| Summary: | Nisha Rani Agarwal,1,* Masoumeh Dowlatshahi Pour,2,* Maria Siekkeri Vandikas,3 Noora Neittaanmäki,4 Amra Osmancevic,3 Per Malmberg21Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden; 2Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden; 3Department of Dermatology, Sahlgrenska University Hospital at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; 4Department of Clinical Pathology, Institutes of Biomedicine and Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden*These authors contributed equally to this workBackground: Psoriasis is a systemic inflammatory disease characterized by epidermal proliferation in the skin. Altered lipid metabolism is considered to be a central factor in the psoriatic etiopathogenesis. Thus, it is necessary to visualize chemical specificity of the samples for better medical diagnosis and treatment. Here, we investigate its role in the development of psoriatic lesions, before and after ultraviolet phototherapy, in a case study.Methods: The distribution and morphology of different lipids and fibrous proteins in psoriatic (lesional) tissues were visualized by two complementary label-free imaging techniques: 1) non-linear microscopy (NLM), providing images of lipids/proteins throughout the skin layers at submicrometer resolution; and 2) mass spectrometry imaging (MSI), offering high chemical specificity and hence the detection of different lipid species in the epidermal and dermal regions. A conventional method of histological evaluation was performed on the tissues, with no direct comparison with NLM and MSI.Results: Psoriatic tissues had a higher lipid content, mainly in cholesterol, in both the epidermal and dermal regions, compared to healthy tissues. Moreover, the collagen and elastin fibers in the psoriatic tissues had a tendency to assemble as larger bundles, while healthy tissues showed smaller fibers more homogeneously spread. Although phototherapy significantly reduced the cholesterol content, it also increased the amounts of collagen in both lesional and non-lesional tissues.Conclusion: This study introduces NLM and MSI as two complementary techniques which are chemical specific and can be used to assess and visualize the distribution of lipids, collagen, and elastin in a non-invasive and label-free manner.Keywords: psoriasis skin tissue, non-linear microscopy, lipids, collagen, time-of-flight secondary ion mass spectrometry (ToF-SIMS)
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