The Association Study Between Genetic Variation Of LncRNA? MAPK/ERK And Knee Osteoarthritis

Knee osteoarthritis(KOA)is the most common joint disease worldwide,characterized by progressive degeneration of articular cartilage,synovitis,osteophyte formation,and subchondral bone sclerosis.KOA has the highest incidence in all kinds of osteoarthritis.It can cause severe pain and physicaldisability thus substantially reduces elder people's quality of life.The expenditure for KOA has increased enormously recent years and causes a huge burden on medical insurance system.With the aging situation in China continuously accelerating,the burden of KOA caused on people's health and finance system is more and more heavy,so how to solve this problem becomes an urgent issue.Although the incidence of osteoarthritis is still increasing,affecting approximately 10% of men and 18% of women over 60 years old,its pathophysiology is still evolving and undetermined.KOA lacks specific diagnostic criteria,so patients were often found in late stage of KOA when felt uncomfortable and visiting hospital.The treatment for KOA includes conservative treatment or surgery.Conservative treatment includes physical therapy,drug therapy,brace therapy and so on.Conservative treatment is only effective for part of patients and some patients have side effects.Surgery includes arthroscopy,arthroplasty,arthrodesis and periarticular osteotomy.Surgery is effective against late stage KOA but its cost increases greatly.But some patients are still not satisfied with the results of surgery and some of them may encounter operative complications like periprosthetic joint infection,periprosthetic joint fracture,prosthetic loosening and so on.Therefore in future,better understanding of biomarkers of KOA would be helpful for individualized diagnosis and treatment of KOA patients.Twin-pair studies and family-based segregation analyses have both showed clear evidence of a heritable component in the susceptibility of KOA.Researches have shown evidence that genetic factors may play a vital role in the development of OA,although little of them have been identified so far.Long noncoding RNAs(lncRNA)have been tentatively defined as a type of RNA molecule more than 200 nucleotides in length(while microRNAs are of 20–22 nucleotides in size)and are characterized by their complexity and diversity of sequences and mechanisms of action.Several lncRNAs have been reported play an important role in the pathogenesis of osteoarthritis.Aberrant expression profile of lncRNAs in damaged bone and cartilage of OA patients has been reported recently,indicating its potential contributions in OA development and a promising target for disease diagnosis and treatment.However,the role of lncRNAs played in cartilage metabolism and their overall contributions to the degradation of chondrocyte extracellular matrix and the pathogenesis of OA are still not fully understood.Considering the important roles lncRNA played in cartilage anabolism and catabolism,we hypothesized that single nucleotide polymorphisms(SNPs)in lncRNA gene may individually or jointly contribute to the risk of osteoarthritis.Previous studies have indicated that the mitogen-activated protein kinase(MAPK)pathway is a fundamental pathway for IL-1?-induced catabolic metabolism in human articular chondrocytes.The MAPK pathway is comprised of ERK1/2,JNK family and p38.Some studies have demonstrated that IL-1? induces the release of MMP3 and MMP13 in articular chondrocytes through the activation of ERK1/2.On the other hand,the MAPK/ERK pathway is also involved in IL-1?-induced decrease of type II collagen and aggrecan expression in chondrocyte-laden agarose constructs.Other studies have shown that inhibition of the MEK/ERK pathway can decrease the development of structural changes in OA.Taken together,these researches indicate that MAPK/ERK pathway may be an important therapeutic target for OA therapy.ERK1 and ERK2 are two isoforms of ERK.However,the roles of ERK1 and ERK2 in the IL-1?