Long‐term and in vivo assessment of Aβ protein‐induced brain atrophy in a zebrafish model by optical coherence tomography

In this study, a neurotoxicity model of zebrafish induced by amyloid beta (Aβ) protein was developed and evaluated in vivo by optical coherence tomography (OCT). Aβ protein and phosphate buffer saline (PBS) were separately injected into the head of two groups of adult zebrafish (n = 6 per group). Congo‐red staining results confirmed that Aβ protein had penetrated into brain tissue. All zebrafish were imaged with OCT on the 0th, 5th, 10th, 15th and 20th day postinjection. OCT images showed that PBS is not toxic to brain tissue. However, significant brain atrophy could be seen in the OCT images of zebrafish injected with Aβ‐protein that was verified by histological consequences. In addition, zebrafish in the model group showed memory decline in behavioral tests. This study verified the feasibility of in vivo long‐term assessment of Aβ protein‐induced brain atrophy in adult zebrafish by OCT that has great potential to be applied in the neurological diseases research.     

Superparamagnetic graphene quantum dot as a dual‐modality contrast agent for confocal fluorescence microscopy and magnetomotive optical coherence tomography

A magnetic graphene quantum dot (MGQD) nanoparticle, synthesized by hydrothermally reducing and cutting graphene oxide‐iron oxide sheet, was demonstrated to possess the capabilities of simultaneous confocal fluorescence and magnetomotive optical coherence tomography (MMOCT) imaging. This MGQD shows low toxicity, significant tunable blue fluorescence and superparamagnetism, which can thus be used as a dual‐modality contrast agent for confocal fluorescence microscopy (CFM) and MMOCT. The feasibility of applying MGQD as a tracer of cells is shown by imaging and visualizing MGQD labeled cells using CFM and our in‐house MMOCT. Since MMOCT and CFM can offer anatomical structure and intracellular details, respectively, the MGQD for cell tracking could provide a more comprehensive diagnosis.      

In vivo pump‐probe optical coherence tomography imaging in Xenopus laevis

Currently, optical coherence tomography (OCT), is not capable of obtaining molecular information often crucial for identification of disease. To enable molecular imaging with OCT, we have further developed a technique that harnesses transient changes in light absorption in the sample to garner molecular information. A Fourier‐domain Pump‐Probe OCT (PPOCT) system utilizing a 532 nm pump and 830 nm probe has been developed for imaging hemoglobin. Methylene blue, a biological dye with well‐know photophysics, was used to characterize the system before investigating the origin of the hemoglobin PPOCT signal. The first in vivo PPOCT images were recorded of the vasculature in Xenopus laevis. The technique was shown to work equally well in flowing and nonflowing vessels. Furthermore, PPOCT was compared with other OCT extensions which require flow, such as Doppler OCT and phase‐variance OCT. PPOCT was shown to better delineate tortuous vessels, where nodes often restrict Doppler and phase‐variance reconstruction. (© 2013 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Measuring polarization changes in the human outer retina with polarization‐sensitive optical coherence tomography

Morphological changes in the outer retina such as drusen are established biomarkers to diagnose age‐related macular degeneration. However, earlier diagnosis might be possible by taking advantage of more subtle changes that accompany tissues that bear polarization‐altering properties. To test this hypothesis, we developed a method based on polarization‐sensitive optical coherence tomography with which volumetric data sets of the macula were obtained from 10 young (<25 years) and 10 older (>54 years) subjects. All young subjects and 5 of the older subjects had retardance values induced by the retinal pigment epithelium and Bruch's membrane (RPE‐BM) complex that were just above the noise floor measurement (5°‐13° at 840 nm). In contrast, elevated retardance, up to 180°, was observed in the other 5 older subjects. Analysis of the degree of polarization uniformity (DOPU) demonstrates that reduced DOPU (<0.4) in the RPE is associated with elevated double pass phase retardation (DPPR) below the RPE‐BM complex, suggesting that the observed elevated DPPR in older subjects is the result of increased scattering or polarization scrambling. Collectively, our measurements show that the outer retina can undergo dramatic change in its polarization properties with age, and in some cases still retain its clinically normal appearance.      

