In vitro growth of mouse hair root.

Hair roots from mouse dorsal skin continued to grow in culture medium for 10 h or more after isolation. Under observation by time-lapse cinematography, the cultured hair roots appeared to grow downward. We observed both the downward growth of the cultured hair roots as well as the transfer of melanosomes from melanocytes to cortical cells. The hair roots were also capable of incorporating the labelled amino acid and thymidine.