Visualization and Detection of Ciliary Beating Pattern and Frequency in the Upper Airway using Phase Resolved Doppler Optical Coherence Tomography

Quantitative assessment of chlorine gas inhalation injury based on endoscopic OCT and spectral encoded interferometric microscope imaging with deep learning

Chlorine exposure can cause severe airway injuries. While the acute effects of chlorine inhalation are well-documented, the structural changes resulting from the post-acute, high-level chlorine exposure remain less understood. Airway sloughing is one of the standards for doctors to evaluate the lung function. Here, we report the application of a high-resolution swept-source optical coherence tomography system to investigate the progression of injury based on airway sloughing evaluation in a chlorine inhalation rabbit model. This system employs a 1.2 mm diameter flexible fiberoptic endoscopic probe via an endotracheal tube to capture in vivo large airway anatomical changes before and as early as 30 min after acute chlorine exposure. We conducted an animal study using New Zealand white rabbits exposed to acute chlorine gas (800 ppm, 6 min) during ventilation and monitored them using optical coherence tomography (OCT) for 6 h. To measure the volume of airway sloughing induced by chlorine gas, we utilized deep learning for the segmentation task on OCT images. The results showed that the volume of chlorine induced epithelial sloughing on rabbit tracheal walls initially increased, peaked around 30 min, and then decreased. Furthermore, we utilized a spectral encoded interferometric microscopy system to study ex vivo airway cilia beating dynamics based on Doppler shift, aiding in elucidating how chlorine gas affects cilia beating function. Cilia movability and beating frequency were decreased because of the epithelium damage. This quantitative approach has the potential to enhance the diagnosis and monitoring of injuries from toxic gas inhalation and to evaluate the efficacy of antidote treatments for these injuries.

Poc1 bridges basal body inner junctions to promote triplet microtubule integrity and connections

Basal bodies (BBs) are conserved eukaryotic structures that organize cilia. They are comprised of nine, cylindrically arranged, triplet microtubules (TMTs) connected to each other by inter-TMT linkages which stabilize the structure. Poc1 is a conserved protein important for BB structural integrity in the face of ciliary forces transmitted to BBs. To understand how Poc1 confers BB stability, we identified the precise position of Poc1 in the Tetrahymena BB and the effect of Poc1 loss on BB structure. Poc1 binds at the TMT inner junctions, stabilizing TMTs directly. From this location, Poc1 also stabilizes inter-TMT linkages throughout the BB, including the cartwheel pinhead and the inner scaffold. The full localization of the inner scaffold protein Fam161A requires Poc1. As ciliary forces are increased, Fam161A is reduced, indicative of a force-dependent molecular remodeling of the inner scaffold. Thus, while not essential for BB assembly, Poc1 promotes BB interconnections that establish an architecture competent to resist ciliary forces.

Modelling bronchial epithelial-fibroblast cross-talk in idiopathic pulmonary fibrosis (IPF) using a human-derived in vitro air liquid interface (ALI) culture

