| [Objective]To study the changes of temporomandibular joint condylar osteoarthritis(TMJ OA)in rats under intermittent and persistent compressive stress.[Method]1.126 8-week-old male SD rats were selected and randomly divided into 5 groups:Control group(C)×18,6 rats per time period;1-day intermittent group(Il)×27,9 rats per time period;3-day intermittent group(13)×27,9 rats per time period;7-day intermittent group(17)×27,9 rats per time period;Persistent group(P)×27,9 rats per time period.The modified device of the stress-loaded animal model of temporomandibular joint was designed by the experimental group,and the compressive stress stimulation on the condylar cartilage of the rat(40g/on each side,loaded on bilateral condyle)was applied.Daily weight changes were recorded,seven days,14 days and 28 days after the death of materials,4%poly formaldehyde solution fixed.2.Paraffin-embedded sections,HE staining,Saffron O staining,Ascension blue staining,Masson staining and TUNEL staining,observed and measured condylar morphology,thickness of cartilage layers,extracellular matrix and number of chondrocytes,immunohistochemical detection of mice condylar chondrocytes of pro-inflammatory factors TNF-,IL-6 and PCNA expression level.Changes of apoptosis of condylar cartilage in rats detected by TUNEL staining3.Micro-CT scanned the condyles.Bone mineral density(BMD),Bone volume fraction(BV/TV),Trabecular separation(Tb.Sp),Trabecular number(Tb.N.),and Trabecular thickness(Tb.Th.)were measured in the central 50x50x50μm3 size of the cartilage.Reconstruction of the three-dimensional image to measure the width and thickness of the anterior and posterior diameters of the condyle.[Results]1.The weight of rats in the persistent group decreased by 20.5%in 28 days.Cartilage thickness changed by-53.6%,-51.2%and-40.7%in 7 days,14 days and 28 days compared with the control group.Cell number changed by-45.0%,-35.7%and-32.8%respectively.Trabecular fraction changed by-14.7%,-19.7%and32.4%,respectively.OARSI score was 25 times,30.5times and 18.9 times of the control group.The percentage of ECM changed by-18.8%,-42.2%,-54.4%respectively.The rate of TNF-α positive cells changed by+8.4%,+5.9%,and+8.0%respectively compared with the control group.The rate of IL-6 positive cells changed by+17.3%,+26.7%,+30.1%respectively compared with the control group.The rate of PCNA positive cells changed by-0.8%,-2.0%,-2.7%respectively compared with the control group.The number of apoptosis of chondrocytes was 20.1 times,11.8 times and 8.4 times respectively of the control group.Subchondral bone height changed by-37.5%,-29.5%and-43.1%respectively.Trabecular separation changed by+7.0%,-34.0%,-0.5%respectively.Trabecular number changed by+28.8%,+41.2%,4.7%respectively.2.The weight loss of rats in the 1-day intermittent group was similar to that of the persistent group;the cartilage thickness,cell number,extracellular matrix,trabecular fraction,and OARSI score at different time points showed the same trend of decrease,but to a lesser extent,compared with the sustained stress group.The trends of TNF-α,IL-6,PCNA,and apoptosis were similar.3.The weight of rats in the 3-day intermittent group increased slightly by 12.3%.The cartilage thickness,cell number,extracellular matrix,trabecular fraction,and OARSI score showed more active and normal reconstruction than those in the persistent group,and the reconstruction in the 3-day intermittent group was better than those in the 1-day intermittent group.The trends of TNF-α,IL-6,PCNA,and apoptosis were more active.4.The weight of rats in the 7-day intermittent group eventually decreased by only 2.3%,but the cartilage thickness and cell-matrix eventually increased,and the OARSI scores tended to be normal,but the changes of the trabecular fraction were similar to those in the persistent group.The positive expression of TNF-α and IL-6 decreased,the expression of PCNA increased,and the number of apoptosis of chondrocytes was similar to those in the control group.[Conclusion]1.In the model of persistent and intermittent compressive stress of temporomandibular joint in rats,cartilage thinning,loss of cartilage matrix,expression of subchondral inflammatory response and other osteoarthritis changes occurred under the condition of stress,while after removing stress,cartilage thickness restored,matrix secretion increased,cell proliferation level increased and other repair reactions occurred.2.The main morphological changes of the condyle process under compressive stress in the three-dimensional direction were the decrease of the height of the vertical plane.Under persistent compressive stress,the trabecular separation decreased,and trabecular number increased,typically in the persistent group and 7day intermittent group.When unloaded the stress,the trabecular separation increased,and trabecular number decreased typically in 1-day intermittent group and 3-day intermittent group.3.The 3-day intermittent group could reflect the destructive changes of joints such as thinning of cartilage,necrosis of inflammation and apoptosis,and also was of good nutrition and adaptability.The 7-day discontinuous group had obvious characteristics of cell proliferation,matrix secretion and the increase of cartilage thickness.They may become the selections for further research. |
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