375 Mechanical Vibration Induces Differential Responses In Osteocytes Versus Cementoblasts

Thursday, March 22, 2012: 2 p.m. - 3:15 p.m.
Presentation Type: Poster Session
D. LIU1, C. LIU2, and L. YOU2, 1Dept. of Development Sciences/Orthodontics, Marquette University, Milwaukee, WI, 2Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada

To explore differential biological responses of cementoblasts versus osteocytes to mechanical vibration  


Mouse osteocyte cell line MLO-Y4 and cementoblatic cell line OCCM.30 cells were cultured in α-MEM supplemented by 2.5% FBS and 2.5% CS (for MLO-Y4), and 10% FBS (for OCCM.30). The cells (up to the 10th passage) were seeded in 6-well plates coated with type I collagen and grew to 70% (for MLO-Y4) and 100% (for OCCM.30) confluency. Completely filled up with α-MEM with 0.5% FBS and sealed, the 6-well plates were subjected to a low-magnitude (0.3g) and high-frequency (30, 60 and 90Hz respectively) mechanical vibration for 1 hour. To explore the possible involvement of MAPK signaling pathway, a specific MEK1 inhibitor - PD98059 (15μM) was added in designated groups during the vibration. After vibration, the cells were lysed to collect total RNA. Total RNA was extracted and reverse-transcribed to synthesize cDNA. For the genes of RANKL, OPG, and 18S, quantitative PCR was used to amplify the cDNA of the samples using gene-specific primers and SYBR Green I. The copy numbers of RANKL and OPG for each experimental group were normalized to 18S (housekeeping gene) rRNA. Each experiment was repeated at least 3 times, and 3-6 samples for each group. One-way ANOVA was used to compare the results among the groups, with p value being set at 0.05.

Result: Among the 4 experimental groups (0, 30, 60, 90Hz), LMHF mechanical vibration significantly reduced the RANKL/OPG ratio specifically at 60Hz for MLO-Y4 cells (45% down, p<0.01, n=6) and 30Hz for OCCM.30 cells (35% down, p<0.05, n=5). When PD98059 was added during vibration, the vibration-induced reduction of RANKL/OPG ratio was obliterated only in MLO-Y4 cells.   

Conclusion: LMHF mechanical vibration induces differential biological responses in osteocyte and cementoblasts by different specific frequencies, which is partially mediated by MAPK signaling pathway.

Keywords: Biophysics, Bone, Cell culture, Loading and Orthodontics
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