Idiopathic Pulmonary Fibrosis (IPF) is a devastating form of respiratory disease with a life expectancy of 3-4 years. Inflammation, epithelial injury and myofibroblast proliferation have been implicated in disease initiation and, recently, epithelial-fibroblastic crosstalk has been identified as a central driver. However, the ability to interrogate this crosstalk is limited due to the absence of in vitro models that mimic physiological conditions. To investigate IPF dysregulated cross-talk, primary normal human bronchial epithelial (NHBE) cells and primary normal human lung fibroblasts (NHLF) or diseased human lung fibroblasts (DHLF) from IPF patients, were co-cultured in direct contact at the air-liquid interface (ALI). Intercellular crosstalk was assessed by comparing cellular phenotypes of co-cultures to respective monocultures, through optical, biomolecular and electrical methods. A co-culture-dependent decrease in epithelium thickness, basal cell mRNA (P63, KRT5) and an increase in transepithelial electrical resistance (TEER) was observed. This effect was significantly enhanced in DHLF co-cultures and lead to the induction of epithelial to mesenchymal transition (EMT) and increased mRNA expression of TGFβ-2, ZO-1 and DN12. When stimulated with exogenous TGFβ, NHBE and NHLF monocultures showed a significant upregulation of EMT (COL1A1, FN1, VIM, ASMA) and senescence (P21) markers, respectively. In contrast, direct NHLF/NHBE co-culture indicated a protective role of epithelial-fibroblastic cross-talk against TGFβ-induced EMT, fibroblast-to-myofibroblast transition (FMT) and inflammatory cytokine release (IL-6, IL-8, IL-13, IL-1β, TNF-α). DHLF co-cultures showed no significant phenotypic transition upon stimulation, likely due to the constitutively high expression of TGFβ isoforms prior to any exogenous stimulation. The model developed provides an alternative method to generate IPF-related bronchial epithelial phenotypes in vitro, through the direct co-culture of human lung fibroblasts with NHBEs. These findings highlight the importance of fibroblast TGFβ signaling in EMT but that monocultures give rise to differential responses compared to co-cultures, when exposed to this pro-inflammatory stimulus. This holds implications for any translation conclusions drawn from monoculture studies and is an important step in development of more biomimetic models of IPF. In summary, we believe this in vitro system to study fibroblast-epithelial crosstalk, within the context of IPF, provides a platform which will aid in the identification and validation of novel targets.

In vivo volumetric depth-resolved imaging of cilia metachronal waves using dynamic optical coherence tomography

Motile cilia are dynamic hair-like structures covering epithelial surfaces in multiple organs. The periodic coordinated beating of cilia creates waves propagating along the surface, known as the metachronal waves, which transport fluids and mucus along the epithelium. Motile ciliopathies result from disrupted coordinated cilia beating and are associated with serious clinical complications, including reproductive disorders. Despite the recognized clinical significance, research of cilia dynamics is extremely limited. Here, we present quantitative imaging of cilia metachronal waves volumetrically through tissue layers using dynamic optical coherence tomography (OCT). Our method relies on spatiotemporal mapping of the phase of intensity fluctuations in OCT images caused by the ciliary beating. We validated our new method ex vivo and implemented it in vivo to visualize cilia metachronal wave propagation within the mouse fallopian tube. This method can be extended to the assessment of physiological cilia function and ciliary dyskinesias in various organ systems, contributing to better management of pathologies associated with motile ciliopathies.

Role of Biomaterials in the Development of Epithelial Support in 3D In Vitro Airway Epithelium Development: A Systematic Review

Respiratory diseases have a major impact on global health. The airway epithelium, which acts as a frontline defence, is one of the most common targets for inhaled allergens, irritants, or micro-organisms to enter the respiratory system. In the tissue engineering field, biomaterials play a crucial role. Due to the continuing high impact of respiratory diseases on society and the emergence of new respiratory viruses, in vitro airway epithelial models with high microphysiological similarities that are also easily adjustable to replicate disease models are urgently needed to better understand those diseases. Thus, the development of biomaterial scaffolds for the airway epithelium is important due to their function as a cell-support device in which cells are seeded in vitro and then are encouraged to lay down a matrix to form the foundations of a tissue for transplantation. Studies conducted in in vitro models are necessary because they accelerate the development of new treatments. Moreover, in comparatively controlled conditions, in vitro models allow for the stimulation of complex interactions between cells, scaffolds, and growth factors. Based on recent studies, the biomaterial scaffolds that have been tested in in vitro models appear to be viable options for repairing the airway epithelium and avoiding any complications. This review discusses the role of biomaterial scaffolds in in vitro airway epithelium models. The effects of scaffold, physicochemical, and mechanical properties in recent studies were also discussed.

