Image: Breast tissue with a nerve coursing through intact fat cells (Photo courtesy of Richard Levenson / UCD).
A new study describes how microscopy with ultraviolet surface excitation (MUSE) can deliver non-destructive, slide-free histological images.
Developed at the University of California Davis (UCD; USA), the University of Rochester (NY, USA), and Lawrence Livermore National Laboratory (Livermore, CA, USA), MUSE uses ultraviolet (UV) light at wavelengths at the ~280 nm range to penetrate into tissue samples by just a few microns. Nuclei, cytoplasm, and extracellular components reflect signals from the UV surface excitation that can be detected by conventional color cameras using sub-second exposure times. The process allows for rapid imaging of large areas, as well as immediate interpretation.
The tight UV wavelength range restricts the excitation of conventional fluorescent stains to just the tissue surface, thus providing high-resolution diagnostic histological images resembling those obtained from conventional haematoxylin and eosin staining, as well enhanced morphology and color-contrast information. In addition, the researchers found no significant effects on downstream molecular assays, including fluorescence-in-situ hybridization and RNA sequencing. The study was published on December 4, 2017, in Nature Biomedical Engineering.
“It has become increasingly important to submit relevant portions of often tiny tissue samples for DNA and other molecular functional tests, and sometimes just preparing conventional microscope slices can consume most of or even all of small specimens,” said senior author Professor Richard Levenson, MD, of the department of pathology and laboratory medicine at UCD. “MUSE is important because it quickly provides images from fresh tissue without exhausting the sample.”
“MUSE eliminates any need for conventional tissue processing with formalin fixation, paraffin embedding, or thin-sectioning,” concluded Professor Levenson. “It doesn't require lasers, confocal, multiphoton or optical coherence tomography instrumentation, and the simple technology makes it well suited for deployment wherever biopsies are obtained and evaluated.”
Unlike light of longer wavelength, 280-nm light only penetrates to a depth of 10 microns or less, and thus excites fluorescent signals only from the cut specimen surface. The fluorescence display mode preserves surface shading and depth cues that allow for appreciation of surface profiles, which are important in understanding the three-dimensional (3D) organization of complex specimens. MUSE can thus provide views beyond what can be seen with standard thin-sectioned material, generating results that can resemble those obtainable with scanning electron microscopy (SEM).
University of California Davis
University of Rochester
Lawrence Livermore National Laboratory