Abstract
Purpose: :
To utilize protein arrays to carry out differential analysis of tears from normals (N), individuals with aqueous deficiency dry eye syndrome (DE) and chronic (CA) and acute (AA) ocular allergies.
Methods: :
Capillary tube collected tear samples from individuals with defined CA, and individuals with DE as defined by BUT, Schirmer strip and clinical symptomology were successively probed using 3 micro well plate arrays using protocols that reduce the impact of tear matrix effects (ARVO 05). Arrays were specific for MMPs 1–3, 8–10, 13, and TIMPs 1 and 2; Th1/2 cytokines IL–2, 4, 5, 8, 9, 10, 13, TNFα and INFγ; and the angiogenic modulators ANG–2, PDGF, TPO–1, HGF, VEGF and EGF–HB. Some samples were also probed using a custom membrane array.
Results: :
The distribution of the probed proteins was decidedly different in the tears from the N, CA and DE populations. MMPs and TIMPs1 and 2 were most often elevated in tears of both chronic pathological populations but exhibited decidedly different patterns of distribution. Tears from the CA population were most commonly enriched in MMPs 2, 3, 8, 9, and 10 while MMPs 9, 10 and sometimes 8 predominated in the DE population. Within the sensitivity range of the assays, the Th1/Th2 cytokine profiles of the N and DE populations proved strikingly similar with IL–8 most often being the only detectable species. In contrast, tears from the CA population usually exhibited very high levels of many of the probed cytokines a finding confirmed by membrane array assays. VEGF and to lesser extent HGF could be detected in many tear samples with no obvious pattern of preferential distribution in the N and pathological populations. In contrast, the vast majority of the tear samples from both the CA and to a lesser extent the DE populations exhibited elevated levels of FGFb and EGF–HB two growth factor that were absent in the vast majority of the N tear samples. Other than an increase in IL–8 none of these changes could be observed in tear fluid after induction of an AA reaction.
Conclusions: :
Tear fluid from the CA and DE pathologies are markedly different with respect to the distribution of cytokines and MMPs but exhibit in common elevated levels of FGFb and Hb–EGF. We postulate that the latter two factors are representive of common adaptive cytoprotective processes that modulates epithelial and fibroblast turnover in part through interaction with the EGF receptor.
Keywords: cornea: tears/tear film/dry eye • proteomics • conjunctivitis