Quantitative real-time PCR for (a) NP-specific and (b) IVD-specific cell marker genes, in normal and degenerate human AF and NP cells. Relative gene expression for (a) nucleus pulposus (NP)-specific marker genes (synaptosomal-associated protein, 25 kDa (SNAP25), cytokeratin (KRT) 8, KRT18, KRT19, N-cadherin (CDH2) and integrin-binding sialoprotein (IBSP)) and the notochord (NC) marker gene (T), and (b) intervertebral disc (IVD)-specific cell marker genes ((tenomodulin (TNMD), brain abundant, membrane attached signal protein 1 (BASP1), forkhead box F1 (FOXF1), and fibulin 1 (FBLN1)) and the chondrogenic marker genes (aggrecan (ACAN) and type II collagen (COL2A1)), was normalised to the housekeeping gene and normal annulus fibrosus (AF) or NP cells and plotted on a log scale. For each gene, expression in normal NP cells or AF cells was plotted on the baseline (value = 1 +/-standard error) and the relative expression in NP or AF degenerate cells (normalised to the relevant normal cell value) was plotted adjacently. * statistical significance between normal and degenerate NP cells (P < 0.05). † statistical significance between normal and degenerate AF cells (P < 0.05).