Longitudinal monitoring of pancreatic islet damage in streptozotocin-treated mice with optical coherence microscopy.

Pancreatic islets regulate glucose homeostasis in the body, and their dysfunction is closely related to diabetes. Islet transplantation into the anterior chamber of the eye (ACE) was recently developed for both in vivo islet study and diabetes treatment. Optical coherence microscopy (OCM) was previously used to monitor ACE transplanted islets in non-obese diabetic (NOD) mice for detecting autoimmune attack. In this study, OCM was applied to streptozotocin (STZ)-induced diabetic mouse models for the early detection of islet damage. A custom extended-focus OCM (xfOCM) was used to image islet grafts in the ACE longitudinally during STZ-induced beta cell destruction together with conventional bright-field (BF) imaging and invasive glucose level measurement. xfOCM detected local structural changes and vascular degradation during the islet damage which was confirmed by confocal imaging of extracted islet grafts. xfOCM detection of islet damage was more sensitive than BF imaging and glucose measurement. Longitudinal xfOCM images of islet grafts were quantitatively analyzed. All these results showed that xfOCM could be used as a non-invasive and sensitive monitoring method for the early detection of deficient islet grafts in the ACE with potential applications to human subjects.

High-contrast visualization of human skin cancers with combined reflectance confocal and moxifloxacin-based two-photon microscopy: An ex vivo study.

BACKGROUND AND OBJECTIVES: Precise determination of cancer margin during skin cancer surgery is crucial for complete resection and further clinical prognosis. Although reflection confocal microscopy (RCM) has been used for perioperative guiding, its reflection contrast has limitations in detecting cancer cells in the dermis. We previously developed combined reflection confocal (RC) and moxifloxacin-based two-photon (MB-TP) microscopy for sensitive cancer detection by using multiple contrast mechanisms. In this study, the performance of combined microscopy was characterized in various skin cancer specimens and compared with standard methods. MATERIALS AND METHODS: Seven human skin specimens in total including two normal ones, three basal cell carcinomas (BCCs), and two squamous cell carcinomas (SCCs) were collected and imaged in fresh condition. Moxifloxacin ophthalmic solution was topically instilled for cell labeling for 3-5 minutes, then mosaic imaging with the combined microscopy was conducted. The imaged specimens were imaged again after exogenous nuclear labeling for comparison and then processed for standard hematoxylin and eosin histology. RESULTS: Combined RC and MB-TP microscopy visualized both cell and extracellular matrix structures of the skin specimens with multiple contrasts of reflection, moxifloxacin fluorescence, autofluorescence, and second harmonic generation. It distinguished normal cell structures in the skin dermis such as hair follicles, sebaceous and eccrine glands from BCC nests, and SCCs based on cell organization. Normal cell structures had organized cell arrangements for their functions, while cancer cell structures had dense and disorganized cell arrangements. Cellular features found by combined microscopy images were confirmed by both TP microscopy with nuclear labeling and histological examination. CONCLUSIONS: The imaging results showed the potential of combined microscopy for sensitive cancer detection and in vivo guiding of skin cancer surgery.

Deep learning enables reference-free isotropic super-resolution for volumetric fluorescence microscopy.

Volumetric imaging by fluorescence microscopy is often limited by anisotropic spatial resolution, in which the axial resolution is inferior to the lateral resolution. To address this problem, we present a deep-learning-enabled unsupervised super-resolution technique that enhances anisotropic images in volumetric fluorescence microscopy. In contrast to the existing deep learning approaches that require matched high-resolution target images, our method greatly reduces the effort to be put into practice as the training of a network requires only a single 3D image stack, without a priori knowledge of the image formation process, registration of training data, or separate acquisition of target data. This is achieved based on the optimal transport-driven cycle-consistent generative adversarial network that learns from an unpaired matching between high-resolution 2D images in the lateral image plane and low-resolution 2D images in other planes. Using fluorescence confocal microscopy and light-sheet microscopy, we demonstrate that the trained network not only enhances axial resolution but also restores suppressed visual details between the imaging planes and removes imaging artifacts.

Longitudinal Label-Free Two-Photon Microscopy of Cellular Healing Processes in Non-Ablative Fractional Laser Wounds.

