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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.

In this study, researchers investigated whether overexpression of ornithine decarboxylase (ODC) was sufficient for tumor promotion in mouse skin. They used transgenic mice with high ODC expression in epidermal keratinocytes and found that these mice were more sensitive to carcinogen initiation compared to controls. Notably, mice with ODC overexpression in hair follicle keratinocytes developed tumors without the need for additional tumor promoters. The study concluded that ODC overexpression was sufficient to activate target cells in hair follicles, leading to clonal expansion and epidermal tumor formation, indicating that hair follicles are key sites for chemical carcinogen targeting in the skin.

The study investigated the role of ornithine decarboxylase (ODC) in hair follicle function using transgenic mice that overexpressed a mutated ODC transgene in hair follicle keratinocytes. These mice experienced normal initial hair growth but lost their hair completely 2-3 weeks after birth, coinciding with the onset of ODC overexpression and the development of follicular cysts. The study found that the ODC inhibitor 2-difluoromethylornithine could prevent hair loss and partially restore normal skin histology if administered early, and it could also reactivate hair growth in mice with complete hair loss. The results suggested that ODC played a crucial regulatory role in mouse hair follicles.