Time-lapse mechanical imaging of neural tube closure in live embryo using Brillouin microscopy.

Neural tube closure (NTC) is a complex process of embryonic development involving molecular, cellular, and biomechanical mechanisms. While the genetic factors and biochemical signaling have been extensively investigated, the role of tissue biomechanics remains mostly unexplored due to the lack of tools. Here, we developed an optical modality that can conduct time-lapse mechanical imaging of neural plate tissue as the embryo is experiencing neurulation. This technique is based on the combination of a confocal Brillouin microscope and a modified ex ovo culturing of chick embryo with an on-stage incubator. With this technique, for the first time, we captured the mechanical evolution of the neural plate tissue with live embryos. Specifically, we observed the continuous increase in tissue modulus of the neural plate during NTC for ex ovo cultured embryos, which is consistent with the data of in ovo culture as well as previous studies. Beyond that, we found that the increase in tissue modulus was highly correlated with the tissue thickening and bending. We foresee this non-contact and label-free technique opening new opportunities to understand the biomechanical mechanisms in embryonic development.