BACKGROUND AND OBJECTIVES: Wound healing is an important biomedical problem with various associated complications. Although cutaneous wound healing has been studied in vivo extensively using various optical imaging methods, early-stage cellular healing processes were difficult to study due to scab formation. The objective of this study is to demonstrate that minimal laser wounds and optical microscopy can access the detailed cellular healing processes of cutaneous wounds from the early stage. STUDY DESIGN/MATERIALS AND METHODS: A non-ablative fractional laser (NAFL) and label-free two-photon microscopy (TPM) were used to induce minimal cutaneous wounds and to image the wounds in three-dimension. Sixteen hairless mice and a single human volunteer were used. NAFL wounds were induced in the hindlimb skin of the mice and in the forearm skin of the human subject. The NAFL wounds were longitudinally imaged during the healing period, starting from an hour post wound induction in the earliest and until 21 days. Cells in the wound and surrounding normal skin were visualized based on two-photon excited auto-fluorescence (TPAF), and cellular changes were tracked by analyzing longitudinal TPM images both qualitatively and quantitatively. Damage and recovery in the skin dermis were tracked by using the second harmonic generation (SHG) signal of collagen. Immunofluorescence and hematoxylin and eosin histology analysis were conducted to validate the TPM results of the murine skin. RESULTS: Cellular healing processes in NAFL wounds and surroundings could be observed by longitudinal TPM. In the case of murine skin, various healing phases including inflammation, re-epithelization, granulation tissue formation, and late remodeling phase including collagen regeneration were observed in the same wounds owing to minimal or no scab formation. The re-epithelization process was analyzed quantitatively by measuring cell density and thickness of the epithelium in the wound surroundings. In the case of the human skin, the access inside the wound was blocked for a few days post wound induction due to scabs but the cellular changes in the wound surroundings were observed from the early stage. Cellular healing processes in the NAFL wound of the human skin were similar to those in murine skin. CONCLUSIONS: The minimal NAFL wound model and label-free TPM demonstrated the cell level assessment of wound healing processes with applicability to human subjects. © 2021 Wiley Periodicals LLC.

Open-top axially swept light-sheet microscopy.

Open-top light-sheet microscopy (OT-LSM) is a specialized microscopic technique for high throughput cellular imaging of large tissue specimens including optically cleared tissues by having the entire optical setup below the sample stage. Current OT-LSM systems had relatively low axial resolutions by using weakly focused light sheets to cover the imaging field of view (FOV). In this report, open-top axially swept LSM (OTAS-LSM) was developed for high-throughput cellular imaging with improved axial resolution. OTAS-LSM swept a tightly focused excitation light sheet across the imaging FOV using an electro tunable lens (ETL) and collected emission light at the focus of the light sheet with a camera in the rolling shutter mode. OTAS-LSM was developed by using air objective lenses and a liquid prism and it had on-axis optical aberration associated with the mismatch of refractive indices between air and immersion medium. The effects of optical aberration were analyzed by both simulation and experiment, and the image resolutions were under 1.6µm in all directions. The newly developed OTAS-LSM was applied to the imaging of optically cleared mouse brain and small intestine, and it demonstrated the single-cell resolution imaging of neuronal networks. OTAS-LSM might be useful for the high-throughput cellular examination of optically cleared large tissues.

Characterization of early-stage cutaneous radiation injury by using optical coherence tomography angiography.

Cutaneous radiation injury (CRI) is a skin injury caused by exposure to high dose ionizing radiation (IR). Diagnosis and treatment of CRI is difficult due to its initial clinically latent period and the following inflammatory bursts. Early detection of CRI before clinical symptoms will be helpful for effective treatment, and various optical methods have been applied with limitations. Here we show that optical coherence tomography angiography (OCTA) could detect changes in the skin during the latent period in CRI mouse models non-invasively. CRI was induced on the mouse hindlimb with exposure to various IR doses and the injured skin regions were imaged longitudinally by OCTA until the onset of clinical symptoms. OCTA detected several changes in the skin including the skin thickening, the dilation of large blood vessels, and the irregularity in vessel boundaries. Some of OCTA findings were confirmed by histology. The study results showed that OCTA could be used for early CRI detection.

