Micro-optical Coherence Tomography Research Articles

Imaging human coronary cholesterol/urate crystals with cross-polarized micro-optical coherence tomography.

Birefringent crystals such as monosodium-urate (MSU) and cholesterol crystals (CC) likely contribute to the progression of coronary artery disease (CAD) due to their potential to exacerbate inflammation through inflammatory cytokine activation. Here, we present cross-polarized micro-optical coherence tomography (CP-µOCT) for visualizing individual birefringent crystals in human coronary arteries. Human cadaver coronary arteries with a history of CAD with or without gout were dissected for CP-µOCT imaging. Specimens were processed for histological identification of birefringence under polarization light microscopy (PLM). CP-µOCT visualized needle-crystals that appeared as long projections in orthogonal planes, and PLM confirmed that CP-µOCT-delineated needle-crystals demonstrated negative birefringence. The needle-crystals were dissolved after immersion in uricase (p < 0.05), and thus were MSU. CP-µOCT was three-dimensionally volume-rendered for counting MSU and CCs in 79 regions of interest sized [750 (x) × 500 (y) × 400 (z) µm]. Crystal counts were normalized by the total coronary length utilized. The relationship between CP-µOCT-delineated MSU counts and those seen in corresponding histology, and the difference in coronary MSU amongst gout vs. non-gout patients was analyzed. CP-µOCT-delineated MSU counts were significantly correlated with MSU counted by PLM-based histology (R = 0.98, p < 0.01), and with histology-derived intimal thickening (R = 0.51, p < 0.01). MSU and CCs were both significantly greater in gout patients compared with non-gout patients (p < 0.05). These results demonstrate a significant increase in CP-µOCT-delineated crystals in gout vs. non-gout patients, suggesting that this technology can be used to improve our understanding of crystal-driven coronary pathogenesis.

Metachrony drives effective mucociliary transport via a calcium-dependent mechanism.

The mucociliary transport apparatus is critical for maintaining lung health via the coordinated movement of cilia to clear mucus and particulates. A metachronal wave propagates across the epithelium when cilia on adjacent multiciliated cells beat slightly out of phase along the proximal-distal axis of the airways in alignment with anatomically directed mucociliary clearance. We hypothesized that metachrony optimizes mucociliary transport (MCT) and that disruptions of calcium signaling would abolish metachrony and decrease MCT. We imaged bronchi from human explants and ferret tracheae using micro-optical coherence tomography (µOCT) to evaluate airway surface liquid depth (ASL), periciliary liquid depth (PCL), cilia beat frequency (CBF), MCT, and metachrony in situ. We developed statistical models that included covariates of MCT. Ferret tracheae were treated with BAPTA-AM (chelator of intracellular Ca2+), lanthanum chloride (nonpermeable Ca2+ channel competitive antagonist), and repaglinide (inhibitor of calaxin) to test calcium dependence of metachrony. We demonstrated that metachrony contributes to mucociliary transport of human and ferret airways. MCT was augmented in regions of metachrony compared with nonmetachronous regions by 48.1%, P = 0.0009 or 47.5%, P < 0.0020 in humans and ferrets, respectively. PCL and metachrony were independent contributors to MCT rate in humans; ASL, CBF, and metachrony contribute to ferret MCT rates. Metachrony can be disrupted by interference with calcium signaling including intracellular, mechanosensitive channels, and calaxin. Our results support that the presence of metachrony augments MCT in a calcium-dependent mechanism.NEW & NOTEWORTHY We developed a novel imaging-based analysis to detect coordination of ciliary motion and optimal coordination, a process called metachrony. We found that metachrony is key to the optimization of ciliary-mediated mucus transport in both ferret and human tracheal tissue. This process appears to be regulated through calcium-dependent mechanisms. This study demonstrates the capacity to measure a key feature of ciliary coordination that may be important in genetic and acquired disorders of ciliary function.

Dynamic micro-optical coherence tomography enables structural and metabolic imaging of the mammalian cochlea.

