Transcriptomic Characterization of Human Choroidal Neovascular Membranes Identifies Calprotectin as a Novel Biomarker for Patients with Age-related Macular Degeneration

Although genome-wide association studies, animal models, and cell culture systems have yielded important insights into the pathogenesis of neovascular age-related macular degeneration (nAMD), the underlying molecular pathways remain ill defined. Recent studies have deciphered the transcriptional profile of choroidal neovascularisation (CNV) of body donor eyes and were thus limited by the time span from death to preservation and the associated rapid 5'-RNA degradation. In this study, CNVs were therefore formalin-fixed immediately after surgical extraction from patients with nAMD and analyzed using a 3' RNA sequencing approach called Massive Analysis of cDNA Ends (MACE). Age-matched formalin-fixed paraffin-embedded (FFPE) RPE-choroidal specimens obtained from the macular region of enucleated eyes with ciliary body melanoma served as controls. Transcriptome profiles were generated and disease-associated gene signatures were identified using statistical and bioinformatic methods. Calprotectin (S100A8/A9) protein expression was investigated by immunohistochemistry and ELISA.We identified 158 differentially-expressed genes (DEG) that were significantly increased in CNV compared to control tissue. Gene ontology enrichment analysis demonstrated that these DEG contributed to biological processes, such as Blood Vessel Development, Extracellular Structure Organization, Response to Wounding and several immune-related terms. The S100 calcium-binding protein A8 (S100A8) and S100A9 emerged among the top DEG, as confirmed by immunohistochemistry on CNV tissue and protein analysis of vitreous samples from nAMD patients and controls. This study provides a high-resolution RNA-sequencing-based transcriptional signature of choroidal neovascular membranes in AMD patients and reveals S100A8/A9 as a novel biomarker and promising target for AMD-directed therapeutics and diagnostics. Overall design: MACE RNA sequencing of four human CNV-membranes (from patients undergoing subretinal CNV extraction) and four control samples