Sebaceous gland: Milestones of 30-year modelling research dedicated to the "brain of the skin".

In 2018, Schneider and Zouboulis analysed the available tools for studying sebaceous gland pathophysiology in vitro. Since then, the interest in this field remains unbroken, as demonstrated by recent reviews on sebaceous gland physiology, endocrinology and neurobiology, the role of sebaceous glands beyond acne, and several original works on different areas of sebaceous gland function, including sebaceous lipogenesis. Landmark developments in the first part of the 30-year modelling research dedicated to the sebaceous gland, which is considered by several scientists as the brain of the skin, were the short-term culture of human sebaceous glands, the culture of human sebaceous gland cells and the development of immortalized sebaceous gland cell lines exhibiting characteristics of normal sebocytes. On the other hand, current developments represent the establishment of sebaceous gland spheroids, the 3D-SeboSkin model of viable skin explants ex vivo, the combination of culture-expanded epidermal stem cells of mice and adult humans to form de novo hair follicles and sebaceous glands, when they are transplanted into excisional wounds in mice, and 3D-printed scaffolds coated with decellularized matrix of adipose-derived mesenchymal stromal cells and SZ95 sebocytes. These novel tools may become useful platforms for better understanding of cellular and molecular mechanisms governing sebocyte biology and sebaceous gland homeostasis, such as the changes in sebum synthesis and composition, the infundibular differentiation and the influence of the innate immunity and the cutaneous microbiome and for identifying potential therapeutic targets of skin diseases affecting the sebaceous glands.