Sensorineural hearing loss (SNHL) is caused by damage to the mechanosensory hair cells and auditory neurons of the cochlea. The development of imaging tools that can directly visualize or provide functional information about a patient's cochlear cells is critical to identify the pathobiological defect and determine the cells' receptiveness to emerging SNHL treatments. However, the cochlea's small size, embedded location within dense bone, and sensitivity to perturbation have historically precluded high-resolution clinical imaging. Previously, we developed micro-optical coherence tomography (μOCT) as a platform for otologic imaging in animal models and human cochleae. Here we report on advancing μOCT technology to obtain simultaneously acquired and co-localized images of cell viability/metabolic activity through dynamic μOCT (DμOCT) imaging of intracellular motion. DμOCT obtains cross-sectional images of ATP-dependent movement of intracellular organelles and cytoskeletal polymerization by acquiring sequential μOCT images and computing intensity fluctuation frequency metrics on a pixel-wise basis. Using a customized benchtop DμOCT system, we demonstrate the detailed resolution of anatomical and metabolic features of cells within the organ of Corti, via an apical cochleostomy, in freshly-excised adult mouse cochleae. Further, we show that DμOCT is capable of capturing rapid changes in cochlear cell metabolism following an ototoxic insult to induce cell death and actin stabilization. Notably, as few as 6 frames can be used to reconstruct cochlear DμOCT images with sufficient detail to discern individual cells and their metabolic state. Taken together, these results motivate future development of a DμOCT imaging probe for cellular and metabolic diagnosis of SNHL in humans.

Hypoxia-induced cystic fibrosis transmembrane conductance regulator dysfunction is a universal mechanism underlying reduced mucociliary transport in sinusitis.

Hypoxia due to sinus obstruction is a major pathogenic mechanism leading to sinusitis. The objective of the current study is to define the electrophysiologic characteristics of hypoxia in vitro and in vivo. Cystic fibrosis bronchoepithelial cells expressing wild-type cystic fibrosis transmembrane conductance regulator (CFTR) and human sinonasal epithelial cells were exposed to 1% or atmospheric O2 for 24h. Time-dependent production of cytoplasmic free radicals was measured. Cells were subjected to Ussing chamber and patch clamp technique where CFTR currents were recorded in whole-cell and cell-attached mode for single channel studies. Indices of mucociliary transport (MCT) were measured using micro-optical coherence tomography. In a rabbit hypoxic maxillary sinus model, tissue oxygenation, relative mRNA expression of HIF-1α, pH, sinus potential difference (SPD), and MCT were determined. Ussing chamber (p<0.05), whole-cell (p<0.001), and single channel patch-clamp (p<0.0001) showed significant inhibition of Cl- currents in hypoxic cells. Cytoplasmic free radicals showed time-dependent elevation peaking at 4h (p<0.0001). Airway surface liquid (p<0.0001), periciliary liquid (p<0.001), and MCT (p<0.01) were diminished. Co-incubation with the free radical scavenger glutathione negated the impact of hypoxia on single channel currents and MCT markers. In sinusitis rabbits, mucosa exhibited low tissue oxygenation (p<0.0001), increased HIF1α mRNA (p<0.05), reduced pH (p<0.01), and decreased MCT (p<0.001). SPD measurements demonstrated markedly diminished transepithelial Cl- transport (p<0.0001). Hypoxia induces severe CFTR dysfunction via free radical production causing reduced MCT in vitro and in vivo. Improved oxygenation is critical to reducing the impact of persistent mucociliary dysfunction.

Glutathione and bicarbonate nanoparticles improve mucociliary transport in cystic fibrosis epithelia.

