Imaging zebrafish embryonic development with multimodal optical coherence tomography and light-sheet fluorescence microscopy

Zebrafish are a widely used developmental model because of their transparent embryos and external development. These distinctive characteristics provide valuable insights into embryonic development. Optical coherence tomography (OCT) offers label-free structural imaging and has emerged as a preferred tool for embryonic imaging. On the other hand, light sheet fluorescence microscopy (LSFM) enables time-lapse molecular imaging of multi-hour to multi-day developmental processes due to its low phototoxicity and photobleaching compared to traditional confocal fluorescence microscopy. We developed a multimodal imaging system to obtain concurrent structural and molecular information by combining OCT and LSFM for embryonic imaging. A Michelson-type swept-source OCT system with a central wavelength of 1050 nm, the bandwidth of 100 nm, and sweep rate of 100 kHz captured the structural information with a lateral resolution of ~15 μm and an axial resolution of ~7 μm. The LSFM system captured the molecular information with a transverse resolution of ~2.1 μm and an axial resolution of ~13 μm. The optically co-aligned OCT and LSFM beams were scanned through the same scan head for trivial co-registration of the multimodal images. We imaged 1-5 μm green fluorescence microbeads to show the capability of this system. We then conducted imaging of zebrafish vasculature development with a transgenic line, Tg(kdrl:EGFP), where the erythroblasts express GFP. The results show that the multimodal system enables us to provide co-registered zebrafish structural and functional imaging.