A novel mouse model for the study of the inhibitory effects of chronic ethanol exposure on direct bone formation

Excessive alcohol consumption has been reported to interfere with human bone homeostasis and repair in multiple ways. Previous studies have demonstrated that chronic ethanol exposure in the rat via an intragastric dietary delivery system inhibits direct bone formation during distraction osteogenesis (DO, limb lengthening). The opportunity to extend the rat ethanol studies to mice is now possible due to the development of mouse models of DO. This study employed a novel combination of liquid ethanol diet delivery and a murine DO model to test the hypothesis that chronic ethanol exposure would result in deficits in direct bone formation during DO in contrast to the pair-fed controls. Twenty-eight 12-month-old C57BL/6 male mice were acclimated to the Lieber-DeCarli liquid control diet #710027 (Dyets Inc.) over a 1-week period. The mice were separated into two diet groups (n=14/group): pair-fed control and ethanol (diet #710260). After being on diet for 82 days, all mice underwent placement of an external fixator and osteotomy on the left tibia. Following a 6-day latency period, distraction began at a rate of 0.075 mm twice a day (b.i.d.) for 14 days. The weight changes were equivalent for both groups. The hypothesis that chronic ethanol exposure would inhibit direct bone formation and produce skeletal toxicity was supported by radiographic (P=.011) and histologic (P=.002) analyses of the % new bone formation in the DO gaps, by peripheral quantitative computed tomography analysis of the total volumetric bone mineral density of the contralateral proximal tibias (P<.001) and contralateral femoral necks (P=.012), by three-point bending on the contralateral tibias (P<.001 energy to break), by pin site bone formation measures (P<.001), and by ethanol-associated increased adipocyte area (adjacent to the gap) percentages (P<.002). We conclude that this model can be used to study the mechanisms underlying inhibition of bone formation by chronic ethanol exposure and to test preclinical interventions.