Vibration exposure uncovers a critical early developmental window for zebrafish caudal fin development.

Mechanical influencers have long been shown to affect mature bone. Bone mechanosensation is a key feature that allows the skeleton to adapt to environmental constraints. In this study, we describe the response of immature, developing bones to a mechanical stimulus. To do so, zebrafish larvae at different stages of development were exposed to whole-body vibration (WBV) at a low frequency of 20 Hz, for up to 4 days. Whole mount Alizarin red and Alcian blue staining revealed age-related and bone type-specific defects. Specifically, the parhypural and hypural 1 caudal fin endoskeletal elements were affected when the exposure to WBV started early during their development. We show that these WBV-induced parhypural and hypural 1 patterning defects are triggered by a Sox9-independent pathway, potentially by reducing the distance separating adjacent chondrogenic condensations in the developing tail skeleton. The remaining hypurals were unaffected by the WBV treatment. Altogether, our results indicate that, upon exposure to vibration, chondrogenic cell progenitors can react to mechanical stimuli early during their development, which ultimately affects the skeletal patterning of the growing zebrafish larvae. These findings open a new research avenue to better understand the cellular processes involved in developing, patterning, and maintaining skeletal tissue.