Analysis of impedance-based cellular growth assays

Optimizing Ex Vivo CAR-T Cell-Mediated Cytotoxicity Assay through Multimodality Imaging

CAR-T cell-based therapies have demonstrated remarkable efficacy in treating malignant cancers, especially liquid tumors, and are increasingly being evaluated in clinical trials for solid tumors. With the FDA's initiative to advance alternative methods for drug discovery and development, full human ex vivo assays are increasingly essential for precision CAR-T development. However, prevailing ex vivo CAR-T cell-mediated cytotoxicity assays are limited by their use of radioactive materials, lack of real-time measurement, low throughput, and inability to automate, among others. To address these limitations, we optimized the assay using multimodality imaging methods, including bioluminescence, impedance tracking, phase contrast, and fluorescence, to track CAR-T cells co-cultured with CD19, CD20, and HER2 luciferase reporter cancer cells in real-time. Additionally, we varied the ratio of CAR-T cells to cancer cells to determine optimal cytotoxicity readouts. Our findings demonstrated that the CAR-T cell group effectively attacked cancer cells, and the optimized assay provided superior temporal and spatial precision measurements of ex vivo CAR-T killing of cancer cells, confirming the reliability, consistency, and high throughput of the optimized assay.

Assessment of chemotherapeutic effects on cancer cells using adhesion noise spectroscopy

With cancer as one of the leading causes of death worldwide, there is a need for the development of accurate, cost-effective, easy-to-use, and fast drug-testing assays. While the NCI 60 cell-line screening as the gold standard is based on a colorimetric assay, monitoring cells electrically constitutes a label-free and non-invasive tool to assess the cytotoxic effects of a chemotherapeutic treatment on cancer cells. For decades, impedance-based cellular assays extensively investigated various cell characteristics affected by drug treatment but lack spatiotemporal resolution. With progress in microelectrode fabrication, high-density Complementary Metal Oxide Semiconductor (CMOS)-based microelectrode arrays (MEAs) with subcellular resolution and time-continuous recording capability emerged as a potent alternative. In this article, we present a new cell adhesion noise (CAN)-based electrical imaging technique to expand CMOS MEA cell-biology applications: CAN spectroscopy enables drug screening quantification with single-cell spatial resolution. The chemotherapeutic agent 5-Fluorouracil exerts a cytotoxic effect on colorectal cancer (CRC) cells hampering cell proliferation and lowering cell viability. For proof-of-concept, we found sufficient accuracy and reproducibility for CAN spectroscopy compared to a commercially available standard colorimetric biological assay. This label-free, non-invasive, and fast electrical imaging technique complements standardized cancer screening methods with significant advances over established impedance-based approaches.

In situ detection and viability assessment of target microorganisms

Rapid detection and viability assessment of pathogenic microorganisms, without the need for pre-enrichment steps, is critical in clinical microbiology, food safety, environmental quality assessment, and biosecurity. We demonstrate a powerful analytical concept and the related platform that enable in situ rapid detection, separation, sensitive quantification, and viability assessment of targeted microorganisms (bacteria and fungi) from minimally processed samples. This is based on a novel integration of magneto-affine selection and electrical impedance assay. The entire process, from capture to measurement, is executed using controlled magnetic fields to manipulate magnetic particles (MPs)-microbe affinity-based clusters, in a compact, portable setup equipped with cost-effective, single-use chambers. The system was tested for non-invasive in situ evaluation of model bacteria (Escherichia coli) and fungi (Saccharomyces cerevisiae) within clinically relevant concentration ranges, and it was demonstrated amenable for both commercial and custom MPs, proving its high versatility. The high capture efficiency, the ability to provide analytic results within 30 min directly from unprocessed samples (buffer and synthetic urine), and the high sensitivity in distinguishing live and dead cells in dynamic exposures represent significant advancements over existing assays and recommend the system as a screening tool for pathogen presence and antimicrobial susceptibility in clinical and environmental samples.

RGO-PANI composite Au microelectrodes for sensitive ECIS analysis of human gastric (MKN-1) cancer cells

Microelectrode-based cell chip studies for cellular responses often require improved adhesion and growth conditions for efficient cellular diagnosis and high throughput screening in drug discovery. Cell-chip studies are often performed on gold electrodes due to their biocompatibility, and stability, but the electrode-electrolyte interfacial capacitance is the main drawback to the overall sensitivity of the detection system. Thus, here, we developed reduced graphene oxide-polyaniline-modified gold microelectrodes for real-time impedance-based monitoring of human gastric adenocarcinoma cancer (MKN-1) cells. The impedance characterization on modified electrodes showed 28-fold enhanced conductivity than the bare electrodes, and the spectra were modeled with proper equivalent circuits to extrapolate the values of circuit elements. The impedance of both time-and frequency-dependent measurements of cell-covered modified electrodes with equivalent model circuits was analyzed to achieve cellular behavior, such as adhesion, spreading, proliferation, and influence of anti-cancer agents. The normalized impedance at 41.5 kHz (|Z|_{norm 41 kHz}) was selected to monitor the cell growth analysis, which was found linear with the proliferation of adherent cells along with the influence of the anticancer drug agent on the MKN-1 cells. The synergistic effects and biocompatible nature of PANI-RGO modifications improved the overall sensitivity for the cell-growth studies of MKN-1 cells.

