The expression of Notch-2 and Hey-2/Hes1 induced by JAG2. a, b The expression of JAG2 mRNA increased following TNF-α treatment. c, d Western blot and densitometric analyses showed similar results. e–g The expression changes in Notch-1, Notch-2, and Notch-3 mRNA and the Notch target genes Hes1/5 and Hey1/2 mRNA were regulated by the JAG2 treatment. h–k Western blot and densitometric analyses showed similar results. h Representative MRI images of different degenerative discs (from left, grades I, II, III, IV, and V). IHC showed that the expression of JAG2 (j) and Notch-2 (k) increased with the severity of IVD degeneration, with significantly higher positive incidences in mild and moderately degenerated IVDs (l). m–o Correlation analysis revealed that the expression levels of JAG2 and Notch-2 were significantly correlated. P values were computed vs. non-stimulated controls*; *P < 0.05. ns, no signifcant.