Immunocytochemical localization of laminin in the epithelial rests of Malassez of immature rat molars.

Immediately after disruption of Hertwig's root sheath, epithelial cells were found near the root apex, singly or in groups of two or three cells. They were irregular in shape with only a partial lining of basal lamina. Immunoreactivity for laminin was intense in the basal lamina and weak between projections of the epithelial cells. In 5-week-old rats, the epithelial rests consisted of about five cells and still had an incomplete basal lamina with collagen fibrils in the intercellular spaces. Immunoreaction products were seen in the basal lamina and diffusely in the intercellular spaces. The epithelial rests of 9-week-old rats had more cells, an almost complete lining of basal lamina, and narrowed intercellular spaces. Immunoreaction products were seen in the basal lamina but not in the intercellular spaces. These findings indicate the basal lamina is involved in the formation of the epithelial rests.