title: Short time administration of antirheumatic drugs - methotrexate as a strong inhibitor of osteoblast's proliferation in vitro.
abstract: BACKGROUND
  Due to increasing use of disease modifying antirheumatic drugs (DMARDs) as first line therapy in rheumatic diseases, dental and maxillofacial practitioner should be aware of drug related adverse events. Especially effects on bone-metabolism and its cells are discussed controversially. Therefore we investigate the in vitro effect of short time administration of low dose methotrexate (MTX) on osteoblasts as essential part of bone remodelling cells.
  
  
  METHODS
  Primary bovine osteoblasts (OBs) were incubated with various concentrations of MTX, related to tissue concentrations, over a period of fourteen days by using a previously established standard protocol. The effect on cell proliferation as well as mitochondrial activity was assessed by using 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyltetrazolium bromide (MTT) assay, imaging and counting of living cells. Additionally, immunostaining of extracellular matrix proteins was used to survey osteogenic differentiation.
  
  
  RESULTS
  All methods indicate a strong inhibition of osteoblast`s proliferation by short time administration of low dose MTX within therapeutically relevant concentrations of 1 to 1000 nM, without affecting cell differentiation of middle-stage differentiated OBs in general. More over a significant decrease of cell numbers and mitochondrial activity was found at these MTX concentrations. The most sensitive method seems to be the MTT-assay. MTX-concentration of 0,01 nM and concentrations below had no inhibitory effects anymore.
  
  
  CONCLUSIONS
  Even low dose methotrexate acts as a potent inhibitor of osteoblast's proliferation and mitochondrial metabolism in vitro, without affecting main differentiation of pre-differentiated osteoblasts. These results suggest possible negative effects of DMARDs concerning bone healing and for example osseointegration of dental implants. Especially the specifics of the jaw bone with its high vascularisation and physiological high tissue metabolism, suggests possible negative effects of DMARD therapy concerning oral and cranio-maxillofacial bone surgery as could be seen in a similar way in bisphosphonate related osteonecrosis of the jaw.
authors.affiliation: Department of Cranio-Maxillofacial Surgery, University Hospital Muenster, Germany. tobias.annussek@ukmuenster.de
authors.forename: Tobias
authors.initials: T
authors.lastname: Annussek
authors.forename: Johannes
authors.initials: J
authors.lastname: Kleinheinz
authors.forename: Szuwart
authors.initials: S
authors.lastname: Thomas
authors.forename: Ulrich
authors.initials: U
authors.lastname: Joos
authors.forename: Kai
authors.initials: K
authors.lastname: Wermker
mesh_terms: D000818:Animals; D018501:Antirheumatic Agents / Q000009:adverse effects* / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000503:physiopathology; D016723:Bone Remodeling / Q000187:drug effects; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008727:Methotrexate / Q000009:adverse effects* / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects*; D015675:Osteocalcin / Q000378:metabolism; D012016:Reference Values; D018570:Risk Assessment
chemical_list: D018501:Antirheumatic Agents; D015675:Osteocalcin; D008727:Methotrexate