title: Tissue transglutaminase expression and activity in human ligamentum flavum cells derived from thoracic ossification of ligamentum flavum.
abstract: METHODS
  The study was undertaken to compare the expression and activity of tissue transglutaminase (TG2) in human ligamentum flavum cells derived from ossification of the ligamentum flavum (OLF) and non-OLF patients.
  
  
  OBJECTIVE
  To determine whether TG2 is involved in the pathologic process of OLF.
  
  
  BACKGROUND
  OLF is a disease characterized by heterotopic formation of new bone in the flavum ligament. Recently, TG2 is proved to directly promote skeletal matrix mineralization and play an important role in the ossification. TG2 activity is vital to the differentiation of osteoblasts and the formation of mineralization. But whether TG2 is involved in the pathologic process of OLF is unknown. We investigated the relations between TG2 expression and OLF.
  
  
  METHODS
  OLF and non-OLF cells were cultured and osteocalcin, bone morphogenetic protein-2(BMP-2) and TG2 mRNA expressions were assayed by reverse transcription polymerase chain reaction. Meanwhile, alkaline phosphatase activity and calcified nodules were compared between OLF and non-OLF cells. To detect TG2 expression, Western blot and immunohistochemical analysis were carried out, and TG2 activity was compared between OLF and non-OLF cells.
  
  
  RESULTS
  Our experiments demonstrated that OLF cells showed osteoblast-like activity and increased mRNA expression of BMP-2. More interesting, compared with non-OLF cells, OLF cells showed elevated expression levels of TG2 mRNA and protein, as well as enzyme activity.
  
  
  CONCLUSIONS
  TG2 expression and enzyme activity are upregulated in the OLF cells and TG2 may be involved in the pathologic process of OLF.
authors.affiliation: Department of Orthopaedics, Peking University Third Hospital, Beijing, China.
authors.forename: Xiaoxue
authors.initials: X
authors.lastname: Yin
authors.forename: Zhongqiang
authors.initials: Z
authors.lastname: Chen
authors.forename: Zhaoqing
authors.initials: Z
authors.lastname: Guo
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Liu
authors.forename: Haiyan
authors.initials: H
authors.lastname: Yu
mesh_terms: D000328:Adult; D000368:Aged; D000469:Alkaline Phosphatase / Q000378:metabolism; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D017843:Ligamentum Flavum / Q000378:metabolism* / Q000473:pathology; D008875:Middle Aged; D009999:Ossification, Heterotopic / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D015675:Osteocalcin / Q000378:metabolism; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012333:RNA, Messenger / Q000378:metabolism; D013904:Thoracic Vertebrae / Q000378:metabolism* / Q000473:pathology; D011503:Transglutaminases / Q000378:metabolism*
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D012333:RNA, Messenger; D015675:Osteocalcin; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D000469:Alkaline Phosphatase; D019204:GTP-Binding Proteins