Formation of hair follicles from a single-cell suspension of embryonic rat skin by a two-step procedure in vitro.

A technique for culturing skin was devised whereby hair follicles in a normal state were generated from a single-cell suspension of embryonic rat skin. Dissociated cells obtained by trypsinization of the day-15 embryonic lip were cultured by a two-step procedure in vitro. Reorganization of hair-follicle rudiments was accompanied by reaggregation of the cells during a 24-hour initial culture with rotation, and the rudiments differentiated into hair follicles within a week during subsequent subculture of the cell aggregates by floatation. The light-microscopic features and the size of the follicles were similar to those of day-18 vibrissa follicles during normal development in vivo. Furthermore, the stratification of cells, including subcellular differentiation, and the ultrastructure of the hair follicles generated in vitro were similar to those of normal hair follicles with well-keratinized hair shafts. The present system appears to be a useful model for analytical studies in vitro on the formation of hair follicles and for studies designed to facilitate the transplantation of human hair.