Abstract
Purpose: :
To determine which proteoglycans (PGs) are present in the human retinal pigment epithelium (RPE)/choroid complex by proteomic analysis.
Methods: :
Postmortem human eye tissue was obtained, following removal of the cornea for transplantation, from consenting adult eye donors without known retinal disease. The tissue complex of choroid, Bruch’s membrane and the RPE was dissected and pooled from ten globes. PGs were extracted from the tissue in 4M guanidine, and dialysed into 6M urea. Anion exchange chromatography was performed, eluting with a 1M NaCl gradient. Relevant fractions underwent buffer exchange, reduction, alkylation and trypsinisation. Trypsinised peptides were separated using size exclusion spin columns (3 kDa molecular weight cut-off). Following tandem mass spectrometry, peptides were identified by database search using MASCOT software.
Results: :
PGs identified in human chorioretinal tissue complex included the basement membrane PGs perlecan, agrin and collagen-XVIII, the hyalectans versican and aggrecan, the small leucine-rich repeat PGs (SLRPs) decorin, biglycan, lumican, mimecan and PRELP. In addition, CD44 and the chondroitin sulfate PG SPACRCAN were identified. To our knowledge, this is the first report of the presence of versican and aggrecan in the human RPE/choroid complex.
Conclusions: :
This comprehensive proteoglycomic analysis of the human retina reveals that many distinct PGs are present in the chorioretinal tissue complex, including basement membrane PGs, hyalectans and SLRPs. Their distribution and glycosaminoglycan composition will have important implications for eye disease, particularly their interactions with complement factor H in the context of age-related macular degeneration.
Keywords: proteoglycans/glycosaminoglycans • Bruch's membrane • age-related macular degeneration