In vivo observation of metamorphosis of Plodia interpunctella Hübner using three‐dimensional optical coherence tomography

Morphological assessment and three‐dimensional reconstructions of internal structures of Plodia interpunctella Hübner during metamorphosis stages were experimentally demonstrated using optical coherence tomography (OCT) for the first time. The conventional, complex sectioning methods were significantly simplified owing to the non‐invasive three‐dimensional imaging capability of OCT. Further, this study demonstrates the use of OCT as a non‐invasive detection tool for in vivo morphological observation of metamorphosis stages to gain a better understanding about the growth of internal organs, which can be considered a useful discovery in the field of entomology. Thus, the metamorphosis stages starting from the larva, three pupa stages to the adult stage were periodically visualized to examine the development of internal organs at each specific stage. This study essentially offers real‐time morphological information by non‐destructive observation of the organism and can also be useful for the investigation of other agricultural pests.     

Assessment of the influence of viscoelasticity of cornea in animal ex vivo model using air‐puff optical coherence tomography and corneal hysteresis

Application of the air‐puff swept source optical coherence tomography (SS‐OCT) instrument to determine the influence of viscoelasticity on the relation between overall the air‐puff force and corneal apex displacement of porcine corneas ex vivo is demonstrated. Simultaneous recording of time‐evolution of the tissue displacement and air pulse stimulus allows obtaining valuable information related in part to the mechanical properties of the cornea. A novel approach based on quantitative analysis of the corneal hysteresis of OCT data is presented. The corneal response to the air pulse is assessed for different well‐controlled intraocular pressure (IOP) levels and for the progression of cross‐linking‐induced stiffness of the cornea. Micrometer resolution, fast acquisition and noncontact character of the air‐puff SS‐OCT measurements have potential to improve the in vivo assessment of mechanical properties of the human corneas.      

Real‐time in vivo imaging of adult Zebrafish brain using optical coherence tomography

We report noninvasive imaging of the brain of adult Zebrafish (Danio rerio) using real time optical coherence tomography (OCT) capable of acquiring cross sectional 2D OCT images @ 8 frames/sec. Anatomic features such as telencephalon, tectum opticum, eminentia Granularis and cerebellum were clearly resolved in the OCT images. A 3D model of Zebrafish brain was reconstructed, for the first time to our knowledge, using these 2D OCT images. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

General model for depth‐resolved estimation of the optical attenuation coefficients in optical coherence tomography

We present the proof of concept of a general model that uses the tissue sample transmittance as input to estimate the depth‐resolved attenuation coefficient of tissue samples using optical coherence tomography (OCT). This method allows us to obtain an image of tissue optical properties instead of intensity contrast, guiding diagnosis and tissues differentiation, extending its application from thick to thin samples. The performance of our method was simulated and tested with the assistance of a home built single‐layered and multilayered phantoms (~100 μm each layer) with known attenuation coefficient on the range of 0.9 to 2.32 mm^?1. It is shown that the estimated depth‐resolved attenuation coefficient recovers the reference values, measured by using an integrating sphere followed by the inverse adding doubling processing technique. That was corroborated for all situations when the correct transmittance value is used with an average difference of 7%. Finally, we applied the proposed method to estimate the depth‐resolved attenuation coefficient for a thin biological sample, demonstrating the ability of our method on real OCT images.     

In vivo monitoring the dynamic process of acute retinal hemorrhage and repair in zebrafish with spectral‐domain optical coherence tomography

Retina, the only light sensor in the human eye, is hidden and extremely fragile. Optimized animal models and efficient imaging techniques are very important for the study of retinopathy. In this work, the rapid retinal injury process and the long‐term retinal repair process were in vivo continuously evaluated with a novel imaging technology spectral‐domain optical coherence tomography (SD‐OCT) in a unique animal model zebrafish. Acute retinal injury was constructed on adult zebrafish by needle injection surgery. SD‐OCT imaging was carried out immediately after the mechanical injury. The retinal hemorrhage, which lasted only 5 seconds, could be visualized dynamically by SD‐OCT. The process of blood clearance and retinal repair was also evaluated because SD‐OCT imaging is nondestructive. Both SD‐OCT imaging results and behavioral analyzing results demonstrated that zebrafish retina could be repaired by itself within 15 days, which was confirmed by the results of pathological experiment.     

