Living scaffolds in monogenic genodermatoses: 3D skin models for physiopathology, gene therapy, and drug testing.

Keratinocytes have been cultured in vitro for more than 50 years to produce long-lasting epithelial grafts containing stem cells, transient amplifying progenitors, and differentiated cells. They have been widely used to study the molecular mechanisms underlying skin physiology, pathology (e.g. functional alterations causing monogenic genodermatoses), and to develop cell and gene therapy treatments. However, 2D models present the major limit of not recapitulating the 3D structure and functions of the whole skin. As the human skin is a complex organ composed of multiple layers, 3D models represent a valuable approach to study the interactions between dermis and epidermis, and to recapitulate skin impairment typical of genodermatoses. Importantly, the advent of induced pluripotent stem cell (iPSC) technology has further expanded the repertoire of available tools for disease modelling, enabling the generation of patient-specific skin equivalents. Together, these advances position 3D skin models as valuable platforms for the validation of novel therapeutic strategies, potentially reducing reliance on animal models. In this review, we summarize the last decades of advances in 3D skin modelling applied to the study of monogenic genodermatoses, such as Ichthyosis and Epidermolysis Bullosa. We describe types of matrices used, their cellular composition, and their application in physiopathological studies, gene therapy development, and drug testing.