Tuning levels of low-complexity domain interactions to modulate endogenous oncogenic transcription

Gene activation by mammalian transcription factors (TFs) requires multivalent interactions of their low-complexity domains (LCDs), but how such interactions regulate transcription remains unclear. It has been proposed that extensive LCD-LCD interactions culminating in liquid-liquid phase separation (LLPS) of TFs is the dominant mechanism underlying transactivation. Here, we investigated how tuning the amount and localization of LCD-LCD interactions in vivo affects transcription of endogenous human genes. Quantitative single-cell and single-molecule imaging reveals that the oncogenic TF EWS::FLI1 requires a narrow optimum of LCD-LCD interactions to activate its target genes associated with GGAA microsatellites. Increasing LCD-LCD interactions toward putative LLPS represses transcription of these genes in patient-derived cells. Likewise, ectopically creating LCD-LCD interactions to sequester EWS::FLI1 into a well-documented LLPS compartment, the nucleolus, inhibits EWS::FLI1-driven transcription and oncogenic transformation. Our findings show how altering the balance of LCD-LCD interactions can influence transcriptional regulation and suggest a potential therapeutic strategy for targeting disease-causing TFs.

DNA-structured mathematical model of cell-cycle progression in cyclic hypoxia

New experimental data have shown how the periodic exposure of cells to low oxygen levels (i.e., cyclic hypoxia) impacts their progress through the cell-cycle. Cyclic hypoxia has been detected in tumours and linked to poor prognosis and treatment failure. While fluctuating oxygen environments can be reproduced in vitro, the range of oxygen cycles that can be tested is limited. By contrast, mathematical models can be used to predict the response to a wide range of cyclic dynamics. Accordingly, in this paper we develop a mechanistic model of the cell-cycle that can be combined with in vitro experiments, to better understand the link between cyclic hypoxia and cell-cycle dysregulation. A distinguishing feature of our model is the inclusion of impaired DNA synthesis and cell-cycle arrest due to periodic exposure to severely low oxygen levels. Our model decomposes the cell population into five compartments and a time-dependent delay accounts for the variability in the duration of the S phase which increases in severe hypoxia due to reduced rates of DNA synthesis. We calibrate our model against experimental data and show that it recapitulates the observed cell-cycle dynamics. We use the calibrated model to investigate the response of cells to oxygen cycles not yet tested experimentally. When the re-oxygenation phase is sufficiently long, our model predicts that cyclic hypoxia simply slows cell proliferation since cells spend more time in the S phase. On the contrary, cycles with short periods of re-oxygenation are predicted to lead to inhibition of proliferation, with cells arresting from the cell-cycle in the G2 phase. While model predictions on short time scales (about a day) are fairly accurate (i.e, confidence intervals are small), the predictions become more uncertain over longer periods. Hence, we use our model to inform experimental design that can lead to improved model parameter estimates and validate model predictions.

Modelling and Differential Quantification of Electric Cell-Substrate Impedance Sensing Growth Curves

Measurement of cell surface coverage has become a common technique for the assessment of growth behavior of cells. As an indirect measurement method, this can be accomplished by monitoring changes in electrode impedance, which constitutes the basis of electric cell-substrate impedance sensing (ECIS). ECIS typically yields growth curves where impedance is plotted against time, and changes in single cell growth behavior or cell proliferation can be displayed without significantly impacting cell physiology. To provide better comparability of ECIS curves in different experimental settings, we developed a large toolset of R scripts for their transformation and quantification. They allow importing growth curves generated by ECIS systems, edit, transform, graph and analyze them while delivering quantitative data extracted from reference points on the curve. Quantification is implemented through three different curve fit algorithms (smoothing spline, logistic model, segmented regression). From the obtained models, curve reference points such as the first derivative maximum, segmentation knots and area under the curve are then extracted. The scripts were tested for general applicability in real-life cell culture experiments on partly anonymized cell lines, a calibration setup with a cell dilution series of impedance versus seeded cell number and finally IPEC-J2 cells treated with 1% and 5% ethanol.

Novel Cost-Efficient Graphene-Based Impedance Biosensor for the Analysis of Viral Cytopathogenicity and the Effect of Antiviral Drugs

Biosensors become increasingly relevant for medical diagnostics, pharmaceutical industry, and environmental technology, for example, to test new drugs easily and reliably or to detect cell growth in changing environmental conditions. Novel materials like graphene are promising candidates to produce biosensors on an industrial scale by means of printing processes. To reach this aim, methods for the reliable and automated production of electrode structures and their coating are required. We present an impedance biosensor in the format of a microtiter plate, fabricated by highly efficient roll-to-roll printing of graphene-based microstructures on large-area polymer foils. Proof-of-principle experiments show the evidence of the suitability of the printed graphene biosensors for impedance-based monitoring of viral cytopathogenicity and its inhibition in the presence of antiviral drugs. The developed system is a promising approach toward cost-efficient impedimetric biosensors for high-throughput screening in vaccine research and antiviral drug development.