Integrin αvβ3 enhances the suppressive effect of interferon‐γ on hematopoietic stem cells

Hematopoietic homeostasis depends on the maintenance of hematopoietic stem cells (HSCs), which are regulated within a specialized bone marrow (BM) niche. When HSC sense external stimuli, their adhesion status may be critical for determining HSC cell fate. The cell surface molecule, integrin αvβ3, is activated through HSC adhesion to extracellular matrix and niche cells. Integrin β3 signaling maintains HSCs within the niche. Here, we showed the synergistic negative regulation of the pro‐inflammatory cytokine interferon‐γ (IFNγ) and β3 integrin signaling in murine HSC function by a novel definitive phenotyping of HSCs. Integrin αvβ3 suppressed HSC function in the presence of IFNγ and impaired integrin β3 signaling mitigated IFNγ‐dependent negative action on HSCs. During IFNγ stimulation, integrin β3 signaling enhanced STAT1‐mediated gene expression via serine phosphorylation. These findings show that integrin β3 signaling intensifies the suppressive effect of IFNγ on HSCs, which indicates that cell adhesion via integrin αvβ3 within the BM niche acts as a context‐dependent signal modulator to regulate the HSC function under both steady‐state and inflammatory conditions.     

Origin of improved depth penetration in dual‐axis optical coherence tomography: a Monte Carlo study

Recent studies have demonstrated that extended imaging depth can be achieved using dual‐axis optical coherence tomography (DA‐OCT). By illuminating and collecting at an oblique angle, multiple forward scattered photons from large probing depths are preferentially detected. However, the mechanism behind the enhancement of imaging depth needs further illumination. Here, the signal of a DA‐OCT system is studied using a Monte Carlo simulation. We modeled light transport in tissue and recorded the spatial and angular distribution of photons exiting the tissue surface. Results indicate that the spatial separation and offset angle created by the non‐telecentric scanning configuration promote the collection of more deeply propagating photons than conventional on‐axis OCT.      

Automated three‐dimensional cell counting method for grading uveitis of rodent eye in vivo with optical coherence tomography

In preclinical vision research, cell grading in small animal models is essential for the quantitative evaluation of intraocular inflammation. Here, we present a new and practical optical coherence tomography (OCT) image analysis method for the automated detection and counting of aqueous cells in the anterior chamber (AC) of a rodent model of uveitis. Anterior segment OCT images are acquired with a 100 kHz swept‐source OCT system. The proposed method consists of 2 steps. In the first step, we first despeckle and binarize each OCT image. After removing AS structures in the binary image, we then apply area thresholding to isolate cell‐like objects. Potential cell candidates are selected based on their best fit to roundness. The second step performs the cell counting within the whole AC, in which additional cell tracking analysis is conducted on the successive OCT images to eliminate redundancy in cell counting. Finally, 3D cell grading using the proposed method is demonstrated in longitudinal OCT imaging of a mouse model of anterior uveitis in vivo. Rendering of anterior segment (orange) of mouse eye and automatically counted anterior chamber cells (green). Inset is a top view of the rendering, showing the cell distribution across the anterior chamber.      

K‐distribution three‐dimensional mapping of biological tissues in optical coherence tomography

Probability density function (PDF) analysis with K‐distribution model of optical coherence tomography (OCT) intensity signals has previously yielded a good representation of the average number of scatterers in a coherence volume for microspheres‐in‐water systems, and has shown initial promise for biological tissue characterization. In this work, we extend these previous findings, based on single point M‐mode or two‐dimenstional slice analysis, to full three‐dimensional (3D) imaging maps of the shape parameter α of the K‐distribution PDF. After selecting a suitably sized 3D evaluation window, and verifying methodology in phantoms, the resultant parametric α images obtained in different animal tissues (rat liver and brain) show new contrasting ability not seen in conventional OCT intensity images.      

