Meeting Abstract
To better understand how dynamic loading plays a role in zebrafish (Danio rerio) bone development and growth, we have designed, built, and characterized a water tunnel. Boundary layer theory was used to design the water channel contraction ensuring thin boundary layers constrained to the near-wall, yielding a uniform flow field for the fish to swim in. Furthermore, turbulent flow theory was used to ensure an isotropic and homogeneous flow field void of velocity gradients. Our design encouraged fish to swim for the duration of the experiment, which is not the case for other swim chambers where fish have been observed to rest on walls to avoid swimming. Thus, we are able to investigate the role of increased swimming speeds on zebrafish bone remodeling in a well-defined flow field. Starting ~30 days post fertilization (dpf), sibling zebrafish groups were either exposed to an exercise regimen starting at a velocity of 1 body length per second (BL/s) for 6hrs/day for 7 days, or maintained in a standard 2.8-L tank of comparable water volume. The velocity was increased in the exercise group by ~10% each day. We noted structural differences between groups in the skeletal architecture of several functional units, including the caudal fin and pectoral apparatus. To determine the role of the Hedgehog (Hh) signaling pathway on bone due to exercise-induced mechanical load, we used two different transgenic fish wherein Hh levels can be up- or down-regulated in a time-specific manner. These experiments revealed a strong gene-by-environment effect, confirming that the Hh pathway is mechanically sensitive with respect to bone formation. Overall, our results provide a better understanding of how mechanical forces affect skeletal remodeling as well as the molecular genetic mechanisms that regulate this process.