High-speed combined reflectance confocal and moxifloxacin based two-photon microscopy.

Reflectance confocal microscopy (RCM) is a non-invasive high-resolution optical imaging technique used in clinical settings as a diagnostic method. However, RCM has limited diagnostic ability by providing non-specific morphological information only based on reflection contrast. Various multimodal imaging techniques have been developed to compensate the limitations of RCM, but multimodal techniques are often slow in imaging speed compared to RCM alone. In this report, we combined RCM with moxifloxacin based two-photon microscopy (TPM) for high-speed multimodal imaging. Moxifloxacin based TPM used clinically compatible moxifloxacin for cell labeling and could do non-invasive cellular imaging at 30 frames/s together with RCM. Performance of the combined microscopy was characterized in the imaging of mouse skin and cornea, in vivo. Detail tissue microstructures including cells, extra-cellular matrix (ECM), and vasculature were visualized. The combined microscopy was applied to human skin cancer specimens, and both cells and ECM in the skin cancer and normal skin regions were visualized at high imaging speeds. The combined microscopy can be useful in the clinical applications of RCM by providing multiple contrasts.

Fast and sensitive delineation of brain tumor with clinically compatible moxifloxacin labeling and confocal microscopy.

Delineation of brain tumor margins during surgery is critical to maximize tumor removal while preserving normal brain tissue to obtain optimal clinical outcomes. Although various imaging methods have been developed, they have limitations to be used in clinical practice. We developed a high-speed cellular imaging method by using clinically compatible moxifloxacin and confocal microscopy for sensitive brain tumor detection and delineation. Moxifloxacin is a Food and Drug Administration (FDA) approved antibiotic and was used as a cell labeling agent through topical administration. Its strong fluorescence at short visible excitation wavelengths allowed video-rate cellular imaging. Moxifloxacin-based confocal microscopy (MBCM) was characterized in normal mouse brain specimens and visualized their cytoarchitecture clearly. Then, MBCM was applied to both brain tumor murine models and two malignant human brain tumors of glioblastoma and metastatic cancer. MBCM detected tumors in all the specimens by visualizing dense and irregular cell distributions, and tumor margins were easily delineated based on the cytoarchitecture. An image analysis method was developed for automated detection and delineation. MBCM demonstrated sensitive delineation of brain tumors through cytoarchitecture visualization and would have potentials for human applications, such as a surgery-guiding method for tumor removal.

Moxifloxacin Labeling-Based Multiphoton Microscopy of Skin Cancers in Asians.

BACKGROUND AND OBJECTIVES: Although multiphoton microscopy (MPM) can visualize both cell and extracellular matrix (ECM) structures of the skin in high-contrast without exogenous labeling, label-free MPM is usually too slow to image clinically relevant large regions. A high-speed MPM method would be beneficial for evaluating clinical skin specimens by increasing the imaging area. In this study, moxifloxacin labeling-based MPM (moxifloxacin MPM) was characterized in various human skin cancer specimens. STUDY DESIGN/MATERIALS AND METHODS: Moxifloxacin ophthalmic solution was used for cell-labeling and MPM imaging was conducted afterwards. Moxifloxacin MPM was characterized in ex vivo normal human skin and skin cancer specimens in comparison with the label-free MPM and fluorescence confocal microscopy (FCM) using acridine orange as a labeling agent. Then, moxifloxacin MPM was applied to various ex vivo human skin cancer specimens including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), dermatofibrosarcoma protuberans (DFSP). Results of moxifloxacin MPM were compared with bright-field clinical and histopathologic findings. RESULTS: Moxifloxacin MPM imaged both cells and collagen in the skin, similarly to label-free MPM, but with enhanced fluorescence intensities in cells and enhanced imaging speeds. Moxifloxacin MPM imaged cells in the skin similarly to acridine orange-based FCM. Moxifloxacin MPM of various human skin cancer specimens imaged their specific cellular features. The microscopic features detected in moxifloxacin MPM were confirmed with histological images. CONCLUSIONS: This observational pilot study demonstrated that moxifloxacin MPM could detect specific cellular features of various skin cancers in good correlation with histopathological images in Asian patients at the higher imaging speed than label-free MPM. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Morphological features of mucous secretory organ and mucous secretion of loach Misgurnus anguillicaudatus skin for friction drag reduction.