In vivo detection of tumor boundary using ultrahigh‐resolution optical coherence angiography and fluorescence imaging

Accurate detection of early tumor margin is of great preclinical and clinical implications for predicting the survival rate of subjects and assessing the response of tumor microenvironment to chemotherapy or radiation therapy. Here, we report a multimodality optical imaging study on in vivo detection of tumor boundary by analyzing neoangiogenesis of tumor microenvironment (microangiography), microcirculatory blood flow (optical Doppler tomography) and tumor proliferation (green fluorescent protein [GFP] fluorescence). Microangiography demonstrates superior sensitivity (77.7 ± 6.4%) and specificity (98.2 ± 1.7%) over other imaging technologies (eg, optical coherence tomography) for tumor margin detection. Additionally, we report longitudinal in vivo imaging of tumor progression and show that the abrupt tumor cell proliferation did not occur until local capillary density and cerebral blood flow reached their peak approximately 2 weeks after tumor implantation. The unique capability of longitudinal multimodality imaging of tumor angiogenesis may provide new insights in tumor biology and in vivo assessment of the treatment effects on anti‐angiogenesis therapy for brain cancer.     

Biocompatibility evaluation of bioprinted decellularized collagen sheet implanted in vivo cornea using swept‐source optical coherence tomography

Corneal transplantation by full‐thickness penetrating keratoplasty with human donor tissue is a widely accepted treatment for damaged or diseased corneas. Although corneal transplantation has a high success rate, a shortage of high‐quality donor tissue is a considerable limitation. Therefore, bioengineered corneas could be an effective solution for this limitation, and a decellularized extracellular matrix comprises a promising scaffold for their fabrication. In this study, three‐dimensional bioprinted decellularized collagen sheets were implanted into the stromal layer of the cornea of five rabbits. We performed in vivo noninvasive monitoring of the rabbit corneas using swept‐source optical coherence tomography (OCT) after implanting the collagen sheets. Anterior segment OCT images and averaged amplitude‐scans were acquired biweekly to monitor corneal thickness after implantation for 1 month. The averaged cornea thickness in the control images was 430.3 ± 5.9 μm, while the averaged thickness after corneal implantation was 598.5 ± 11.8 μm and 564.5 ± 12.5 μm at 2 and 4 weeks, respectively. The corneal thickness reduction of 34 μm confirmed the biocompatibility through the image analysis of the depth‐intensity profile base. Moreover, hematoxylin and eosin staining supported the biocompatibility evaluation of the bioprinted decellularized collagen sheet implantation. Hence, the developed bioprinted decellularized collagen sheets could become an alternative solution to human corneal donor tissue, and the proposed image analysis procedure could be beneficial to confirm the success of the surgery.      

Designed synthetic analogs of the α‐helical peptide temporin‐La with improved antitumor efficacies via charge modification and incorporation of the integrin αvβ3 homing domain

How to target cancer cells with high specificity and kill cancer cells with high efficiency remains an urgent demand for anticancer drugs. Temporin‐La, which belongs to the family of temporins, presents antitumor activity against many cancer cell lines. We first used a whole bioinformatic analysis method as a platform to identify new anticancer antimicrobial peptides (AMPs). On the basis of these results, we designed a temporin‐La analog (temporin‐Las) and related constructs containing the Arg‐Gly‐Asp (RGD) tripeptide, the integrin αvβ3 homing domain (RGD‐La and RGD‐Las). We detected a link between the net charges and integrin αvβ3 expression of cancer cell lines and the antitumor activities of these peptides. Temporin‐La and its synthetic analogs inhibited cancer cell proliferation in a dose‐dependent manner. Evidence was provided that the affinity between RGD‐Las and tumor cell membranes was stronger than other tested peptides using a pull‐down assay. Morphological changes on the cell membrane induced by temporin‐La and RDG‐Las, respectively, were examined by scanning electron microscopy. Additionally, time‐dependent morphological changes were detected by confocal microscopy, where the binding process of RGD‐Las to the cell membrane could be monitored. The results indicate that the electrostatic interaction between these cationic peptides and the anionic cell membrane is a major determinant of selective cell killing. Thus, the RGD tripeptide is a valuable ligand motif for tumor targeting, which leads to an increased anticancer efficiency by RGD‐Las. These AMP‐derived peptides have clinical potential as specifically targeting agents for the treatment of αvβ3 positive tumors. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Evaluation of corneal epithelial thickness in glaucomatous patients using anterior‐segment optical coherence tomography