RNA-seq analysis reveals significant transcriptome changes in huntingtin-null human neuroblastoma cells

BACKGROUND

Huntingtin (Htt) protein is the product of the gene mutated in Huntington's disease (HD), a fatal, autosomal dominant, neurodegenerative disorder. Normal Htt is essential for early embryogenesis and the development of the central nervous system. However, the role of Htt in adult tissues is less defined. Following the recent promising clinical trial in which both normal and mutant Htt mRNA were knocked down in HD patients, there is an urgent need to fully understand the molecular consequences of knocking out/down Htt in adult tissues. Htt has been identified as an important transcriptional regulator. Unbiased investigations of transcriptome changes with RNA-sequencing (RNA-Seq) have been done in multiple cell types in HD, further confirming that transcriptional dysregulation is a central pathogenic mechanism in HD. However, there is lack of direct understanding of the transcriptional regulation by normal Htt.

METHODS

To investigate the transcriptional role of normal Htt, we first knocked out Htt in the human neuroblastoma SH-SY5Y cell line using the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 (CRISPR-associated protein 9) gene editing approach. We then performed RNA-seq analysis on Htt-null and wild type SH-SY5Y cells to probe the global transcriptome changes induced by Htt deletion.

RESULTS

In general, Htt has a widespread effect on gene transcription. Functional analysis of the differentially expressed genes (DEGs) using various bioinformatic tools revealed irregularities in pathways related to cell communication and signaling, and more specifically those related to neuron development, neurotransmission and synaptic signaling. We further examined the transcription factors that may regulate these DEGs. Consistent with the disrupted pathways associated with cellular development, we showed that Htt-null cells exhibited slower cell proliferation than wild type cells. We finally validated some of the top DEGS with quantitative RT-PCR.

CONCLUSIONS

The widespread transcriptome changes in Htt-null cells could be directly caused by the loss of Htt-mediated transcriptional regulation or due to the secondary consequences of disruption in the gene regulatory network. Our study therefore provides valuable information about key genes associated with Htt-mediated transcription and improves our understanding of the molecular mechanisms underlying the cellular functions of normal and mutant Htt.

Application of xCELLigence real-time cell analysis to the microplate assay for pertussis toxin induced clustering in CHO cells

The microplate assay with Chinese Hamster Ovary (CHO) cells is currently used as a safety test to monitor the residual pertussis toxin (PT) amount in acellular pertussis antigens prior to vaccine formulation. The assay is based on the findings that the exposure of CHO cells to PT results in a concentration-dependent clustering response which can be used to estimate the amount of PT in a sample preparation. A major challenge with the current CHO cell assay methodology is that scoring of PT-induced clustering is dependent on subjective operator visual assessment using light microscopy. In this work, we have explored the feasibility of replacing the microscopy readout for the CHO cell assay with the xCELLigence Real-Time Cell Analysis system (ACEA BioSciences, a part of Agilent). The xCELLigence equipment is designed to monitor cell adhesion and growth. The electrical impedance generated from cell attachment and proliferation is quantified via gold electrodes at the bottom of the cell culture plate wells, which is then translated into a unitless readout called cell index. Results showed significant decrease in the cell index readouts of CHO cells exposed to PT compared to the cell index of unexposed CHO cells. Similar endpoint concentrations were obtained when the PT reference standard was titrated with either xCELLigence or microscopy. Testing genetically detoxified pertussis samples unspiked or spiked with PT further supported the sensitivity and reproducibility of the xCELLigence assay in comparison with the conventional microscopy assay. In conclusion, the xCELLigence RTCA system offers an alternative automated and higher throughput method for evaluating PT-induced clustering in CHO cells.

Application of a real-time cell analysis system in the process development and quantification of Rift Valley fever virus clone 13

Conventional cell-culture viral quantification methods, namely viral plaque and 50 % tissue culture infective dose assays, are time-consuming, subjective and are not suitable for routine testing. The viral plaque formation assay is the main method utilized for Rift Valley fever virus (RVFV) clone 13 quantification. The RVFV is a mosquito-borne RNA Phlebovirus belonging to the family Bunyaviridae. The virus comprises a single serotype and causes the zoonotic Rift Valley fever disease. The real-time cell analysis (RTCA) system has been developed for the monitoring of cell growth, cell adhesion, cell viability and mortality using electronic impedance technology. In this study, Vero cell growth kinetics and RVFV clone 13 replication kinetics were investigated in a roller bottle and RTCA systems. In roller bottles, Vero cell growth was measured by cell counts through trypan blue staining, whilst impedance expressed as the cell index (CI) was used for Vero growth measurement in the RTCA system. Similar growth patterns were observed in both roller bottle and RTCA systems. Exponential growth phase was observed between 48 and 100 h, followed by a stationary phase from 100 to 120 h, before cell death was observed. Viral plaque assay quantification of RVFV clone 13 in the roller bottle system and the time required for the CI to decrease 50 % after virus infection (CIT50) in the RTCA system were comparable. The highest RVFV clone 13 titre was obtained at 120 h in both roller bottle and RTCA systems. An increase in time for cytopathic effect (CPE) formation was observed with a decrease in the concentration of the virus used to infect the RTCA plates. A positive correlation was observed between the viral concentration and the time for a CPE and was used to calculate CIT50. A similar correlation was observed between the viral concentration and the time for a CPE in the roller bottle system. This study shows that the RTCA system can be used as an alternative method for conducting cell culture kinetics and viral quantification.

