Background: Quercetin is one of the best known flavonoids being present in a variety of fruits and vegetables. It has cardioprotective, anticarcinogenic, antioxidant, anti-inflammatory and antiapoptotic properties. Some studies suggest that quercetin has protective effects on bone. However, its influence on qualitative and quantitative histological characteristics of compact bone is still unknown. In our study, 12 clinically healthy five-month-old female rabbits were divided into four groups of three animals each. Quercetin was applied intramuscularly in various concentrations; 10 µg/kg body weight (bw) in the E1 group, 100 µg/kg bw in the E2 group, and 1000 µg/kg bw in the E3 group for 90 days, 3 times per week. Three rabbits without exposure to quercetin served as a control (C) group. Differences in femoral bone microstructure among groups were evaluated.
Results: Qualitative histological characteristics of compact bone differed between rabbits from the E1 and E2 groups. Primary vascular longitudinal bone tissue was not found in some areas near the endosteal surface due to increased endocortical bone resorption. In addition, periosteal border of rabbits from the E1 group was composed of a thicker layer of primary vascular longitudinal bone tissue than in the other groups. In all groups of rabbits administered quercetin, a lower density of secondary osteons was observed. Histomorphometrical evaluations showed significantly decreased sizes of the primary osteons' vascular canals in individuals from the E1 and E2 groups. Secondary osteons were significantly smaller in rabbits from the E1, E2, E3 groups when compared to the C group. Cortical bone thickness was significantly increased in females from the E1 and E2 groups.
Conclusions: The results indicate that quercetin has not only a positive dose-response on qualitative and quantitative histological characteristics of the compact bone of female rabbits as it would be expected.
Keywords: Bone microstructure; Histomorphometry; Intramuscular administration; Quercetin; Rabbit.