Modest Effects of Age on Inflammatory Markers and Histological Features in the Murine Intervertebral Disc Injury Model.

OBJECTIVE

The aim of the study was to determine the effects of age on inflammatory markers and histological features in the injured mouse tail intervertebral disc.

DESIGN

Inflammatory marker gene (e.g., Cxcl1 , Il6 , Adam8 , and Tipe2 ) expression and morphological changes (histological score and % red in Safranin O staining) in the injured intervertebral discs are recorded in 3-, 10-, and 18-mo-old mice 1 wk after injury.

RESULTS

The injured intervertebral discs had higher histological scores (more degenerative) than intact discs at all ages post injury ( P < 0.01). However, there was no significant difference among the histological scores of injured intervertebral discs from mice of three ages ( P > 0.05). Expression of inflammatory marker genes (e.g., Cxcl1 and Il6 ) was elevated in the injured compared with intact discs in mice of all ages ( P < 0.01). The injury-induced increase in gene expression was greater in 10-mo and 18-mo-old mouse discs than in the 3-mo-old mice ( P < 0.01).

CONCLUSIONS

The intervertebral discs responded to injuries similarly, regardless of age. Because of the modest age-related differences in injury effects, using mice of the same age in experiments is essential, unless one aims to examine age-related differences. Given the costs of maintaining an aged mouse colony, the necessity of using old animals may need justification.