Four-Channel Photothermal Plate Reader for High-Throughput Nanoparticle-Amplified Immunoassay

We enhanced the sample throughput of microplate-based photothermal detection by using a semicylindrical prism to expand a point laser source to a long beam for illuminating multiple wells. Coupled with four epoxy-coated thermocouples in alignment with wells on a 96-well microplate, four parallel immunoassays of C-reaction protein (CRP) with antibody-conjugated gold nanoparticles can be simultaneously performed. The sample throughput is further increased by mounting the Styrofoam-enclosed microplate onto a translational/elevator stage so that immunoassays and thermocouple rinse/drying cycles can be implemented in a programmed fashion. The automated assay with three rinse/drying cycles takes only 34.5 min for four samples or 8.62 min/sample, whereas the manual mode with a single thermocouple and a point light source requires at least 66 min for just one sample. With careful calibration of the energy distribution of the expanded laser beam and controllable immersion of the thermocouples, excellent well-to-well (RSD = 1.3%) and cycle-to-cycle (RSD = 4.0%) reproducibility can be attained. The temperature changes can be correlated with the CRP concentration by the Langmuir isotherm, and the low limit of detection, 0.52 ng/mL or 4.33 pM, is well below the plasma CRP levels of both healthy people (<5 μg/mL) and patients (10-500 μg/mL). The serum CRP concentrations quantified by our plate reader are in excellent agreement with the immunoturbidimetric results, demonstrating that this cost-effective, robust, and high-throughput mode for microplate-based immunoassays is amenable to detecting biomarkers in many clinical samples.

Understanding the effect of measurement time on drug characterization

In order to determine correct dosage of chemotherapy drugs, the effect of the drug must be properly quantified. There are two important values that characterize the effect of the drug: εmax is the maximum possible effect of a drug, and IC50 is the drug concentration where the effect diminishes by half. There is currently a problem with the way these values are measured because they are time-dependent measurements. We use mathematical models to determine how the εmax and IC50 values depend on measurement time and model choice. Seven ordinary differential equation models (ODE) are used for the mathematical analysis; the exponential, Mendelsohn, logistic, linear, surface, Bertalanffy, and Gompertz models. We use the models to simulate tumor growth in the presence and absence of treatment with a known IC50 and εmax. Using traditional methods, we then calculate the IC50 and εmax values over fifty days to show the time-dependence of these values for all seven mathematical models. The general trend found is that the measured IC50 value decreases and the measured εmax increases with increasing measurement day for most mathematical models. Unfortunately, the measured values of IC50 and εmax rarely matched the values used to generate the data. Our results show that there is no optimal measurement time since models predict that IC50 estimates become more accurate at later measurement times while εmax is more accurate at early measurement times.

Mathematical deconvolution of CAR T-cell proliferation and exhaustion from real-time killing assay data

Chimeric antigen receptor (CAR) T-cell therapy has shown promise in the treatment of haematological cancers and is currently being investigated for solid tumours, including high-grade glioma brain tumours. There is a desperate need to quantitatively study the factors that contribute to the efficacy of CAR T-cell therapy in solid tumours. In this work, we use a mathematical model of predator-prey dynamics to explore the kinetics of CAR T-cell killing in glioma: the Chimeric Antigen Receptor T-cell treatment Response in GliOma (CARRGO) model. The model includes rates of cancer cell proliferation, CAR T-cell killing, proliferation, exhaustion, and persistence. We use patient-derived and engineered cancer cell lines with an in vitro real-time cell analyser to parametrize the CARRGO model. We observe that CAR T-cell dose correlates inversely with the killing rate and correlates directly with the net rate of proliferation and exhaustion. This suggests that at a lower dose of CAR T-cells, individual T-cells kill more cancer cells but become more exhausted when compared with higher doses. Furthermore, the exhaustion rate was observed to increase significantly with tumour growth rate and was dependent on level of antigen expression. The CARRGO model highlights nonlinear dynamics involved in CAR T-cell therapy and provides novel insights into the kinetics of CAR T-cell killing. The model suggests that CAR T-cell treatment may be tailored to individual tumour characteristics including tumour growth rate and antigen level to maximize therapeutic benefit.