Cystic fibrosis (CF) airway disease is characterized by thick mucus and impaired mucociliary transport (MCT). Loss of functional cystic fibrosis transmembrane receptor (CFTR) leads to acidification and oxidation of airway surface mucus. Replacing bicarbonate (HCO3 -) topically fails due to rapid reabsorption and neutralization, while the scavenging antioxidant, glutathione sulfhydryl (GSH), is also rapidly degraded. The objective of this study is to investigate GSH/NaHCO3 nanoparticles as novel strategy for CF airway disease. GSH/NaHCO3 poly (lactic-co-glycolic acid) nanoparticles were tested on primary CF (F508del/F508del) epithelial cultures to evaluate dose-release curves, surface pH, toxicity, and MCT indices using micro-optical coherence tomography. In vivo tests were performed in three rabbits to assess safety and toxicity. After 1week of daily injections, histopathology, computed tomography (CT), and blood chemistries were performed and compared to three controls. Fluorescent nanoparticles were injected into a rabbit with maxillary sinusitis and explants visualized with confocal microscopy. Sustained release of GSH and HCO3 - with no cellular toxicity was observed over 2weeks. Apical surface pH gradually increased from 6.54±0.13 (baseline) to 7.07±0.10 (24h) (p<0.001) and 6.87 ± 0.05 at 14 days (p<0.001). MCT, ciliary beat frequency, and periciliary liquid were significantly increased. When injected into the maxillary sinuses of rabbits, there were no changes to histology, CT, or blood chemistries. Nanoparticles penetrated rabbit sinusitis mucus on confocal microscopy. Findings suggest that GSH/NaHCO3 - nanoparticles are a promising treatment option for viscous mucus in CF and other respiratory diseases of mucus obstruction such as chronic rhinosinusitis.

Red ginseng aqueous extract improves mucociliary transport dysfunction and histopathology in CF rat airways

BackgroundWe previously discovered that Korean red ginseng aqueous extract (RGAE) potentiates the TMEM16A channel, improved mucociliary transport (MCT) parameters in CF nasal epithelia in vitro, and thus could serve as a therapeutic strategy to rescue the MCT defect in cystic fibrosis (CF) airways. The hypothesis of this study is that RGAE can improve epithelial Cl− secretion, MCT, and histopathology in an in-vivo CF rat model. MethodsSeventeen 4-month old CFTR–/– rats were randomly assigned to receive daily oral control (saline, n = 9) or RGAE (Ginsenosides 0.4mg/kg/daily, n = 8) for 4 weeks. Outcomes included nasal Cl− secretion measured with the nasal potential difference (NPD), functional microanatomy of the trachea using micro-optical coherence tomography, histopathology, and immunohistochemical staining for TMEM16a. ResultsRGAE-treated CF rats had greater mean NPD polarization with UTP (control = -5.48 +/- 2.87 mV, RGAE = -9.49 +/- 2.99 mV, p < 0.05), indicating, at least in part, potentiation of UTP-mediated Cl− secretion through TMEM16A. All measured tracheal MCT parameters (airway surface liquid, periciliary liquid, ciliary beat frequency, MCT) were significantly increased in RGAE-treated CF rats with MCT exhibiting a 3-fold increase (control, 0.45+/-0.31 vs. RGAE, 1.45+/-0.66 mm/min, p < 0.01). Maxillary mucosa histopathology was markedly improved in RGAE-treated cohort (reduced intracellular mucus, goblet cells with no distention, and shorter epithelial height). TMEM16A expression was similar between groups. ConclusionRGAE improves TMEM16A-mediated transepithelial Cl− secretion, functional microanatomy, and histopathology in CF rats. Therapeutic strategies utilizing TMEM16A potentiators to treat CF airway disease are appropriate and provide a new avenue for mutation-independent therapies.

Nicotine aerosols diminish airway CFTR function and mucociliary clearance.

Electronic cigarettes (e-cigs) are often promoted as safe alternatives to smoking based on the faulty perception that inhaling nicotine is safe until other harmful chemicals in cigarette smoke are absent. Previously, others and we have reported that, similar to cigarette smoke, e-cig aerosols decrease CFTR-mediated ion transport across airway epithelium. However, it is unclear whether such defective epithelial ion transport by e-cig aerosols occurs in vivo and what the singular contribution of inhaled nicotine is to impairments in mucociliary clearance (MCC), the primary physiologic defense of the airways. Here, we tested the effects of nicotine aerosols from e-cigs in primary human bronchial epithelial (HBE) cells and two animal models, rats and ferrets, known for their increasing physiologic complexity and potential for clinical translation, followed by in vitro and in vivo electrophysiologic assays for CFTR activity and micro-optical coherence tomography (μOCT) image analyses for alterations in airway mucus physiology. Data presented in this report indicate nicotine in e-cig aerosols causes 1) reduced CFTR and epithelial Na+ channel (ENaC)-mediated ion transport, 2) delayed MCC, and 3) diminished airway surface hydration, as determined by periciliary liquid depth analysis. Interestingly, the common e-cig vehicles vegetable glycerin and propylene glycol did not affect CFTR function or MCC in vivo despite their significant adverse effects in vitro. Overall, our studies contribute to an improved understanding of inhaled nicotine effects on lung health among e-cig users and inform pathologic mechanisms involved in altered host defense and increased risk for tobacco-associated lung diseases.

