ABSTRACT
Objective@#To study the effect of continuous static pressure on the endoplasmic reticulum of human periodontal ligament cells (hPDLCs) and the mechanism of osteogenic differentiation.@*Methods@#hPDLCs cultured in vitro were subjected to 1 g/cm 2 of continuous compressive pressure (CCP) by custom-made, round, glass panes for 0, 2, 4, and 6 h, respectively. Alkaline phosphatase staining was used to detect osteogenic differentiation, and real-time quantitative PCR was used to detect the expression of protein kinase receptor-like ER kinase (PERK), eukaryotic translation initiation factor 2α (eIF2α), and transcription activation factor 4 (ATF-4). The 0 h loading group was the control group.@*Results@#After CCP treatment, the alkaline phosphatase staining of hPDLCs was blue-violet and significantly stronger than that of cells in the control group. The expression levels of PERK and ATF4 in the hPDLCs after CCP treatment were higher than those of cells in the control group (P < 0.05) and increased over time (P < 0.05). The expression of eIF2α was lower in the experimental groups than in the control group (P < 0.05) and decreased over time (P < 0.05).@*Conclusion @#Mechanical stimulation can activate ERS in hPDLCs, leading to enhanced PERK-eIF2α-ATF4 signaling and inducing osteogenic differentiation.
ABSTRACT
Objective To study the effect of continuously compressive pressure(CCP) and human periodontal ligament cells(HPDLCs) on the differentiation of osteoclast-like cells(OLC) induced from umbilical cord blood cells in vitro,and to investigate the role of continuously compressive pressure and human periodontal ligament cells in alveolar bone rebuilding during orthordontic tooth movement.Methods Mononucleared cells of umbilical cord blood(HCMNCs) were separated by density gradient centrifugation,HPDLCs were isolated from human periodontal ligament by explanting enzymatic digestion with trypsin and collagenase.We also established transwell co-culture system with HCMNCs in the lower layer and HPDLCs in the upper layer.Group A: HCMNCs and HPDLCs were co-cultured with 150 kPa CCP for 1.5 hours on the model.Group B: only HCMNCs were cultured with the same CCP as Group A.Groups A'and B' were the respective control group of Groups A and B with no CCP exerted.The cell appearance was observed under the phase contrast microscope,and its identification was performed by histochemical analysis of tartrater-resistant acid phosphatase(TRAP).The capacity of bone resorption of the cell was assessed by lacunae forming ability on bone slice.Results HCMNCs in Group A began to fuse on the 2nd day,More positive multinucleated cells could be seen with TRAP staining and cortical bone pit formation on the 3rd day.Only a few multinucleated cells formed in the other groups,with no cortical bone pit formation.Conclusion HCMNCs can fuse into multinucleated OLC under CCP with the induction of HPDLCs.