Estimating Dynamic Cellular Morphological Properties via the Combination of the RTCA System and a Hough-Transform-Based Algorithm

The xCELLigence real-time cell analysis (RTCA) system has the potential to detect cellular proliferation, migration, cytotoxicity, adherence, and remodeling. Although the RTCA system is widely recognized as a noninvasive and efficient tool for real-time monitoring of cellular fate, it cannot describe detailed cell morphological parameters, such as length and intensity. Transforming growth factor beta(TGF-β) induced the epithelial–mesenchymal transition (EMT), which produces significant changes in cellular morphology, so we used TGF-β to treat A549 epithelial cells in this study. We compared it with lipopolysaccharide (LPS) and cigarette smoke extract (CSE) as stimulators. We developed an efficient algorithm to quantify the morphological cell changes. This algorithm is comprised of three major parts: image preprocessing, Hough transform (HT), and post-processing. We used the RTCA system to record the A549 cell index. Western blot was used to confirm the EMT. The RTCA system showed that different stimulators produce different cell index curves. The algorithm determined the lengths of the detected lines of cells, and the results were similar to the RTCA system in the TGF-β group. The Western blot results show that TGF-β changed the EMT markers, but the other stimulator remained unchanged. Optics-based computer vision techniques can supply the requisite information for the RTCA system based on good correspondence between the results.

miR-34c-5p modulates X-box-binding protein 1 (XBP1) expression during the adaptive phase of the unfolded protein response

During endoplasmic reticulum (ER) stress conditions, an adaptive signaling network termed the unfolded protein response (UPR) is activated. The UPR's function is to increase ER protein-folding capacity in order to attenuate ER stress, restore ER homeostasis, and, most importantly, promote cell survival. X-box-binding protein 1 (XBP1) is one component of the UPR and is a proadaptive transcription factor that is subject to transcriptional, post-transcriptional, and post-translational control. In the present study, we identified a post-transcriptional mechanism mediated by miR-34c-5p that governs the expression of both the spliced (active) and unspliced (latent) forms of XBP1 mRNAs. We showed that miR-34c-5p directly attenuates spliced XBP1 (XBP1s) mRNA levels during ER stress and thus regulates the proadaptive component of the UPR that is mediated by XBP1s without interfering with the induction of apoptotic responses.-Bartoszewska, S., Cabaj, A., Dąbrowski, M., Collawn, J. F., Bartoszewski, R. miR-34c-5p modulates X-box-binding protein 1 (XBP1) expression during the adaptive phase of the unfolded protein response.

A Multidisciplinary Approach Toward High Throughput Label-Free Cytotoxicity Monitoring of Superparamagnetic Iron Oxide Nanoparticles

Abstract: This paper focuses on cytotoxicity examination of superparamagnetic iron oxide nanoparticles (SPIONs) using different methods, including impedance spectroscopy. Recent advances of SPIONs for clinical and research applications have triggered the need to understand their effects in cells. Despite the great advances in adapting various biological and chemical methods to assess in-vitro toxicity of SPIONs, less attention has been paid on the development of a high throughput label-free screening platform to study the interaction between the cells and nanoparticles including SPIONs. In this paper, we have taken the first step toward this goal by proposing a label-free impedimetric method for monitoring living cells treated with SPIONs. We demonstrate the effect of SPIONs on the adhesion, growth, proliferation, and viability of neuroblastoma 2A (N2a) cells using impedance spectroscopy as a label-free method, along with other standard microscopic and cell viability testing methods as control methods. Our results have shown a decreased viability of the cells as the concentration of SPIONs increases with percentages of 59%, 47%, and 40% for 100 µg/mL (C4), 200 µg/mL (C5), 300 µg/mL (C6), respectively. Although all SPIONs concentrations have allowed the growth of cells within 72 hours, C4, C5, and C6 showed slower growth compared to the control (C1). The growth and proliferation of N2a cells are faster in the absence or low concentration of SPIONS. The percent coefficient of variation (% CV) was used to compare cell concentrations obtained by TBDE assay and a Scepter cell counter. Results also showed that the lower the SPIONs concentration, the lower the impedance is expected to be in the sensing electrodes without the cells. Meanwhile, the variation of surface area (∆S) was affected by the concentration of SPIONs. It was observed that the double layer capacitance was almost constant because of the higher attachment of cells, the lower surface area coated by SPIONs. In conclusion, impedance changes of electrodes exposed to the mixture of cells and SPIONs offer a wide dynamic range (>1 MΩ using Electric Cell-substrate Impedance electrodes) suitable for cytotoxicity studies. Based on impedance based, viability testing and microscopic methods' results, SPIONs concentrations higher than 100 ug/mL and 300 ug/mL cause minor and major effects, respectively. We propose that a high throughput impedance-based label-free platform provides great advantages for studying SPIONs in a cell-based context, opening a window of opportunity to design and test the next generation of SPIONs with reduced toxicity for biomedical or medical applications.

