Variation of differentiation in nail and bovine hoof cells.

Human nail plate contains two distinct types of keratins, skin-type and hair-type keratins. To elucidate that nature of the differentiation pathway of nail, we examined the expression of these keratins in human nail as well as in cultured cells taken from bovine hoof matrix. In this study we succeeded in showing that human nail matrix is characterized by the segregated localization of skin- and hair-type keratins except for the apical matrix in which both types of keratins are co-expressed. These results allow us to infer that some of the nail cells possibly divert the pattern of keratin expression during differentiation in vivo. Cultured cells taken from the ventral matrix of bovine hoof, which undergo the pathway of hair-type differentiation in vivo, expressed skin-type keratins together with hair-type keratins, thereby indicating that these cells develop into another pathway of differentiation (skin-type differentiation) from hair-type differentiation developed in vivo. These results provide us with a further insight into nail differentiation under which nail cells develop into multiple patterns of differentiation in vivo and in vitro.