Intravital multiphoton tomography as an appropriate tool for non-invasive in vivo analysis of human skin affected with atopic dermatitis

Increasing incidence of inflammatory skin diseases such as Atopic Dermatitis (AD) has been noted in the past years. According to recent estimations around 15% of newborn subjects are affected with a disease severity that requires medical treatment. Although its pathogenesis is multifactorial, recent reports indicate that an impaired physical skin barrier predispose for the development of AD. The major part of this barrier is formed by the stratum corneum (SC) wherein corneocytes are embedded in a complex matrix of proteins and lipids. Its components were synthesized in the stratum granulosum (SG) and secreted via lamellar bodies at the SC/SG interface. Within a clinical in vivo study we focused on the skin metabolism at the SC/SG interface in AD affected patients in comparison to healthy subjects. Measurement of fluorescence life-time of NADH provides access to the metabolic state of skin. Due to the application of a 5D intravital tomographic skin analysis we facilitate the non-invasive investigation of human epidermis in the longitudinal course of AD therapy. We could ascertain by blinded analysis of 40 skin areas of 20 patients in a three month follow-up that the metabolic status at the SC/SG interface was altered in AD compromised skin even in non-lesional, apparent healthy skin regions. This illustrates an impaired skin barrier formation even at nonaffected skin of AD subjects appearing promotive for the development of acute skin inflammation. Therefore, our findings allow a deeper understanding of the individual disease development and the improved management of the therapeutic intervention in clinical application.