title: Palatal fibroblasts reduce osteoclastogenesis in murine bone marrow cultures.
abstract: BACKGROUND
  Preclinical studies support the assumption that connective tissue grafts preserve the alveolar bone from resorption; the underlying cellular mechanisms, however, remain unknown. The cellular mechanisms may be attributed to the paracrine activity of the palatal fibroblasts. It was thus reasonable to suggest that palatal connective tissue grafts reduce the formation of osteoclasts.
  
  
  METHODS
  To test this hypothesis, human palatal fibroblasts were examined for their capacity to modulate the formation of osteoclasts in murine bone marrow cultures exposed to RANKL, M-CSF and TGF-β1. Osteoclastogenesis was determined by tartrate-resistant acid phosphatase (TRAP) staining and gene expression analysis. The formation of antigen presenting cells was based on the expression of CD14 and costimmulatory molecules of antigen presenting cells. The paracrine interaction of fibroblasts and the bone marrow was modeled in vitro with inserts of cell-occlusive membranes.
  
  
  RESULTS
  In cocultures without cell-to-cell contact, palatal fibroblasts caused a decrease in the expression of the osteoclast marker genes in bone marrow cells; calcitonin receptors, cathepsin K, TRAP, and osteoclast-associated receptor. Also the number of TRAP positive multinucleated cells was decreased in the presence of fibroblasts. Notably, palatal fibroblasts increased the expression of CD14 and the co-stimulatory proteins CD40, CD80, and CD86 in bone marrow cells. Bone marrow cells had no considerable impact on fibroblast viability and proliferation marker genes. With regard to cell distribution, osteoclasts were most prominent in the center of the membranes, while fibroblasts accumulated immediately adjacent to the border of the insert forming a ring-like structure on the surface of the culture plate.
  
  
  CONCLUSIONS
  The data suggest that palatal fibroblasts provide a paracrine environment that reduces osteoclastogenesis and increases markers of antigen presenting cells. Morover, the paracrine model revealed a joint activity between palatal fibroblasts and bone marrow cells visualized by the characteristic cell distribution in the two separated compartments.
authors.affiliation: Department of Periodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.|Laboratory of Oral Cell Biology, School of Dental Medicine, University of Bern, Bern, Switzerland.
authors.forename: Victoria
authors.initials: V
authors.lastname: Voisin
authors.affiliation: Laboratory of Oral Cell Biology, School of Dental Medicine, University of Bern, Bern, Switzerland.|Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland.|Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Universitat Internacional de Catalunya, Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Caballé-Serrano
authors.affiliation: Department of Periodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.
authors.forename: Anton
authors.initials: A
authors.lastname: Sculean
authors.affiliation: Department of Periodontology, School of Dental Medicine, University of Bern, Bern, Switzerland. reinhard.gruber@zmk.unibe.ch.|Laboratory of Oral Cell Biology, School of Dental Medicine, University of Bern, Bern, Switzerland. reinhard.gruber@zmk.unibe.ch.|Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland. reinhard.gruber@zmk.unibe.ch.|Department of Preventive, Restorative and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland. reinhard.gruber@zmk.unibe.ch.|Department of Oral Biology, Medical University of Vienna, Wien, Austria. reinhard.gruber@zmk.unibe.ch.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Gruber
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000166:cytology; D001854:Bone Marrow Cells / Q000166:cytology*; D001862:Bone Resorption; D002454:Cell Differentiation; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology*; D006801:Humans; D051379:Mice; D010010:Osteoclasts / Q000166:cytology*; D010012:Osteogenesis; D010159:Palate / Q000166:cytology
keywords: Co-culture; Inserts; Macrophages; Murine bone marrow cultures; Osteoclast; Palatal fibroblasts