Research Paper Advance Articles

Figure 2. EGR1 expression is upregulated in human degenerative intervertebral disc tissue and in TBHP-treated NPCs. (A) Representative magnetic resonance images showing different grades of degeneration in human tissue: mild (grades I and II) and severe (grades III–V). (B) EGR1 protein expression levels were examined in severely degenerated discs (SDD) and mildly degenerated discs (MDD) by immunohistochemical (IHC) staining (magnification: ×400). (C, D) The EGR1 expression level in human nucleus pulposus (NP) tissue was analyzed by western blotting. ImageJ Software was used for quantitative analysis, and the data were normalized to GAPDH. (E–J) Human nucleus pulposus cells (NPCs) were treated with different concentrations (0, 25, 50, or 100 μM) of TBHP for 24 h, after which the proteins were extracted and the expression levels of EGR1, Bax, Bcl-2, aggrecan, and collagen II were determined by western blotting. (K) Human NPCs were treated with 50 μM tributyl hydrogen peroxide (TBHP) for 24 h, and EGR1 mRNA expression was examined by qRT-PCR. (L) EGR1 protein expression was examined in TBHP-treated NPCs by immunofluorescence staining. ^*p < 0.05, ^***p < 0.001, ^****p < 0.0001.