Fig. 4

Effect of diet-induced obesity on the intervertebral disc. a Representative histological sections of the L6/S1 spinal level of the lumbar spine stained with safranin-o/fast green from mice fed control chow, high-fat, or western diet for 12, 24, or 40 weeks. The accumulation of hypertrophic cells was detected within the inner annulus fibrosus of mice fed the high-fat and western diets for 40 weeks (highlighted by black arrows). b Evaluation of the grade of histopathological IVD degeneration using the modified Boos scoring system showed no significant differences between mice fed the control chow, high-fat, or western diets at the 24- and 40-week timepoints. At the 12-week timepoint, mice fed the western diet showed a significant decrease in the degenerative score compared to mice fed chow and high-fat diets. n = 9–16 animals per timepoint, per diet. Data are analyzed by Kruskal-Wallis test. c SYBR-based qPCR of intact thoracic intervertebral discs showed no significant difference between mice fed a chow, high-fat, or western diet at the 12-week timepoint for any genes investigated. At the 24-week timepoint, significant increases in Il-1b and Ptgs2 expression were seen in mice fed the western diet compared to control. By 40 weeks, significant increases in Il-6, Ptgs2, Bdnf, and Adamts5 expression were seen in mice fed the high-fat diet compared to control. n = 5–8 animals per diet/per timepoint. Analyzed by one-way ANOVA. All data are plotted mean ± 95% CI; data points for each mouse are graphed within each group. *P < 0.05, ***P < 0.001