Rationalized deep learning super-resolution microscopy for sustained live imaging of rapid subcellular processes

The goal when imaging bioprocesses with optical microscopy is to acquire the most spatiotemporal information with the least invasiveness. Deep neural networks have substantially improved optical microscopy, including image super-resolution and restoration, but still have substantial potential for artifacts. In this study, we developed rationalized deep learning (rDL) for structured illumination microscopy and lattice light sheet microscopy (LLSM) by incorporating prior knowledge of illumination patterns and, thereby, rationally guiding the network to denoise raw images. Here we demonstrate that rDL structured illumination microscopy eliminates spectral bias-induced resolution degradation and reduces model uncertainty by five-fold, improving the super-resolution information by more than ten-fold over other computational approaches. Moreover, rDL applied to LLSM enables self-supervised training by using the spatial or temporal continuity of noisy data itself, yielding results similar to those of supervised methods. We demonstrate the utility of rDL by imaging the rapid kinetics of motile cilia, nucleolar protein condensation during light-sensitive mitosis and long-term interactions between membranous and membrane-less organelles.

The effects of acute hydrogen peroxide exposure on respiratory cilia motility and viability

COVID-19 has seen the propagation of alternative remedies to treat respiratory disease, such as nebulization of hydrogen peroxide (H₂O₂). As H₂O₂ has known cytotoxicity, it was hypothesised that H₂O₂ inhalation would negatively impact respiratory cilia function. To test this hypothesis, mouse tracheal samples were incubated with different H₂O₂ concentrations (0.1-1%) then cilia motility, cilia generated flow, and cell death was assessed 0-120 min following H₂O₂ treatment. 0.1-0.2% H₂O₂ caused immediate depression of cilia motility and complete cessation of cilia generated flow. Higher H₂O₂ concentrations (≥0.5%) caused immediate complete cessation of cilia motility and cilia generated flow. Cilia motility and flow was restored 30 min after 0.1% H₂O₂ treatment. Cilia motility and flow remained depressed 120 min after 0.2-0.5% H₂O₂ treatment. No recovery was seen 120 min after treatment with ≥1% H₂O₂. Live/dead staining revealed that H₂O₂ treatment caused preferential cell death of ciliated respiratory epithelia over non-ciliated epithelia, with 1% H₂O₂ causing 35.3 ± 7.0% of the ciliated epithelia cells to die 120 min following initial treatment. This study shows that H₂O₂ treatment significantly impacts respiratory cilia motility and cilia generated flow, characterised by a significant impairment in cilia motility even at low concentrations, the complete cessation of cilia motility at higher doses, and a significant cytotoxic effect on ciliated respiratory epithelial cells by promoting cell death. While this data needs further study using in vivo models, it suggests that extreme care should be taken when considering treating respiratory diseases with nebulised H₂O₂.

Light-sheet laser speckle imaging for cilia motility assessment

Mucociliary clearance is an important innate defense mechanism predominantly mediated by ciliated cells in the upper respiratory tract. Ciliary motility on the respiratory epithelium surface and mucus pathogen trapping assist in maintaining healthy airways. Optical imaging methods have been used to obtain several indicators for assessing ciliary movement. Light-sheet laser speckle imaging (LSH-LSI) is a label-free and non-invasive optical technique for three-dimensional and quantitative mapping of velocities of microscopic scatterers. Here, we propose to use an inverted LSH-LSI platform to study cilia motility. We have experimentally confirmed that LSH-LSI can reliably measure the ciliary beating frequency and has the potential to provide many additional quantitative indicators for characterizing the ciliary beating pattern without labeling. For example, the asymmetry between the power stroke and the recovery stroke is apparent in the local velocity waveform. PIV (particle imaging velocimetry) analysis of laser speckle data could determine the cilia motion directions in different phases.

Non-contact optical in-vivo sensing of cilia motion by analyzing speckle patterns

Cilia motion is an indicator of pathological-ciliary function, however current diagnosis relies on biopsies. In this paper, we propose an innovative approach for sensing cilia motility. We present an endoscopic configuration for measuring the motion frequency of cilia in the nasal cavity. The technique is based on temporal tracking of the reflected spatial distribution of defocused speckle patterns while illuminating the cilia with a laser. The setup splits the optical signal into two channels; One imaging channel is for the visualization of the physician and another is, defocusing channel, to capture the speckles. We present in-vivo measurements from healthy subjects undergoing endoscopic examination. We found an average motion frequency of around 7.3 Hz and 9.8 Hz in the antero-posterior nasal mucus (an area rich in cilia), which matches the normal cilia range of 7–16 Hz. Quantitative and precise measurements of cilia vibration will optimize the diagnosis and treatment of pathological-ciliary function. This method is simple, minimally invasive, inexpensive, and promising to distinguish between normal and ciliary dysfunction.

