Focuses on the molecular and cellular fundamentals of homeostatic and defense responses of tissue barriers to damaging impacts and exposure to pathogens and engineered nanomaterials. There will be a special emphasis on role of mesenchymal stoma, vascular, epithelial, telocyte, myofibroblast, lymphoid, and reticuloendothelial cells in development of reactions that bridge effects of ambient factors, medical treatments, drag delivery systems with alterations in barrier integrity, tissue/organ functions and in metabolic status. In conjunction with the above, a particular role of progenitor cells of different origins in remodeling and regeneration of tissue stroma, vasculature of blood-tissue barriers, mucosa and external epithelium will be also addressed and discussed.