Fibroblast Differentiation and Models of Human Skin

Sammanfattning: This thesis combines three publications and one manuscript, covering two principal topics: functional differentiation of human fibroblasts and laboratory models of human skin. The two topics favourably unite in the realm of tissue engineering. This thesis is therefore split into three main parts: 1. a discussion of phenotypic plasticity as it pertains to fibroblasts and the stem cell continuum; 2. a short review of engineered tissue, with particular focus on soluble factors and materials; and, 3. a motivated review of the biology, diversity and culture of skin, including skin construction.The intended goal of our research endeavor was to achieve the  formulation of a bioactive therapy for skin regeneration. The main hypothesis was that fibroblast-to-keratinocyte differentiation would facilitate wound healing, and that the protocol for such a method could be adapted to clinical translation. The foundation for the hypothesis lay in the differentiation capabilities of primary dermal fibroblasts (Paper I). However, the goal has not yet been achieved. Instead, intermediate work on the construction of skin for the purpose of creating a model test-bed has resulted in two other publications. The use of excised human skin, a formidable reference sample for tissue engineered skin, has been used to investigate a gelatinbased material in re-epithelialization (Paper II). A first attempt at standardizing a constructed skin model also resulted in a publication: an evaluation of melanocyte influences on keratinocyte-mediated contraction (Paper III).The introduction of melanocytes into a skin model raised questions about other appendages of the integumentary system. Our previous experience with preadipocyte isolation and identification, and our attempts at constructing three-dimensional adipose tissue, motivated further investigations into fibroblast-to-adipocyte differentiation. We investigated the possibility of activating thermogenesis in fibroblasts, a property otherwise reserved for cells of the adipogenic and myogenic lineages. Our attempts were successful, and are presently in manuscript form (Paper IV). Some further experiments and optimizations are necessary before establishing a reproducible protocol for thermogenic induction.The knowledge obtained through these scientific inquiries have moved us closer to achieving our goals, but methodological advances are still necessary. In the meantime, we have new test-beds for investigating different interactions in skin, and that enables many new questions to be asked and answered.