Dynamic volumetric imaging and cilia beat mapping in the mouse male reproductive tract with optical coherence tomography

Spermatozoa transport within the male reproductive tract is a highly dynamic and biologically important reproductive event. However, due to the lack of live volumetric imaging technologies and quantitative measurements, there is little information on the dynamic aspect and regulation of this process. Here, we presented ex vivo dynamic volumetric imaging of the mouse testis, efferent duct, epididymis, and vas deferens at a micro-scale spatial resolution with optical coherence tomography (OCT). Micro computed tomography imaging is presented as a reference for the proposed OCT imaging. Application of functional OCT analysis allowed for 3D mapping of the cilia beat frequency in the efferent duct, which volumetrically visualized the spatial distribution of the ciliated cells and corresponding ciliary activities. Potentially these analyses could be expanded to in vivo settings through intravital approach. In summary, this study demonstrated that OCT has a great potential to investigate the microstructure and dynamics, such as cilia beating, muscle contractions, and sperm transport, within the male reproductive tract.

An Adverse Outcome Pathway for Decreased Lung Function Focusing on Mechanisms of Impaired Mucociliary Clearance Following Inhalation Exposure

Adverse outcome pathways (AOPs) help to organize available mechanistic information related to an adverse outcome into key events (KEs) spanning all organizational levels of a biological system(s). AOPs, therefore, aid in the biological understanding of a particular pathogenesis and also help with linking exposures to eventual toxic effects. In the regulatory context, knowledge of disease mechanisms can help design testing strategies using in vitro methods that can measure or predict KEs relevant to the biological effect of interest. The AOP described here evaluates the major processes known to be involved in regulating efficient mucociliary clearance (MCC) following exposures causing oxidative stress. MCC is a key aspect of the innate immune defense against airborne pathogens and inhaled chemicals and is governed by the concerted action of its functional components, the cilia and airway surface liquid (ASL). The AOP network described here consists of sequences of KEs that culminate in the modulation of ciliary beat frequency and ASL height as well as mucus viscosity and hence, impairment of MCC, which in turn leads to decreased lung function.

Vaping and Lung Inflammation and Injury

The use of electronic (e)-cigarettes was initially considered a beneficial solution to conventional cigarette smoking cessation. However, paradoxically, e-cigarette use is rapidly growing among nonsmokers, including youth and young adults. In 2019, this rapid growth resulted in an epidemic of hospitalizations and deaths of e-cigarette users (vapers) due to acute lung injury; this novel disease was termed e-cigarette or vaping use-associated lung injury (EVALI). Pathophysiologic mechanisms of EVALI likely involve cytotoxicity and neutrophilic inflammation caused by inhaled chemicals, but further details remain unknown. The undiscovered mechanisms of EVALI are a barrier to identifying biomarkers and developing therapeutics. Furthermore, adverse effects of e-cigarette use have been linked to chronic lung diseases and systemic effects on multiple organs. In this comprehensive review, we discuss the diverse spectrum of vaping exposures, epidemiological and clinical reports, and experimental findings to provide a better understanding of EVALI and the adverse health effects of chronic e-cigarette exposure.

A spatial resolution evaluation method of endoscopic optical coherence tomography system using the annular phantom

As an important biomedical imaging method, endoscopic optical coherence tomography (OCT) is necessary to check its performance regularly. The ordinary plane phantoms are only able to evaluate part of image tangent to the probe. In this research, a spatial resolution estimate method of the endoscope OCT system is proposed. The annular phantom, made by uniformly distributing golden scattered microparticles in polydimethylsiloxane (PDMS), can provide dynamic scanning imaging evaluation of endoscopic OCT system, closer to its actual working status. The point spread function analysis method is used to analyze the imaging results of the annular phantom with the endoscopic OCT system. And many scattered particles are statistically analyzed to determine the spatial resolution of the endoscope OCT system. The method is low in cost, simple and convenient. It is valuable for the development of test standards for endoscope OCT systems.

