The impact of flavonoid epicatechin on compact bone microstructure in rabbits

Epicatechin is one of the dozens of potent natural antioxidants with beneficial activities on many biological systems. However, its impact on bone structure has not been sufficiently investigated. The purpose of our study was to examine the effect of pure epicatechin on compact bone microstructure in five-month-old female rabbits. Twelve rabbits were intramuscularly (i.m.) injected with various doses of epicatechin: 10 μg kg −1 body weight (bw) (Epi10 group; n = 4), 100 μg kg −1 bw (Epi100 group; n = 4) and 1000 μg kg −1 bw (Epi1000 group; n = 4) for 30 days, 3 times per week. Four individuals from the control (C) group were i.m. administrated with physiological saline solution. Compact bone arrangement in all epicatechin-exposed groups was similar to the C group. We identified only intensive apposition of primary vascular longitudinal bone tissue under periosteum in Epi10, Epi100 and Epi1000 groups. On the contrary, significantly increased sizes of the primary osteons’ vascular canals were observed in rabbits from Epi10 group in comparison with C group. Interestingly, females from the Epi100 and Epi1000 groups had significantly decreased values of primary osteons’ vascular canals as compared to C and Epi10 groups. Haversian canals’ parameters were decreased in all rabbits exposed to epicatechin. Sizes of secondary osteons did not differ significantly among all analysed groups. Our results demonstrate that subacute intramuscular exposure to epicatechin influences bone vascularization (higher doses lead to vasoconstriction of blood vessels) and did not cause any demonstrable changes in compact bone arrangement.