Gap-junction-mediated Communication in Human Periodontal Ligament Cells

Abstract

Periodontal tissue homeostasis depends on a complex cellular network that conveys cell-cell communication. Gap junctions (GJs), one of the intercellular communication systems, are found between adjacent human periodontal ligament (hPDL) cells; however, the functional GJ coupling between hPDL cells has not yet been elucidated. In this study, we investigated functional gap-junction-mediated intercellular communication in isolated primary hPDL cells. SEM images indicated that the cells were in contact with each other via dendritic processes, and also showed high anti-connexin43 (Cx43) immunoreactivity on these processes. Gap-junctional intercellular communication (GJIC) among hPDL cells was assessed by fluorescence recovery after a photobleaching (FRAP) analysis, which exhibited dye coupling between hPDL cells, and was remarkably down-regulated when the cells were treated with a GJ blocker. Additionally, we examined GJs under hypoxic stress. The fluorescence recovery and expression levels of Cx43 decreased time-dependently under the hypoxic condition. Exposure to GJ inhibitor or hypoxia increased RANKL expression, and decreased OPG expression. This study shows that GJIC is responsible for hPDL cells and that its activity is reduced under hypoxia. This is consistent with the possible role of hPDL cells in regulating the biochemical reactions in response to changes in the hypoxic environment.

Infliximab attenuates inflammatory osteolysis in a model of periodontitis in Wistar rats

“…Our data are in agreement with those of other studies showing that periodontal ligament cells, gingival fibroblasts, and epithelial cells are capable of OPG secretion. 42,43 OPG soluble receptors could act through a decoy antagonism to inhibit RANK-L-driven osteoclast activation, that is, OPG can prevent RANK-L from binding to RANK, ultimately leading to a reduction in osteoclast function. 44 To assess the degree of bone resorption, we conducted 1/-8 metalloproteinase (MMP-1/-8) immunohistochemistry.…”

Three-dimensional ultrastructural analysis of cells in the periodontal ligament using focused ion beam/scanning electron microscope tomography

“…In particular, fibroblasts are known to have important roles in the synthesis of collagen bundles in the PDL. Additionally, fibroblasts of the PDL are interconnected by gap- and adherence-type junctions81011 and have been suggested to form a highly structured and interconnected network8. In single sections, it is recognized that PDL cells are oriented parallel to the collagen bundles.…”

Role of intracellular Ca2+–based mechanotransduction of human periodontal ligament fibroblasts

“…The behavior of hPDL fibroblasts displayed direct cell-cell communication via the functional GJs (20). We determined whether this intercellular network contributes to the [Ca 2+ ] i -based mechanotransduction of hPDL using a GJ inhibitor, 18α-GA.…”

“…Cultures were also treated with A23187 (MilliporeSigma, Burlington, MA, USA), a Ca 2+ -transporting ionophore, or vehicle (PBS) to evaluate the role of [Ca 2+ ] i signal in primary cultured hPDL fibroblasts at the indicated concentrations. 18 α-glycyrrhetinic acid (18α-GA; MilliporeSigma), a gap junction (GJ) inhibitor, was used to examine the involvement of GJ-mediated intercellular communication on the MS-induced [Ca 2+ ] i dynamics as previously described (19, 20). To visualize mineralized nodule formation, cells were replated in 12-well plates, and differentiation was initiated 24 h after plating by replacing the growth medium with 10% HIFBS and antibiotics, including 0.05 mM l -ascorbic acid, 100 nM dexamethasone, and 10 mM β-glycerophosphate (all obtained from MilliporeSigma).…”