Development, structure, and keratin expression in C57BL/6J mouse eccrine glands.

Eccrine sweat glands in the mouse are found only on the footpads and, when mature, resemble human eccrine glands. Eccrine gland anlagen were first apparent at 16.5 days postconception (DPC) in mouse embryos as small accumulations of cells in the mesenchymal tissue beneath the developing epidermis resembling hair follicle placodes. These cells extended into the dermis where significant cell organization, duct development, and evidence of the acrosyringium were observed in 6- to 7-postpartum day (PPD) mice. Mouse-specific keratin 1 (K1) and 10 (K10) expression was confined to the strata spinosum and granulosum. In 16.5 and 18.5 DPC embryos, K14 and K17 were both expressed in the stratum basale and diffusely in the gland anlagen. K5 expression closely mimicked K17 throughout gland development. K6 expression was not observed in the developing glands of the embryo but was apparent in the luminal cell layer of the duct by 6 to 7 PPD. By 21 PPD, the gland apertures appeared as depressions in the surface surrounded by cornified squames, and the footpad surface lacked the organized ridge and crease system seen in human fingers. These data serve as a valuable reference for investigators who use genetically engineered mice for skin research.