Fig 2: The upregulation of CTGF and VEGF-A accelerated the fibrotic progression of NP cells. NP cells were treated, as mentioned above. (A, D) IF staining of collagen I and II (magnification: 400×), and (B, E) quantification analysis. (C, F) The mRNA expression level of aggrecan and collagen III was assayed by RT-PCR. The values are mean ± SD of three independent experiments. (*P<0.05, **P<0.01, ***P<0.001)

Fig 3: CTGF and VEGF-A highly expressed in the late-term of IVDD. NP tissues of different degeneration degrees were collected. (A) Representative images of Masson staining (magnification: 400×). (B) Representative images of IHC (magnification: 400×), and (C) quantification analysis. (D) mRNA level of CTGF and VEGF-A was determined by RT-PCR. The values are mean ± SD of three independent experiments. (*P<0.05, ***P<0.001)

Fig 4: The interaction between CTGF and VEGF-A in NP cells in vitro. NP cells were treated with exogenic CTGF (2 ng/mL) or VEGF-A (3 ng/mL) protein for 3 days to upregulated the CTGF and VEGF-A expression of NP cells. Meanwhile, the siRNA transfected NP cells targeting null or CTGF were treated with exogenic CTGF protein (5 ng/mL) for 3 days as well. Besides, BEV (20 ng/mL) was also used to co-cultured NP cells with VEGF-A protein (3 ng/mL) for 3 days. (A, D) The protein expression level of CTGF and VEGF-A was determined by Western blotting and (B, E) quantification analysis. (C, F) The mRNA expression level of CTGF and VEGF-A was assayed by RT-PCR. The values are mean ± SD of three independent experiments. (**P<0.01, ***P<0.001)