Shang Wang

SignificancePeritoneal dissemination is the major mechanism of how ovarian cancer (OC) spreads. It features tumor outgrowths in the form of multicellular spheroids, their detachment from the primary site, and their implantation in the peritoneal cavity. To understand this process, analyzing the outgrowths at their native locations within the female reproductive system is essential. However, in vivo study of the OC outgrowths remains unattainable primarily due to the lack of in vivo imaging approaches to probe such small tumor structures at a high resolution.AimWe address this technical challenge by establishing in vivo high-resolution 3D imaging of the OC outgrowths in the mouse model.ApproachThis in vivo imaging approach relies on optical coherence tomography (OCT) for 3D label-free imaging and an intravital window to bypass the mouse skin and muscle layers. To demonstrate the imaging capability, we use TgMISIIR-TAg transgenic mice that develop spontaneous epithelial OC. The normalized surface lengths of the ovary and the OC outgrowth are measured from OCT images to characterize the tissue morphology. Immunohistochemistry staining is employed to confirm the presence of transgene-positive cells in OC and outgrowths.ResultsWe present the first in vivo high-resolution 3D image of the OC outgrowths in the mouse model. The tissue morphology and structure of OC outgrowths have striking differences from the normal ovary, which is quantitatively assessed and compared. We further show that OC outgrowths within and growing out of the ovarian bursa, revealing the difference in their surface morphologies. We also present the detached OC outgrowths and the fluid-filled chambers inside OC, both with 3D quantifications showing the heterogeneity of their volumes.ConclusionsThis in vivo OCT imaging approach in the mouse model enables high-resolution assessment of detailed 3D structures of OC outgrowths, paving the way for in vivo study of the OC dissemination process.

The mammalian oviduct (also called the fallopian tube) is an essential organ for natural pregnancy. As one of its major functions, the oviduct transports preimplantation embryos to the uterus for implantation. This is a critical process, and abnormalities are responsible for a range of reproductive disorders, such as tubal ectopic pregnancy and infertility, whose etiologies are unclear. For transporting embryos, the oviduct is fundamentally a tubular mechanical pump with motile cilia lining the luminal epithelium and smooth muscle surrounding the mucosa wall. Although bidirectional movement of embryos has been observed during the transport process, how the oviduct produces this type of embryo movement remains unknown. Understanding this pumping mechanism is vital to identifying the functional causes of oviduct-related reproductive disorders, but answering this question requires dynamic imaging of the transport process in its native environment, which is difficult to achieve in mammalian models. Here, we use optical coherence tomography and apply in vivo dynamic 3D imaging of the mouse oviduct to uncover the oviduct pumping mechanism in transporting preimplantation embryos toward pregnancy. By inhibiting the oviduct smooth muscle contraction, we first show that the oviduct muscular activity drives the bidirectional embryo movement. We then present a quantitative assessment of the oviduct contraction wave. This analysis, together with the embryo movement information, indicates that the forward movement of embryos is produced by peristalsis, while the backward embryo movement is generated by a suction process driven by the oviduct relaxation at earlier contraction sites, showing a leaky peristaltic pump. Finally, we reveal how the net displacement of embryos is created under this pumping mechanism, which effectively transports embryos toward the uterus. This work elucidates, for the first time, the oviduct pumping mechanism in transporting preimplantation embryos, paving the way for understanding the biomechanics of the mammalian oviduct.

Stereolithography bioprinting relies heavily on costly photoinitiators for polymerization, limiting its potential for further technical advancement to meet growing needs in tissue engineering and regenerative medicine. Thermal initiators, in contrast, are low cost, and rapid growth of the photothermal conversion field offers a wide range of materials and tools to convert light into heat. However, high‐resolution photothermal stereolithography bioprinting remains unattainable due to the difficulty of confining heat in an aqueous environment. Here, this challenge has been fully addressed by establishing imaging‐guided microscale photothermal stereolithography bioprinting (ImPSB). This technique is achieved through building a novel imaging‐guided stereolithography system that provides depth‐resolved visualization of the printing dynamics, creating a unique photothermal initiator in the second near‐infrared window, and developing a new bioink by seeing and controlling the photothermal gelation process. ImPSB achieves a printing resolution of ≈47 µm and generates smooth lines of arbitrarily designed shapes with a cross‐sectional diameter as small as ≈104 µm, representing an unprecedented scale from photothermal aqueous stereolithography. Its cellular biocompatibility in printing both bioscaffold and cell‐laden hydrogel is demonstrated, and its feasibility of transdermal printing is also shown. This work sets a new path for high‐resolution stereolithography bioprinting where the vast photothermal resources can be utilized.

