Lipid Metabolic Heterogeneity\nduring Early Embryogenesis\nRevealed by Hyper-3D Stimulated Raman Imaging

Studying embryogenesis is fundamental to understanding\ndevelopmental\nbiology and reproductive medicine. Its process requires precise spatiotemporal\nregulations in which lipid metabolism plays a crucial role. However,\nthe spatial dynamics of lipid species at the subcellular level remains\nobscure due to technical limitations. To address this challenge, we\ndeveloped a hyperspectral 3D imaging and analysis method based on\nstimulated Raman scattering microscopy (hyper-3D SRS) to quantitatively\nassess lipid profiles in individual embryos through submicrometer\nresolution (<i>x</i>–<i>y</i>), 3D optical\nsectioning (<i>z</i>), and chemical bond-selective (Ω)\nimaging. Using hyper-3D SRS, individual lipid droplets (LDs) in single\ncells were identified and quantified. Our findings revealed that the\nLD profiles within a single embryo are not uniform, even as early\nas the 2-cell stage. Notably, we also discovered a dynamic relationship\nbetween the LD size and unsaturation degree as embryos develop, indicating\ndiverse lipid metabolism during early development. Furthermore, abnormal\nLDs were observed in oocytes of a progeria mouse model, suggesting\nthat LDs could serve as a potential biomarker for assessing oocyte/embryo\nquality. Overall, our results highlight the potential of hyper-3D\nSRS as a noninvasive method for studying lipid content, composition,\nand subcellular distribution in embryos. This technique provides valuable\ninsights into lipid metabolism during embryonic development and has\nthe potential for clinical applications in evaluating oocyte/embryo\nquality.