Study of the role of the neurovascular interplays in rosacea using in vitro skin models. – NEUROSKIN

Rosacea is a chronic and multi-factorial skin disease with a prevalence among adults in some countries as high as 20%. Unpleasant sensations such as stinging and burning, pain, and significant skin dryness are associated with the pathology. Moreover, rosacea is localized primarily on the face and thus negatively affects self-esteem, social relations and generally the quality of life of patients including being a cause of depression. Rosacea pathogenesis remains largely unclear and efficient treatments are lacking. We suggest that rosacea is modulated by a neurovascular cutaneous interplay. Two-dimensional (2D) and three-dimensional (3D) in vitro human co-culture models will be developed. Human sensory neurons and Schwann cells will be prepared from induced pluripotent stem cells; human endothelial cells and fibroblasts will be isolated from human skin samples. In the 2D model, microfluidic devices able to mimic in vitro the cellular interactions between sensory neurons, endothelial cells and fibroblasts, in normal and rosacea contexts, will be used, allowing the evaluation of the dysregulation of specific mediators and receptors implicated in neurovascular communication. This microfluidic system provides physical separation between neuronal cell bodies and their neuronal endings in contact with other cell types, allowing evaluation of each population without using complex cell separation techniques. For the 3D model, a dedicated chamber will be designed i) to assess the innervation process of a reconstructed vascularized skin in normal and rosacea contexts, ii) to analyze the neurovascular interactions using markers for nerves, endothelial cells and fibroblasts, and then iii) to study the impact on these structures of active components used for skin regeneration. The involvement of the neurocutaneous axis, as well as the impact on angiogenesis in the pathophysiology of rosacea, requires confirmation. Various cytokine cocktails associated with different well-known triggers of rosacea (UV, heat, specific bacteria treatment) can be used to reproduce in animals the environment of this pathology but developing a human model is needed. Development of 2D and 3D in vitro relevant culture models will permit us to evaluate and understand the cellular and molecular interplay between these main players. These 2D and 3D models will allow us to study the role of innervation in conditions mimicking this disease. These innovative models will help in the investigation of the mechanisms of action of the different cellular players involved in rosacea. Particularly, the involvement of the vanilloid type (TRPV) and of the melastatin type (TRPM) TRP channels which can be activated by many trigger factors of rosacea, will be investigated. These data will then be used for the screening of molecules with therapeutic and regenerative potential. The project execution is based on the expertise of four academic partners, three French and one Canadian, involved in tissue engineering, and in the role of vascularization and innervation on skin homeostasis. An industrial partner with a strongly involvement in skin treatment completes this consortium. This work should lead to a better understanding of the pathophysiology of the rosacea disease. In particular, the role of the neurovascular cutaneous interactions will be demonstrated by studies performed on 2D co-culture models and 3D skin equivalent models, and, thanks to the device generated (a double chamber), products used for skin regeneration and acting on these interactions will be tested. Furthermore, rosacea is a good "model" through which it will be possible to better investigate the complexity of neurovascular communication, and its roles in chronic inflammation and fibrosis development.