Noninvasive, label-free image approaches to predict multimodal molecular markers in pluripotency assessment.

Manufacturing regenerative medicine requires continuous monitoring of pluripotent cell culture and quality assessment while eliminating cell destruction and contaminants. In this study, we employed a novel method to monitor the pluripotency of stem cells through image analysis, avoiding the traditionally used invasive procedures. This approach employs machine learning algorithms to analyze stem cell images to predict the expression of pluripotency markers, such as OCT4 and NANOG, without physically interacting with or harming cells. We cultured induced pluripotent stem cells under various conditions to induce different pluripotent states and imaged the cells using bright-field microscopy. Pluripotency states of induced pluripotent stem cells were assessed using invasive methods, including qPCR, immunostaining, flow cytometry, and RNA sequencing. Unsupervised and semi-supervised learning models were applied to evaluate the results and accurately predict the pluripotency of the cells using only image analysis. Our approach directly links images to invasive assessment results, making the analysis of cell labeling and annotation of cells in images by experts dispensable. This core achievement not only contributes for safer and more reliable stem cell research but also opens new avenues for real-time monitoring and quality control in regenerative medicine manufacturing. Our research fills an important gap in the field by providing a viable, noninvasive alternative to traditional invasive methods for assessing pluripotency. This innovation is expected to make a significant contribution to improving regenerative medicine manufacturing because it will enable a more detailed and feasible understanding of cellular status during the manufacturing process.

Cloning and mutagenetic modification of the firefly luciferase gene and its use for bioluminescence microscopy of engrailed expression during Drosophila metamorphosis.

Bioluminescence microscopy is an area attracting considerable interest in the field of cell biology because it offers several advantages over fluorescence microscopy, including no requirement for excitation light and being phototoxicity free. This method requires brighter luciferase for imaging; however, suitable genetic resource material for this purpose is not available at present. To achieve brighter bioluminescence microscopy, we developed a new firefly luciferase. Using the brighter luciferase, a reporter strain of Drosophila Gal4-UAS (Upstream Activating Sequence) system was constructed. This system demonstrated the expression pattern of engrailed, which is a segment polarity gene, during Drosophila metamorphosis by bioluminescence microscopy, and revealed drastic spatiotemporal change in the engrailed expression pattern during head eversion in the early stage of pupation.

Cell competition corrects noisy Wnt morphogen gradients to achieve robust patterning in the zebrafish embryo.

Morphogen signalling forms an activity gradient and instructs cell identities in a signalling strength-dependent manner to pattern developing tissues. However, developing tissues also undergo dynamic morphogenesis, which may produce cells with unfit morphogen signalling and consequent noisy morphogen gradients. Here we show that a cell competition-related system corrects such noisy morphogen gradients. Zebrafish imaging analyses of the Wnt/ß-catenin signalling gradient, which acts as a morphogen to establish embryonic anterior-posterior patterning, identify that unfit cells with abnormal Wnt/ß-catenin activity spontaneously appear and produce noise in the gradient. Communication between unfit and neighbouring fit cells via cadherin proteins stimulates apoptosis of the unfit cells by activating Smad signalling and reactive oxygen species production. This unfit cell elimination is required for proper Wnt/ß-catenin gradient formation and consequent anterior-posterior patterning. Because this gradient controls patterning not only in the embryo but also in adult tissues, this system may support tissue robustness and disease prevention.

Evaluation of chemical chaperones based on the monitoring of Bip promoter activity and visualization of extracellular vesicles by real-time bioluminescence imaging.

It is known that endoplasmic reticulum (ER) stress in cells and extracellular vesicles (EVs) plays a significant role in cancer cells, therefore the evaluation of compounds that can regulate ER stress and EV secretion would be a suitable system for further screening and development of new drugs. In this study, we evaluated chemical chaperones derived from natural products based on monitoring Bip/GRP78 promoter activity during cancer cell growth, at the level of the single cell, by a bioluminescence microscopy system that had several advantages compared with fluorescence imaging. It was found that several chemical chaperones, such as ferulic acid (FA), silybin, and rutin, affected the activity. We visualized EVs from cancer cells using bioluminescence imaging and showed that several EVs could be observed when using CD63 fused with NanoLuc luciferase, which has a much smaller molecular weight and higher intensity than conventional firefly luciferase. We then examined the effects of the chemical chaperones on EVs from cancer cells by bioluminescence imaging and quantified the expression of CD63 in these EVs. It was found that the chemical chaperones examined in this study affected CD63 levels in EVs. These results showed that imaging at the level of the single cell using bioluminescence is a powerful tool and could be used to evaluate chemical chaperones and EVs from cancer cells. This approach may produce new information in this field when taken together with conventional and classical methods.

