Comparison of Effects of 2D and 3D Simulated Microgravity Rotation on Ossification in Larval Danio Rerio (Zebrafish)

Simulated microgravity (SMG) is an environmental condition that affects bone density in vertebrates. Ground-based studies typically use a random positioning machine in either a 2D or a 3D mode to assess the effects of SMG, however the meaning of these results is difficult to compare between studies due to different experimental parameters. Here, we exposed larval Danio rerio at 3dpf to 23 h of SMG using a 2D and a 3D mode of rotation, using the same experimental setup. Zebrafish larvae were anaesthetized during the experiment. Our results showed that anesthesia (MS222) did not affect the amount of ossification while SMG-2D treatment slightly reduced the amount of ossification compared with the controls. On the other hand, SMG-3D treatment significantly reduced the overall ossification level of the skeleton. Specifically, the anterior end of the notochord, the ceratobranchial-5, the lower jaw articulation, the pharyngeal teeth, and the operculum were affected compared with control treatments. Overall, these results indicate that SMG-3D produced a more effective SMG effect compared with the SMG-2D. This research provides valuable insight into how different external stimuli such as SMG can cause negative effects on ossification in the developing skeleton in zebrafish.