Mucociliary transport deficiency and disease progression in Syrian hamsters with SARS-CoV-2 infection.

Substantial clinical evidence supports the notion that ciliary function in the airways is important in COVID-19 pathogenesis. Although ciliary damage has been observed in both in vitro and in vivo models, the extent or nature of impairment of mucociliary transport (MCT) in in vivo models remains unknown. We hypothesize that SARS-CoV-2 infection results in MCT deficiency in the airways of golden Syrian hamsters that precedes pathological injury in lung parenchyma. Micro-optical coherence tomography was used to quantitate functional changes in the MCT apparatus. Both genomic and subgenomic viral RNA pathological and physiological changes were monitored in parallel. We show that SARS-CoV-2 infection caused a 67% decrease in MCT rate as early as 2 days postinfection (dpi) in hamsters, principally due to 79% diminished airway coverage of motile cilia. Correlating quantitation of physiological, virological, and pathological changes reveals steadily descending infection from the upper airways to lower airways to lung parenchyma within 7 dpi. Our results indicate that functional deficits of the MCT apparatus are a key aspect of COVID-19 pathogenesis, may extend viral retention, and could pose a risk factor for secondary infection. Clinically, monitoring abnormal ciliated cell function may indicate disease progression. Therapies directed toward the MCT apparatus deserve further investigation.

Real-time delineation of basement membrane in human oral and esophageal mucosa with micro-optical coherence tomography

Basement membrane is a thin, extracellular matrix-like structure, separating the epithelium from the stroma and having a vital role in determining cancer progression. Identification of this diagnostically important structure with histology is invasive and labor-intensive. Micro-optical coherence tomography (µOCT) which has the capability to recognize subcellular-level microstructures underneath the surface offers the possibility to resolve basement membrane noninvasively in situ and in vivo. In this study, we conducted numerical analysis of the back-scattering intensity of basement membrane and experimental µOCT imaging of human labial mucosa in vivo and esophageal mucosa ex vivo, in an attempt to characterize the basement membrane underlying stratified squamous epithelial tissues. The results disclose that the layered structure of mucosa could be clearly delineated and the basement membrane presented as a steep, low-scattering linear structure in between the relatively high-scattering epithelium and stroma. Besides, according to the knowledges on its ultrastructure, we assume the low-scattering signal is collectively determined by basal lamina and reticular lamina since the former alone is extremely thin to be recognized by µOCT. This study clarifies the scattering features of basement membrane and the capability of real-time delineation of basement membrane which will help to determine the progression of epithelial cancers without the need of resection and histology.

Intracoronary Imaging-Can It Make Difference in State of the Art PCI?

There is an anatomy and there is an anatomy. Angiography is a rough method used for estimating dimensions. By completing the intervention with intracoronary imaging, one can directly characterize lesion composition, elucidate pathophysiology, and luminal size measurement. This review describes patients and lesions where imaging may be most beneficial, along with up-to-date evidence of the impact induced on cardiovascular events by the intracoronary imaging. It summarizes the importance of organizing procedural strategies and the use of various imaging methods such as optical coherence tomography or intravascular ultrasound for percutaneous coronary intervention (PCI) to improve stent optimization. Further, various advantages and disadvantages are associated with the use of imaging methods OCT and IVUS in the management of PCI and the elucidation of the causes of stent failure are discussed. It also explains the use of OCT or IVUS in various severe pathological conditions such as severe kidney disease (CKD), left main disease, bifurcation lesion, acute coronary syndrome (ACS), and patients present with high bleeding risk. It also describes diagnostic imaging of patients with vulnerable plaques. We will also talk about various other advanced imaging methods such as investigational Micro-optical Coherence Tomography and near-infrared spectroscopy (NIRS).

