title: Interleukin-6 inhibits bone formation in vitro.
abstract: Interleukin-6 (IL-6) is a pluripotent cytokine which is made by osteoblasts, but its role in bone metabolism is uncertain. The aim of this study was to test the effect of IL-6 on bone formation in vitro using a nodule-forming assay. Osteoblast-enriched calvaria cells were isolated from 2-day-old Sprague-Dawley rats and cultured in the presence of 10(-8) M dexamethasone. After 2 days, calvaria cells were treated with recombinant human IL-6 for 72 h, washed and maintained for a further 18 days before fixation. IL-6 caused a dose-dependent inhibition of bone nodule formation, with a maximum reduction of 53% with 5000 U/ml IL-6. IL-6 also inhibited alkaline phosphatase activity in a dose-dependent manner (e.g. control: 114 +/- 9.2; IL-6: 68 +/- 10.6 nmol p-nitrophenol (pNP)/mg/min). IL-6 did not affect cell numbers during early cell growth up to 6 days but caused a small but significant reduction in cell number at confluence (8 days). These results demonstrate that IL-6 inhibits bone nodule formation by rat calvaria cells in vitro and suggest that IL-6 may inhibit osteoblast differentiation.
authors.affiliation: Department of Oral Medicine and Periodontology, London Hospital Medical College, UK.
authors.forename: F J
authors.initials: FJ
authors.lastname: Hughes
authors.forename: G L
authors.initials: GL
authors.lastname: Howells
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002452:Cell Count; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015850:Interleukin-6 / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects*; D010012:Osteogenesis / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D015850:Interleukin-6; D011994:Recombinant Proteins; D000469:Alkaline Phosphatase