Establishment, molecular and biological characterization of HCB-514: a novel human cervical cancer cell line

Cervical cancer is the fourth most common cancer in women. Although cure rates are high for early stage disease, clinical outcomes for advanced, metastatic, or recurrent disease remain poor. To change this panorama, a deeper understanding of cervical cancer biology and novel study models are needed. Immortalized human cancer cell lines such as HeLa constitute crucial scientific tools, but there are few other cervical cancer cell lines available, limiting our understanding of a disease known for its molecular heterogeneity. This study aimed to establish novel cervical cancer cell lines derived from Brazilian patients. We successfully established one (HCB-514) out of 35 cervical tumors biopsied. We confirmed the phenotype of HCB-514 by verifying its’ epithelial and tumor origin through cytokeratins, EpCAM and p16 staining. It was also HPV-16 positive. Whole-exome sequencing (WES) showed relevant somatic mutations in several genes including BRCA2, TGFBR1 and IRX2. A copy number variation (CNV) analysis by nanostring and WES revealed amplification of genes mainly related to kinases proteins involved in proliferation, migration and cell differentiation, such as EGFR, PIK3CA, and MAPK7. Overexpression of EGFR was confirmed by phospho RTK-array and validated by western blot analysis. Furthermore, the HCB-514 cell line was sensitive to cisplatin. In summary, this novel Brazilian cervical cancer cell line exhibits relevant key molecular features and constitutes a new biological model for pre-clinical studies.

Proliferation characteristics of cells cultured under periodic versus static conditions

In vitro culture models have become an indispensable tool for assessing a vast variety of biological questions in many scientific fields. However, common in vitro cultures are maintained under static conditions, which do not reflect the in vivo situation and create a non-physiological environment. To assess whether the growth characteristics of cells cultured at pulsed-perfused versus static conditions differ, we observed the growth of differentially cultured cells in vitro by life-cell time-lapse imaging of recombinant HEK293^YFPI152L cells, stably expressing yellow fluorescent protein. Cells were grown for ~ 30 h at 37 °C and ambient CO₂ concentration in biochips mounted into a custom-designed 3D printed carrier and were imaged at a rate of ten images per hour using a fluorescence microscope with environment control infrastructure. Cells in one chip were maintained under static conditions whereas cells in another chip were recurrently perfused with fresh media. Generated image series were quantitatively analyzed using a custom-modified cell detection software. Imaging data averaged from four biological replicates per culturing condition demonstrate that cells cultured under conventional conditions exhibit an exponential growth rate. In contrast, cells cultured in periodic mode exhibited a non-exponential growth rate. Our data clearly indicate differential growth characteristics of cells cultured under periodic versus static conditions highlighting the impact of the culture conditions on the physiology of cells in vitro.

A high-throughput impedimetric platform for cellular analysis: Design, Implementation and Experimental Results

A high-throughput impedance spectroscopy measurement system was designed and developed for the purpose of biological analysis. This platform consists of a microchip containing a microelectrode array and a multiplexing interface system. Herein we put forward the proposed platform and demonstrate its functionality by performing impedance analysis using N2a cells and its associated medium. The early experimental results demonstrated the high-through impedimetric system to be a strong basis for future modification and development.

Towards non-invasive characterisation of coronary stent re-endothelialisation - An in-vitro, electrical impedance study

The permanent implantation of a stent has become the most common method for ameliorating coronary artery narrowing arising from atherosclerosis. Following the procedure, optimal arterial wall healing is characterised by the complete regrowth of an Endothelial Cell monolayer over the exposed stent surface and surrounding tissue, thereby reducing the risk of thrombosis. However, excessive proliferation of Smooth Muscle Cells, within the artery wall can lead to unwanted renarrowing of the vessel lumen. Current imaging techniques are unable to adequately identify re-endothelialisation, and it has previously been reported that the stent itself could be used as an electrode in combination with electrical impedance spectroscopic techniques to monitor the post-stenting recovery phase. The utility of such a device will be determined by its ability to characterise between vascular cell types. Here we present in-vitro impedance spectroscopy measurements of pulmonary artery porcine Endothelial Cells, Human Umbilical Vein Endothelial Cells and coronary artery porcine Smooth Muscle Cells grown to confluence over platinum black electrodes in clinically relevant populations. These measurements were obtained, using a bespoke impedance spectroscopy system that autonomously performed impedance sweeps in the 1kHz to 100kHz frequency range. Analysis of the reactance component of impedance revealed distinct frequency dependent profiles for each cell type with post confluence reactance declines in Endothelial Cell populations that have not been previously reported. Such profiles provide a means of non-invasively characterising between the cell types and give an indication that impedance spectroscopic techniques may enable the non-invasive characterisation of the arterial response to stent placement.

