Aging-associated microstructural deterioration of vertebra in zebrafish

Zebrafish, a small teleost fish, is currently emerging as an animal model of local and systemic aging. In this study, we assessed age-related degenerative changes in the vertebral bone of zebrafish (3–12 month-post-fertilisation [mpf]) using micro-CT scanning. The bone volume (BV) of the trabecular bone in the male and female fish peaked at 6 mpf and reduced with age. In contrast to BV, bone mineral density and tissue volume did not change after 6 mpf, implying that the total mineral volume in the trabecular area remains unchanged, retaining the strength of vertebra. In addition, we performed micro-structural analysis of the trabecular thickness, trabecular number, and star volume of the tissue space and trabeculae, and found that the size of the trabecular bone reduced with age. Furthermore, aged zebrafish (45 mpf) exhibited ectopic ossification inside or outside of their vertebrae. In summary, we analysed bone structural parameters in adult zebrafish vertebra, which are also used in humans, and demonstrated that aged zebrafish have deteriorated microarchitecture (trabecular thickness and number, tissue space star volume and trabecular star volume) with reduction of trabecular bones, similar to that observed during aging in humans. Zebrafish can be utilised as an animal model to understand the pathology of human bone aging, and the discovery of new therapeutic agents against age-related osteoporosis.