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Purpose: The aim of this study was to investigate the tear proteins and peptides between 2- 5000 Dalton (Da) via MALDI-TOF (Matrix-assisted laser desorption/ionisation time of flight mass spectrometry) in a KCS predisposed breed (West Highland White Terrier, WHWT) and in a healthy control-group of dogs of different breeds. Additionally changes in the tear protein pattern during Ciclosporin A (CsA) therapy were monitored.
Methods: Tear specimens from 15 normal WHWTs, 4 untreated diseased WHWTs, 15 diseased WHWTs under CsA treatment and 15 healthy control-dogs were studied. Ophthalmologic examination and the Schimer-Tear-Test I (Tearex®, Dioptrix, France) were performed on all dogs. Tear proteins were eluted from the strips with 70% Methanol, applied to anchor targets (Bruker Daltonics, GmbH) and analyzed by MALDI-TOF (Bruker Daltonics GmbH) according to their molecular weight/charge ratio. The results were interpreted with an inhouse developed proteomics workflow software and Statistika 8® (StatSoft, USA) .
Results: High intensity peaks were detected in all samples at 2086.90, 2221.04, 2600.68, and 3012.58 Da. The peak at 2600.68 Da shows significant differences between the groups: the WHWTs suffering from KCS exhibited a significant reduction of intensity in this area compared to the healthy WHWTs (p= 0.035, Mahalanobis distance 5.99). The peak in CsA treated WHWTs approximated the peak of normal WHWTs. The comparison of tear protein pattern between the healthy control dogs and the different groups of WHWTs revealed that the healthy control dogs are significantly different from the healthy WHWTs and resemble more the pattern detected in diseased untreated WHWTs (p= 0.03, Mahalanobis distance 3.61).
Conclusion: Tear protein pattern in diseased and untreated WHWTs exhibit significant changes in the area 2600.68 Da. These changes are reversible with CsA treatment. Further investigation is needed to identify the protein causing this peak and to determine whether this protein can be used as a biological marker.