title: Expression of BMP-receptor type 1A correlates with progress of osteoarthritis in human knee joints with focal cartilage lesions.
abstract: OBJECTIVE
  Bone morphogenetic protein-2 (BMP-2) and its receptor type 1A (BMPR-1A) play significant roles in cartilage metabolism. The aim of this study was to evaluate a possible correlation between intra-articular expression of these proteins and the degree of osteoarthritis (OA) in human knees.
  
  
  METHODS
  Biopsies of synovia and debrided cartilage were taken in 15 patients undergoing autologous chondrocyte implantation. Expression of BMP-2 and BMPR-1A was evaluated semi-quantitatively by immunohistologic staining. These data were complemented by grading of cartilage lesions according to International Cartilage Repair Society (ICRS), defect size, duration of complaints, knee osteoarthritis scoring system (KOSS) and Henderson and Kellgren-Lawrence scores. General histologic stainings were used to determine Mankin, Pritzker and Krenn scores.
  
  
  RESULTS
  The expression of BMPR-1A but not of BMP-2 was significantly higher in cartilage biopsies taken in type 3 lesions with intact subchondral layer compared with type 4 defects (P < 0.05). In cartilage areas of bordering sectors, the intensity of immunohistologic staining of BMPR-1A was statistically significantly higher in mature cartilage compared with repair zones (P < 0.05). Expression of BMP-2 and its receptor 1A correlated in the cartilage biopsies (P < 0.02) but not in the synovia. The degree of OA was scored in all biopsies according to Mankin and Pritzker, and these scores correlated statistically significantly with BMPR-1A expression in the synovia (P < 0.05). In patients with an osteochondritis dissecans, the degree of OA was higher compared with other causes of chondromalacia, as evaluated by defect size, ICRS score, duration of complaints, Pritzker score and expression of BMPR-1A in cartilage (P < 0.05).
  
  
  CONCLUSIONS
  These data support the role of BMPR-1A as an indicator of OA progression in human knees with circumscribed cartilage lesions.
authors.affiliation: Department of Orthopaedic Surgery, University of Freiburg Medical Center, Freiburg, Germany. hagen.schmal@freenet.de
authors.forename: Hagen
authors.initials: H
authors.lastname: Schmal
authors.forename: Ingo H
authors.initials: IH
authors.lastname: Pilz
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Mehlhorn
authors.forename: David
authors.initials: D
authors.lastname: Dovi-Akue
authors.forename: Christina
authors.initials: C
authors.lastname: Kirchhoff
authors.forename: Norbert P
authors.initials: NP
authors.lastname: Südkamp
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gerlach
authors.forename: Philipp
authors.initials: P
authors.lastname: Niemeyer
mesh_terms: D000328:Adult; D001706:Biopsy; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000235:genetics / Q000378:metabolism; D002356:Cartilage / Q000378:metabolism / Q000473:pathology; D018450:Disease Progression; D005260:Female; D015870:Gene Expression; D006801:Humans; D007719:Knee Joint / Q000378:metabolism / Q000473:pathology; D008297:Male; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D013582:Synovial Fluid / Q000378:metabolism
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D052005:Bone Morphogenetic Protein Receptors, Type I