Role Of LncRNA H19 In Mice With Post-traumatic Osteoarthritis

Objective:Osteoarthritis(OA)is a chronic degenerative disease characterized by articular cartilage degeneration,subchondral bone remodeling,osteophyte formation,synovial inflammation and angiogenesis.The occurrence of OA may be influenced by heredity,environment,metabolism and mechanical stress.Post traumatic arthritis(PTOA)is a kind of OA,which occurs frequently in teenagers.Violent trauma,load-bearing imbalance and excessive activity or load-bearing often led to PTOA.However,the specific pathogenesis is not understanded clearly.In recent years,there are more and more researches on long-chain noncoding RNAs(lncRNAs).LncRNA H19 is highly conservative in the evolution process.It plays an important regulatory role in many diseases such as tumor,inflammation and skeletal muscle disease,and may participate in the regulation of chondropathy in PTOA.Therefore,in this study,high-intensity treadmill exercise was used to induce PTOA on mice and medium-intensity treadmill exercise was used to carry out rehabilitation training,to explore the expression changes of lncRNA H19 in the process of pathogenesis and rehabilitation of the mice with PTOA,so as to provide the basis for the study of the relevant mechanism of exercise recover PTOA.Methods:Twenty-week-old male C57BL/6 mice were randomly divided into 5 groups:model control group(MC group,n=6),treadmill model group(TM group,n=6),rehabilitation control group(RC group,n=6),treadmill model+rehabilitation training group(TM+R group,n=6)and treadmill model+convalescent group(TM+C group,n=6).MC group as model control group did not carry out any exercise intervention.In group TM,one week’s pre adaptation exercise and four week’s high-intensity treadmill exercise were performed,and the mice in group TM and MC were killed at the age of 25 weeks;as for group RC,as the rehabilitation control group,no exercise intervention was conducted,and in Group TM+R,four week’s pre adaptation exercise and four week’s high-intensity treadmill exercise were performed,and in group TM+C,one week’s pre adaptation exercise and four week’s high-intensity treadmill exercise were performed,without any exercise intervention in next four weeks.The mice of RC group,TM+R group and TM+C group were sacrificed at 29 weeks old.Mice in each group were fasted and fed water normally the day before the deadline.Decalcification and paraffin embedding were used to observe the pathological changes of the knee joint of mice in each group.Micro CT was used to scan the subchondral bone of mice knee joint to obtain the morphological indexes of the tibial plateau bone;real-time PCR was used to detect the mRNA levels of inflammatory factors,synthetic and catabolic factors in the knee joint cartilage.All results were expressed as mean standard deviation(X±SD)and analyzed using SPSS 20.0 software.To judge whether the PTOA model is successful,the independent sample T test was used in MC group and TM group;to judge the rehabilitation effect,the univariate anova was used in RC group,TM+R group and TM+C group,and the bonferrori method was used in the comparison between the two groups,P<0.05,indicating that the results were statistically different.Results:(1)Body weight change:The body weight of MC group dynamicly fluctuate with no significant change as age increase.The weight of mice in TM group decreased continuously during the model period of high-intensity treadmill exercise.The change of body weight in RC group was almost the same as that in MC group.In TM+R group,the body weight decreased continuously during high-intensity treadmill exercise and moderate intensity rehabilitation training,and there was statistical difference after the first week of moderate intensity training intervention.In TM+C group,the body weight decreased continuously during the high-intensity treadmill exercise,but the body weight increased in the first week after the exercise modeling,and then remained stable.(2)Pathological changes of mouse knee joint:The results of hematoxylin eosin staining showed that the cartilage of knee joint in MC group was normal,cracks appeared on the surface of knee joint in TM group,and the arrangement of chondrocytes was disordered.There was significant difference in Mankin’s score between the two groups.Compared with MC group,there was significant cartilage loss in knee joint of M group,OARSI score showed the same.Further study showed that the above pathological changes of the knee joint of mice were partially reversed after the four-week moderate intensity training,and the Mankin’s score of the knee joint of mice in TM+R group was significantly lower than that in TM+C group.(3)Morphological changes of subchondral bone in mice:Micro CT showed that BMD,BV/TV,TB.N and TB.Th of subchondral bone in TM group were higher than those in MC group,while TB.SP was lower.After four weeks of moderate intensity treadmill rehabilitation training,the BMD,BV/TV,TB.N and TB.Th values of the subchondral bone in the tibial plateau of TM+R group were higher than those of TM+C group.Compared with RC group,the above-mentioned bone morphology parameters were also higher in TM+C group.(4)Changes of mRNA expression in mouse knee joint cartilage:After four weeks of high-intensity treadmill exercise,the expression of TNF-α and MMP-13 mRNA in TM group was higher than that in MC group,while the mRNA expression of COL2 and ACAN was lower,and the expression of lncRNA H19 owns same trend.After four weeks of moderate intensity rehabilitation training,compared with TM+C group,the expression of TNF-αand MMP-13 in the articular cartilage of TM+R group decreased,while the expression of COL2 and ACAN increased,and the expression of lncRNA H19 in the cartilage of TM+R group mice was significantly higher than that of TM+C group.Conclusion:High intensity treadmill exercise can cause knee cartilage injury of C57BL/6 mice which led to PTOA,decreasing the expression of lncRNA H19 in articular cartilage;while moderate intensity treadmill exercise can partially reverse the low expression of lncRNA H19 in articular cartilage of PTOA mice.