Label-free intratissue activity imaging of alveolar organoids with dynamic optical coherence tomography

Abstract

An organoid is a three-dimensional (3D) in vitro cell culture emulating human organs. We applied 3D dynamic optical coherence tomography (DOCT) to visualize the intratissue and intracellular activities of human induced pluripotent stem cells (hiPSCs)-derived alveolar organoids in normal and fibrosis models. 3D DOCT data were acquired with an 840-nm spectral domain optical coherence tomography with axial and lateral resolutions of 3.8 µm (in tissue) and 4.9 µm, respectively. The DOCT images were obtained by the logarithmic-intensity-variance (LIV) algorithm, which is sensitive to the signal fluctuation magnitude. The LIV images revealed cystic structures surrounded by high-LIV borders and mesh-like structures with low LIV. The former may be alveoli with a highly dynamics epithelium, while the latter may be fibroblasts. The LIV images also demonstrated the abnormal repair of the alveolar epithelium.

Dynamic contrast optical coherence tomography (DyC-OCT) for label-free live cell imaging

“…Another advantage of DyC-OCT is its ability to monitor morphological changes over time. For example, DyC-OCT has been used to monitor organoid development, such as retinal organoids 29 and alveolar organoids 43 . DyC-OCT enables differentiation of cellular lifetime stages inside a single cell based on scattering particles’ movements in the organelles of HeLa cells 30 .…”

“…DyC-OCT has captured a signal of dynamics decay in hepatocytes in a rat liver treated with a glycolysis inhibitor, indicating that the inhibitor suppressed the hepatocytes’ activity 15 . In alveolar organoids, DyC-OCT has revealed changes in the size and shape of alveoli after bleomycin was applied 43 . In plant science, DyC-OCT was applied to evaluate the effects of LED illumination as well as iron and phosphate deficiency on photosynthetic cells under various environmentally relevant stress challenges 28 .…”

“…Moreover, correlating DyC-OCT signals with established biological activities aids in interpreting DyC-OCT data and linking it to specific dynamic events. Researchers have observed OCT fluctuation pattern changes following stimulations known to alter activities, like ATP-γ-S 16 , inhibitors 15 , 43 and cancer drugs 18 , 48 . These findings reinforce DyC-OCT’s validity and provide insights into dynamic activities in biological systems.…”

Mathematical modeling of intracellular and intratissue activities for understanding dynamic optical coherence tomography signals

“…Recently, dynamic optical coherence tomography (DOCT) is developed for label-free assessment of tissue functional activity 2 . It has been used for the evaluation of tissue activity for wide spectrum of tissues, including in vitro tumor spheroid 2 , organoid 3 , and fresh ex vivo animal tissues 4 .…”

Neural-network based high-speed volumetric dynamic optical coherence tomography

“…Recently, an OCT-based non-invasive imaging modality called dynamic optical coherence tomography (DOCT) was proposed for visualization and quantification of tissue dynamics [ 2 ]. DOCT has been used to investigate ex-vivo tissue metabolism [ 3 , 4 ], the cellular activity of tumor spheroids [ 5 – 7 ], and the cellular activity and differentiation processes of alveolar organoids [ 8 ], retinal organoids [ 9 ], and several other tissues [ 2 , 10 – 15 ].…”