Raman microspectroscopy/micro-optical coherence tomography approach for chairside diagnosis of periodontal diseases: A pilot study.

Our objective was to develop and test a combined Raman microspectroscopy (RMS) and micro-optical coherence tomography (μOCT) approach for chairside quantification of gingival collagen, DNA, epithelium, and connective tissue. We hypothesized that a high-resolution RMS/μOCT can characterize healthy and inflamed periodontal tissues for diagnosis and disease activity monitoring. A prototype instrument was developed, tested ex vivo on gingival specimens and optimized for in vivo intraoral use. The primary outcome measures were the ratios of oral epithelium to connective tissue thickness (OE:CT) and the amount of DNA to collagen type I (DNA/Col 1), and the thickness of sulcular epithelium (SE). For ex vivo testing, eight subjects with healthy periodontal tissues or with Stage II to IV periodontitis were included in the study and underwent crown-lengthening or periodontal surgical procedures, respectively. Gingival biopsies were scanned by RMS/μOCT and histometric analyses were performed. The proof-of-concept study included OE/CT, DNA/Col 1, and SE assessed in six volunteers with or without signs of gingival inflammation (n=3/group). The spatially co-registered RMS spectra revealed opposing changes in the collagen and DNA peaks of inflamed compared with healthy tissues (P<0.05). Combined RMS/μOCT analysis showed that OE/CT, DNA/Col, and SE are significantly different between healthy and inflamed sites (P<0.05). Histological assessments confirmed the differences detected by RMS/μOCT. Qualitative analysis of DNA/Col 1 ratios indicated Col I content as the main distinguishing feature for health and DNA content for periodontitis. Results suggest that combined RMS/μOCT chairside imaging may distinguish between healthy and diseased sites by evaluating marginal periodontal morphological and biochemical features.

PDE4 Inhibitor Reverses Alcohol Impairment of CFTR Function and Protects Against Bacterial Pneumonia

INTRODUCTIONAlcohol is a significant risk factor for respiratory infections. Excessive alcohol users suffer from more frequent lung infections, severe symptoms, and poor antibiotic response. Mucociliary clearance (MCC) is a primary lung defense mechanism against inhaled/aspirated pathogens and is impaired by alcohol use. Previously, we found diminished MCC associates with reduced CFTR‐mediated ion transport in alcohol‐fed rats. In addition, CFTR dysfunction correlated with increased cAMP degradation by phosphodiesterase‐4 (PDE4) enzymes and reduced channel gating. Here, we test whether roflumilast, a clinically used PDE4 inhibitor, can preserve cAMP levels in alcohol‐fed rats and promote CFTR function and clearance of Klebsiella pneumoniae (KP, ATCC 43816), to which alcohol users are disproportionately susceptible.METHODSAge and gender‐matched rats (CFTR+/+) were pair‐fed with Lieber‐DeCarli alcohol diet or isocaloric control diet for eight weeks. CFTR activity was assayed by Ussing chamber electrophysiology of tracheal explants. Rats were randomly treated with vehicle/roflumilast (5mg/kg/day) by oral gavage starting 7 days before the end of 8‐week alcohol diet. Airway surface liquid (ASL) depth, periciliary layer (PCL) height, mucus viscosity, and transport (MCT) on excised trachea were quantified with micro‐optical coherence tomography (µOCT) imaging. In addition, lung function was assessed by flexivent oscillometry.RESULTSAlcohol administration reduced CFTR‐mediated ion transport in rat airways. µOCT image analysis of excised trachea from these rats indicated decreased PCL depth and increased mucus viscosity. Despite the normal ciliary beating, there was a noticeable delay in MCT in alcohol‐fed rats. Roflumilast treatment significantly increased CFTR activity in both control and alcohol‐administered rats. Increased CFTR activation by roflumilast resulted in augmented PCL depth, reduced mucus viscosity, and significantly accelerated MCT rate. While roflumilast partially improved clearance of KP, there was pronounced protection against increased airway resistance and lung injury. Histopathological examination of lung sections indicates roflumilast reduced the severity of multifocal pneumonia with edema, fibrin deposition, and numerous bacteria in alveolar spaces. These improvements were more evident in control rats over those administered with alcohol. Ongoing studies are exploring how roflumilast altered immune cell recruitment and inflammatory signaling to reduce infectious injury.CONCLUSIONSAcquired (non‐genetic) CFTR dysfunction may be a suitable target to improve mucus clearance impaired by alcohol use. Administration of PDE4 inhibitors such as roflumilast may boost lung host defense against bacterial pathogens and improve pneumonia outcomes in individuals affected by excessive alcohol use.