Methods for seeing inside volumetric images are increasingly important with the rapid advancements in 3D and 4D (3D + time) biomedical imaging techniques. Here, we report a novel volume clipping method and its open-source implementation which enables unprecedented 4D visualization and analysis of embryonic mouse heart development with data from optical coherence tomography (OCT). Clipping a volume to extract information inside has long been a vital approach in biomedical image analysis; however, it is challenging to make a dynamic non-planar cutaway view that is simultaneously smooth, adjustable, efficient to compute, easy to control, and interactive in real time. We addressed this challenge by applying the thin plate spline (TPS) to create a new way of volume clipping, called the clipping spline. Specifically, the clipping spline produces a cutaway view by generating a binary mask based on the unique TPS surface that intersects with a set of 3D control points while having minimal curvature. We implemented this method in an open-source platform where the clipping spline can be interactively controlled for real-time, adjustable, and dynamic cutaway views into a volume. We also developed an algorithm that automatically connects and interpolates different sets of control points over time, providing 4D volume clipping. In addition to characterizing the clipping spline, we demonstrate its application by revealing a series of never-before-seen dynamics and processes of embryonic mouse heart development based on OCT data. We also show a TPS-based method for tracking the embryonic myocardium with control points over two timescales (heartbeat and development). Our results indicate that the clipping spline promises to be broadly used in volumetric biomedical image visualization and analysis, especially by the OCT community.

Time-lapse 3D imaging is fundamental for studying biological processes but requires software able to handle terabytes of voxel data. Although many multidimensional viewing applications exist, they mostly lack support for heterogeneous voxel counts, datatypes, and modalities in a single timeline. Open Chrono-Morph Viewer provides a straightforward graphical user interface to quickly investigate multi-timescale datasets represented as separate volume files in the common NRRD format for compatibility between toolchains. It features dynamic clipping surfaces for rapid investigation of 3D morphology and a scriptable animation API for quantitative, repeatable, publication-quality visualization. It is implemented in pure Python using common libraries to facilitate community-driven development. OCMV is available at https://github.com/ShangWangLab/OpenChronoMorphViewer for Windows, Linux, and macOS. Supporting tutorials, documentation, and installation instructions can be found in the supplementary information . Our modified Fiji I/O plugin for up to 5D NRRD file conversion is available at https://github.com/afaubert/IO. Supplementary Figures, Tables, Videos, and Notes are available at Bioinformatics online.

The mammalian oviduct (or fallopian tube) is a tubular organ hosting reproductive events leading to pregnancy. Dynamic 3D imaging of the mouse oviduct with optical coherence tomography (OCT) has recently emerged as a promising approach to study the hidden processes vital to elucidate the role of oviduct in mammalian reproduction and reproductive disorders. In particular, with an intravital window, in vivo OCT imaging is a powerful solution to studying how the oviduct transports preimplantation embryos towards the uterus for pregnancy, a long-standing question that is critical for uncovering the functional cause of tubal ectopic pregnancy. However, simultaneously tracking embryo movement and acquiring large-field-of-view images of oviduct activity in 3D has been challenging due to the generally limited volumetric imaging rate of OCT. A lack of OCT-based 3D velocimetry method for large, sparse particles acts as a technical hurdle for analyzing the mechanistic process of the embryo transport. Here, we report a new particle streak velocimetry method to address this hurdle. The method relies on the 3D streak of a moving particle formed during the acquisition of a single OCT volume, where double B-scans are acquired at each B-scan location to resolve ambiguity in assessing the movement of particle. We validated this method with the gold-standard, direct volumetric particle tracking in a flow phantom, and we demonstrated its in vivo applications for simultaneous velocimetry of embryos and imaging of oviduct. This work sets the stage for quantitative understanding of the oviduct transport function in vivo, and the method fills in a gap in OCT-based velocimetry, providing the potential to enable new applications in 3D flow imaging.

