title: Impact of extracellular matrix derived from osteoarthritis subchondral bone osteoblasts on osteocytes: role of integrinβ1 and focal adhesion kinase signaling cues.
abstract: BACKGROUND
  Our recent study indicated that subchondral bone pathogenesis in osteoarthritis (OA) is associated with osteocyte morphology and phenotypic abnormalities. However, the mechanism underlying this abnormality needs to be identified. In this study we investigated the effect of extracellular matrix (ECM) produced from normal and OA bone on osteocytic cells function.
  
  
  METHODS
  De-cellularized matrices, resembling the bone provisional ECM secreted from primary human subchondral bone osteoblasts (SBOs) of normal and OA patients were used as a model to study the effect on osteocytic cells. Osteocytic cells (MLOY4 osteocyte cell line) cultured on normal and OA derived ECMs were analyzed by confocal microscopy, scanning electron microscopy (SEM), cell attachment assays, zymography, apoptosis assays, qRT-PCR and western blotting. The role of integrinβ1 and focal adhesion kinase (FAK) signaling pathways during these interactions were monitored using appropriate blocking antibodies.
  
  
  RESULTS
  The ECM produced by OA SBOs contained less mineral content, showed altered organization of matrix proteins and matrix structure compared with the matrices produced by normal SBOs. Culture of osteocytic cells on these defective OA ECM resulted in a decrease of integrinβ1 expression and the de-activation of FAK cell signaling pathway, which subsequently affected the initial osteocytic cell's attachment and functions including morphological abnormalities of cytoskeletal structures, focal adhesions, increased apoptosis, altered osteocyte specific gene expression and increased Matrix metalloproteinases (MMP-2) and -9 expression.
  
  
  CONCLUSIONS
  This study provides new insights in understanding how altered OA bone matrix can lead to the abnormal osteocyte phenotypic changes, which is typical in OA pathogenesis.
authors.forename: Indira
authors.initials: I
authors.lastname: Prasadam
authors.forename: Saba
authors.initials: S
authors.lastname: Farnaghi
authors.forename: Jian Q
authors.initials: JQ
authors.lastname: Feng
authors.forename: Wenyi
authors.initials: W
authors.lastname: Gu
authors.forename: Samuel
authors.initials: S
authors.lastname: Perry
authors.forename: Ross
authors.initials: R
authors.lastname: Crawford
authors.forename: Yin
authors.initials: Y
authors.lastname: Xiao
mesh_terms: D000368:Aged; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002448:Cell Adhesion; D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000378:metabolism*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D019012:Integrin beta1 / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D010006:Osteoblasts / Q000378:metabolism; D010011:Osteocytes / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D019012:Integrin beta1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9