B-scan-sectioned dynamic micro-optical coherence tomography for bulk-motion suppression

In this Letter, we present B-scan-sectioned dynamic micro-optical coherence tomography (BD-MOCT) for high-quality sub-cellular dynamic contrast imaging. Dynamic micro-optical coherence tomography (D-MOCT) is a functional optical coherence tomography (OCT) technique performed on high-resolution (micron level) OCT systems; hundreds of consecutive B-scans need to be acquired for dynamic signal extraction, which requires relatively long data acquisition time. Bulk motions occurring during data acquisition (even at the micron level) may degrade the quality of the obtained dynamic contrast images. In BD-MOCT, each full B-scan is divided into several sub-B-scans, and each sub-B-scan repeats multiple times before the sample beam moves to the next sub-B-scan. After all of the sub-B-scans for a full B-scan are completely acquired, we stitch all of the sub-B-scans into the same number of full B-scans. In this way, the time interval between two consecutive stitched B-scans could be reduced multiple times for bulk-motion suppression. The performed scanning protocol modulates the scanning sequences of fast scanning and repeat scanning for improving the dynamic contrast image quality, while the total data acquisition time remains almost the same.

Advances in Imaging of Subbasal Corneal Nerves With Micro-Optical Coherence Tomography.

PurposeTo investigate the most peripheral corneal nerve plexus using high-resolution micro–optical coherence tomography (µOCT) imaging and to assess µOCT's clinical potential as a screening tool for corneal and systemic diseases.MethodsAn experimental high-resolution (1.5 × 1.5 × 1 µm) µOCT setup was applied for three-dimensional imaging of the subbasal nerve plexus in nonhuman primates (NHPs) and swine within 3 hours postmortem. Morphologic features of subbasal nerves in µOCT were compared to β3 tubulin-stained fluorescence confocal microscopy (FCM). Parameters such as nerve density, nerve distribution, and imaging repeatability were evaluated, using semiautomatic image analysis in form of a custom corneal surface segmentation algorithm and NeuronJ.ResultsSwine and NHP corneas showed the species-specific nerve morphology in both imaging modalities. Most fibers showed a linear course, forming a highly parallel pattern, converging in a vortex with overall nerve densities varying between 9.51 and 24.24 mm/mm2. The repeatability of nerve density quantification of the µOCT scans as approximately 88% in multiple image recordings of the same cornea.ConclusionsCompared to the current gold standard of FCM, µOCT's larger field of view of currently 1 × 1 mm increases the conclusiveness of density measurements, which, coupled with µOCT's feature of not requiring direct contact, shows promise for future clinical application. The nerve density quantification may be relevant for screening for systemic disease (e.g., peripheral neuropathy).Translational RelevanceTechnological advances in OCT technology may enable a quick assessment of corneal nerve density, which could be valuable evaluating ophthalmic and systemic peripheral innervation.

Ivacaftor restores delayed mucociliary transport caused by Pseudomonas aeruginosa-induced acquired cystic fibrosis transmembrane conductance regulator dysfunction in rabbit nasal epithelia.

