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

Biomimetic quantum dot-labeled B16F10 murine melanoma cells as a tool to monitor early steps of lung metastasis by in vivo imaging

Background

Numerous studies have proposed the use of fluorescent semiconductor nanoparticles or quantum dots (QDs) as novel tools to label cells and tumors. However, QD applications are limited by their toxicity in biological systems and little is known about whether QDs affect the capacity of cancer cells to metastasize. Previously, we described the “biomimetic” synthesis of CdTe-QDs (QDs-glutathione [GSH]) with increased biocompatibility and the potential utility in labeling cells.

Purpose

In order to determine the feasibility of using QDs-GSH as a tool for tracking tumor cells during early metastasis, we characterized here for the first time, the in vitro and in vivo effects of the incorporation of green or red biomimetic QDs-GSH into B16F10 cells, a syngeneic mouse melanoma line for metastasis assays in C57BL/6 mice.

Methods

B16F10 cells were labeled with green or red biomimetic QDs-GSH in the presence or absence of n-acetylcysteine. Then, migration, invasion and proliferation of labeled B16F10 were evaluated in vitro. Finally, the B16F10 cells labeled with red QDs-GSH were used to monitor in vivo lung metastasis at early time points (5 minutes to 24 hours) or after 21 days in C57BL/6 mice.

Results

We developed a methodology that allows obtaining QDs-GSH-labeled B16F10 cells (nearly 100% viable labeled cells), which remained viable for at least 5 days and migrated similarly to control cells. However, proliferation, invasion, and the capacity to form metastatic nodules in the lungs were severely attenuated. Fluorescence imaging revealed that distribution/accumulation of QDs-GSH-labeled B16F10 cells could be tracked following injection into C57BL/6 mice (syngeneic preclinical metastasis model) and that these cells preferentially accumulated in the perialveolar area in lungs as early as 5 minutes post-injection.

Conclusion

The methodology described here represents a useful alternative for monitoring initial events during tumor cell metastasis.

Comparison of Acalabrutinib, A Selective Bruton Tyrosine Kinase Inhibitor, with Ibrutinib in Chronic Lymphocytic Leukemia Cells

Purpose: Ibrutinib inhibits Bruton tyrosine kinase (BTK) by irreversibly binding to the Cys-481 residue in the enzyme. However, ibrutinib also inhibits several other enzymes that contain cysteine residues homologous to Cys-481 in BTK. Patients with relapsed/refractory or previously untreated chronic lymphocytic leukemia (CLL) demonstrate a high overall response rate to ibrutinib with prolonged survival. Acalabrutinib, a selective BTK inhibitor developed to minimize off-target activity, has shown promising overall response rates in patients with relapsed/refractory CLL. A head-to-head comparison of ibrutinib and acalabrutinib in CLL cell cultures and healthy T cells is needed to understand preclinical biologic and molecular effects.Experimental Design: Using samples from patients with CLL, we compared the effects of both BTK inhibitors on biologic activity, chemokine production, cell migration, BTK phosphorylation, and downstream signaling in primary CLL lymphocytes and on normal T-cell signaling to determine the effects on other kinases.Results: Both BTK inhibitors induced modest cell death accompanied by cleavage of PARP and caspase-3. Production of CCL3 and CCL4 chemokines and pseudoemperipolesis were inhibited by both drugs to a similar degree. These drugs also showed similar inhibitory effects on the phosphorylation of BTK and downstream S6 and ERK kinases. In contrast, off-target effects on SRC-family kinases were more pronounced with ibrutinib than acalabrutinib in healthy T lymphocytes.Conclusions: Both BTK inhibitors show similar biological and molecular profile in primary CLL cells but appear different on their effect on normal T cells. Clin Cancer Res; 23(14); 3734-43. ©2016 AACR.

Near-Infrared Emitting PbS Quantum Dots for in Vivo Fluorescence Imaging of the Thrombotic State in Septic Mouse Brain

Near-infrared (NIR) fluorescent imaging is a powerful tool for the non-invasive visualization of the inner structure of living organisms. Recently, NIR fluorescence imaging at 1000–1400 nm (second optical window) has been shown to offer better spatial resolution compared with conventional NIR fluorescence imaging at 700–900 nm (first optical window). Here we report lead sulfide (PbS) quantum dots (QDs) and their use for in vivo NIR fluorescence imaging of cerebral venous thrombosis in septic mice. Highly fluorescent PbS QDs with a 1100 nm emission peak (QD1100) were prepared from lead acetate and hexamethyldisilathiane, and the surface of QD1100 was coated with mercaptoundecanoic acid so as to be soluble in water. NIR fluorescence imaging of the cerebral vessels of living mice was performed after intravascular injection (200–300 μL) of QD1100 (3 μM) from a caudal vein. By detecting the NIR fluorescence of QD1100, we achieved non-invasive NIR fluorescence imaging of cerebral blood vessels through the scalp and skull. We also achieved NIR fluorescence imaging of cerebral venous thrombosis in septic mice induced by the administration of lipopolysaccharide (LPS). From the NIR fluorescence imaging, we found that the number of thrombi in septic mice was significantly increased by the administration of LPS. The formation of thrombi in cerebral blood vessels in septic mice was confirmed by enzyme-linked immunosorbent assay (ELISA). We also found that the number of thrombi significantly decreased after the administration of heparin, an inhibitor of blood coagulation. These results show that NIR fluorescence imaging with QD1100 is useful for the evaluation of the pathological state of cerebral blood vessels in septic mice.

