Abstract
Introduction
Objective
To investigate TGFβ regulation of galectin-3 expression in nucleus pulposus (NP) cells and its role in degenerative disc disease.
Materials and Methods
qRT-PCR and Western blot were used to measure galectin-3 expression in NP. Transfections were used to determine role of Smad3 on TGFβ-mediated galectin-3 promoter activity. Lentiviral knockdown of Smad3 was performed to assess the role of Smad3 in galectin-3 expression.
Results
A decrease in galectin-3 expression and promoter activity was observed in NP cells after TGFβ treatment. The same trend was observed in degenerative disc samples. CA-ALK5 treatment resulted in a decrease in basal galectin-3 promoter activity. While DN-ALK5 treatment can block the abolished the suppressive effect of TGFβ on galectin-3 promoter activity. The suppressive effect of Smad3 on galectin-3 promoter was confirmed through gain and loss of function studies. When cells are treated with DN-Smad3 (dominant negative Smad3) or Smad7, cytokine-mediated suppression in galectin-3 promoter activity is completely abolished. To further validate the role of Smad3 and to determine if there is cell type specificity, we measured galectin-3 promoter activity in Smad3 null and wild type mouse fibroblasts. Only in wild type cells is the promoter activity cytokine suppressible. Lentiviral transduction with sh-Smad3 significantly blocked TGFβ dependent decrease in galectin-3 expression.
Conclusion
By controlling the activation of Smad3 signaling, TGFβ modulates the expression of galectin-3 in NP cells. Galectin-3 may play an important role in degenerative disc diseases.
To our knowledge, this is first study that shows that in NP cells TGFβ control galectin-3 transcription in Smad3-dependent fashion.
None declared