Separation of functionally divergent muscle precursor cell populations from porcine juvenile muscles by discontinuous Percoll density gradient centrifugation

BACKGROUND

Satellite cells (SC) and their descendants, muscle precursor cells (MPC), play a key role in postnatal muscle development, regeneration, and plasticity. Several studies have provided evidence that SC and MPC represent a heterogeneous population differing in their biochemical and functional properties. The identification and characterization of functionally divergent SC subpopulations should help to reveal the precise involvement of SC/MPC in these myogenic processes. The aim of the present work was therefore to separate SC subpopulations by using Percoll gradients and to characterize their myogenic marker profiles and their functional properties (adhesion, proliferation, and differentiation).

RESULTS

SC/MPC from muscles of 4-day-old piglets were isolated by trypsin digestion and enriched by Percoll density gradient centrifugation. A mixed myogenic cell population was obtained from the 40/70% interface (termed: mixed P40/70) of a 25/40/70% Percoll gradient. Thereafter, by using a more stepped 25/40/50/70% Percoll gradient, mixed P40/70 was divided into subpopulation 40/50 (SP40/50) collected from the 40/50% interface and subpopulation 50/70 (SP50/70) collected from the 50/70% interface. All three isolated populations proliferated and showed a myogenic phenotype characterized by the ability to express myogenic markers (Pax7, MyoD1, Desmin, and MyoG) and to differentiate into myotubes. However, compared with mixed P40/70, SP40/50 and SP50/70 exhibited distinct functional behavior. Growth kinetic curves over 90 h obtained by the xCELLigence system and proliferation assays revealed that SP40/50 and mixed P40/70 constituted a fast adhering and fast proliferating phenotype. In contrast, SP50/70 showed considerably slower adhesion and proliferation. The fast-proliferating SP40/50 showed the highest myogenic differentiation potential with higher fusion rates and the formation of more middle-sized and large myotubes.

CONCLUSIONS

The described Percoll density gradient centrifugation represents a useful tool for subdividing pig SC/MPC populations with divergent myogenic functions. The physiological role of SC subpopulations during myogenesis and the interaction of these populations can now be analyzed to a greater extent, shedding light on postnatal growth variations in pigs and probably in other animals.

Co-expression of 1α-hydroxylase and vitamin D receptor in human articular chondrocytes

BACKGROUND

The aim was to investigate whether resident chondrocytes in human articular cartilage and in subculture express vitamin D receptor (VDR) and the enzyme that hydroxylates the prohormone 25(OH)D₃ to the active hormone 1α,25(OH)₂D₃, namely 1α-hydroxylase (CYP27B1). Any putative effects of vitamin D on chondrocytes were also explored.

METHODS

Cartilage from human osteoarthritic knee joints, cultured chondrocytes and cells grown in 3D spheroids were examined for the expression of VDR and 1α-hydroxylase by PCR, Western blots and immunolabelling. Receptor engagement was judged by visualizing nuclear translocation. The effects of 25(OH)D₃ and 1α,25(OH)₂D₃ on chondrocyte functions were assessed in proliferation-, chondrogenesis- and cartilage signature-gene expression assays. The capability of chondrocytes to hydroxylate 25(OH)D₃ was determined by measuring the concentration of metabolites. Finally, a putative regulation of receptor and enzyme expression by 1α,25(OH)₂D₃ or interleukin (IL)-1β, was investigated by Western blot.

RESULTS

Gene expression was positive for VDR in freshly isolated cells from native cartilage, cells subcultured in monolayers and in spheroids, whereas protein expression, otherwise judged low, was apparent in monolayers. Nuclear translocation of VDR occurred upon 1α,25(OH)₂D₃ treatment. Transcripts for 1α-hydroxylase were detected in freshly isolated cells, cultured cells and spheroids. Western blots and immunolabelling detected 1α-hydroxylase protein in all materials, while staining of tissue appeared confined to cells at the superficial layer. A dose-dependent 1α,25(OH)₂D₃ production was measured when the enzyme substrate was supplied to cell cultures. Western blots revealed that the VDR, but not 1α-hydroxylase, was induced by IL-1β treatment in adherent cells. Proliferation in monolayers was enhanced by both 25(OH)D₃ and 1α,25(OH)₂D₃, and both compounds had negative effects on chondrogenesis and cartilage-matrix genes.

CONCLUSIONS

VDR expression in resident cartilage chondrocytes, generally considered differentiated cells, is elusive. A similar pattern applies for redifferentiated chondrocytes in spheroid cultures, whereas dedifferentiated cells, established in monolayers, stably express VDR. Both 25(OH)D₃ and 1α,25(OH)₂D₃ are able to potentiate cell proliferation but have a negative impact in proteoglycan synthesis. Chondrocytes express 1α-hydroxylase and may contribute to the production of 1α,25(OH)₂D₃ into the joint environment. Effects of vitamin D could be unfavourable in the context of cartilage matrix synthesis.