Oxygenation as a driving factor in epithelial differentiation at the air-liquid interface

Culture at the air-liquid interface is broadly accepted as necessary for differentiation of cultured epithelial cells towards an in vivo-like phenotype. However, air-liquid interface cultures are expensive, laborious and challenging to scale for increased throughput applications. Deconstructing the microenvironmental parameters that drive these differentiation processes could circumvent these limitations, and here we hypothesize that reduced oxygenation due to diffusion limitations in liquid media limits differentiation in submerged cultures; and that this phenotype can be rescued by recreating normoxic conditions at the epithelial monolayer, even under submerged conditions. Guided by computational models, hyperoxygenation of atmospheric conditions was applied to manipulate oxygenation at the monolayer surface. The impact of this rescue condition was confirmed by assessing protein expression of hypoxia-sensitive markers. Differentiation of primary human bronchial epithelial cells isolated from healthy patients was then assessed in air-liquid interface, submerged and hyperoxygenated submerged culture conditions. Markers of differentiation, including epithelial layer thickness, tight junction formation, ciliated surface area and functional capacity for mucociliary clearance, were assessed and found to improve significantly in hyperoxygenated submerged cultures, beyond standard air-liquid interface or submerged culture conditions. These results demonstrate that an air-liquid interface is not necessary to produce highly differentiated epithelial structures, and that increased availability of oxygen and nutrient media can be leveraged as important strategies to improve epithelial differentiation for applications in respiratory toxicology and therapeutic development.

In vivo and in vitro observation of nasal ciliary motion in a guinea pig model

IMPACT STATEMENT

Cilia play an important role in the airway defense mechanism. So far, studies on ciliary function have mainly been based on in vitro methods. Images of in vivo ciliary motion are very difficult to capture. In this study, we describe a novel approach to observe and analyze nasal ciliary motion in living animals with comparison to in vitro observation. Such images of ciliary motion from living animals have not been reported to date. The result of the study indicates that in vivo ciliary physiological function differs from ex vivo and in vitro conditions in many ways, such as the stability over time and response to temperature variation. This is a good foundation for further in vivo analysis of airway ciliary physiological function in animals as well as humans.

Intraoperative use of optical coherence tomography to differentiate normal and diseased thyroid and parathyroid tissues from lymph node and fat

The purpose of this study is twofold: (1) to determine the feasibility of optical coherence tomography (OCT) to differentiate normal and diseased tissue of the neck region intraoperatively and (2) to evaluate how accurately a cohort of test subjects can identify various tissue types when shown a sample set of OCT images. In this in vivo, prospective, single institutional study, an OCT imaging system (Niris, Imalux, Cleveland, OH) was used to image parathyroid, thyroid, lymph node, and fat tissue in 76 patients during neck surgery. Biopsies were performed for comparison of OCT images with histology in select cases (n = 20). Finally, a group of either surgeons or scientists familiar with OCT (n = 17) were shown a sample of OCT images and asked to identify the tissue. A total of 437 OCT images were analyzed, and characteristic features of each tissue type were identified. OCT demonstrated distinct differences in structural architecture and signal intensity that allows differentiation between thyroid and parathyroid tissues, lymph nodes, and fat. OCT images were also compared with histology with good correlation. There was no difference in correctly identifying OCT-imaged tissue type between surgeons and scientists. This study is the first in vivo OCT imaging study to evaluate both normal and diseased tissues that may be encountered during neck surgery. OCT has the potential to become a valuable intraoperative tool to differentiate diseased and normal thyroid tissue intraoperatively to obtain an "optical biopsy" in real time without fixation, staining, or tissue resection.

