Immunohistochemical analysis of various serum proteins in living mouse thymus with "in vivo cryotechnique"

Human serum albumin gradient in serous ovarian cancer cryosections measured by fluorescence lifetime

Human serum albumin (HSA) is a depot and carrier for many endogenous and exogenous molecules in blood. Many studies have demonstrated that the transport of HSA in tumor microenvironments contributes to tumor development and progression. In this report, we set up a multimodal nonlinear optical microscope system, combining two-photon excitation fluorescence, second harmonic generation, and two-photon fluorescence lifetime imaging microscopy. The fluorescence lifetime of a small squaraine dye (SD) is used to evaluate HSA concentrations in tumor tissue based on specific binding between SD and HSA. We used SD to stain the cryosections from serous ovarian cancer patients in high-grade (HGSOC) and low-grade (LGSOC), respectively, and found a gradient descent of HSA concentration from normal connective tissue to extracellular matrix to tumor masses from 13 to 2 µM for LGSOC patients and from 36 to 12 µM for HGSOC patients. We demonstrated that multimodal nonlinear optical microscopy can obtain similar results as those from traditional histologic staining, thus it is expected to move to clinical applications.

Immunohistochemical study of mouse sciatic nerves under various stretching conditions with "in vivo cryotechnique"

BACKGROUND

In living animal bodies, some morphological changes of nerve fibers will probably occur when peripheral nerves are stretched or not stretched during various joint exercises. We aimed to capture the dynamic structures of nerves under various stretching conditions and to keep soluble serum proteins in their tissue sections.

NEW METHOD

Morphological changes of stretched or non-stretched sciatic nerve fibers were examined with "in vivo cryotechnique" (IVCT). Fibers were directly frozen with liquid isopentane-propane cryogen (-193°C). Immunolocalizations of protein 4.1G and albumin were also examined in the fibers.

RESULTS

The structures of IVCT-prepared sciatic nerves under the stretched condition showed a beaded appearance. By immunostaining for membrane skeletal protein 4.1G, Schmidt-Lanterman incisures (SLIs) were clearly identified, and the heights of their circular truncated cones were increased at narrow sites of the nerve fibers under the stretched condition, compared to those of non-stretched nerve fibers. Albumin was immunolocalized in blood vessels and also along endoneurium including regions near the node of Ranvier.

COMPARISON WITH EXISTING METHODS

With the conventional perfusion-fixation method (PF), it was difficult to keep stable postures of living mouse limbs for tissue preparation. In nerve fibers after PF, the structures of SLI were easily modified, and albumin was heterogeneously immunolocalized due to diffusion artifacts.

CONCLUSIONS

IVCT revealed (1) the structures of peripheral nerve fibers under dynamically different conditions, indicating that the morphological changes of SLIs play a functional role as a bumper structure against mechanical forces, and (2) accurate immunolocalization of serum albumin in the sciatic nerve fibers.

Immuno- and Enzyme-histochemistry of HRP for Demonstration of Blood Vessel Permeability in Mouse Thymic Tissues by "In Vivo Cryotechnique"

It is difficult to understand the in vivo permeability of thymic blood vessels, but “in vivo cryotechnique” (IVCT) is useful to capture dynamic blood flow conditions. We injected various concentrations of horseradish peroxidase (HRP) with or without quantum dots into anesthetized mice via left ventricles to examine architectures of thymic blood vessels and their permeability at different time intervals. At 30 sec after HRP (100 mg/ml) injection, enzyme reaction products were weakly detected in interstitium around some thick blood vessels of corticomedullary boundary areas, but within capillaries of cortical areas. At 1 and 3 min, they were more widely detected in interstitium around all thick blood vessels of the boundary areas. At 10 min, they were diffusely detected throughout interstitium of cortical areas, and more densely seen in medullary areas. At 15 min, however, they were uniformly detected throughout interstitium outside blood vessels. At 30 min, phagocytosis of HRP by macrophages was scattered throughout the interstitium, which was accompanied by decrease of HRP reaction intensity in interstitial matrices. Thus, time-dependent HRP distributions in living mice indicate that molecular permeability and diffusion depend on different areas of thymic tissues, resulting from topographic variations of local interstitial flow starting from corticomedullary areas.