Advances in Multiscale Myelin Imaging: From Classical Histology to Functional Insights

Kentaro Okuyama¹Yuji Komaki²Motonari Ishihara³Yuma Kurosaki³Saki Tsuchiya³Manabu Hayatsu³Junpei Nakayama⁴Keiko Uchiyama¹Kosuke Itoh⁵Toshihiro Nagai⁶Tomoko Shindo⁶Nobuko Moritoki⁶Hiroyuki Kawashima⁷Shinsuke Shibata^1,6*

• ¹Division of Microscopic Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
• ²Bioimaging Center, Central Institute for Experimental Medicine and Life Science, Kanagawa, Japan
• ³DIvision of Microscopic Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
• ⁴Division of Orthopedic Surgery, Graduate School of Medical and Dental Sciences; Division of Microscopic Anatomy, Graduate School of Medical and Dental Sciences;, Niigata University, Niigata, Japan
• ⁵Center for Integrated Human Brain Science, Brain Research Institute, Niigata University, Niigata, Japan
• ⁶Electron Microscope Laboratory, School of Medicine, Keio University, Tokyo, Japan
• ⁷Division of Orthopedic surgery, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan

Scientific understanding of myelin, the lipid-rich sheath of axons essential for vertebrate rapid neuronal communication, has evolved considerably. Enabled by major advances in imaging technology, research has shifted from viewing myelin as a static insulator to investigating the dynamic roles of myelinating glia in nervous system development, function, and pathophysiology. This review aimed to provide a comprehensive, multi-scale overview of the imaging toolkit for myelin biology, from foundational histology to cutting-edge advances. At the macro- and meso-scales, non-invasive modalities like magnetic resonance imaging and positron emission tomography reveal in vivo myelin architecture and molecular changes, offering critical insights into large-scale pathology. At the micro-scale, advanced light microscopy now visualizes cellular dynamics and molecular interactions with remarkable clarity. Finally, at the nano-scale, sophisticated electron microscopy techniques—including volume electron microscopy and correlative approaches—resolve the ultrastructural basis of biological phenomena with unparalleled detail. As no single modality can capture the full biological context, a holistic understanding of glial biology requires the strategic integration of these multi-scale techniques with advanced computational analysis. This integrated approach is essential for revealing the full spectrum of myelin biology and uncovering novel targets for therapeutic intervention.