We examined the functional morphology of loach Misgurnus anguillicaudatus skin by using synchrotron X-ray micro-computed tomography (SR-µCT) and high-contrast staining using osmium tetroxide or phosphotungstic acid (PTA), which enhances the image contrast of soft tissues. The captured high-spatial resolution images revealed that the surface ornamentations were stuck in the basement membrane of the loach scales. The ornamentations consisting of grooves (radii) and ridges (circuli) that can move freely and bend flexibly. The cross-sectional lateral microstructures of flat, concave and convex loach skins were observed from a live image of loach skin obtained through dark-field optical coherence tomography (OCT) imaging. The thickness of loach skin was changed with varying empty space between the mucous-cell layer and the scales by bending motion of loach. In addition, through direct measurement of drag reduction of loach skin, the mucous layer was found to have a strong influence on the reduction of skin friction. The present results enhance the understanding of the functional morphologies of mucous layer of loach to secrete mucus for skin friction reduction.

Tumor-Associated Macrophages Enhance Tumor Hypoxia and Aerobic Glycolysis.

Tumor hypoxia and aerobic glycolysis are well-known resistance factors for anticancer therapies. Here, we demonstrate that tumor-associated macrophages (TAM) enhance tumor hypoxia and aerobic glycolysis in mice subcutaneous tumors and in patients with non-small cell lung cancer (NSCLC). We found a strong correlation between CD68 TAM immunostaining and PET 18fluoro-deoxyglucose (FDG) uptake in 98 matched tumors of patients with NSCLC. We also observed a significant correlation between CD68 and glycolytic gene signatures in 513 patients with NSCLC from The Cancer Genome Atlas database. TAM secreted TNFα to promote tumor cell glycolysis, whereas increased AMP-activated protein kinase and peroxisome proliferator-activated receptor gamma coactivator 1-alpha in TAM facilitated tumor hypoxia. Depletion of TAM by clodronate was sufficient to abrogate aerobic glycolysis and tumor hypoxia, thereby improving tumor response to anticancer therapies. TAM depletion led to a significant increase in programmed death-ligand 1 (PD-L1) expression in aerobic cancer cells as well as T-cell infiltration in tumors, resulting in antitumor efficacy by PD-L1 antibodies, which were otherwise completely ineffective. These data suggest that TAM can significantly alter tumor metabolism, further complicating tumor response to anticancer therapies, including immunotherapy. SIGNIFICANCE: These findings show that tumor-associated macrophages can significantly modulate tumor metabolism, hindering the efficacy of anticancer therapies, including anti-PD-L1 immunotherapy.

Mesenchymal Stem Cell Engineered Nanovesicles for Accelerated Skin Wound Closure.

We report development and characterization of cell-engineered nanovesicles made from mesenchymal stem cells (MSCNVs), which have more than 300 times higher productivity than natural extracellular vesicles (EVs). MSCNVs had similar morphological characteristics to MSCEVs but have molecular characteristics that more resemble MSCs than MSCEVs. In vitro MSCNV treatment increased the proliferation and migration of primary skin fibroblasts and showed better effects than treatment using natural MSCEVs. Quantitative real-time PCR analysis showed increased expression of growth factors in MSCNV-treated skin fibroblasts. Intraperitoneal injection of MSCNVs into syngeneic mice induced mild local inflammation, which resulted in recruitment of immune cells to the injection site. In vivo MSCNV treatment of a mouse skin wound accelerated its healing; this acceleration by MSCNVs may occur by promoting blood vessel formation at the wound site. These results indicate the promise of MSCNVs as agents for regenerative medicine.

Three-photon tissue imaging using moxifloxacin.

