctival fibrosis driven by inflammation. In over 50% of cases, disease progresses in the absence of clinically visible inflammation. The purpose of this study was to analyse tear washings to identify components of inflammation and fibrosis that could be used as putative biomarkers of disease activity and response to therapy.
Methods :
Tear washings were obtained by applying 100μL 0.9% NaCl onto the ocular surface and aspirating with a lacrimal canula from 21 OcMMP patients (42 eyes; mean age 74.6(±8.9 SD) years, 14(66%) female, 17(81%) biopsy-positive) and 15 age-matched cataract patient controls(30 eyes; age 72.3(±10.9) years, 8(53%) female). Total protein content (DC Protein Assay (BioRad, USA)) was used to correct for the variation in sample volume. Matrix metalloproteinases (MMP) 8 and 9, myeloperoxidase (MPO), epithelial growth factor (EGF), interleukin (IL)-1β, 6, 8, 10, 13 and TNF-α were quantified with a Luminex Assay (Thermo Fisher Scientific, USA). Total aldehyde dehydrogenase (ALDH) activity was measured using BioVision PicoProbe™ ALDH assay. Statistical analyses were performed using GraphPad Prism 8 (Mann Whitney U non-parametric test).
Results :
Based upon the cicatrising conjunctivitis assessment tool (CCAT©Score) the majority of OcMMP eyes had none/minimal inflammation (mean score 0.79±1.58SD) at the time of sampling and 29(69.0%) had >50% symblepharon. MMP8, MPO and IL-6 were significantly elevated whereas EGF was significantly lower in OcMMP versus controls (p=0.025, p=0.010, p=<0.001 and p=0.001 respectively, Figure 1). There was no significant difference in the other measured cytokines . Mean ALDH activity was higher in OcMMP eyes (0.4 vs 0.05 mAU/mg, p=0.025, Figure 2).
Conclusions :
Despite the absence of clinically visible conjunctival inflammation significant differences in tear film MMP8, MPO, IL-6, EGF and ALDH expression were observed in OcMMP eyes compared to controls. MMP8 and MPO are primarily produced by neutrophils and macrophages. IL-6 is a pro-inflammatory cytokine playing a role in chronic inflammation. ALDH has been linked to progressive conjunctival fibrosis in OcMMP. Taken together, these data could represent a pharmacodynamic biomarker panel for OcMMP to enable measurement of treatment response to novel therapies, and as predictors of disease progression in quiescent eyes.
This is a 2021 ARVO Annual Meeting abstract.