Influence of Genetic Background and Sex on Gene Expression in the Mouse (Mus musculus) Tail in a Model of Intervertebral Disc Injury.

To facilitate rational experimental design and fulfill the NIH requirement of including sex as a biologic variable, we examined the influences of genetic background and sex on responses to intervertebral disc (IVD) injury in the mouse tail. The goal of this study was to compare gene expression and histologic changes in response to a tail IVD injury (needle puncture) in male and female mice on the DBA and C57BL/6 (B6) backgrounds. We hypothesized that extracellular matrix gene expression in response to IVD injury differs between mice of different genetic backgrounds and sex. Consistent changes were detected in gene expression and histologic features after IVD injury in mice on both genetic backgrounds and sexes. In particular, expression of col1a1 and adam8 was higher in the injured IVD of DBA mice than B6 mice. Conversely, col2a1 expression was higher in B6 mice than DBA mice. Sex-associated differences were significant only in B6 mice, in which col2a1 expression was greater in male mice than in female. Histologic differences in response to injury were not apparent between DBA and B6 mice or between males and females. In conclusion, mouse tail IVD showed sex- and strain-related changes in gene expression and histology after needle puncture. The magnitude of change in gene expression differed with regard to genetic background and, to a lesser degree, sex.