Suppression of osteoblastic phenotypes and modulation of pro- and anti-apoptotic features in normal human osteoblastic cells under a vector-averaged gravity condition.
Spaceflight and bed rest induce loss of bone mass. A number of in vivo and in vitro studies have been conducted to clarify the mechanisms, however, the results have been conflicting. The purpose of this study was to investigate the effects of gravity unloading on proliferation, phenotypes, and apoptosis of normal human osteoblastic cells in the presence of 1alpha,25-dihydroxyvitamin D3. We used a vector-averaged gravity condition generated by clinostat rotation to simulate gravity unloading. Clinostat rotation did not affect the cell proliferation. On the first day, the mRNA levels for osteocalcin, ALP, CBFA1, VDR, RANKL, and OPG were reduced by clinostat rotation to 21%, 65%, 62%, 52%, 43%, and 54% of control, respectively. ALP activity was decreased to 75% of control. On the second day, the mRNA levels for osteocalcin and RANKL were reduced to 77% and 61% of control, respectively. The decreased VDR mRNA level might be responsible for the reduction for mRNA levels for osteocalcin, RANKL, and OPG. Clinostat rotation increased the pro-apoptotic index (Bax/Bcl-2 ratio) but did not induce apoptosis due to the simultaneous upregulation of the anti-apoptotic XIAP. Reduction of osteoblast responsiveness to 1alpha,25-dihydroxyvitamin D3 might be involved in osteopenia that is induced by gravity unloading.
Nakamura
Hiroshi
H
Section of Orthopedic Spinal Surgery, Department of Frontier Surgical Therapeutics, Division of Advanced Therapeutical Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. nakamura.orth@tmd.ac.jp
Kumei
Yasuhiro
Y
Morita
Sadao
S
Shimokawa
Hitoyata
H
Ohya
Keiichi
K
Shinomiya
Kenichi
K
D000469:Alkaline Phosphatase / Q000096:biosynthesis; D017209:Apoptosis; D002117:Calcitriol / Q000494:pharmacology; D002352:Carrier Proteins / Q000096:biosynthesis; D002455:Cell Division; D050659:Core Binding Factor Alpha 1 Subunit; D006023:Glycoproteins / Q000096:biosynthesis; D006801:Humans; D058574:Integrin-Binding Sialoprotein; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D009363:Neoplasm Proteins; D010006:Osteoblasts / Q000187:drug effects / Q000502:physiology*; D015675:Osteocalcin / Q000096:biosynthesis; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger / Q000032:analysis; D053246:Receptor Activator of Nuclear Factor-kappa B; D018167:Receptors, Calcitriol / Q000096:biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis; D018124:Receptors, Tumor Necrosis Factor; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012399:Rotation; D012795:Sialoglycoproteins / Q000096:biosynthesis; D014157:Transcription Factors / Q000096:biosynthesis; D018474:Weightlessness Simulation
D002352:Carrier Proteins; D050659:Core Binding Factor Alpha 1 Subunit; D006023:Glycoproteins; C546871:IBSP protein, human; D058574:Integrin-Binding Sialoprotein; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D018167:Receptors, Calcitriol; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; D012795:Sialoglycoproteins; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; D014157:Transcription Factors; D015675:Osteocalcin; D000469:Alkaline Phosphatase; D002117:Calcitriol