Imaging cells in their 3D environment with molecular specificity is important to cell biology study. Widely used microscopy techniques, such as confocal microscopy, have limited imaging depth when probing cells in optically scattering media. Optical coherence tomography (OCT) can provide millimeter-level depth for the imaging of highly scattered media but lacks the contrast to distinguish cells from the extracellular matrix or to distinguish between different types of cells. Photothermal OCT (PT-OCT) is a promising technique to obtain molecular contrast at the imaging scale of OCT. Here, we report PT-OCT imaging of live, nanoparticle-labeled cells in 3D. In particular, we demonstrate detection and mapping of a single cell in 3D without causing cell death, and show the feasibility of 3D cell mapping through optically scattering media. This work presents live cell detection and mapping at an imaging scale that complements the major microscopy techniques, which is potentially useful to study cells in their 3D native or culture environment.

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.

In brief In vivo imaging of gametes and embryos in the oviduct enables new studies of the native processes that lead to fertilization and pregnancy. This review article discusses recent advancements in the in vivo imaging methods and insights which contribute to understanding the oviductal function. Abstract Understanding the physiological dynamics of gametes and embryos in the fallopian tube (oviduct) has significant implications for managing reproductive disorders and improving assisted reproductive technologies. Recent advancements in imaging of the mouse oviduct in vivo uncovered fascinating dynamics of gametes and embryos in their native states. These new imaging approaches and observations are bringing exciting momentum to uncover the otherwise-hidden processes orchestrating fertilization and pregnancy. For mechanistic investigations, in vivo imaging in genetic mouse models enables dynamic phenotyping of gene functions in the reproductive process. Here, we review these imaging methods, discuss insights recently revealed by in vivo imaging, and comment on emerging directions, aiming to stimulate new in vivo studies of reproductive dynamics. Abstract In brief In vivo imaging of gametes and embryos in the oviduct enables new studies of the native processes that lead to fertilization and pregnancy. This review article discusses recent advancements in the in vivo imaging methods and insights which contribute to understanding the oviductal function. Abstract Understanding the physiological dynamics of gametes and embryos in the fallopian tube (oviduct) has significant implications for managing reproductive disorders and improving assisted reproductive technologies. Recent advancements in imaging of the mouse oviduct in vivo uncovered fascinating dynamics of gametes and embryos in their native states. These new imaging approaches and observations are bringing exciting momentum to uncover the otherwise-hidden processes orchestrating fertilization and pregnancy. For mechanistic investigations, in vivo imaging in genetic mouse models enables dynamic phenotyping of gene functions in the reproductive process. Here, we review these imaging methods, discuss insights recently revealed by in vivo imaging, and comment on emerging directions, aiming to stimulate new in vivo studies of reproductive dynamics.

Dynamic imaging of the beating embryonic heart in 3D is critical for understanding cardiac development and defects. Optical coherence tomography (OCT) plays an important role in embryonic heart imaging with its unique imaging scale and label-free contrasts. In particular, 4D (3D + time) OCT imaging enabled biomechanical analysis of the developing heart in various animal models. While ultrafast OCT systems allow for direct volumetric imaging of the beating heart, the imaging speed remains limited, leading to an image quality inferior to that produced by post-acquisition synchronization. As OCT systems become increasingly available to a wide range of biomedical researchers, a more accessible 4D reconstruction method is required to enable the broader application of OCT in the dynamic, volumetric assessment of embryonic heartbeat. Here, we report an open-source, highly efficient, post-acquisition synchronization method for 4D cardiodynamic and hemodynamic imaging of the mouse embryonic heart. Relying on the difference between images to characterize heart wall movements, the method provides good sensitivity to the cardiac activity when aligning heartbeat phases, even at early stages when the heart wall occupies only a small number of pixels. The method works with a densely sampled single 3D data acquisition, which, unlike the B-M scans required by other methods, is readily available in most commercial OCT systems. Compared with an existing approach for the mouse embryonic heart, this method shows superior reconstruction quality. We present the robustness of the method through results from different embryos with distinct heart rates, ranging from 1.24 Hz to 2.13 Hz. Since the alignment process operates on a 1D signal, the method has a high efficiency, featuring sub-second alignment time while utilizing ∼100% of the original image files. This allows us to achieve repeated, dual-contrast imaging of mouse embryonic heart development. This new, open-source method could facilitate research using OCT to study early cardiogenesis.