Hair Strengthening Evaluation of Anisotropic Osmolite Solutions (Inositol + Arginine): Cross-Talk between Dermal Papilla Fibroblast and Keratinocytes of the Outer Root Sheath Using a µHair Follicle 3D Model

The hair follicle (HF) is a dynamic “mini-organ” which undergoes bi-continuous cycles of growth, destruction and rest. The molecular mechanisms underlying the HF cycle are complex yet not fully understood. Anyhow, it is clear that the epithelial–mesenchymal interactions, and in particular the cross-talk between dermal papilla fibroblast (DPF) and the keratinocytes of the outer root sheath (ORSK) play a pivotal role. Aim of this study is the evaluation of the biological activity of anisotropic osmolyte solutions on the HF cycle. As reported in recent studies, dermal papilla cells deeply modify their gene expression profile when cultured as monolayers, but their transcriptional pattern can be partially restored when they are cultured as 3-dimensional spheroids. This draws our attention to the discovery that the spatial distribution of cells in the growth medium is fundamental in order to produce a verisimilar model. Therefore, we used the hanging drop technology to produce a scaffold-free micro-tissue model applied to a DPF-ORSK co-culture in order to create a µHF 3-dimensional model. As a result, this system was capable of evaluating the efficacy of the anisotropic osmolyte solutions on the progressive increase of the follicle turnover and ‘health’. Moreover, an in silico model was used in order to screen the most promising combination of osmolyte molecules. In vivo objective evaluations were finally carried out on volunteers having hair disorders.