TiLIA: a software package for image analysis of firefly flash patterns.

As flash signaling patterns of fireflies are species specific, signal-pattern analysis is important for understanding this system of communication. Here, we present time-lapse image analysis (TiLIA), a free open-source software package for signal and flight pattern analyses of fireflies that uses video-recorded image data. TiLIA enables flight path tracing of individual fireflies and provides frame-by-frame coordinates and light intensity data. As an example of TiLIA capabilities, we demonstrate flash pattern analysis of the fireflies Luciola cruciata and L. lateralis during courtship behavior.

Combining fluorescence and bioluminescence microscopy.

Bioluminescence microscopy has revealed that gene expression in individual cells can respond differently to the same stimulus. To understand this phenomenon, it is important to sequentially observe the series of events from cellular signal transduction to gene expression regulated by specific transcription factors derived from signaling cascades in individual cells. However, these processes have been separately analyzed with fluorescence and bioluminescence microscopy. Furthermore, in culture medium, the background fluorescence of luciferin-a substrate of luciferase in promoter assays of gene expression in cultured cells-confounds the simultaneous observation of fluorescence and bioluminescence. Therefore, we optimized conditions for optical filter sets based on spectral properties and the luciferin concentration based on cell permeability for fluorescence observation combined with bioluminescence microscopy. An excitation and emission filter set (492-506 nm and 524-578 nm) was suitable for green fluorescent protein and yellow fluorescent protein imaging of cells, and >100 µM luciferin was acceptable in culture medium based on kinetic constants and the estimated intracellular concentration. Using these parameters, we present an example of sequential fluorescence and bioluminescence microscopic observation of signal transduction (translocation of protein kinase C alpha from the cytoplasm to the plasma membrane) coupled with activation of gene expression by nuclear factor of kappa light polypeptide B in individual cells and show that the gene expression response is not completely concordant with upstream signaling following stimulation with phorbol-12-myristate-13-acetate. Our technique is a powerful imaging tool for analysis of heterogeneous gene expression together with upstream signaling in live single cells.

Bioluminescence imaging to track real-time armadillo promoter activity in live Drosophila embryos.

We established a method for bioluminescence imaging (BLI) to track real-time gene expression in live Drosophila embryos. We constructed a transgenesis vector containing multiple cloning sites and enhanced green-emitting luciferase (ELuc; Emerald Luc), a brighter and pH-insensitive luciferase for promoter analysis. To evaluate the utility of BLI using an ELuc reporter together with an optimized microscope system, we visualized the expression pattern of armadillo (arm), a member of the Wnt pathway in Drosophila, throughout embryogenesis. We generated transgenic flies carrying the arm:: ELuc fusion gene, and successfully performed BLI continuously for 22 h in the same embryos. Our study showed, for the first time, that arm::Eluc expression was dramatically increased in the anterior midgut rudiment, myoblasts of the dorsal/lateral musculature, and the posterior spiracle after stage 13, and the cephalic region at stage 17. To further demonstrate the application of our BLI system, we revealed that arm transcriptional activity in embryos was modulated inversely by treatment with ionomycin or 6-bromoindirubin-3-oxime (BIO), an inhibitor and activator of Wnt/ß-catenin signaling, respectively. Therefore, our microscopic BLI system is useful for monitoring gene expression in live Drosophila embryos, and for investigating regulatory mechanisms by using chemicals and mutations that might affect expression.

Transfection efficiency of normal and cancer cell lines and monitoring of promoter activity by single-cell bioluminescence imaging.

The bioluminescence system (luciferase reporter assay system) is widely used to study gene expression, signal transduction and other cellular activities. Although transfection of reporter plasmid DNA to mammalian cell lines is an indispensable experimental step, the transfection efficiency of DNA varies among cell lines, and several cell lines are not suitable for this type of assay because of the low transfection efficiency. In this study, we confirm the transfection efficiency of reporter DNA to several cancer and normal cell lines after transient transfection by single-cell imaging. Luminescence images could be obtained from living single cells after transient transfection, and the calculated transfection efficiency of this method was similar to that of the conventional reporter assay using a luminometer. We attempted to measure the activity of the Bip promoter under endoplasmic reticulum stress conditions using both high and low transfection efficiency cells for plasmid DNA at the single-cell level, and observed activation of this promoter even in cells with the lowest transfection efficiency. These results show that bioluminescence imaging of single cells is a powerful tool for the analysis of gene expression based on a reporter assay using limited samples such as clinical specimens or cells from primary culture, and could provide additional information compared with the conventional assay.