A Simple In Vivo System for Studying Epithelialization, Hair Follicle Formation, and Invasion Using Primary Epidermal Cells from Wild-Type and Transgenic Ornithine Decarboxylase-Overexpressing Mouse Skin

The study presented a tracheal xenotransplantation assay as a simple in vivo system to evaluate epithelialization, hair follicle formation, and tumorigenesis using primary epidermal cells from wild-type and transgenic mice. This method involved seeding epithelial cells into deepithelialized rat tracheas, which were then transplanted into athymic nude mice. The study found that keratinocytes overexpressing ornithine decarboxylase (ODC) and infected with v-Ha-ras became invasive, penetrating all layers of the tracheal wall, similar to malignant skin carcinomas in ODC/Ras transgenic mice. The assay also demonstrated its utility in hair follicle reconstitution, showing that freshly harvested epithelial cells were more effective than cultured ones in forming hair follicles. The method proved advantageous for studying keratinocyte stem cell colonies and factors affecting hair follicle development, especially when cell numbers were limited.