title: Effect of Crohn's disease on bone metabolism in vitro: a role for interleukin-6.
abstract: Circulating proinflammatory cytokines may be involved in osteopenia associated with Crohn's disease (CD). Therefore, the effect of interleukin (IL)-6, IL-1beta, and tumor necrosis factor (TNF) a contained in Crohn's serum on bone formation was examined in a bone organ culture system. Initially, serum levels of IL-6, IL-1beta, and TNF-a were determined by ELISA in newly diagnosed, untreated children with CD and healthy age-matched controls. Serum IL-6 levels were significantly higher in patients with CD than in controls (23.9 +/- 2.8 pg/ml vs. 0.7 pg/ml +/- 0.2; p < 0.001), whereas IL-1beta and TNF-alpha serum levels were not. In the organ culture studies, 20-day-old fetal rat parietal bones were incubated for 96 h with CD or control serum, serum preincubated with a neutralizing antibody to each cytokine or a nonimmune immunoglobulin control, and with IL-6. Bone formation measured by assaying calcium content and dry weight was significantly decreased in bones exposed to Crohn's serum. Light microscopy of the bones treated with CD serum revealed a discontinuous, uneven mineralized bone matrix and disorganized osteoblasts with altered morphology. Incubation with an antibody that neutralized IL-6 activity prevented the change in osteoblast and bone morphology. TNF-a and IL-1beta antibodies had no apparent effects. Collagen synthesis and DNA content were not affected by CD serum. Also, addition of IL-6 to the culture medium decreased mineralization. These results suggest that IL-6 is a mediator of the effects of Crohn's serum on in vitro mineralization and may be a contributing factor to the osteopenia associated with CD.
authors.affiliation: Department of Pediatrics, Connecticut Children's Medical Center, University of Connecticut, Hartford 06106, USA.
authors.forename: Francisco A
authors.initials: FA
authors.lastname: Sylvester
authors.forename: Nancy
authors.initials: N
authors.lastname: Wyzga
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Hyams
authors.forename: Gloria A
authors.initials: GA
authors.lastname: Gronowicz
mesh_terms: D000293:Adolescent; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001851:Bone Diseases, Metabolic / Q000209:etiology / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism*; D016022:Case-Control Studies; D002648:Child; D003424:Crohn Disease / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007375:Interleukin-1 / Q000097:blood; D015850:Interleukin-6 / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D009924:Organ Culture Techniques / Q000379:methods; D010006:Osteoblasts / Q000378:metabolism / Q000473:pathology; D010294:Parietal Bone / Q000196:embryology / Q000378:metabolism; D051381:Rats; D019947:Receptors, Interleukin-6 / Q000097:blood; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D007375:Interleukin-1; D015850:Interleukin-6; D019947:Receptors, Interleukin-6; D014409:Tumor Necrosis Factor-alpha