Seamless Tiling and Scalable Coherent Raman Spectroscopic Analysis Reveals Developmental Maturation of Lipids in the Mouse Brain

Lipids constitute approximately half of the dry weight of the brain and play a crucial role in the rapid conduction of action potentials and neurotransmission. However, the maturation of the lipid composition underlying complex brain functions matures during development remains unclear. We developed a sensitive coherent Raman spectroscopic imaging system in which the laser beam is always aligned with the optical axis of the microscope. This system enables seamless stitching-free imaging with a scalable field-of-view and broadband wavelength coverage. Using this unique combination system, we analyzed temporal and spatial changes in lipid composition from the fetal stage to adulthood across mouse brain regions. Our findings revealed that regions with a high total lipid ratio gradually expanded throughout the brain during size growth. While the total lipid ratio continuously increased, changes in lipid composition, particularly ceramide accumulation, were observed in the fiber regions during periods of increasing axonal myelination. High-resolution coherent Raman imaging of the fetal brain revealed that radial glial cells (the most undifferentiated cells) exhibited a higher total lipid ratio than the more differentiated cells. These results can be detected using this system and provide fundamental insights into lipid maturation across different brain regions and developmental stages.