Effect of defective calcium metabolism on otolith formation in zebrafish

Benign paroxysmal positional vertigo (BPPV) is the most common vertigo disease and is more likely to occur in perimenopausal women, suggesting an association with osteoporosis. Since otoconia are primarily composed of calcium carbonate, abnormal calcium metabolism may lead to otoconia dislocation. However, the detailed mechanism is currently unknown. In this study, we investigated the effects of drugs (cadmium and dexamethasone) that cause abnormal calcium metabolism on otolith formation in zebrafish larvae. Here, otolith size was clearly reduced in the cadmium group, and the calcium content of the larvae was also markedly reduced. In contrast, in the dexamethasone group, which also had a lower calcium content than the control group, otolith size increased. Our results suggest that, as in bone, calcium metabolism influences the repeated dissolution and recrystallization of otoliths and maintains homeostasis in response to calcium concentrations in the endolymphatic fluid.