Recent development of in vivo cryotechnique to cryobiopsy for living animals

Various microscopic methods have been used to analyze the morphology and molecular distribution of cells and tissues. Using conventional procedures, however, ischemic or anoxic artifacts are inevitably caused by tissue-resection or perfusion-fixation. The in vivo cryotechnique (IVCT) was developed to overcome these problems, and was found to be useful with light microscopy for analyses of the distribution of water-soluble molecules without anoxic effects at high time resolution. But there are limitations to the application of IVCT, such as exposure of target organs of living small animals and immunoreactivity of lipid-soluble molecules owing to freeze-substitution with acetone. Recently, a new cryotechnique called "cryobiopsy" has been developed, which enables one to obtain tissue specimens of large animals including humans without ischemia or anoxia, and has almost the same technical advantages as IVCT. Both IVCT and cryobiopsy complement other live-imaging techniques, and are useful for not only the morphological observation of cells and tissues under normal conditions, but also the preservation of all components in frozen tissue specimens. Therefore, morphofunctional information in vivo would be obtained by freeze-substituion for light or electron microscopy, and also by other analytical methods, such as freeze-fracture replication, X-ray microanalyses, or Raman microscopy. Considering the merits of both IVCT and cryobiopsy, their application should be expanded into other microscopic fields and also from experimental animal studies to clinical medicine.