title: Effects of bilirubin and sera from jaundiced patients on osteoblasts: contribution to the development of osteoporosis in liver diseases.
abstract: Low bone formation is considered to be the main feature in osteoporosis associated with cholestatic and end-stage liver diseases, although the consequences of retained substances in chronic cholestasis on bone cells have scarcely been studied. Therefore, we analyzed the effects of bilirubin and serum from jaundiced patients on viability, differentiation, mineralization, and gene expression in the cells involved in bone formation. The experiments were performed in human primary osteoblasts and SAOS-2 human osteosarcoma cells. Unconjugated bilirubin or serum from jaundiced patients resulted in a dose-dependent decrease in osteoblast viability. Concentrations of bilirubin or jaundiced serum without effects on cell survival significantly diminished osteoblast differentiation. Mineralization was significantly reduced by exposure to 50 μM bilirubin at all time points (from -32% to -55%) and jaundiced sera resulted in a significant decrease on cell mineralization as well. Furthermore, bilirubin down-regulated RUNX2 (runt-related transcription factor 2) gene expression, a basic osteogenic factor involved in osteoblast differentiation, and serum from jaundiced patients significantly up-regulated the RANKL/OPG (receptor activator of nuclear factor-κB ligand/osteoprotegerin) gene expression ratio, a system closely involved in osteoblast-induced osteoclastogenesis.
  
  
  CONCLUSIONS
  Besides decreased cell viability, unconjugated bilirubin and serum from jaundiced patients led to defective consequences on osteoblasts. Moreover, jaundiced serum up-regulates the system involved in osteoblast-induced osteoclastogenesis. These results support the deleterious consequences of increased bilirubin in advanced chronic cholestasis and in end-stage liver diseases, resulting in disturbed bone formation related to osteoblast dysfunction.
authors.affiliation: Centro de Investigación Biomédica en Red en Enfermedades Hepáticas y Digestivas (CIBERehd), Institut d’Investigacions Biome`diques August Pi i Sunyer, University of Barcelona, Barcelona, Spain. silvia.ruiz@ciberehd.org
authors.forename: Silvia
authors.initials: S
authors.lastname: Ruiz-Gaspà
authors.forename: Angels
authors.initials: A
authors.lastname: Martinez-Ferrer
authors.forename: Nuria
authors.initials: N
authors.lastname: Guañabens
authors.forename: Marta
authors.initials: M
authors.lastname: Dubreuil
authors.forename: Pilar
authors.initials: P
authors.lastname: Peris
authors.forename: Anna
authors.initials: A
authors.lastname: Enjuanes
authors.forename: Maria Jesús
authors.initials: MJ
authors.lastname: Martinez de Osaba
authors.forename: Luisa
authors.initials: L
authors.lastname: Alvarez
authors.forename: Ana
authors.initials: A
authors.lastname: Monegal
authors.forename: Andrés
authors.initials: A
authors.lastname: Combalia
authors.forename: Albert
authors.initials: A
authors.lastname: Parés
mesh_terms: D001663:Bilirubin / Q000494:pharmacology*; D002113:Calcification, Physiologic / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D050659:Core Binding Factor Alpha 1 Subunit / Q000096:biosynthesis; D015536:Down-Regulation; D006801:Humans; D007565:Jaundice / Q000097:blood*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010024:Osteoporosis / Q000209:etiology*; D012516:Osteosarcoma / Q000503:physiopathology; D053245:RANK Ligand / Q000096:biosynthesis; D015854:Up-Regulation
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D053245:RANK Ligand; C493709:RUNX2 protein, human; C505688:TNFSF11 protein, human; D001663:Bilirubin