TNF-α enhanced the expression of Wnt-related genes and proteins in nucleus pulposus cells. (A) Wnt-related mRNA expression after exposure of nucleus pulposus cells to TNF-α (10 ng/mL) for 6 and 24 h, as assessed by real-time PCR. (B) Western blot analysis of β-catenin activation after treatment of nucleus pulposus cells with TNF-α (10 ng/mL). *P < 0.05 indicates significant differences between groups. Error bars represent the SD. n.s., not significant. (C) Detection of β-catenin protein expression by immunofluorescence microscopy. Nucleus pulposus cells were cultured with or without 10 ng/mL TNF-α for 24 h, fixed, and stained with an antibody against c-fos. Left: cells stained with an antibody to β-catenin; middle: cells stained with 4′,6-diamidino-2-phenylindole (DAPI), to identify healthy nuclei; right: cells stained with an antibody to β-catenin and with DAPI. Scale bar, 50 μm (original magnification, 20×).