Activation of Notch signaling suppressed expression of genes encoding key matrix-degrading enzymes in rNP cells. (a–d) qPCR analyses of Notch signaling target genes (a), matrix anabolic genes (b), and matrix catabolic genes (c,d) in rNP cells infected with Ad-GFP or Ad-NICD1 for 3 days. Relative gene expression was calculated by 2−ΔΔCt method after normalizing first to house-keeping Gapdh, and then to the control groups (Ad-GFP-infected cells). Data are means ± SD. *p <0.05, n = 3. (e) Western blot analysis of Mmp13 in rNP cells infected with Ad-GFP or Ad-NICD1 for 3 days