C. acnes-induced changes of pro-inflammatory markers in intervertebral disc (IVD) cells. The black bars display results obtained with the ATCC C. acnes strain, whereas light grey shows results obtained with the clinical strain (n = 4 donors with 2 technical replicates for each donor). (a) Gene expression of Interleukin (IL)-1β, IL-6, IL-8, cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS), and prostaglandin E synthase 2 (PTGES2). Fold changes (2−ΔΔCt) are indicated on a logarithmic scale and normalized to the endogenous control glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as well as the negative control; * p < 0.05. Data represent the mean with standard deviation (SD). (b) Protein expression of IL-6 and IL-8 in ng/mL. Mean with SD is shown. (c) Correlation of IL-6 between qPCR and ELISA results. (d) Correlation of IL-8 between qPCR and ELISA results. Spearman correlation coefficients: r = 0.86; p = 0.01.