A proteomics approach to the identification of biomarkers for psoriasis utilising keratome biopsy.

The discovery of plasma biomarkers for psoriasis vulgaris may aid clinicians in disease grading and monitoring of treatment response. We have therefore developed a proteomics/mass spectrometry based workflow which enables biomarker discovery from psoriasis patient samples. We have utilised keratome skin biopsy, which results in reduced cellular complexity compared to punch biopsy. Furthermore, we applied short term ex vivo culture in order to enrich for a "secretome" sub-proteome reflective of the disease and enriched in potential biomarkers. Using these sample preparation techniques we performed a quantitative proteomics screen of four patients with psoriasis using stable isotope dimethyl labelling and identified over 50 proteins consistently altered in abundance in psoriasis lesional versus non-lesional skin. This includes several canonical psoriasis related proteins (e.g. S100A7 [Psoriasin] and FABP5 [Epidermal Fatty Acid Binding Protein]) and more than 30 novel alterations. From this disease localised dataset we further assessed several proteins as potential biomarkers in the plasma of patients with psoriasis versus healthy controls utilising selected reaction monitoring mass spectrometry (SRM-MS/MS). BIOLOGICAL SIGNIFICANCE: The significance of this study for proteome research in psoriasis and dermal disease is threefold. 1) A novel sample preparation method for isolation of dermal proteomes enriched in extracellular proteins is described, which may be of interest to other researchers in the field. 2) Novel psoriasis associated alterations in protein abundance are described at the disease site, bolstering knowledge in an area dominated by transcript level studies and 3) Profilin 1 is described as a candidate plasma biomarker of psoriasis, this is of value in itself and it proves that our workflow can yield results in terms of biomarker discovery.