Proteomics in ocular fluids

Abstract

The focus of this article is to review recent techniques in proteomic analysis of ocular fluids. These fluids include tears, aqueous humor, and vitreous, they will also be compared to serum analysis. Furthermore, we attempt to summarize some disease correlated biomarkers in ocular fluids that were discovered through different proteomic techniques in eye diseases like dry eye, glaucoma, age-related macular degeneration, uveitis, or diabetic retinopathy. This review is trying to point out the importance of these biomarkers for clinical applications.

Comparison of two methods of tear sampling for protein quantification by Bradford method

“…Although standard results can be obtained using only capillary tubes, the insistence on using STT for protein analysis is due to the minimal invasiveness of the method, which makes it an interesting option for proteomics studies (Grus et al 2007, Li et al 2008. Besides that, the strip retains ocular surface proteins, considered by some authors an advantage to provide an enriched sample to compare normal and pathological environment if the analysis of the ocular surface is desirable (Li et al 2008).…”

“…The main focus in clinical proteomics is the discovery of new proteins or peptides that work as biomarkers correlated to a specific disease (Couture et al 2006, Grus et al 2007, Campos et al 2008. Metalloproteinases were identified in the dog (Couture et al 2006) and equine tears from corneal injury (Ollivier et al 2004), and dogs with cancer showed a different expression pattern of proteins (Campos et al 2008).…”

“…Lowry (Li et al 2010) and Bradford (Sitaramamma et al 1998, Ananthi et al 2008, Li et al 2010) methods were used to quantify proteins from tear samples (Ananthi et al 2008, Lu et al 2010. For proteomic analysis, tear samples can be obtained from microcapillary tubes (Gachon et al 1982, Jones et al 1997, Couture et al 2006, Grus et al 2007, Green-Church et al 2008 or from Schirmer tear test strips (Grus et al 2007, Li et al 2008, Roberts & Erickson 2008.…”

Diabetic retinopathy: Proteomic approaches to help the differential diagnosis and to understand the underlying molecular mechanisms

“…Nevertheless, plasma proteins like albumin, globulins [68], and transferrin [69] are present in the aqueous humour [70]. A study comparing the aqueous humour proteins between DR and control groups shown the upregulation of APOA1, serotransferrin, keratin type I cytoskeletal 9, keratin type I cytoskeletal 10, growth factor receptor-bound protein 10, brain-specific angiogenesis inhibitor 1-associated protein 2 and cystathionine β-synthase, and downregulation of matrix metalloproteinase 13, podocan and selenoprotein P in the DR group [71].…”

“…LL-37 cathelicidin is an α-helix type AMP of the tear fluid mainly produced by the corneal epithelial cells. Similar to the defensins, cathelicidin exerts various antimicrobial [102] and immunomodulatory functions [54] Complement C4b [64] Brain-specific angiogenesis inhibitor 1-associated protein 2 [70] Lysozyme C [38] VEGF [56] Complement C9 [64] Cystathionine b-synthase [70] Lipophilin A [38] Complement factor B [64] MMP-13 [70] Immunoglobulin lambda chain [38] Pigment epithelial-derived factor [64] Podocan [70] Hsp27 [76] Interstitial retinol-binding protein [64] Selenoprotein P [70] β 2 -Microglobulin [76] Inter-α trypsin inhibitor heavy chain [64] Enolase [77] [95]. In addition, it has an important role in re-epithelialization during wound healing [107].…”