Expression of Osterix in mechanical stress‐induced osteogenic differentiation of periodontal ligament cells in vitro

Abstract

Osterix (Osx) is an osteoblast-specific transcription factor required for the differentiation of pre-osteoblasts into functional osteoblasts. This study sought to examine the changes of Osx expression in periodontal ligament cells (PDLC) subjected to mechanical force, and to investigate whether Osx is involved in the mechanical stress-induced differentiation of PDLC. Human PDLC were exposed to centrifugal force for 1-12 h. Real-time polymerase chain reaction (PCR), western blot, and immunofluorescence assays were used to examine the mRNA and protein expression of Osx and its subcellular localization. Furthermore, PDLC were transfected with the expression vector pcDNA3.1 flag-Osx and subjected to mechanical force for 6 h. The changes in alkaline phosphatase (ALP) activity and in the expression of core-binding factor alpha1 (Cbfa1), ALP, osteopontin, bone sialoprotein, osteocalcin, and collagen I were measured. After the application of mechanical force, Osx was upregulated in a time-dependent manner at both mRNA and protein levels, and Osx protein was translocated from the cytosol into the cell nuclei. Overexpression of Osx did not affect the expression of Cbfa1, but it significantly enhanced the ALP activity and the mRNA expression of all the aforementioned osteogenic marker genes, all of which increased further under mechanical stress. These results suggest that Osx might play an important role in the mechanical stress-induced osteogenic differentiation of PDLC and therefore be involved in alveolar bone remodeling during orthodontic therapy.

miR-93/Sp7 function loop mediates osteoblast mineralization

“…Many pivotal genes in mineralization of the bone matrix such as collagen 1 (a1), bone sialoprotein, osteopontin, and osteocalcin were regulated by Sp7. (26,27) Furthermore, Baek and colleagues (28) have concluded that Sp7 continues to be required for bone formation in growing and adult bones. Due to this critical regulation of the osteoblast phenotype by Sp7, identifying upstream regulators of this gene is the key to our understanding of osteoblast mineralization.…”

p38 Regulates Expression of Osteoblast-specific Genes by Phosphorylation of Osterix

“…Several evidences also indicate that p38 activity modulates Osx expression induced by BMP in calvarial as well as bone marrow-derived mesenchymal stem cells (17,20,24,27). Similarly, other osteogenic stimuli such as mechanical stress, drugs, or cytokines exert their osteogenic effects through activation of p38 followed by an increase in Osx expression and function (17,(45)(46)(47). Our results provide a mechanism by which BMP-2-activated p38 could enhance transcriptional activity of Osx through direct phosphorylation on Ser-73 and Ser-77.…”

Localization of osteopontin and osterix in periodontal tissue during orthodontic tooth movement in rats

“…OPN reactivity in the cement line and surface of cementum and alveolar bone might be induced by osterix expression. Their strong localization in periodontal tissues when 100 g of heavy force was applied indicates that they might be molecules linking mechanostressing and osteogenic and odontogenic differentiation 20,23,24 and might be involved in bone, PDL, and cementum remodeling during orthodontic tooth movement. The precise relationship between OPN and osterix during periodontal tissue remodeling in response to heavy force could not be ascertained with the current methodology.…”