Abnormal chloride (Cl- ) transport dehydrates airway surface liquid (ASL) in sinonasal epithelium leading to mucus stasis and chronic rhinosinusitis. As an experimental epithelium, rabbit tissue provides an excellent representation of human sinus disease, and the rabbit sinusitis model is both established and well suited for therapeutic interventions in vivo. Our objective in this study was to evaluate whether ivacaftor reverses the consequences of Pseudomonas aeruginosa-induced acquired cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction. Rabbit nasal cavities were assessed for responsiveness to ivacaftor in vivo (by nasal potential difference [NPD] assay). Rabbit nasal epithelial (RNE) cultures were incubated with an ultrafiltrate of P aeruginosa (PAO1 strain) for 4hours and tested for acquired CFTR dysfunction. Markers of mucociliary function, including airway surface liquid depth (ASL), periciliary liquid depth (PCL), ciliary beat frequency (CBF), and mucociliary transport (MCT), were measured by micro-optical coherence tomography (μOCT) after PAO1 and/or ivacaftor incubation. Ivacaftor resulted in a significant mean NPD polarization of 21.8 ± 2.1mV, which was significantly greater than that seen in the low Cl- control (12.9 ± 1.3; p=0.01). PAO1 exposure induced a state of acquired CFTR dysfunction in rabbit nasal epithelium as measured byforskolin-stimulated short-circuit current (ISC ) (control, 37.0 ± 1.1μA/cm2 ; PAO1, 24.4 ± 1.1 μA/cm2 ;p<0.001). RNE cultures exposed to PAO1 had inhibited mucociliary function, whereas coincubation with ivacaftor restored mucociliary clearance, as measured by μOCT. In rabbit nasal epithelium, ivacaftor robustly stimulates CFTR-mediated Cl- secretion and normalizes ASL and CBF in PAO1-induced acquired CFTR dysfunction. Preclinical testing of CFTR potentiators as therapy for P aeruginosa rabbit sinusitis is planned.

Endomicroscopy of the human cochlea using a micro-optical coherence tomography catheter

Sensorineural hearing loss (SNHL) is one of the most profound public health concerns of the modern era, affecting 466 million people today, and projected to affect 900 million by the year 2050. Advances in both diagnostics and therapeutics for SNHL have been impeded by the human cochlea’s inaccessibility for in vivo imaging, resulting from its extremely small size, convoluted coiled configuration, fragility, and deep encasement in dense bone. Here, we develop and demonstrate the ability of a sub-millimeter-diameter, flexible endoscopic probe interfaced with a micro-optical coherence tomography (μOCT) imaging system to enable micron-scale imaging of the inner ear’s sensory epithelium in cadaveric human inner ears.

Resolution enhancement and realistic speckle recovery with generative adversarial modeling of micro-optical coherence tomography.

A resolution enhancement technique for optical coherence tomography (OCT), based on Generative Adversarial Networks (GANs), was developed and investigated. GANs have been previously used for resolution enhancement of photography and optical microscopy images. We have adapted and improved this technique for OCT image generation. Conditional GANs (cGANs) were trained on a novel set of ultrahigh resolution spectral domain OCT volumes, termed micro-OCT, as the high-resolution ground truth (∼1 μm isotropic resolution). The ground truth was paired with a low-resolution image obtained by synthetically degrading resolution 4x in one of (1-D) or both axial and lateral axes (2-D). Cross-sectional image (B-scan) volumes obtained from in vivo imaging of human labial (lip) tissue and mouse skin were used in separate feasibility experiments. Accuracy of resolution enhancement compared to ground truth was quantified with human perceptual accuracy tests performed by an OCT expert. The GAN loss in the optimization objective, noise injection in both the generator and discriminator models, and multi-scale discrimination were found to be important for achieving realistic speckle appearance in the generated OCT images. The utility of high-resolution speckle recovery was illustrated by an example of micro-OCT imaging of blood vessels in lip tissue. Qualitative examples applying the models to image data from outside of the training data distribution, namely human retina and mouse bladder, were also demonstrated, suggesting potential for cross-domain transferability. This preliminary study suggests that deep learning generative models trained on OCT images from high-performance prototype systems may have potential in enhancing lower resolution data from mainstream/commercial systems, thereby bringing cutting-edge technology to the masses at low cost.