The corneal epithelium represents one of the main structures that undergo degenerative alterations due to antiglaucomatous therapy. Chronic glaucoma therapy containing benzalkonium chloride induces epithelial cellular changes and inflammatory infiltration that in turn causes ocular surface changes resulting in ocular discomfort. Also, age‐related changes can involve the tear film stability and the corneal epithelium surface with reduction of microvilli. The objective of this study is to gain insights about the changes in corneal epithelium in glaucomatous patients divided according to age, type and duration of therapy using anterior‐segment optical coherence tomography (AS‐OCT). This study evaluated a total of 81 eyes of 42 patients for whom corneal epithelium thickness (CET) was measured in different sectors of the cornea. Our results showed no significant differences in CET among patients divided according to type and duration of treatment, while younger patients showed a thinner CET in comparison with older patients. AS‐OCT results demonstrated that the physiological age‐related alterations contributed to corneal epithelium changes in patients undergo chronic antiglaucoma therapy.     

Reversing microtubule‐directed chemotherapeutic drug resistance by co‐delivering α2β1 inhibitor and paclitaxel with nanoparticles in ovarian cancer

Previous reports indicated that integrins associated signals are tightly related to tumor progression. Here, we observed elevated expression of integrin α2β1 in tumor tissues from microtubule‐directed chemotherapeutic drugs (MDCDs) resistant patients compared with the samples from chemosensitive patients. More importantly, we sorted the integrin α2β1⁺ tumor cells and found those cells revealed high MDCDs resistance, whereas MDCDs shows effective cytotoxicity to those integrin α2β1^? tumor cells in vitro and in vivo. Mechanistically, we demonstrated that integrin α2β1 could induce MDCDs resistance through the activation of the PI3K/AKT pathway. Applying MPEG‐PLA to co‐encapsulate the integrin α2β1 inhibitor E7820 and MDCDs could effectively reverse MDCDs resistance, resulting in enhanced anticancer effects while avoiding potential systemic toxicity in vitro and in vivo. In conclusion, the expression of integrin α2β1 contributes to MDCDs resistance, while applying E7820 combination treatment by MPEG‐PLA nanoparticles could reverse the resistance.     

In vivo detection of endotracheal tube biofilms in intubated critical care patients using catheter‐based optical coherence tomography

The formation of biofilms in the endotracheal tubes (ETTs) of intubated patients on mechanical ventilation is associated with a greater risk of ventilator‐associated pneumonia and death. New technologies are needed to detect and monitor ETTs in vivo for the presence of these biofilms. Longitudinal OCT imaging was performed in mechanically ventilated subjects at 24‐hour intervals until extubation to detect the formation and temporal changes of in vivo ETT biofilms. OCT‐derived attenuation coefficient images were used to differentiate between mucus and biofilm. Extubated ETTs were examined with optical and electron microscopy, and all imaging results were correlated with standard‐of‐care clinical test reports. OCT and attenuation coefficient images from four subjects were positive for ETT biofilms and were negative for two subjects. The processed and stained extubated ETTs and clinical reports confirmed the presence/absence of biofilms in all subjects. Our findings confirm that OCT can detect and differentiate between biofilm‐positive and biofilm‐negative groups (P < 10^?5). OCT image‐based features may serve as biomarkers for direct in vivo detection of ETT biofilms and help drive investigation of new management strategies to reduce the incidence of VAP.