437 A suitable Raman microspectroscopy data processing: The key to understand atopic dermatitis in vivo at the molecular level

Molecular descriptors involved in the disruption of atopic skin barrier function are classically investigated by invasive biopsies. Our study aimed to highlight in vivo and non-invasively the molecular signature of atopic skin. For this purpose, we used an innovative approach based on in vivo confocal Raman microspectroscopy. This technology generates a lot of data that need suitable and secured approach important for precise, discriminating and quantifiable results. Acquisitions were conducted on the elbow or the elbow crease from the surface to 12.5μm of depth on 11 healthy and 10 atopic patients with mild to moderate atopic dermatitis (AD) (mean SCORAD: 37). A specific 8 steps pre-processing protocol was applied on spectra follow-up by an orthogonal partial least square analysis to generate high-quality data. Discriminating frequencies in four distinct regions (corresponding to spectral vibrations of lipids, proteins and water) were identified between healthy and atopic skins spectra. Our results revealed a decrease of the lipid content (P < 0.01) and an alteration of the lipid conformation (P < 0.01) and organization (P < 0.05) in atopic patients compared with healthy one. These results support the alteration of the skin barrier function currently observed in AD. We also demonstrated a reduction of the total (P < 0.01) and the bound (P < 0.01) water content in atopic patients compared with healthy subjects. Finally, the secondary structure of proteins increased in atopic skin (P < 0.01). These results are in correlation with the rise of TEWL frequently measured in atopic skin. The loss of bound water promotes the formation of proteins in highly organized secondary structures and makes the SC rigid. Indeed, this innovative approach based on in vivo confocal Raman microspectroscopy will support the development of suitable molecules to an efficient treatment of AD targeting these molecular descriptors.