Cartilaginous Metabolomic Profiling Of Osteophyte In Osteoarthritis Via UPLC/MS-MS

BackgroundKnee osteoarthritis is one of the most common degenerative joint disorders,characterized by cartilage breakdown,osteophyte formation,and subchondral bone sclerosis.Although pathological endochondral ossification is the mean reason of the degenerative process,the molecular mechanisms are not clear to date.Metabolomics is a a new branch of science,which is able to detect all small metabolites of body fluids,perform various statistical analyses,identify specific biomarkers,and then reveal the mechanisms of the occurrence and developing of diseases.ObjectiveThis study was aimed to explore the mechanism of osteophyte formation based on the metabolomic platform and multivariate analysis software.MethodsThe study subjects consisted of 34 osteophyte tissues and 32 control cartilage tisues.Ultra-performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS)was adopted in the detecting of the metabolomic profiles of the two groups of cartilage tissues based on reversed-phase liquid chromatography(RPLC)and Hydrophilic interaction liquid chromatography(HILIC)columns.The raw data were standardized and exported by using Markerview software,and then principal component analysis(PCA)and orthogonal partial least-squares discriminant analysis(OPLS-DA)were performed by using Simca-P software.Variable important in the projection(VIP)values of each peak were exported from best-fitted OPLS-DA models.Univariate statistical analysis was also performed by using SPSS software(paired t-test or signed rank test).Features with both multivariate statistical and univariate statistical significance were further identified by mass spectrum match,tandem mass spectrum match,and standards match.Identified metabolites were included to the metabolic pathway analysis by using Metaboanalyst.ResultsThe samples were recruited from cartilage tissues of osteophyte or posterior femoral condyle among 34 patients with total knee arthroplasty.The average age of the patients was 65.88 ± 9.45,and the average duration of knee pain was about 9 years.PCA models failed to distinguish the difference between the 2 groups,while by using OPLS-DA models,osteophyte group was significantly separated from control group in all 4 modes.After the selection and identification of features,there were 28 metabolites including amino acids,sulfonic acids,glycerophospholipids and fatty acyls.These metabolites were related to some specific physiological or pathological processes(collagen dissolution,boundary layers destroyed,self-restoration triggered,etc)which might be associated with the procedure of osteophyte formation.Pathway analysis showed phenylalanine metabolism(PI=0.168,p=0.004)was highly correlative to this degenerative process.Our findings provided a direction for targeted metabolomic study and an insight to further reveal the molecular mechanism of ostophyte formation.ConclusionThis metabolomic study was carried in order to investigate the metabolic profiles of osteophyte via UPLC-MS/MS platform as well as multivariate statistical analysis models.Many metabolites like phenylalanine,taurine,tyrosine,and several glycerophospholipids,were all found associated with osteophyte formation.Phenylalanine was the most relevant pathway of this degenerative process.Our findings provided a direction for targeted metabolomic study and an insight to further reveal the molecular mechanism of ostophyte formation.