Synthesis of cementum‐like tissue in vitro by cells cultured from bone: a light and electron microscope study

Abstract

Cells obtained from calvariae of fetal rats, human gingival connective tissue and periodontal ligament of rat molars were each co‐cultured in vitro with non‐demineralized and partly demineralized root slices in nutrient medium containing 50 μGg/ml ascorbic acid and 10 mM B‐glyeerophosphate, in order to determine whether the root slices could affect the phenotype expressed by the cells. The cultures were examined by light and transmission electron microscopy. Nodules of bone‐like tissue, resembling those previously described by others, were observed in the multilayers of cells obtained from rat calvariae. but not in the multilayers of gingival and periodontal ligament cells, after 30 days of culture. Calvaria cells associated with the root slices produced tissues exhibiting ultrastructure that resembled that of bone or cellular cementum. acellular cemenlum and afibrillar cementum in vivo when examined after the same length of time. The tissues were never found in cultures of gingival fibroblasts or periodontal ligament cells. These observations suggest, first, that cells derived from bone can express in vitro the phenotype for the cementums; second, that cells obtained from human gingival and rat periodontal ligament do not do so when cultured under similar conditions; and third, the possibility that the osteoblasts, cementoblasts and their progenitors that are found in the periodontal ligament could, at least in part, have their origin and migrate there from the endosteal spaces of the alveolar process.

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

“…The thesis that cementoblasts and osteoblasts in the periodontium commonly originate from precursor cells residing in the alveolar bone is also supported by previous observations (Gould et al, 1977;Melcher et al, 1986). Our data are also consistent with the data reported by Rajishankar and colleagues (Rajishankar et al, 1998).…”

“…Since fibroblasts are predominant in the PDL (Berkovitz and Shore, 1995;Beertsen et al, 1997) and are capable of producing and digesting matrix components, fibroblastic cells have been assumed to be responsible for self-renewal of the PDL and regeneration of periodontal tissue. Indeed, experiments dealing with periodontal wound healing have suggested that PDL fibroblast populations may play an integral role in PDL regeneration (Melcher et al, 1986;McCulloch et al, 1987;Magnusson et al, 1990;Beertsen et al, 1997). Since these experiments were carried out with mixed cell populations of PDL tissues and/or cells of endosteal spaces, however, it is difficult to determine the cellular phenotypes that are required for regeneration.…”

Experimental Regeneration of The Periodontium

“…At least one study has shown that in vitro only cells derived from embryonic rat calvaria have the capacity to form a cementum-like material. 29 There are no studies demonstrating the ability of gingival cells, either in vivo or in vitro, to form periodontal tissues such as cementum and bone. Although attempts have been made, 30 the results are inconclusive on the ability of cells derived from gingiva.…”

“…Cementoid matrix and oriented bundles of collagen fibrils (presumably ligament fibers) are seen deposited over the electron-dense layer during cementum regeneration ( Figures 3B and 4). 13 In their study on the formation of cementum-like tissue by bone cells cultured from calvaria of rats, Melcher et al 29 also describe "osmiophilic incremental lines" between the curetted roots and the new matrix. This osmiophilic structure resembles the electrondense layer described by others.…”

Periodontal regeneration using ex vivo autologous stem cells engineered to express the BMP-2 gene: an alternative to alveolaplasty

“…31 The similar staining patterns of osteoblasts and cementoblasts in cellular cementum indicate that they are phenotypically similar and may be derived from a common osteoprogenitor cell. [32][33][34] Therefore, it has been hypothesized that reparative cementum is derived from osteoblasts.…”