title: X-ray radiation at low doses stimulates differentiation and mineralization of mouse calvarial osteoblasts.
abstract: Radiotherapy is considered to cause detrimental effects on bone tissue eventually increasing bone loss and fracture risk. However, there is a great controversy on the real effects of irradiation itself on osteoblasts, and the mechanisms by which irradiation affects osteoblast differentiation and mineralization are not completely understood. We explored how X-ray radiation influences differentiation and bone-specific gene expression in mouse calvarial osteoblasts. Irradiation at 2 Gy not only increased differentiation and mineralization of the cells, but also upregulated the expression of alkaline phosphatase, type I collagen, osteopontin, and osteocalcin at early stages of differentiation. However, irradiation at higher doses (>2 Gy) did not stimulate osteoblast differentiation, rather it suppressed DNA synthesis by the cells without a toxic effect. Additional experiments suggested that transforming growth factor-beta 1 and runt-transcription factor 2 play important roles in irradiation- stimulated bone differentiation by acting as upstream regulators of bone-specific markers.
authors.affiliation: Department of Orthodontics, Chonbuk National University, Jeonju, Korea.
authors.forename: Soon-Sun
authors.initials: SS
authors.lastname: Park
authors.forename: Kyoung-A
authors.initials: KA
authors.lastname: Kim
authors.forename: Seung-Youp
authors.initials: SY
authors.lastname: Lee
authors.forename: Shin-Saeng
authors.initials: SS
authors.lastname: Lim
authors.forename: Young-Mi
authors.initials: YM
authors.lastname: Jeon
authors.forename: Jeong-Chae
authors.initials: JC
authors.lastname: Lee
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002113:Calcification, Physiologic / Q000528:radiation effects; D002454:Cell Differentiation / Q000528:radiation effects*; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011839:Radiation, Ionizing; D012886:Skull / Q000166:cytology; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D024042:Collagen Type I; D050659:Core Binding Factor Alpha 1 Subunit; D016207:Cytokines; D012333:RNA, Messenger; C493716:Runx2 protein, mouse; D053773:Transforming Growth Factor beta1; D015675:Osteocalcin; D053495:Osteopontin; D000469:Alkaline Phosphatase