Moxifloxacin is an antibiotic used in clinics and has recently been used as a clinically compatible cell-labeling agent for two-photon (2P) imaging. Although 2P imaging with moxifloxacin labeling visualized cells inside tissues using enhanced fluorescence, the imaging depth was quite limited because of the relatively short excitation wavelength (<800 nm) used. In this study, the feasibility of three-photon (3P) excitation of moxifloxacin using a longer excitation wavelength and moxifloxacin-based 3P imaging were tested to increase the imaging depth. Moxifloxacin fluorescence via 3P excitation was detected at a >1000 nm excitation wavelength. After obtaining the excitation and emission spectra of moxifloxacin, moxifloxacin-based 3P imaging was applied to ex vivo mouse bladder and ex vivo mouse small intestine tissues and compared with moxifloxacin-based 2P imaging by switching the excitation wavelength of a Ti:sapphire oscillator between near 1030 and 780 nm. Both moxifloxacin-based 2P and 3P imaging visualized cellular structures in the tissues via moxifloxacin labeling, but the image contrast was better with 3P imaging than with 2P imaging at the same imaging depths. The imaging speed and imaging depth of moxifloxacin-based 3P imaging using a Ti:sapphire oscillator were limited by insufficient excitation power. Therefore, we constructed a new system for moxifloxacin-based 3P imaging using a high-energy Yb fiber laser at 1030 nm and used it for in vivo deep tissue imaging of a mouse small intestine. Moxifloxacin-based 3P imaging could be useful for clinical applications with enhanced imaging depth.

Dermoscopy guided dark-field multi-functional optical coherence tomography.

Dermoscopy is a skin surface microscopic technique allowing specular reflection free observation of the skin, and has been used to examine pigmented skin lesions. However, dermoscopy has limitations in providing depth information due to lack of 3D resolution. In order to overcome the limitations, we developed dermoscopy guided multi-functional optical coherence tomography (MF-OCT) providing both high-contrast superficial information and depth-resolved structural, birefringent, and vascular information of the skin simultaneously. Dermoscopy and MF-OCT were combined by using a dichroic mirror, and dark-field configuration was adapted for MF-OCT to reduce specular reflection. After characterization, dermoscopy guided MF-OCT was applied to several human skin lesions such as the scar, port-wine stain (PWS) as well as the normal skin for demonstration. Various features of the scar and PWS were elucidated by both dermoscopy and MF-OCT. Dermoscopy guided MF-OCT may be useful for evaluation and treatment monitoring of skin lesions in clinical applications.

Brain tumor delineation enhanced by moxifloxacin-based two-photon/CARS combined microscopy.

Delineating brain tumor margin is critical for maximizing tumor removal while sparing adjacent normal tissue for better clinical outcome. We describe the use of moxifloxacin-based two-photon (TP)/coherent anti-Stokes Raman scattering (CARS) combined microscopy for differentiating normal mouse brain tissue from metastatic brain tumor tissue based on histoarchitectural and biochemical differences. Moxifloxacin, an FDA-approved compound, was used to label cells in the brain, and moxifloxacin-based two-photon microscopy (TPM) revealed tumor lesions with significantly high cellular density and invading edges in a metastatic brain tumor model. Besides, label-free CARS microscopy showed diminishing of lipid signal due to the destruction of myelin at the tumor site compared to a normal brain tissue site resulting in a complementary contrast for tumor detection. This study demonstrates that moxifloxacin-based TP/CARS combined microscopy might be advantageous for tumor margin identification in the brain that has been a long-standing challenge in the operating room.

NO-dependent attenuation of TPA-induced immunoinflammatory skin changes in Balb/c mice by pindolol, heptaminol or ATRA, but not by verapamil.

Recently a mouse skin carcinogenesis study reported that a ß-blocker carvedilol displayed antitumor-properties via antihyperplastic effects. However, the antihyperplastic mechanism is unclear as the ß-blocker is characterized with multiple pleiotropic effects including stimulation of endothelial NO release and verapamil-like calcium channel blocking activity. To investigate the nature and the origin of the antihyperplastic effects, we tested topical pretreatment with pindolol, heptaminol, ATRA or verapamil against Balb/c mouse ear skin hyperplasia that was induced by TPA. We found that pindolol, heptaminol or ATRA, but not verapamil, inhibited the TPA-induced immunoinflammatory skin changes in an NO-dependent manner, which included epidermal hyperplasia, skin edema and fibrosis. Furthermore, we also observed NO-dependent alleviation of the TPA-induced NK cell depletion in the ear tissues by heptaminol pretreatment. Together our results suggest that stimulation of NO generation from constitutive synthases may be primarily responsible for the reported antihyperplastic and NK cell-preserving effects of the ß-blockers, and that similar effects may be observed in other immunity normalizing compounds that also promote endothelial NO synthesis.

