The Effects Of Compressive Stress On Proliferation And Apoptosis In SD Rat's Condylar Subchondral Bone Osteoblast In A Vitro Study

[Objective] To establish an experimental model of primary Subchondral bone osteoblasts culture of neonatal SD rat's condylar process in vitro. Discuss the effects of compressive stress on subchondral bone osteoblast in vitro. The flow cytometry method was used to examine the osteoblast proliferation and apoptosis after loading. Researching the changes of osteoblast biological and biomechanical characteristics is to provide the theory basis for the temporomandibular reconstruction and the basic study.[Methods] Cells were cultured with modified repeating enzymatic digestion-adherent explants method. The identification was performed by the invert microscope, immunohistochermistry stain of osteocalcin, alkaline phosphorase (ALP) stain and calcified nodules (by alizarin red S, ARS). The proliferation of the acquired cells was examined by methyl thiazolyl tetrazolium (MTT) assay. Osteoblasts were subjected to mechanical compress strain with four-point bending system at2000μstrain and0.5Hz frequency for lh at the time points of Oh,6h,12h,18h and24h after the stimulation of stress. The flow cytometry method was used to examine the osteoblast proliferation and apoptosis. To set control groups, stress-free cells were also cultured in the same conditions and tested on the same time points accroding to the experiment groups.[Results] This method is an efficient method to culture and obtain purified neonatal SD rat's Subchondral bone osteoblasts. The cultured cells which present the typical morphological characteristics of osteoblasts mineralized nodules:staining of ALP and ARS were positive. One hour after2000μstrain tension loading, the cell proliferation was significantly increased (P<0.05). But it was similar to that of control group at the time points of6h,12h,18h and24h, and there was no significant differences between the experiment and the control groups respectively (P>0.05).The activity of the percentage of cells in S phase was significantly increased (P<0.05) from Oh to24h between the experiment and control groups. It had significantly improved the activity of the percentage of cells in S phase and cell proliferation (P<0.05) from Oh to24h were observed in the experiment groups, but S Phase and cell proliferation have no simple linear relationship. The apoptosis index was significantly decreased (P<0.05) at Oh between the experiment and control groups. But the apoptosis cells were similar to those of control group at the time points of6h,12h,18h and24h, and there was no significant difference between the experiment and control groups respectively (P>0.05).[Conclusions] The experimental, modified repeating enzymatic digestion-adherent explants method can culture and obtain purified neonatal SD rat's Subchondral bone osteoblasts. Appropriate continuous pressure stress can improve the osteoblast proliferation and inhibit apoptosis, but this effect was decreased along with the prolonged time. It meas that the continued pressure stress can promote the growth of osteoblasts, the formation of new bone and remodelling of cartilage bone.