title: Direct cell-cell contact between periodontal ligament fibroblasts and osteoclast precursors synergistically increases the expression of genes related to osteoclastogenesis.
abstract: The formation of bone resorbing osteoclasts in vivo is orchestrated by cells of the osteoblast lineage such as periodontal ligament fibroblasts that provide the proper signals to osteoclast precursors. Although the requirement of cell-cell interactions is widely acknowledged, it is unknown whether these interactions influence the expression of genes required for osteoclastogenesis and the ultimate formation of osteoclasts. In the present study we investigated the effect of cell-cell interaction on the mRNA expression of adhesion molecules and molecules involved in osteoclast formation in cultures of peripheral blood mononuclear cells (PBMCs) and human primary periodontal ligament fibroblasts, both as solitary cultures and in co-culture. We further analyzed the formation of multinucleated, tartrate resistant acid phosphatase (TRACP) positive cells and assessed their bone resorbing abilities. Interestingly, gene expression of intercellular adhesion molecule-1 (ICAM-1) and of osteoclastogenesis-related genes (RANKL, RANK, TNF-alpha, and IL-1beta) was highly up-regulated in the co-cultures compared to mono-cultures and the 5-10-fold up-regulation reflected a synergistic increase due to direct cell-cell interaction. This induction strongly overpowered the effects of known osteoclastogenesis inducers 1,25(OH)(2)VitD(3) and dexamethasone. In case of indirect cell-cell contact mRNA expression was not altered, indicating that heterotypic adhesion is required for the increase in gene expression. In addition, the number of osteoclast-like cells that were formed in co-culture with periodontal ligament fibroblasts was significantly augmented compared to mono-cultures. Our data indicate that cell-cell adhesion between osteoclast precursors and periodontal ligament fibroblasts significantly modulates the cellular response which favors the expression of osteoclast differentiation genes and the ultimate formation of osteoclasts.
authors.affiliation: Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, Research Institute MOVE, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Veerle
authors.initials: V
authors.lastname: Bloemen
authors.forename: Ton
authors.initials: T
authors.lastname: Schoenmaker
authors.forename: Teun J
authors.initials: TJ
authors.lastname: de Vries
authors.forename: Vincent
authors.initials: V
authors.lastname: Everts
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D001862:Bone Resorption / Q000235:genetics; D002117:Calcitriol / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics*; D002450:Cell Communication / Q000187:drug effects / Q000235:genetics*; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D002478:Cells, Cultured; D018920:Coculture Techniques; D003907:Dexamethasone / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D053583:Interleukin-1beta / Q000235:genetics; D007527:Isoenzymes / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism*; D010513:Periodontal Ligament / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D053245:RANK Ligand / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics; D000071681:Tartrate-Resistant Acid Phosphatase; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
chemical_list: D053583:Interleukin-1beta; D007527:Isoenzymes; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D003907:Dexamethasone; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D002117:Calcitriol