Tissue Transglutaminase Expression and Activity in Human Ligamentum Flavum Cells Derived From Thoracic Ossification of Ligamentum Flavum

Abstract

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. To determine whether TG2 is involved in the pathologic process of OLF. 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. 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. 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. TG2 expression and enzyme activity are upregulated in the OLF cells and TG2 may be involved in the pathologic process of OLF.