Choroidal and retinal expression of microfibrillar-associated protein 4 (MFAP4) in neovascular age-related macular degeneration (nAMD) and diabetic retinopathy (DR)

Abstract

Purpose : Current therapeutic approaches for age-related macular degeneration (AMD) are effective only in a subset of patients, fail to target associated fibrotic changes and cause considerable difficulties. Thus, development of new treatment strategies for AMD is required to improve the disease management.
MFAP4 is in extracellular matrix protein with the capacity to activate integrin a_Vb₃. We have previously demonstrated that intravitreal (IVT) injection of antibodies blocking MFAP4 (humanized anti-MFAP4 hAS0326 antibody) shows efficacy in reducing vascular leakage in rodent models of nAMD and DR. Now, we aim to characterize MFAP4 expression pattern in clinical ocular samples and the distribution of anti-MFAP4 within the treated eye.

Methods : Formalin-fixed human eye sections from patients with AMD, DR or controls (n=3-5) were retrieved from the tissue bank of the Eye Pathology Institute, University of Copenhagen. FITC-labeled anti-MFAP4 monoclonal antibody and isotype control were used for immunohistochemistry (IHC) and detected with anti-FITC-HRP secondary antibody. Mfap4^+/+ and Mfap4^-/- mouse tissue was IHC specificity control. NZW rabbits were injected with 50 μl 40 mg/ml anti-MFAP4 antibody (hAS0326) or vehicle and formaldehyde-fixed eyes sections were prepared after 1 week and stained. Alternatively, Mfap4 expression within the sections was detected using specific probes by in situ hybridization (ISH).

Results : In all eyes, ISH showed Mfap4 mRNA expression in vascular walls and in cells dispersed around the inner nuclear layer of the retina.
The strongest MFAP4/Mfap4 mRNA expression was found in large choroidal vessels (IHC/ISH), while choriocapillaris showed heterogenous expression in case eyes. In contrast, no or low expression was found in choriocapillaris of control sections.
Anti-MFAP4 was retrieved with high IHC intensity through-out all layers of the rabbit eye one week after one dose of IVT anti-MFAP4 injection into a rabbit eye.

Conclusions : MFAP4 is present at relevant locations for pathologies of DR and nAMD in the human eye, which supports MFAP4 as therapeutic target. After IVT administration, anti-MFAP4 antibody is able to penetrate and is retained at high levels in all relevant layers of the eye, which supports the therapeutic potential of anti-MFAP4 strategy.

This is a 2020 ARVO Annual Meeting abstract.