Spatial mapping of tracheal ciliary beat frequency using real time phase-resolved Doppler spectrally encoded interferometric microscopy

Ciliary motion in the upper airway is the primary mechanism by which the body transports foreign particulates out of the respiratory system in order to maintain proper respiratory function. The ciliary beating frequency (CBF) is often disrupted with the onset of disease as well as other conditions, such as changes in temperature or in response to drug administration. Current imaging of ciliary motion relies on microscopy and high-speed cameras, which cannot be easily adapted to in-vivo imaging. M-mode optical coherence tomography (OCT) imaging is capable of visualization of ciliary activity, but the field of view is limited. We report on the development of a spectrally encoded interferometric microscopy (SEIM) system using a phase-resolved Doppler (PRD) algorithm to measure and map the ciliary beating frequency within an en face region. This novel high speed, high resolution system allows for visualization of both temporal and spatial ciliary motion patterns as well as propagation of metachronal wave. Rabbit tracheal CBF ranging from 9 to 13 Hz has been observed under different temperature conditions, and the effects of using lidocaine and albuterol have also been measured. This study is the stepping stone to in-vivo studies and the translation of imaging spatial CBF to clinics.

An optimized, robust and reproducible protocol to generate well-differentiated primary nasal epithelial models from extremely premature infants

Extremely premature infants are prone to severe respiratory infections, and the mechanisms underlying this exceptional susceptibility are largely unknown. Nasal epithelial cells (NEC) represent the first-line of defense and adult-derived ALI cell culture models show promising results in mimicking in vivo physiology. Therefore, the aim of this study was to develop a robust and reliable protocol for generating well-differentiated cell culture models from NECs of extremely premature infants. Nasal brushing was performed in 13 extremely premature infants at term corrected age and in 11 healthy adult controls to obtain NECs for differentiation at air-liquid interface (ALI). Differentiation was verified using imaging and functional analysis. Successful isolation and differentiation was achieved for 5 (38.5%) preterm and 5 (45.5%) adult samples. Preterm and adult ALI-cultures both showed well-differentiated morphology and ciliary function, however, preterm cultures required significantly longer cultivation times for acquiring full differentiation (44 ± 3.92 vs. 23 ± 1.83 days; p < 0.0001). Moreover, we observed that recent respiratory support may impair successful NECs isolation. Herewithin, we describe a safe, reliable and reproducible method to generate well-differentiated ALI-models from NECs of extremely premature infants. These models provide a valuable foundation for further studies regarding immunological and inflammatory responses and respiratory disorders in extremely premature infants.

Advances in Doppler optical coherence tomography and angiography

Since the first demonstration of Doppler optical coherence tomography (OCT) in 1997, several functional extensions of Doppler OCT have been developed, including velocimetry, angiogram, and optical coherence elastography. These functional techniques have been widely used in research and clinical applications, particularly in ophthalmology. Here, we review the principles, representative methods, and applications of different Doppler OCT techniques, followed by discussion on the innovations, limitations, and future directions of each of these techniques.

Characterization of oviduct ciliary beat frequency using real time phase resolved Doppler spectrally encoded interferometric microscopy

Ciliary activity, characterized by the coordinated beating of ciliary cells, generates the primary driving force for oviduct tubal transport, which is an essential physiological process for successful pregnancies. Malfunction of the cilium in the fallopian tube, or oviduct, may increase the risk of infertility and tubal pregnancy that can result in maternal death. While many ex-vivo studies have been carried out using bright field microscopy, this technique is not feasible for the in-vivo investigation of oviduct ciliary beating frequency (CBF). Optical coherence tomography (OCT) has been able to provide in-vivo CBF imaging in a mouse model, but its resolution may be insufficient to resolve the spatial and temporal features of the cilium. Our group has recently developed the phase resolved Doppler (PRD) OCT method to visualize ciliary strokes at ultra-high displacement sensitivity. However, the cross-sectional field of view (FOV) may not be ideal for visualizing the surface dynamics of ciliated tissue. In this study, we report on the development of phase resolved Doppler spectrally encoded interferometric microscopy (PRD-SEIM) to visualize the oviduct ciliary activity within an en face FOV. This novel real time imaging system offers micrometer spatial resolution, sub-nanometer displacement sensitivity, and the potential for in-vivo endoscopic adaptation. The feasibility of the approach has been validated through ex-vivo experiments where the porcine oviduct CBF has been measured across different temperature conditions and the application of a drug. CBF ranging from 8 to 12 Hz have been observed at different temperatures, while administration of lidocaine decreased the CBF and deactivated the motile cilia. This study will serve as a stepping stone to in-vivo oviduct ciliary endoscopy and future clinical translations.