Impact of Mycotoxins Secreted by Aspergillus Molds on the Inflammatory Response of Human Corneal Epithelial Cells

Exposure to molds and mycotoxins not only contributes to the onset of respiratory disease, it also affects the ocular surface. Very few published studies concern the evaluation of the effect of mycotoxin exposure on ocular cells. The present study investigates the effects of aflatoxin B₁ (AFB₁) and gliotoxin, two mycotoxins secreted by Aspergillus molds, on the biological activity of the human corneal epithelial (HCE) cells. After 24, 48, and 72 h of exposure, cellular viability and inflammatory response were assessed. Both endpoint cell viability colorimetric assays and continuous cell impedance measurements, providing noninvasive real-time assessment of the effect on cells, were performed. Cytokine gene expression and interleukin-8 release were quantified. Gliotoxin appeared more cytotoxic than AFB₁ but, at the same time, led to a lower increase of the inflammatory response reflecting its immunosuppressive properties. Real-time cell impedance measurement showed a distinct profile of cytotoxicity for both mycotoxins. HCE cells appeared to be a well-suited in vitro model to study ocular surface reactivity following biological contaminant exposure. Low, but persistent inflammation, caused by environmental factors, such as fungal toxins, leads to irritation and sensitization, and could be responsible for allergic manifestations which, in turn, could lead to mucosal hyper-reactivity.

Real-time cell analysis and heat shock protein gene expression in the TcA Tribolium castaneum cell line in response to environmental stress conditions

The rust red flour beetle, Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae), is a pest of stored grain and one of the most studied insect model species. Some of the previous studies involved heat response studies in terms of survival and heat shock protein expression, which are regulated to protect other proteins against environmental stress conditions. In the present study, we characterize the impedance profile with the xCELLigence Real-Time Cell Analyzer and study the effect of increased temperature in cell growth and viability in the cell line BCIRL-TcA-CLG1 (TcA) of T. castaneum. This novel system measures cells behavior in real time and is applied for the first time to insect cells. Additionally, cells are exposed to heat shock, increased salinity, acidic pH and UV-A light with the aim of measuring the expression levels of Hsp27, Hsp68a, and Hsp83 genes. Results show a high thermotolerance of TcA in terms of cell growth and viability. This result is likely related to gene expression results in which a significant up-regulation of all studied Hsp genes is observed after 1 h of exposure to 40 °C and UV light. All 3 genes show similar expression patterns, but Hsp27 seems to be the most affected. The results of this study validate the RTCA method and reveal the utility of insect cell lines, real-time analysis and gene expression studies to better understand the physiological response of insect cells, with potential applications in different fields of biology such as conservation biology and pest management.

In silico cytotoxicity assessment on cultured rat intestinal cells deduced from cellular impedance measurements

Early and reliable identification of chemical toxicity is of utmost importance. At the same time, reduction of animal testing is paramount. Therefore, methods that improve the interpretability and usability of in vitro assays are essential. xCELLigence's real-time cell analyzer (RTCA) provides a novel, fast and cost effective in vitro method to probe compound toxicity. We developed a simple mathematical framework for the qualitative and quantitative assessment of toxicity for RTCA measurements. Compound toxicity, in terms of its 50% inhibitory concentration IC₅₀ on cell growth, and parameters related to cell turnover were estimated on cultured IEC-6 cells exposed to 10 chemicals at varying concentrations. Our method estimated IC₅₀ values of 113.05, 7.16, 28.69 and 725.15 μM for the apparently toxic compounds 2-acetylamino-fluorene, aflatoxin B1, benzo-[a]-pyrene and chloramphenicol in the tested cell line, in agreement with literature knowledge. IC₅₀ values of all apparent in vivo non-toxic compounds were estimated to be non-toxic by our method. Corresponding estimates from RTCA's in-built model gave false positive (toxicity) predictions in 5/10 cases. Taken together, our proposed method reduces false positive predictions and reliably identifies chemical toxicity based on impedance measurements. The source code for the developed method including instructions is available at https://git.zib.de/bzfgupta/toxfit/tree/master.

Effects of RAF inhibitors on PI3K/AKT signalling depend on mutational status of the RAS/RAF signalling axis

Targeted therapies within the RAS/RAF/MEK/ERK signalling axis become increasingly popular, yet cross-talk and feedbacks in the signalling network lead to unexpected effects. Here we look systematically into how inhibiting RAF and MEK with clinically relevant inhibitors result in changes in PI3K/AKT activation. We measure the signalling response using a bead-based ELISA, and use a panel of three cell lines, and isogenic cell lines that express mutant forms of the oncogenes KRAS and BRAF to interrogate the effects of the MEK and RAF inhibitors on signalling. We find that treatment with the RAF inhibitors have opposing effects on AKT phosphorylation depending on the mutational status of two important oncogenes, KRAS and BRAF. If these two genes are in wildtype configuration, RAF inhibitors reduce AKT phosphorylation. In contrast, if BRAF or KRAS are mutant, RAF inhibitors will leave AKT phosphorylation unaffected or lead to an increase of AKT phosphorylation. Down-regulation of phospho-AKT by RAF inhibitors also extends to downstream transcription factors, and correlates with apoptosis induction. Our results show that oncogenes rewire signalling such that targeted therapies can have opposing effects on parallel pathways, which depend on the mutational status of the cell.