title: FGF23-regulated production of Fetuin-A (AHSG) in osteocytes.
abstract: BACKGROUND
  AHSG, a serum glycoprotein with recognized anti-calcification activity, has also been suggested to modulate both bone formation and resorption. Though the bulk of AHSG is mostly synthesized in the liver, it has been claimed that also bone cells might produce it. However, the extent of the bone AHSG production and the potential controlling factors remain to be definitively proven. A relevant number of studies support the notion that FGF23, a bone-derived hormone, not only regulates the most important mineral metabolism (MM) related factors (phosphate, parathyroid hormone, vitamin D, etc.), but might be also involved in cardiovascular (CV) outcome, both in chronic kidney disease (CKD) patients and in the general population. Furthermore, in addition to some direct autocrine and paracrine effects in bone, FGF23 has been suggested to interact with AHSG. In this study we investigated if AHSG is really produced by bone cells, and if its bone production is related and/or controlled by FGF23, using cultured bone cells, according to a new method recently published by our group.
  
  
  RESULTS
  Our data show that AHSG is consistently produced in osteocytes and to a far lesser extent in osteoblasts. Both FGF23 addition to the culture medium and its over-expression in osteocytes were associated with a consistent increase of both AHSG mRNA and protein, while FGF23 silencing was followed by opposite effects. Though most of these results were largely affected by the blockage of FGF23 receptors, the role of these receptors in the different experimental sets is still not completely clarified. In addition, we found that FGF23 and AHSG proteins co-localized both in cytoplasm and nucleus, which suggests a possible reciprocal interactivity.
  
  
  CONCLUSIONS
  Our data not only confirm that AHSG is produced in bone, mainly in osteocytes, but show for the first time that its production is modulated by FGF23. Since both proteins play important roles in the bone and cardiovascular pathology, these results add new pieces to the puzzling relationship between bone and vascular pathology, in particular in CKD patients, prompting future investigations in this field.
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: deborah.mattinzoli@gmail.com.
authors.forename: D
authors.initials: D
authors.lastname: Mattinzoli
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: mariapia.rastaldi@policlinico.mi.it.
authors.forename: M P
authors.initials: MP
authors.lastname: Rastaldi
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: aquamarine0321@libero.it.
authors.forename: M
authors.initials: M
authors.lastname: Ikehata
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: armellonis@libero.it.
authors.forename: S
authors.initials: S
authors.lastname: Armelloni
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: chiarapignatari@gmail.com.
authors.forename: C
authors.initials: C
authors.lastname: Pignatari
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: giardinolaura@gmail.com.
authors.forename: L A
authors.initials: LA
authors.lastname: Giardino
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: li_min@libero.it.
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: carlo.alfieri1@gmail.com.
authors.forename: C M
authors.initials: CM
authors.lastname: Alfieri
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: anna.regalia1@gmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Regalia
authors.affiliation: Division of Pathophysiology and Repair, School of Biosciences, Cardiff University, Cardiff, UK. Electronic address: riccardi@cardiff.ac.uk.
authors.forename: D
authors.initials: D
authors.lastname: Riccardi
authors.affiliation: Renal Research Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico & Fondazione D'Amico per la Ricerca sulle Malattie Renali, via Pace 9, 20122 Milano, Italy. Electronic address: pmessa@policlinico.mi.it.
authors.forename: P
authors.initials: P
authors.lastname: Messa
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D003470:Culture Media; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D008297:Male; D008807:Mice, Inbred BALB C; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D010011:Osteocytes / Q000187:drug effects / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D017468:Receptors, Fibroblast Growth Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D013977:Tibia / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D060749:alpha-2-HS-Glycoprotein / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D003470:Culture Media; C000717427:FGF23 protein, human; C000717428:Fgf23 protein, mouse; D012333:RNA, Messenger; D017468:Receptors, Fibroblast Growth Factor; D011994:Recombinant Proteins; D060749:alpha-2-HS-Glycoprotein; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23
keywords: AHSG; Chronic kidney disease; FGF receptor; FGF23; Osteocyte; Vascular calcification