Abstract
Purpose: :
Proteoglycans (PGs) play crucial roles in development, homeostasis and disease in many tissues. The aim of this study was to investigate the presence and distribution of PG core proteins in the human retina and choroid by proteomics and immunohistochemistry.
Methods: :
Postmortem human ocular tissue was obtained from consenting adult eye donors without known retinal disease. Retinal tissue was dissected, and PGs were extracted and partially purified by anion exchange chromatography. Trypsinized peptides were analyzed by tandem mass spectrometry and were identified by database search; the presence of a PG in retinal tissue was confirmed by Western blotting. PG core proteins were detected by immunohistochemistry and fluorescence microscopy in frozen human macular tissue sections, where secondary antibodies were labeled with FITC.
Results: :
The heparan sulfate PGs perlecan, agrin and collagen-XVIII were identified in the human retina, and were present in the internal limiting membrane (ILM), the basement membrane of retinal and choroidal blood vessels, and in Bruch’s membrane. For the first time to our knowledge, the hyalectans versican and aggrecan were found in the human retina. Versican was present in Bruch’s membrane, while aggrecan was distributed abundantly throughout the neurosensory retina and choroidal stroma. The small leucine-rich repeat PGs decorin, biglycan, lumican, mimecan and prolargin were present, each with distinct distributions in the neurosensory retina, Bruch’s membrane and choroid.
Conclusions: :
The combination of proteomics, Western blot and immunohistochemistry approaches has provided for the first time a comprehensive analysis of the presence and distribution of PG core proteins throughout the adult human retina, choroid and sclera. This complements our knowledge of glycosaminoglycan chain distribution in the human eye (Clark et al. 2011 IOVS 52, 6511-21), and has important implications for understanding the structure and functional regulation of the eye in health and disease.
Keywords: proteoglycans/glycosaminoglycans • retina • immunohistochemistry