KLF4, negatively regulated by miR-7, suppresses osteoarthritis development via activating TGF-β1 signaling

Int Immunopharmacol. 2022 Jan:102:108416. doi: 10.1016/j.intimp.2021.108416. Epub 2021 Dec 8.

Abstract

Osteoarthritis (OA) is a chronic degenerative disease which seriously affects the patients' daily activities and quality of life. In our previous findings, we demonstrated that overexpression of miR-7 was found in OA and promoted OA development. Its exact mechanism remains unclear. Herein, we confirmed that KLF4 was the target gene of miR-7 and KLF4 was down-regulated in human OA tissues and OA chondrocyte. KLF4 was negatively modulated by miR-7 via dual luciferase reporter assay. Cartilage-specific genes (SOX9, COL2A1, RUNX2, MMP13) are crucial regulators in cartilage degeneration. Through qRT-PCR and western blot, we observed that KLF4 overexpression could increase the expression of SOX9 and COL2A1, decrease RUNX2 and MMP13. In the meanwhile, miR-7 was proven to regulate the expression of the above cartilage-specific genes by targeting KLF4, which demonstrated KLF4 could prevent OA development. Subsequently, KLF4 also activated TGF-β1 signaling pathway, thereby affecting OA progression. Excessive KLF4 could up-regulate TGF-β1 and p-Smad2/3 level, and Smad4 level was prevented in OA chondrocytes, while adding TGF-β1 inhibitor SB525334 could rescue this impact, along with reduced TGF-β1 and p-Smad2/3 level, enriched Smad4 level. KLF4 could also reverse the effect of miR-7 on TGF-β1 signaling. Besides, it was confirmed that KLF4 could improve OA in rat OA models by HE and Safranin O-Fast green staining, and immunohistochemistry. Collectively, our findings will give more detailed evidence about miR-7 and KLF4 in OA diagnosis and treatment.

Keywords: Chondrocyte; KLF4; Osteoarthritis; TGF-β1; miR-7.

MeSH terms

  • Animals
  • Blotting, Western
  • Cells, Cultured
  • Chondrocytes / metabolism
  • Down-Regulation
  • Fluorescent Antibody Technique
  • Humans
  • Kruppel-Like Factor 4 / metabolism
  • Male
  • MicroRNAs / metabolism*
  • Osteoarthritis / etiology
  • Osteoarthritis / metabolism*
  • Polymerase Chain Reaction
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction
  • Transforming Growth Factor beta1 / metabolism*

Substances

  • KLF4 protein, human
  • Kruppel-Like Factor 4
  • MIRN7 microRNA, human
  • MicroRNAs
  • Transforming Growth Factor beta1