PERIODONTAL-LIGAMENT CELL-POPULATIONS - THE CENTRAL ROLE OF FIBROBLASTS IN CREATING A UNIQUE TISSUE

Background: Fibroblasts are the predominant cells of the periodontal l igament (PL) and have important roles in the development, function, an d regeneration of the tooth support apparatus. Biological processes in itiated during the formation of the PL contribute to the long-lasting homeostasic properties exhibited by PL fibroblast populations, Develop ment: The formation of the PL is likely controlled by epithelial-mesen chymal and epithelial hard tissue interactions, but the actual mechani sms that contribute to the development of cellular lineages in the PL are unknown. Fibroblasts in the normally functioning PL migrate throug h the tissue along collagen fibres to cementum and bone and in an apic o-coronal direction during tooth eruption, Adult Tissue: Cell kinetic experiments have shown that PL fibroblasts comprise a renewal cell sys tem in steady-state and the progenitors can generate multiple types of more differentiated, specialized cells. Progenitor cell populations o f the PL are enriched in locations adjacent to blood vessels and in co ntiguous endosteal spaces, In normally functioning periodontal tissues , there is a relatively modest turnover of cells in which apoptotic ce ll death balances proliferation, Large increases of cell formation and cell differentiation occur after application of orthodontic forces or wounding, As PL cells comprise multiple cellular phenotypes, it has b een postulated that after wounding, the separate phenotypes repopulati ng the site will ultimately dictate the tissue form and type. Conclusi ons: PL fibroblasts play an essential role in responses to mechanical force loading of the tooth by remodelling and repairing effete or dama ged matrix components. In consideration of the important roles played by fibroblasts in PL homeostasis, they could be described as ''the arc hitect, builder, and caretaker'' of the periodontal ligament. (C) 1996 Wiley-Liss, Inc.