Moxifloxacin: Clinically compatible contrast agent for multiphoton imaging.

Multiphoton microscopy (MPM) is a nonlinear fluorescence microscopic technique widely used for cellular imaging of thick tissues and live animals in biological studies. However, MPM application to human tissues is limited by weak endogenous fluorescence in tissue and cytotoxicity of exogenous probes. Herein, we describe the applications of moxifloxacin, an FDA-approved antibiotic, as a cell-labeling agent for MPM. Moxifloxacin has bright intrinsic multiphoton fluorescence, good tissue penetration and high intracellular concentration. MPM with moxifloxacin was demonstrated in various cell lines, and animal tissues of cornea, skin, small intestine and bladder. Clinical application is promising since imaging based on moxifloxacin labeling could be 10 times faster than imaging based on endogenous fluorescence.

In vivo visualization of skin inflammation by optical coherence tomography and two-photon microscopy.

Inflammation is a non-specific immune response to injury intended to protect biological tissue from harmful stimuli such as pathogens, irritants, and damaged cells. In vivo optical tissue imaging has been used to provide spatial and dynamic characteristics of inflammation within the tissue. In this paper, we report in vivo visualization of inflammation in the skin at both cellular and physiological levels by using a combination of label-free two-photon microscopy (TPM) and optical coherence tomography (OCT). Skin inflammation was induced by topically applying lipopolysaccharide (LPS) on the mouse ear. Temporal OCT imaging visualized tissue swelling, vasodilation, and increased capillary density 30 min and 1 hour after application. TPM imaging showed immune cell migration within the inflamed skin. Combined OCT and TPM was applied to obtain complementary information from each modality in the same region of interest. The information provided by each modality were consistent with previous reports about the characteristics of inflammation. Therefore, the combination of OCT and TPM holds potential for studying inflammation of the skin.

Correlation between polarization sensitive optical coherence tomography and second harmonic generation microscopy in skin.

Both polarization sensitive optical coherence tomography (PS-OCT) and second harmonic generation (SHG) microscopy are 3D optical imaging methods providing information related to collagen in the skin. PS-OCT provides birefringence information which is due to the collagen composition of the skin. SHG microscopy visualizes collagen fibers in the skin based on their SHG property. These two modalities have been applied to the same skin pathologies associated with collagen changes, but their relationship has not been examined. In this study, we tried to find the relationship by imaging the same skin samples with both modalities. Various parts of the normal rat skin and burn damaged skin were imaged ex vivo, and their images were analyzed both qualitatively and quantitatively. PS-OCT images were analyzed to obtain tissue birefringence. SHG images were analyzed to obtain collagen orientation indices by applying 2D Fourier transform. The skin samples having higher birefringence values had higher collagen orientation indices, and a linear correlation was found between them. Burn damaged skin showed decreases in both parameters compared to the control skins. This relationship between the bulk and microscopic properties of skin may be useful for further skin studies.

Dark-field polarization-sensitive optical coherence tomography.

Polarization-sensitive optical coherence tomography (PS-OCT) is a functional OCT providing both structural and birefringent information of the sample, and it has been applied to the studies of various organs having polarization properties. Fiber-based PS-OCT is sensitive to specular reflection from the sample surface, because signal saturation due to the strong specular reflection can make the polarization measurement difficult. We developed a dark-field PS-OCT which can avoid the specular reflection problem. Dark-field PS-OCT was implemented by adapting a hybrid method of Bessel-beam illumination and Gaussian-beam detection, and a PS-OCT method based on passive delay unit (PDU). The new system was characterized in comparison with the conventional Gaussian-beam based method in both polarization components and various samples including the human skin. Dark-field PS-OCT performed as good as the conventional PS-OCT without the specular reflection artifact. Dark-field PS-OCT may be useful in practical situations where the specular reflection is unavoidable.