Human Periodontal Cells Initiate Mineral‐Like Nodules In Vitro

Abstract

A primary objective in the treatment of periodontal diseases is the regeneration of the mineralized and soft connective tissue components of the attachment apparatus. Current theories suggest the cells of the periodontium have the capacity, when appropriately triggered, to actively participate in restoring connective tissues, including mineralized tissues. To evaluate further the role of such cells in periodontal homeostasis, periodontal ligament (PDL) cells and gingival fibroblasts (GF) were cultured and examined for alkaline phosphatase levels and for the ability to produce mineralized nodules in culture. These are two characteristics of osteoblast-like cells in vitro. The levels of alkaline phosphatase produced by these cells were determined by a modified kinetic assay and the ability of these cells to produce mineral-like nodules in vitro was evaluated by Von Kossa staining and light and electron microscopy. PDL cells had significantly higher levels of alkaline phosphatase when compared with gingival fibroblasts obtained from the same patient and the same passage, in vitro. Furthermore PDL cells, but not GF, were capable of producing mineral-like nodules in vitro. These results indicate differences in behavior between PDL cells and GF; such differences may prove important in designing appropriate clinical therapies directed at stimulating periodontal regeneration.

A cell line with characteristics of the periodontal ligament fibroblasts is negatively regulated for mineralization and Runx2/Cbfa1/Osf2 activity, part of which can be overcome by bone morphogenetic protein-2

“…In addition, primary rat PDL cells in culture formed mineralized nodules in vitro, although the mineralized nodules appeared to be different from those produced by osteoblasts (Cho et al, 1992). A similar result was observed with human PDL cells (Arceo et al, 1991). However, since it has been shown that there are subsets of fibroblastic cells in the PDL (Roberts and Chamberlain, 1978;Limeback et al, 1982;Rose et al, 1987), it is not clear whether these osteoblastic phenotypes and functions were due to one type of cell or to a combination of cells in the PDL.…”

PLAP-1/Asporin, a Novel Negative Regulator of Periodontal Ligament Mineralization

“…In vitro maintained PDL cells obtained from rats formed mineralized nodules that were different from those formed by osteoblasts (4). It has also been shown that human PDL cells, but not gingival fibroblasts, form mineral-like nodules in vitro (5). However, in most of the previous studies, the PDL cells were heterogeneous cell populations.…”

“…Recently it has been revealed that PDL tissue possesses multipotential mesenchymal stem cells that can differentiate into mineralized tissue-forming cells such as osteoblasts and cementoblasts (2,3). In fact, in vitro maintained PDL cells have various osteoblast-like properties, including the capacity to form mineralized nodules, expression of bone-associated markers, and response to bone-inductive factors such as bone morphogenetic protein 2 (BMP-2) (4,5). Interestingly, however, PDL tissue is never ossified in vivo under normal circumstances.…”

Platelet-Rich Plasma Provides Nucleus for Mineralization in Cultures of Partially Differentiated Periodontal Ligament Cells

“…This PRP-initiated mineralization required increased cellular ALP activity, as observed in the physiological process of mineralization that is normally observed in the mineralization front of skeletal tissue. However, in contrast to the process of mineralization in vivo, where mineral spicules are closely associated with collagen fibrils (Arceo et al, 1991), the PRP-initiated mineralization is characterized by the gathering of mineralized spicules onto platelet-derived plasma membrane. Because Marsh et al (1995) described the possibility that cellular debris act as nucleating sites for mineralization, we suggest that PRP might initiate mineralization and thereby promote bone regeneration under particular conditions at the site of in vivo application.…”