Short summary

Based on our preliminary results we believe that MFAP4 has a pivotal role in human nAMD and intraocular fibrosis. In order to evaluate the importance of MFAP4 in human intraocular fibrosis and nAMD we will measure the level of MFAP4 during vitrectomy in vitreous samples and fibrotic tissue in patients with epiretinal fibrosis, nAMD or diabetes as compared to patients with floaters. Furthermore we will measure the anterior intracameral level of MFAP4 in patients with and without nAMD undergoing cataract surgery.

Rationale

Age-related macular degeneration (AMD) is one of the most common causes of severe vision loss, with prevalence growing with age. There are two subtypes of AMD: the atrophic dry form and the advanced exudative form called neovascular AMD (nAMD) that accounts for the vast majority of AMD-related vision loss. nAMD results in the growth of new blood vessels from the choroid that penetrates Bruch's membrane, leading to vascular leakage, haemorrhage and scarring. This process, known as choroidal neovascularisation (CNV), is a hallmark of nAMD, responsible for more than 80% of diseased-associated vision loss.

There is no curative treatment for nAMD; existing therapies are only able to slow disease progression. Monthly treatment to inhibit vascular endothelial growth factor (VEGF) is most commonly used, but improvements in visual acuity are only found in approximately 30% of patients. Furthermore, there is only limited evidence that anti-VEGF therapy might reduce fibrosis and inflammation. Recent reports have even indicated that it actually aggravates fibrosis. Subretinal fibrosis develops in half of all treated eyes within two years after anti-VEGF treatment initiation and has been identified as an important cause of unsuccessful outcomes. VEGF inhibition can also result in neurodegenerative processes and give rise to local side effects. In addition, prolonged anti-VEGF therapy presents significant drawbacks, including inconvenient specialist visits, financial burden, safety risk and the possibility of compensatory upregulation of VEGF-receptor pathways. Therefore, new therapeutic strategies that address multiple pathological processes are required to improve nAMD-management.        

Microfibrillar-associated protein 4 (MFAP4) is a extracellular matrix glycoprotein cloned by our research group. It is produced by fibroblasts, smooth muscle cells and endothelial cells. We have generated MFAP4-/- mice and demonstrated that MFAP4 is an integrin alphavbeta3 ligand that can initiate focal adhesion kinase-dependent integrin signal in both smooth muscle cells and macrophages leading to tissue growth, inflammation, and fibrotic deposition.

Furthermore, MFAP4 antibody-mediated inhibition reduces the lesion size and inflammation in a mouse model of nAMD. Mice were subjected to laser-induced CNV and intravitreally injected with anti-MFAP4 antibody, mouse immunoglobulin G (IgG) or anti VEGF-A antibody on day 0 and day 7. Fundus fluorescein angiography showed that anti-MFAP4 treatment reduced average lesion size and density on day 7 as compared with IgG.  On day 14, both anti-MFAP4 and anti-VEGF-A antibodies reduced average lesion size and density compared to IgG controls. Staining for endothelial cell marker isolectin-B4 indicated that both anti-MFAP4 and anti-VEGF-A antibodies reduced lesion fluorescein intensity and leukocyte infiltration into the lesion site.

Based on these initial results, we believe that MFAP4-inhibition might offer additional benefits as compared to anti-VEGF-treatment.

In the human eye, MFAP4-expression has been found in drusens in Bruch's membrane which is a hallmark of AMD. However, there have been no intraocular measurements in patients with active nAMD. It is vital to establish proof-of-concept for the role of MFAP4 in human intraocular fibrosis and nAMD. If demonstrated, this will lead the way for clinical trials for MFAP4-inhibition in nAMD.

Aims

In order to evaluate the importance of MFAP4 in human intraocular fibrosis and nAMD, we aim to:

1. Measure the level of MFAP4 during vitrectomy in vitreous samples and fibrotic tissue (patients with epiretinal fibrosis) in patients with epiretinal fibrosis, nAMD and diabetes as compared to patients with floaters (controls).
2. To measure the anterior intracameral level of MFAP4 during cataract surgery in patients with (cases) and without nAMD (controls).

Description of the cohort

Substudy A

The persons included in the study are patients with epiretinal fibrosis, nAMD, diabetes or floaters undergoing vitrectomy.

All patients will be recruited at the Department of Ophthalmology Odense University Hospital, at their respective preliminary examinations for their upcoming eye operation.

Substudy B

Persons included in the study are patients with or without nAMD undergoing cataract operation.

All patients will be recruited at the Department of Ophthalmology Odense University Hospital, at their respective preliminary examinations for their upcoming eye operation.

Data and biological material

Biological material:

• Samples from vitreous humor
• Epiretinal fibrotic membranes
• Samples from the anterior chamber of the eye

Clinical data:

• Information about age, gender, previous eye operation, previous and present eye disease, other disease as diabetes and liver fibrosis will be used from patient charts.

Collaborating researchers and departments

Department of Ophthalmology, Odense University Hospital and Faculty of Health Science, University of Southern Denmark

• Medical student and pregraduate research fellow Louise Abrahamsen Ravn

Department of Ophthalmology, Odense University Hospital

• Professor Jakob Grauslund, DMSci, PhD, MD
• PhD-student Søren Leer Blindbæk: MD
• Associate Professor Majbrit Lind, MD, PhD

Department of Cancer and Inflammation Research, University of Southern Denmark, Odense

• Professor Uffe Holmskov, MD, DMSc, PhD
• Associate professor Grith Lykke Sørensen, MSc, PhD