Electron microscopy of wet tissues: a case study in renal pathology

In this report we introduce wet-tissue scanning electron microscopy, a novel technique for direct imaging of wet tissue samples using backscattered electrons. Samples placed in sealed capsules are imaged through a resilient, electron-transparent membrane. The contrast of the imaged samples may be enhanced by chemical staining. The samples several millimeters thick and imaged without sectioning, makes this technique suitable for rapid analysis of tissue specimens. We applied this technique to D-limonene-induced nephropathy where accumulation of hyaline protein droplets is induced in proximal and distal convoluted tubules of the kidney. Images obtained by scanning electron microscopy of hydrated kidney specimens exhibited superior resolution, contrast, and magnification compared with those obtained by conventional light microscopy of paraffin sections. The electron micrographs can be obtained within an hour of tissue removal, whereas preparation for light microscopy requires at least 1 day. These advantages of the wet scanning electron microscopy technique indicate its potential utility in a wide range of applications in histopathology and toxicology.