Abstract
Purpose: :
Global profiling of the network of proteins or metabolites found in cells, tissues or fluids can increase our understanding of the multiple interacting processes involved in complex systems. One such approach is metabolomics, which we have applied here to analyse metabolite fingerprints in vitreous humour of patients with vitreoretinal disease, using high–resolution 1H–nuclear magnetic resonance spectroscopy in conjunction with principal component analysis (PCA).
Methods: :
Vitreous humour was obtained from 34 patients with various types of uveitis, proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and rhegmatogenous retinal detachment (RRD). Samples were diluted 1:1 with D2O and one–dimensional 1H spectra acquired using a standard spin–echo pulse sequence with water suppression using excitation sculpting on a Bruker DRX 500MHz NMR spectrometer equipped with a cryoprobe. Spectra were segmented into 0.005–ppm (2.5 Hz) chemical shift ‘bins’ between 0.2 and 9.0 ppm, and the spectral area within each bin was integrated. [PM1] Bins between 4.5 and 5.0 ppm containing residual water were removed. PCA of the pre–processed data was conducted using PLS_Toolbox (Eigenvector Research) within MATLAB.
Results: :
PDR samples could be separated from PVR samples on PC1. Samples from patients with RRD clustered together on PC1 and PC2. Of most interest were patients with lens–induced uveitis (LIU) who were regarded as an acute uveitis and could be separated from patients with chronic uveitis (CU) on PC1 analysis, with the exception of two patients with Fuchs’ heterochromic cyclitis (FHC) that were situated in the lens–induced cluster.
Conclusions: :
The metabolomic fingerprints assessed here reflect disease activity in patients with posterior ocular disease. The separation of LIU from CU patients suggests a role for either metabolites derived from the acute inflammatory response or from treatment modalities. Similarly, the separation of vitreous from patients with FHC from other CU samples suggests a different pathogenesis in these conditions. Thus 1H–NMR–based metabolomics may provide a useful measure of the severity of complex ocular diseases and may complement conventional markers.
Keywords: vitreous • inflammation • vitreoretinal surgery