Single myelin fiber imaging in living rodents without labeling by deep optical coherence microscopy

Abstract

Myelin sheath disruption is responsible for multiple neuropathies in the central and peripheral nervous system. Myelin imaging has thus become an important diagnosis tool. However, in vivo imaging has been limited to either low-resolution techniques unable to resolve individual fibers or to low-penetration imaging of single fibers, which cannot provide quantitative information about large volumes of tissue, as required for diagnostic purposes. Here, we perform myelin imaging without labeling and at micron-scale resolution with >300-μm penetration depth on living rodents. This was achieved with a prototype [termed deep optical coherence microscopy (deep-OCM)] of a high-numerical aperture infrared full-field optical coherence microscope, which includes aberration correction for the compensation of refractive index mismatch and high-frame-rate interferometric measurements. We were able to measure the density of individual myelinated fibers in the rat cortex over a large volume of gray matter. In the peripheral nervous system, deep-OCM allows, after minor surgery, in situ imaging of single myelinated fibers over a large fraction of the sciatic nerve. This allows quantitative comparison of normal and Krox20 mutant mice, in which myelination in the peripheral nervous system is impaired. This opens promising perspectives for myelin chronic imaging in demyelinating diseases and for minimally invasive medical diagnosis.

Volumetric imaging and quantification of cytoarchitecture and myeloarchitecture with intrinsic scattering contrast

“…During the imaging process, rats were ventilated with a mixture of air and O 2 . Imaging was performed through the sealed cranial window, using distilled water as the immersion medium, as described previously [6,7]. An intravenous bolus of pancuronium bromide (2 mg/kg) was administered followed by continuous intravenous infusion at 2 mg/kg/hr to minimize possible animal motion.…”

“…Third-harmonic generation also visualizes neuronal cell bodies due to lack of structural phase matching [5]. Elastic backscattering techniques such as Optical Coherence Microscopy (OCM) and confocal reflectance microscopy provide contrast comparable to third-harmonic generation in brain tissue, depicting both neuronal cell bodies and myelinated axons [6][7][8][9]. The birefringent properties of the myelin sheath can be interrogated with polarization-sensitive imaging to provide additional contrast [10].…”

Rapid, label‐free identification of cerebellar structures using multiphoton microscopy

“…Optical coherence microscopy allows single myelin fiber imaging with > 300 mm penetration depth on living rodents [15]. Spectral confocal reflectance microscopy and near-infrared reflectance microscopy have detected myelinated axons in health and disease on fluorescent transgenic mice [16,17].…”

Cross-validation of serial optical coherence scanning and diffusion tensor imaging: A study on neural fiber maps in human medulla oblongata

“…The development of optical coherence tomography (OCT) (Huang et al, 1991) has shown promise for depicting fiber tracts in the central and peripheral nervous system (Arous et al, 2011; Wang et al, 2011; Leahy et al, 2013) and creating high-resolution brain images that have been correlated with histology (Assayag et al, 2013; Magnain et al, 2014). OCT is a depth-resolved imaging technique that generates cross-sectional images and 3D reconstruction of tissue microstructures.…”