Cellular behaviour in epithelial root sheath following vinblastine administration in mouse.

After injection of vinblastine sulfate (VLB) cells of the epithelial root sheath (ERS) showed accumulation of phagosomes lysosomes and, in particular, of exocytosis vesicles facing the basal lamina. An unusual frequency of cell contacts was also noted between pulp mesenchyme and ERS. In the periradicular zone the cells showed accentuated signs of a squamous-like evolution. In addition, numerous mitotic figures were seen arrested at prometaphase all along the tissue: the mitotic arrest index was higher at the tip of the sheath and decreased more coronally. These findings strongly suggest that ERS participates actively to the formation of the basal lamina. They show that heterogenous cell relations frequently occur during root morphogenesis; however they put into question the role of ERS in cementogenesis. The existence of a high mitotic potential in ERS can explain its consistent morphology and might reflect a process of differential mitotic sequences involved in odontoblast differentiation.