title: Clinical and laboratory characteristics of patients having amyloidogenic transthyretin deposition in osteoarthritic knee joints.
abstract: OBJECTIVE
  Our aim was to investigate clinical and laboratory characteristics of osteoarthritic patients who had amyloid deposition in their knee joints.
  
  
  METHODS
  Synovial membranes were obtained from 36 patients with knee osteoarthritis (OA) who underwent joint replacement surgery. From this sample, the diagnosis of amyloid was determined by Congo red staining, which demonstrated apple-green birefringence under a polarized microscope. All synovial membranes were immunohistochemically characterized for the expressions of amyloid immunoglobulin light chain (AL-κ and AL-λ), serum amyloid-A (SAA), amyloidogenic transthyretin (ATTR), and amyloidogenic β2-microglobulin (Aβ2M). Matrix-assisted laser desorption-ionizaton/time of flight mass spectrometry (MALDI-TOF MS) was used to analyze transthyretin (TTR) isoforms in the serum of each patient.
  
  
  RESULTS
  Nine cases (25%) were found to be amyloid-positive. Immunohistochemically, eight cases (88.9%) had ATTR deposition, and one sample (11.1%) was shown to be AL-κ-positive. MALDI-TOF MS identified that the TTR in the serum of the patients was unmodified wild-type TTR, TTR-Cys-S-S-Cys, and TTR-Cys-S-S-CysGly. The age at surgery and the disease duration were significantly higher in the ATTR-positive group than in the ATTR-negative group. Knee score and function score were significantly lower in the ATTR-positive group than in the ATTR-negative group.
  
  
  CONCLUSIONS
  Amyloid deposition in synovial membranes of OA patients was found to be ATTR and AL-κ. TTR in the serum of the patients was unmodified wild-type TTR together with two isoforms. The high age at surgery, long disease duration, and a deteriorated knee function were associated with ATTR amyloid deposition in the osteoarthritic knee joints.
authors.affiliation: School of Medical Laboratory, Tianjin Medical University, Tianjin 300203, China; Department of Clinical Laboratory, Tianjin Medical University Cancer Institute and Hospital, Tianjin 300060, China; Department of Clinical Laboratory, Tianjin Children's Hospital, Tianjin 300074, China.
authors.forename: Ya-jun
authors.initials: YJ
authors.lastname: Gu
authors.forename: Peng
authors.initials: P
authors.lastname: Ge
authors.forename: Yun
authors.initials: Y
authors.lastname: Mu
authors.forename: Jin-hai
authors.initials: JH
authors.lastname: Lu
authors.forename: Fang
authors.initials: F
authors.lastname: Zheng
authors.forename: Xu-guo
authors.initials: XG
authors.lastname: Sun
mesh_terms: D000368:Aged; D028227:Amyloid Neuropathies, Familial / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D011228:Prealbumin / Q000378:metabolism*; D016059:Range of Motion, Articular
chemical_list: D015415:Biomarkers; D011228:Prealbumin