Morphofunctional Merits of an In Vivo Cryotechnique for Living Animal Organs: Challenges of Clinical Applications from Basic Medical Research

Recent advances in molecular and genetic techniques have led to establishment of new biomedical fields; however, morphological techniques are still required for a more precise understanding of functioning cells and tissues. Conventional preparation procedures involve a series of chemical fixation, alcohol dehydration, paraffin or epoxy resin embedding, sectioning, and staining steps. In these steps, technical artifacts modify original morphologies of the cells being examined. Furthermore, difficulties are associated with capturing dynamic images in vivo using conventional chemical fixation. Therefore, a quick-freezing (QF) method was introduced for biological specimens in the 20th century. However, specimens have to be resected from living animal organs with blood supply, and their dynamical morphologies have not been investigated in detail using the QF method. In order to overcome these issues, the tissue resection step of organs had to be avoided and samples needed to be frozen under blood circulation. Our in vivo cryotechnique (IVCT) was an original technique to cryofix samples without resecting their tissues. The most significant merit of IVCT is that blood circulation into organs is preserved at the exact moment of freezing, which has been useful for arresting transient physiological processes of cells and tissues and maintaining their components in situ.

Involvement of membrane skeletal molecules in the Schmidt-Lanterman incisure in Schwann cells

Membrane skeletal networks form a two-dimensional lattice structure beneath erythrocyte membranes. 4.1R-MPP (membrane palmitoylated protein) 1-glycophorin C is one of the basic molecular complexes of the membrane skeleton. An analogous molecular complex, 4.1G-MPP6-cell adhesion molecule 4 (CADM4), is incorporated into the Schmidt-Lanterman incisure (SLI), a truncated cone shape in the myelin internode that is a specific feature of myelinated nerve fibers formed in Schwann cells in the peripheral nervous system. In this review, the dynamic structure of peripheral nerve fibers under stretching conditions is demonstrated using in vivo cryotechnique. The structures of nerve fibers had a beaded appearance, and the heights of SLI circular-truncated cones increased at the narrow sites of nerve fibers under the stretched condition. The height of SLI-truncated cones was lower in 4.1G-deficient nerve fibers than in wild-type nerve fibers. 4.1G was essential for the molecular targeting of MPP6 and CADM4 in SLI. The signal transduction protein, Src, was also involved in the 4.1G-MPP6-CADM4 molecular complex. The phosphorylation of Src was altered by the deletion of 4.1G. Thus, we herein demonstrate a membrane skeletal molecular complex in SLI that has potential roles in the regulation of adhesion and signal transduction as well as in structural stability in Schwann cells.

Immunohistochemical and morphofunctional studies of skeletal muscle tissues with electric nerve stimulation by in vivo cryotechnique

In this study, morphological and immunohistochemical alterations of skeletal muscle tissues during persistent contraction were examined by in vivo cryotechnique (IVCT). Contraction of gastrocnemius muscles was induced by sciatic nerve stimulation. The IVCT was performed immediately, 3 min or 10 min after the stimulation start. Prominent ripples of muscle fibers or wavy deformation of sarcolemma were detected immediately after the stimulation, but they gradually diminished to normal levels during the stimulation. The relative ratio of sarcomere and A band lengths was the highest in the control group, but it immediately decreased to the lowest level and then gradually recovered at 3 min or 10 min. Although histochemical intensity of PAS reaction was almost homogeneous in muscle tissues of the control group or immediately after the stimulation, it decreased at 3 min or 10 min. Serum albumin was immunolocalized as dot-like patterns within some muscle fibers at 3 min stimulation. These patterns became more prominent at 10 min, and the dots got larger and saccular in some sarcoplasmic regions. However, IgG1 and IgM were immunolocalized in blood vessels under nerve stimulation conditions. Therefore, IVCT was useful to capture the morphofunctional and metabolic changes of heterogeneous muscle fibers during the persistent contraction.

Morphological and immunohistochemical analyses of soluble proteins in mucous membranes of living mouse intestines by cryotechniques

We have performed immunohistochemical or ultrastructural analyses of living mouse small intestines using Epon blocks prepared by 'in vivo cryotechnique' (IVCT). By electron microscopy, intracellular ultrastructures of epithelial cells were well preserved in tissue areas 5-10 μm away from cryogen-contact surface tissues. Their microvilli contained dynamically waving actin filaments, and highly electron-dense organelles, such as mitochondria, were seen under the widely organized terminal web. By quick-freezing of fresh resected tissues (FT-QF), many erythrocytes were congested within blood vessels due to loss of blood pressure. By immersion-fixation (IM-DH) and perfusion-fixation (PF-DH), small vacuoles were often seen in the cytoplasm of epithelial cells, and their intercellular spaces were also dilated. Moreover, actin filament bundles were irregular in cross sections of microvilli, compared with those with IVCT. Epon-embedded thick sections were treated with sodium ethoxide, followed by antigen retrieval and immunostained for immunoglobulin A (IgA), Ig kappa light chain (Igκ), J-chain and albumin. By cryotechniques, IgA immunoreactivity was detected as tiny dot-like patterns in cytoplasm of some epithelial cells. Both J-chain and Igκ immunoreactivities were detected in the same local areas as those of IgA. By FT-QF, however, the IgA immunoreactivity was more weakly detected, compared with that with IVCT. In thick sections prepared by IM-DH and PF-DH, it was rarely observed in both plasma and epithelial cells. Another albumin was diffusely immunolocalized in extracellular matrices of mucous membranes and also within blood vessels. Thus, IVCT was useful for preservation of soluble proteins and ultrastructural analyses of dynamically changing epithelial cells of living mouse small intestines.

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.