The application of carbon dioxide snow under pressure results in necrosis of all the layers of the rat skin. The epidermis is regenerated from the normal epidermis and hair follicles surrounding the area of injury. The deeper parts of the dead corium and the panniculus are gradually absorbed and are replaced by granulation tissue.
Hair neogenesis was observed in the repaired lesions. The new hair germs take origin in the basal layer during the third week after freezing. Ultimately, these primitive structures differentiate and reproduce hair follicles, hair papillae, and sebaceous glands. The new hair crop is nonpigmented and softer in texture than normal hair. Areas which became only sparsely repopulated with hair exhibited keratin cyst formation which seems to be homologous with that in the skin of hairless mice.
GEORGE RIZK MIKHAIL. Hair Neogenesis in Rat Skin. Arch Dermatol. 1963;88(6):713–728. doi:10.1001/archderm.1963.01590240037008