Alcohol abuse is a risk factor for bone damage and fracture-related complications. Through precise β-catenin signaling, canonical Wnt signaling plays a key role in fracture repair by promoting the differentiation of new bone and cartilage cells. In this study, we examined the effects of alcohol on the Wnt pathway in injured bone using a murine model of alcohol-induced impaired fracture healing.
Male C57Bl/6 or T cell factor (TCF)-transgenic mice were administered 3 daily intraperitoneal doses of alcohol or saline. One hour following the final injection, mice were subjected to a stabilized, mid-shaft tibial fracture. Injured and contralateral tibias were harvested at 6, 9, or 14 days post-fracture for the analysis of biomechanical strength, callus tissue composition, and Wnt/β-catenin signaling.
Acute alcohol treatment was associated with a significant decrease in fracture callus volume, diameter, and biomechanical strength at day 14 post-fracture. Histology revealed an alcohol-related reduction in cartilage and bone formation at the fracture site, and that alcohol inhibited normal cartilage maturation. Acute alcohol exposure caused a significant 2.3-fold increase in total β-catenin protein at day 6 and a significant decrease of 53 and 56% at days 9 and 14, respectively. lacZ staining in β-galactosidase-expressing TCF-transgenic mice revealed spatial and quantitative differences in Wnt-specific transcriptional activation at day 6 in the alcohol group. Days 9 and 14 post-fracture showed that acute alcohol exposure decreased Wnt transcriptional activation, which correlates with the modulation of total β-catenin protein levels observed at these time points.
Acute alcohol exposure resulted in significant impairment of fracture callus tissue formation, perturbation of the key Wnt pathway protein β-catenin, and disruption of normal Wnt-mediated transcription. These data suggest that the canonical Wnt pathway is a target for alcohol in bone and may partially explain why impaired fracture healing is observed in alcohol-abusing individuals.
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