Recent Advances in Vascular Imaging.

Recent advances in vascular imaging have enabled us to uncover the underlying mechanisms of vascular diseases both ex vivo and in vivo. In the past decade, efforts have been made to establish various methodologies for evaluation of atherosclerotic plaque progression and vascular inflammatory changes in addition to biomarkers and clinical manifestations. Several recent publications in Arteriosclerosis, Thrombosis, and Vascular Biology highlighted the essential roles of in vivo and ex vivo vascular imaging, including magnetic resonance image, computed tomography, positron emission tomography/scintigraphy, ultrasonography, intravascular ultrasound, and most recently, optical coherence tomography, all of which can be used in bench and clinical studies at relative ease. With new methods proposed in several landmark studies, these clinically available imaging modalities will be used in the near future. Moreover, future development of intravascular imaging modalities, such as optical coherence tomography-intravascular ultrasound, optical coherence tomography-near-infrared autofluorescence, polarized-sensitive optical coherence tomography, and micro-optical coherence tomography, are anticipated for better management of patients with cardiovascular disease. In this review article, we will overview recent advances in vascular imaging and ongoing works for future developments.

Micro-optical coherence tomography for high-resolution morphologic imaging of cellular and nerval corneal micro-structures.

We demonstrate the highest resolution (1.5×1.5×1 µm) micrometer optical coherence tomography (µOCT) imaging of the morphologic micro-structure of excised swine and non-human primate corneas. Besides epithelial, stromal, and endothelial cell morphology, this report focuses on investigating the most peripheral corneal nerve fibers, the nerve fibers of the subbasal plexus (SBP). Alterations of SBP nerve density and composition are reportedly linked to major neurologic disorders, such as diabetic neuropathy, potentially indicating earliest onsets of denervation. Here, the fine, hyperreflective, epithelial nerve structures located just above Bowman's membrane, are i) visualized using our µOCT prototype, ii) validated by comparison to fluorescence confocal microscopy (including selective immunohistochemical staining), and iii) segmented using state-of-the-art image processing. Here, we also introduce polarization sensitive (PS) µOCT imaging, demonstrating, to the best of our knowledge, the highest resolution corneal PS-OCT scans reported to date.

Novel Therapy of Bicarbonate, Glutathione, and Ascorbic Acid Improves Cystic Fibrosis Mucus Transport.

Defective airway mucus clearance is a defining characteristic of cystic fibrosis lung disease, and improvements to current mucolytic strategies are needed. Novel approaches targeting a range of contributing mechanisms are in various stages of preclinical and clinical development. ARINA-1 is a new nebulized product comprised of ascorbic acid, glutathione, and bicarbonate. Using microoptical coherence tomography, we tested the effect of ARINA-1 on central features of mucociliary clearance in F508del/F508del primary human bronchial epithelial cells to assess its potential as a mucoactive therapy in cystic fibrosis. We found that ARINA-1 significantly augmented mucociliary transport rates, both alone and with CFTR (cystic fibrosis transmembrane conductance regulator) modulator therapy, whereas airway hydration and ciliary beating were largely unchanged compared with PBS vehicle control. Analysis of mucus reflectivity and particle-tracking microrheology indicated that ARINA-1 restores mucus clearance by principally reducing mucus layer viscosity. The combination of bicarbonate and glutathione elicited increases in mucociliary transport rate comparable to those seen with ARINA-1, indicating the importance of this interaction to the impact of ARINA-1 on mucus transport; this effect was not recapitulated with bicarbonate alone or bicarbonate combined with ascorbic acid. Assessment of CFTR chloride transport revealed an increase in CFTR-mediated chloride secretion in response to ARINA-1 in CFBE41o- cells expressing wild-type CFTR, driven by CFTR activity stimulation by ascorbate. This response was absent in CFBE41o- F508del cells treated with VX-809 and primary human bronchial epithelial cells, implicating CFTR-independent mechanisms for the effect of ARINA-1 on cystic fibrosis mucus. Together, these studies indicate that ARINA-1 is a novel potential therapy for the treatment of impaired mucus clearance in cystic fibrosis.