Intranasal micro-optical coherence tomography imaging for cystic fibrosis studies

Cystic fibrosis (CF) is a genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. Although impairment of mucociliary clearance contributes to severe morbidity and mortality in people with CF, a clear understanding of the pathophysiology is lacking. This is, in part, due to the absence of clinical imaging techniques capable of capturing CFTR-dependent functional metrics at the cellular level. Here, we report the clinical translation of a 1-μm resolution micro-optical coherence tomography (μOCT) technology to quantitatively characterize the functional microanatomy of human upper airways. Using a minimally invasive intranasal imaging approach, we performed a clinical study on age- and sex-matched CF and control groups. We observed delayed mucociliary transport rate at the cellular level, depletion of periciliary liquid layer, and prevalent loss of ciliation in subjects with CF. Distinctive morphological differences in mucus and various forms of epithelial injury were also revealed by μOCT imaging and had prominent effects on the mucociliary transport apparatus. Elevated mucus reflectance intensity in CF, a proxy for viscosity in situ, had a dominant effect. These results demonstrate the utility of μOCT to determine epithelial function and monitor disease status of CF airways on a per-patient basis, with applicability for other diseases of mucus clearance.

Endoscopic Optical Coherence Tomography for Assessing Inhalation Airway Injury: A Technical Review

Diagnosis of inhalation injury has been clinically challenging. Currently, assessment of inhalation injury relies on subjective clinical exams and bronchoscopy, which provides little understanding of tissue conditions and results in limited prognostics. Endoscopic Optical coherence tomography (OCT) technology has been recently utilized in the airway for direct assessment of respiratory tract disorders and injuries. Endoscopic OCT is capable of capturing high-resolution images of tissue morphology 1-3 mm beneath the surface as well as the complex 3D anatomical shape. Previous studies indicate that changes in airway histopathology can be found in the OCT image almost immediately after inhalation of smoke and other toxic chemicals, which correlates well with histology and pulmonary function tests. This review summarizes the recent development of endoscopic OCT technology for airway imaging, current uses of OCT for inhalation injury, and possible future directions.

Prolonged in vivo functional assessment of the mouse oviduct using optical coherence tomography through a dorsal imaging window

The oviduct (or fallopian tube) serves as an environment for gamete transport, fertilization and preimplantation embryo development in mammals. Although there has been increasing evidence linking infertility with disrupted oviduct function, the specific roles that the oviduct plays in both normal and impaired reproductive processes remain unclear. The mouse is an important mammalian model to study human reproduction. However, most of the current analyses of the mouse oviduct rely on static histology or 2D visualization, and are unable to provide dynamic and volumetric characterization of this organ. The lack of imaging access prevents longitudinal live analysis of the oviduct and its associated reproductive events, limiting the understanding of mechanistic aspects of fertilization and preimplantation pregnancy. To address this limitation, we report a 3D imaging approach that enables prolonged functional assessment of the mouse oviduct in vivo. By combining optical coherence tomography with a dorsal imaging window, this method allows for extended volumetric visualization of the oviduct dynamics, which was previously not achievable. The approach is used for quantitative analysis of oviduct contraction, spatiotemporal characterization of cilia beat frequency and longitudinal imaging. This new approach is a useful in vivo imaging platform for a variety of live studies in mammalian reproduction.

Seeing cilia: imaging modalities for ciliary motion and clinical connections

The respiratory tract is lined with multiciliated epithelial cells that function to move mucus and trapped particles via the mucociliary transport apparatus. Genetic and acquired ciliopathies result in diminished mucociliary clearance, contributing to disease pathogenesis. Recent innovations in imaging technology have advanced our understanding of ciliary motion in health and disease states. Application of imaging modalities including transmission electron microscopy, high-speed video microscopy, and micron-optical coherence tomography could improve diagnostics and be applied for precision medicine. In this review, we provide an overview of ciliary motion, imaging modalities, and ciliopathic diseases of the respiratory system including primary ciliary dyskinesia, cystic fibrosis, chronic obstructive pulmonary disease, and idiopathic pulmonary fibrosis.