Figure 1.

A, A heat map was generated by unsupervised clustering analyses with 23 significantly dysregulated mRNAs in patients with IDD. Hierarchical clustering was performed with average linkage and uncentered correlation. The mRNA expression profile effectively segregated patients with IDD from NCs. B, The expression level of IGFBP5 mRNA in NP cells was measured in 129 patients and 112 NCs (in the training and validation sets) using qRT‐PCR assays (***P < 0.001). C, The IGFBP5 mRNA expression levels were inversely correlated with the Pfirrmann scores (r = −0.72, P < 0.0001). D, The expression of IGFBP5 in degenerative NP tissues was significantly lower than that in normal NP samples, as assessed by Western blot analysis (P < 0.05). IDD, intervertebral disc degeneration; NCs, normal controls; NP, nucleus pulposus