GRIZZLY BEARS (URSUS ARCTOS HORRIBILIS) AND BLACK BEARS (URSUS AMERICANUS) PREVENT TRABECULAR BONE LOSS DURING DISUSE (HIBERNATION)

摘要

Reduced skeletal loading causes cortical and trabecular bone loss in humans and other animals, but trabecular bone responds to disuse more rapidly and shows greater losses than cortical bone for a given period of inactivity [1-2]. Manifestations of disuse on trabecular bone include unbalanced bone remodeling, decreased bone mineral density, and compromised bone architecture [3].Bears undergo 6 months of disuse annually during hibernation but prevent cortical bone loss during this time, probably because bears experience decreased, but balanced, intracortical bone remodeling during hibernation [4]. This suggests that bears possess a biological mechanism to prevent disuse induced bone loss. However, the effects of hibernation on bear trabecular bone are unclear from previous studies due to small sample sizes and low statistical power [5]. The goal of this study was to quantify the effects of hibernation on bear trabecular bone remodeling, architecture, and mineral density. We hypothesized that trabecular bone architectural and mineral properties would not be adversely affected in hibernating bears because histological indices of bone resorption and bone formation remain balanced during hibernation.