[Epithelial cell rests of Malassez: tissue, cell, and molecular biology]

This review presents an analysis of the current data on the structural and functional organization and biological significance of epithelial cell rests of Malassez (ERM), which are formed by persisting fragments of epithelial (Hertwig) sheath that participates in the tooth root development. ERM, found within the periodontal ligament, undergo intensive age-related involution and are traditionally described as small clusters of functionally inactive cells. Meanwhile, recent findings are indicative of high functional activity of ERM which are both producers of and targets for various cytokines, growth factors, adhesive substances, their receptors and other biologically active molecules. It is suggested that ERM participate in sustaining the optimal conditions for the normal functioning and regeneration of periodontium structural components. When periodontal tissue homeostasis is disturbed, ERM may grow up and acquire the capacity to destroy the surrounding tissues.