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

Abstract

Objective: To determine the effects of age on inflammatory markers and histological features in the injured mouse tail intervertebral disc (IVD).

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 IVDs are recorded in 3-, 10- and 18-month-old mice 1 week following injury.

Results: The injured IVDs 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 IVDs 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-month and 18-month-old mouse discs than in the 3-month-old mice (p < 0.01).

Conclusions: The IVDs responded to injuries similarly, regardless of age. Due to 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.