Three-dimensional reconstruction of living mouse liver tissues using cryotechniques with confocal laser scanning microscopy

A Novel Three-Dimensional Imaging System Based on Polysaccharide Staining for Accurate Histopathological Diagnosis of Inflammatory Bowel Diseases

BACKGROUND & AIMS

Tissue-clearing and three-dimensional (3D) imaging techniques aid clinical histopathological evaluation; however, further methodological developments are required before use in clinical practice.

METHODS

We sought to develop a novel fluorescence staining method based on the classical periodic acid-Schiff stain. We further attempted to develop a 3D imaging system based on this staining method and evaluated whether the system can be used for quantitative 3D pathological evaluation and deep learning-based automatic diagnosis of inflammatory bowel diseases.

RESULTS

We successfully developed a novel periodic acid-FAM hydrazide (PAFhy) staining method for 3D imaging when combined with a tissue-clearing technique (PAFhy-3D). This strategy enabled clear and detailed imaging of the 3D architectures of crypts in human colorectal mucosa. PAFhy-3D imaging also revealed abnormal architectural changes in crypts in ulcerative colitis tissues and identified the distributions of neutrophils in cryptitis and crypt abscesses. PAFhy-3D revealed novel pathological findings including spiral staircase-like crypts specific to inflammatory bowel diseases. Quantitative analysis of crypts based on 3D morphologic changes enabled differential diagnosis of ulcerative colitis, Crohn's disease, and non-inflammatory bowel disease; such discrimination could not be achieved by pathologists. Furthermore, a deep learning-based system using PAFhy-3D images was used to distinguish these diseases The accuracies were excellent (macro-average area under the curve = 0.94; F1 scores = 0.875 for ulcerative colitis, 0.717 for Crohn's disease, and 0.819 for non-inflammatory bowel disease).

CONCLUSIONS

PAFhy staining and PAFhy-3D imaging are promising approaches for next-generation experimental and clinical histopathology.

Feature-rich covalent stains for super-resolution and cleared tissue fluorescence microscopy

Fluorescence microscopy is a workhorse tool in biomedical imaging but often poses substantial challenges to practitioners in achieving bright or uniform labeling. In addition, while antibodies are effective specific labels, their reproducibility is often inconsistent, and they are difficult to use when staining thick specimens. We report the use of conventional, commercially available fluorescent dyes for rapid and intense covalent labeling of proteins and carbohydrates in super-resolution (expansion) microscopy and cleared tissue microscopy. This approach, which we refer to as Fluorescent Labeling of Abundant Reactive Entities (FLARE), produces simple and robust stains that are modern equivalents of classic small-molecule histology stains. It efficiently reveals a wealth of key landmarks in cells and tissues under different fixation or sample processing conditions and is compatible with immunolabeling of proteins and in situ hybridization labeling of nucleic acids.

Imaging of thrombosis and microcirculation in mouse lungs of initial melanoma metastasis with in vivo cryotechnique

Microscopic bioimaging of blood flow and distribution of cancer cells in lungs is essential to analyze mechanism of lung metastasis. Such cancer metastasis has been well known to induce hypercoagulable states and thrombosis. In histopathological tissue sections, however, it has been difficult to capture rapid phenomenon of thrombus formation due to technical problems associated with much less retention of soluble serum components as well as dynamic histological features reflecting their living states. In this study, to achieve bioimaging of both hypercoagulable states and thrombosis induced by early metastasis of mouse B16-BL6 melanoma, "in vivo cryotechnique" (IVCT) was used, which retained soluble components at their original sites. Glutathione-coated quantum dots (QDs) were subsequently injected after melanoma cells via right ventricles to examine plasma flow with fluorescence emission. At 5s after the melanoma injection, melanoma cells were mostly stacked and intruded in alveolar capillaries with changing their shapes. Assembly of platelets initially appeared at 1min, and they aggregated around the stacked melanoma cells at 5min. Such aggregated platelets were immunopositive for both phospho-tyrosine 418 and 527 of Src, indicating their partial signal activation. Fibrin monomers were also immunolocalized around both melanoma cells and platelet aggregates, and massive immunoreaction deposits of fibrinogen were also detected near the same areas, but more strongly detected around the melanoma cells, indicating initial thrombus formation. In those areas, QDs were rarely detected, probably because of the lack of blood supply. Thus, IVCT revealed histopathological features of initial thrombosis under their circulatory conditions.

Histochemical analyses and quantum dot imaging of microvascular blood flow with pulmonary edema in living mouse lungs by "in vivo cryotechnique"

Light microscopic imaging of blood vessels and distribution of serum proteins is essential to analyze hemodynamics in living animal lungs under normal respiration or respiratory diseases. In this study, to demonstrate dynamically changing morphology and immunohistochemical images of their living states, "in vivo cryotechnique" (IVCT) combined with freeze-substitution fixation was applied to anesthetized mouse lungs. By hematoxylin-eosin staining, morphological features, such as shapes of alveolar septum and sizes of alveolar lumen, reflected their respiratory conditions in vivo, and alveolar capillaries were filled with variously shaped erythrocytes. Albumin was usually immunolocalized in the capillaries, which was confirmed by double-immunostaining for aquaporin-1 of endothelium. To capture accurate time-courses of blood flow in peripheral pulmonary alveoli, glutathione-coated quantum dots (QDs) were injected into right ventricles, and then IVCT was performed at different time-points after the QD injection. QDs were localized in most arterioles and some alveolar capillaries at 1 s, and later in venules at 2 s, reflecting a typical blood flow direction in vivo. Three-dimensional QD images of microvascular networks were reconstructed by confocal laser scanning microscopy. It was also applied to lungs of acute pulmonary hypertension mouse model. Erythrocytes were crammed in blood vessels, and some serum components leaked into alveolar lumens, as confirmed by mouse albumin immunostaining. Some separated collagen fibers and connecting elastic fibers were still detected in edematous tunica adventitia near terminal bronchioles. Thus, IVCT combined with histochemical approaches enabled us to capture native images of dynamically changing structures and microvascular hemodynamics of living mouse lungs.