To investigate the development of eccrine sweat glands and the expression of Foxa1 genes and proteins in the course of development, the footpads from E15.5 to E21.5, P1-P12, P14, P21, P28 and P56 rats were subjected to immunofluorescence staining of FoxA1 and double immunofluorescence staining of K14/α-SMA, FoxA1/K7 and FoxA1/α-SMA, and were processed for Foxa1 gene detection by RT-qPCR. The results showed that rat eccrine sweat gland germs was first observed emerging from the basal layer of epidermis at E19.5, and then elongated downward into the dermis, forming straight ducts by E21.5. Early development of the secretory segments appeared at P1. The Foxa1 gene was not expressed in rat footpads until P2, but from P2 to P5, its expression up-regulated sharply, and thereafter maintained at a high level until adulthood. FoxA1 protein was first observed at P6 in eccrine sweat glands, four days after initial detection of Foxa1 gene transcripts. In skin, FoxA1-positive cells were present exclusively in secretory coils, with 95% being K7-positive secretory cells and 5% being α-SMA-positive myoepithelial cells. We conclude that Foxa1 can be used as a marker of eccrine sweat glands in skin and also as a marker of secretory coils, and Foxa1 is related to the development of secretory coils.
Keywords: Development; Eccrine sweat glands; Foxa1; K14; K7; α-SMA.