RRC ID 61908
Author Hirao M, Hashimoto J, Yamasaki N, Ando W, Tsuboi H, Myoui A, Yoshikawa H.
Title Oxygen tension is an important mediator of the transformation of osteoblasts to osteocytes.
Journal J Bone Miner Metab
Abstract Osteocytes are derived from osteoblasts, but reside in the mineralized bone matrix under hypoxic conditions. Osteocyte-like cells show higher expression of ORP150, which is induced by hypoxia, than osteoblast-like cells. Accordingly, we hypothesized that the oxygen tension may regulate the transformation of osteoblasts to osteocytes. MC3T3-E1 cells and calvariae from 4-day-old mice were cultured under normoxic (20% O(2)) or hypoxic (5% O(2)) conditions. To investigate osteoblastic differentiation and tranformation to osteocytes, alizarin red staining was done and the expression of various factors was assessed. Hypoxic culture promoted the increased synthesis of mineralized matrix by MC3T3-E1 cells. Alkaline phosphatase activity was initially increased during hypoxic culture, but decreased during osteogenesis. Osteocalcin production was also increased by hypoxic culture, but decreased after mineralization. Furthermore, expression of Dmp1, Mepe, Fgf23, and Cx43, which are osteocyte-specific or osteocyte-predominant proteins, by MC3T3-E1 cells was greater under hypoxic than under normoxic conditions. In mouse calvarial cultures, the number of cells in the bone matrix and cells expressing Dmp1 and Mepe were increased by hypoxia. In MC3T3-E1 cell cultures, ORP150 expression was only detected in the mineralized nodules under normoxic conditions, while its expression was diffuse under hypoxic conditions, suggesting that the nodules were hypoxic zones even in normoxic cultures. These findings suggest that a low oxygen tension promotes osteoblastic differentiation and subsequent transformation to osteocytes.
Volume 25(5)
Pages 266-76
Published 2007-1-1
DOI 10.1007/s00774-007-0765-9
PMID 17704991
MeSH 3T3 Cells Alkaline Phosphatase / metabolism Animals Animals, Newborn Blotting, Western Bone Matrix / cytology Bone Matrix / metabolism Cell Differentiation* Cell Hypoxia Connexin 43 / genetics Connexin 43 / metabolism Enzyme-Linked Immunosorbent Assay Extracellular Matrix Proteins / genetics Extracellular Matrix Proteins / metabolism Fibroblast Growth Factor-23 Fibroblast Growth Factors / genetics Fibroblast Growth Factors / metabolism Gene Expression Regulation Glycoproteins / genetics Glycoproteins / metabolism HSP70 Heat-Shock Proteins Immunohistochemistry Mice Organ Culture Techniques Osteoblasts / cytology* Osteoblasts / metabolism Osteocalcin / genetics Osteocalcin / metabolism Osteocytes / cytology* Osteocytes / metabolism Osteogenesis / genetics Oxygen / metabolism* Phosphoproteins / genetics Phosphoproteins / metabolism Proteins / genetics Proteins / metabolism Reverse Transcriptase Polymerase Chain Reaction Skull / cytology Skull / metabolism
IF 2.297
Human and Animal Cells MC3T3-E1(RCB1126)