title: Calcium induces pro-anabolic effects on human primary osteoblasts associated with acquisition of mature osteocyte markers.
abstract: Calcium, in combination with vitamin D, is an effective treatment for osteoporosis. Since bone mineralisation occurs concurrently with osteoblast to osteocyte transition, we hypothesised that calcium would stimulate this process. The effect of calcium (1.8-11.8mM) was tested on human primary osteoblast (NHBC) differentiation in vitro. Cultures were assayed for cell-associated mineral and gene expression associated with osteoblast differentiation and mineralisation. Treatment with calcium resulted in a striking dose- and time-dependent increase in cell-associated mineralisation. Calcium appeared to promote osteoblast to osteocyte differentiation, as indicated by increased expression of osteocalcin (OCN), E11, dentin matrix protein 1 (DMP1) and SOST mRNA. The expression of the osteoclast inhibitor, osteoprotegerin, was dramatically enhanced by calcium. Calcium also increased the ratio of PHEX mRNA expression relative to that of MEPE, suggesting a mechanism for the pro-anabolic effect. Consistent with this, calcium-dependent mineralisation was reversed in the presence of MEPE-ASARM peptides. This study suggests that calcium promotes osteoblast to osteocyte transition and concurrent matrix mineralisation, at least in part through the PHEX-MEPE axis.
authors.affiliation: Bone Cell Biology Group, Centre for Orthopaedic & Trauma Research, The University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Katie J
authors.initials: KJ
authors.lastname: Welldon
authors.forename: David M
authors.initials: DM
authors.lastname: Findlay
authors.forename: Andreas
authors.initials: A
authors.lastname: Evdokiou
authors.forename: Renee T
authors.initials: RT
authors.lastname: Ormsby
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Atkins
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D015415:Biomarkers / Q000378:metabolism; D019485:Bone Morphogenetic Proteins / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002454:Cell Differentiation; D004305:Dose-Response Relationship, Drug; D016326:Extracellular Matrix Proteins / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D005819:Genetic Markers / Q000235:genetics; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D010011:Osteocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D053244:Osteoprotegerin / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D053402:PHEX Phosphate Regulating Neutral Endopeptidase / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015415:Biomarkers; D019485:Bone Morphogenetic Proteins; C513309:DMP1 protein, human; D016326:Extracellular Matrix Proteins; D005819:Genetic Markers; D006023:Glycoproteins; C486579:MEPE protein, human; D053244:Osteoprotegerin; D010750:Phosphoproteins; D012333:RNA, Messenger; C422903:SOST protein, human; C506030:TNFRSF11B protein, human; D015675:Osteocalcin; D053402:PHEX Phosphate Regulating Neutral Endopeptidase; C506231:PHEX protein, human; D002118:Calcium
keywords: ASARM; Calcium; Gene expression; Human osteoblast; Mineralisation; OPG/RANKL