-regulated expression of MMP3,MMP13,type II collagen and aggrecan in human chondrocytes are still poorly understood.RegulomeDB,a database integrates a big collection of regulatory information from ENCODE and other data sources,is a powerful tool to select functional SNPs in a specified chromosome region.RegulomeDB presents a scoring system with categories ranging from 1 to 6 by the way of integrated annotations data on methylation,chromatin structure,protein motifs and binding.The lower RegulomeDB score indicates stronger evidence for a variant to be located in a functional region.Consequently,clarification of lncRNA and MAPK/ERK pathway roles is of major importance for providing new insights into the pathology of KOA.In the present study,we examined the relationship between lncRNA,MAPK/ERK pathway gene polymorphism and KOA susceptibility.Our study will able to find potential genetic susceptibility to help early diagnosis and individualized treatment for KOA.Part I: Putative functional variants of lncRNAidentified by RegulomeDBwere associated with knee osteoarthritis susceptibilityOsteoarthritis(OA)is the most common form of chronic degenerative joint disease worldwide which may affect all joint tissues.Considering the increase in average life expectancy of Chinese population,its incidence has increased in recent years.Genetic factors play a considerable role in the pathogenesis of osteoarthritis.Long noncoding RNA(lncRNA)correlates with the development of many types of inflammation-related diseases.Aberrant expression profile of lncRNAs in damanged bone and cartilage of OA patients has been reported recently,indicating its potential contributions in OA development and a promising target for disease diagnosis and treatment.However,the role of lncRNAs played in cartilage metabolism and their overall contributions to the degradation of chondrocyte extracellular matrix and the pathogenesis of OA are still not fully understood.The aim of this study was to identify the association between lncRNA polymorphism and osteoarthritis.Venous blood samples were collected from 278 patients with knee osteoarthritis(KOA)and 289 ageand sex-matched OA-free controls of Chinese Han population at Changzhou NO.1 people's hospital between 2014 and 2017.The severity of the osteoarthritis was assessed by the Kellgren-Laurence(K-L)grading system.RegulomeDB,which is a database that annotates regulatory functions of genetic variants,was used to investigate potential regulatory functions of lead single nucleotide polymorphisms(SNPs)identified in all already reported OA related lncRNA genes.The association was further analyzed according to gender,age and body mass index(BMI).Logistic regression revealed that H19 rs2067051 was significantly associated with knee osteoarthritis risk [homozygote genetic model(OR=0.61,95% CI: 0.39-0.95,P=0.03),recessive genetic model(OR=0.63,95% CI: 0.42-0.97,P=0.03)and additive genetic model(OR=0.79,95% CI: 0.64-0.98,P=0.03)respectively].rs4378559(MEG3)was significantly associated with the increased risk of knee osteoarthritis in additive genetic model(OR=1.32,95% CI: 1.01-1.74,P=0.04),but the association no longer exist after adjust.These results indicate that lncRNA plays an important role in the pathogenesis of OA.Taken together it means that H19 may be new biomarkers for diagnosis or novel therapeutic targets of OA.Part II: Putative functional variants of MAPK/ERK identified by RegulomeDB were associated with knee osteoarthritis susceptibilityIt is well recognized that proinflammatory cytokines play important roles in the development of OA.IL-1? is considered to be one of the key cytokines involved in articular cartilage destruction.IL-1? was reported to induce the expression of MMP3 and MMP13 in chondrocytes through activation of the MAPK/ERK pathway.MAPK/ERK pathway may be particularly important for the IL-1?-mediated regulation of catabolism and anabolism responsible for articular cartilage degradation.To investigate the relationship of genetic variations in MAPK/ERK pathway with knee osteoarthritis risk,this study try to find the association between polymorphism of MAPK/ERK pathway gene and susceptibility of KOA.A case-control study was conducted including 278 patients with knee osteoarthritis and 289 age and sex matched healthy controls.A total of 5 potentially functional variations in MAPK/ERK pathyway(MEK1,MEK2,ERK1 and ERK2)selected by RegulomeDB were genotyped by using SequenomMassARRAY.Univariate and multivariate logistic regression models were used to evaluate the association and its strength.In univariate analysis,rs350911 of MEK2 was significantly associated with knee osteoarthritis in recessive model(TT vs.TC+ CC)(OR =1.50,95% CI: 1.01-2.23,P=0.04).After adjustment for age,gender and BMI,the associations remain significant(OR=1.54,95% CI: 1.02-2.31,P=0.04).The stratification analyses revealed that the effect of rs350911 on knee osteoarthritis was significant in male,lower BMI(<25)(all P< 0.05).P value for heterogeneity test was lower than 0.01 in different gender group.The results indicate that potential functional genetic variation in MAPK/ERK plays an important role in the pathogenesis of knee osteoarthritis.