title: Both systemic and local lipopolysaccharide (LPS) burden are associated with knee OA severity and inflammation.
abstract: The microbiome is recognized as a new frontier in medicine with connections to a variety of diseases. We aimed to evaluate the association of lipopolysaccharide (LPS), a key pro-inflammatory product of the microbiome, with severity of inflammation, symptoms and radiographic abnormalities of knee osteoarthritis (OA).
  
  
  
  LPS was measured using a recombinant Factor C (rFC) assay, carefully optimized for systemic and synovial fluid (SF) analyses. LPS binding protein (LBP) was tested in both serum and SF of 25 patients (31 knees) from the Etarfolatide cohort for association with OA phenotypic outcomes. Models were adjusted for age, gender and body mass index.
  
  
  
  Based on LPS spike-and-recovery, both serum and SF dilutions of 0.1% were required to achieve recovery rates of at least 75% in all test specimens. Low coefficients of variation (CVs) (<10%) were achieved with both serum and SF dilutions <0.2%. Serum LPS and LBP were associated with the abundance of activated macrophages in the knee joint capsule and synovium. SF LPS and LBP were associated with the abundance of activated macrophages in the synovium. Serum LPS, LBP and SF LPS were associated with knee osteophyte severity. SF LPS was positively associated with knee joint space narrowing (JSN) severity and total WOMAC score. SF LBP was positively associated with self-reported knee pain score.
  
  
  
  These data strongly support a role for LPS in the pathogenesis and severity of structural abnormalities and symptoms of knee OA.
authors.affiliation: Department of Orthopedic Surgery, West China Hospital, West China Medical School, Sichuan University, Chengdu, Sichuan Province, People's Republic of China; Duke Molecular Physiology Institute, Department of Medicine, Duke University School of Medicine, Durham, NC, USA. Electronic address: zey.huang@gmail.com.
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Huang
authors.affiliation: Duke Molecular Physiology Institute, Department of Medicine, Duke University School of Medicine, Durham, NC, USA. Electronic address: tvs@duke.edu.
authors.forename: T
authors.initials: T
authors.lastname: Stabler
authors.affiliation: Department of Orthopedic Surgery, West China Hospital, West China Medical School, Sichuan University, Chengdu, Sichuan Province, People's Republic of China. Electronic address: peifuxing@vip.163.com.
authors.forename: F X
authors.initials: FX
authors.lastname: Pei
authors.affiliation: Duke Molecular Physiology Institute, Department of Medicine, Duke University School of Medicine, Durham, NC, USA. Electronic address: vbk@duke.edu.
authors.forename: V B
authors.initials: VB
authors.lastname: Kraus
mesh_terms: D006801:Humans; D007249:Inflammation; D007719:Knee Joint; D008070:Lipopolysaccharides; D020370:Osteoarthritis, Knee; D011859:Radiography; D012720:Severity of Illness Index; D013582:Synovial Fluid
chemical_list: D008070:Lipopolysaccharides
keywords: Biomarker; Inflammation; Knee osteoarthritis; LPS; LPS binding protein; Lipopolysaccharide