Effects Of Compressive Strain On The Expression Of Membrane Type-1Matrix Metailoproteinase Of Osteoblast-like Cells MG63in Vitro

Objective and background:The alveolar is the strongest plasticity and the most active metabolicin bone tissue. Under physiological conditions,alveolar with toothfunctional stimulation keep the osteoclasts and osteoblasts dynamicbalance, to make bone tissue stable relatively.After missing teeth, theresidual ridge will occurs chronic,progressive and irreversible absorption.However, the absorption of the residual ridge is the important factors thataffect clinical work.Stress factor is not only the main factors to residualridge resorption, but also the human to take intervention measures tochange.Wang Jingyun etc, found that stress is closely related to residualridge resorption.Chewing stress is too much,it will accelerate theabsorption of residual ridge resorption;Only reasonable chewing stresscan delay the absorption of residual ridge resorption.As a new type of gene expression in the cell membrane surface,membrane type-1matrix metalloproteinase1(MT1-MMP) was foundby Sato from the expression in human embryonic cDNA library,encodingprotein containing582amino acids for the first time. Recently, researchhave found that as the first membrane-type MMPs in a family of MMPs,MT1-MMP plays an important role in normal bone development and remodeling of bone. Not only MT1-MMP is closely related to boneremodeling, but also activating other MMPs and cytokines affect boneremodeling proces;MT1-MMP plays an important role in thesusceptibility of the cell machinery;also it can determine thedifferentiation of osteoblast to osteocyte.To investigate the roleMT1-MMP in bone tissue that it has important significance to mastery ofdiseases and prevention methods related to bone tissue.Using the four-point bending mechanical loading apparatus, theexperiment detect the expression levels of MT1-MMP under the aspect ofstrain dimension and time by Western Blot and RT-PCR in MG-63.Itprovides an experimental basis to research on the mechanism ofMT1-MMP in osteoblast,further to confirm the cell under stress willchange a series of cytology and biology,and to establish theory basisbetween chewing pressure and residual ridge resorption.Methods:Applying Four-point bending mechanical loading apparatus exertcompressive stress on MG63cell that cultured, the frequency of0.5Hz.Setting stress gradient changes and a single level, research compressivestress at different forces (0、1000μstrain、2000μstrain、4000μstrain、6000μstrain) and different times (0、1h、3h、6h、9h、12h) observe itsinfluence on MT1-MMP expression. Each experiment was repeated3times and the control group was not applied strength; In addition to the stress factors, other factors controlled identically.Results:1. When the value of the constant strain of2000μ strain, themechanical stimulation showed a time dependence increase in theexpression of MT1-MMP protein and gene on osteoblast-like cellsMG63.2. When the strain is2000μstrain, MT1-MMP gene and proteinexpression was the strongest on MG63cells,when the strain is6000μstrain, MT1-MMP expressed the least.Conclusion:1. Within the physiological range, when a constant stress applied toMG63cells,MT1-MMP expression was increased in time dependence.2. When the stress loading was the same, with the increase of thestrength,the expression of MT1-MMP increased, beyond thephysiological range,the expression was reduced.3. The suitable stress played an important role in the regulation ofbone remodeling process.