RABiT-II: A Fully-Automated Micronucleus Assay System with Shortened Time to Result

Potentials of cytokinesis blocked micronucleus assay in radiation triage and biological dosimetry

The measurement of micronucleus (MN) in the cytokinesis-block arrested binucleated cells has been extensively used as a biomarker in many radiation biology applications in specific biodosimetry. Following radiation casualties, medical management of exposed individuals begins with triage and biological dosimetry. The cytokinesis blocked micronucleus (CBMN) assay is the alternate for the gold standard dicentric chromosome assay in radiation dose assessment. In recent years, the CBMN assay has become well-validated and emerged as a method of choice for evaluating occupational and accidental exposures scenario. It is feasible due to its cost-effective, simple, and rapid dose assessment rather than a conventional chromosome aberration assay. PubMed search tool was used with keywords of MN, biodosimetry, radiotherapy and restricted to human samples. Since Fenech and Morely developed the assay, it has undergone many technical and technological reforms as a biomarker of various applications. In this review, we have abridged recent developments of the CBMN assay in radiation triage and biodosimetry, focusing on (a) the influence of variables on dose estimation, (b) the importance of baseline frequency and reported dose-response coefficient values among different laboratories, (c) inter-laboratory comparison and (d) its limitations and means to overcome them.

Multiparameter imaging flow cytometry-based cytokinesis-block micronucleus assay: Reduction of culture time and blood volume for improved efficiency

In the event of a large-scale incident involving radiological or nuclear exposures, there is a potential for large numbers of individuals to have received doses of radiation sufficient to cause adverse health effects. It is imperative to quickly identify these individuals in order to provide information to the medical community to assist in making decisions about their treatment. The cytokinesis-block micronucleus assay is a well-established method for performing biodosimetry. This assay has previously been adapted to imaging flow cytometry and has been validated as a high-throughput option for providing dose estimates in the range of 0-10 Gy. The goal of this study was to test the ability to further optimize the assay by reducing the time of culture to 48 h from 68 h as well as reducing the volume of blood required for the analysis to 200 μL from 2 mL. These modifications would provide efficiencies in time and ease of processing impacting the ability to manage large numbers of samples and provide dose estimates in a timely manner. Results demonstrated that either the blood volume or the culture time could be reduced while maintaining dose estimates with sufficient accuracy for triage analysis. Reducing both the blood volume and culture time, however, resulted in poor dose estimates. In conclusion, depending on the needs of the scenario, either culture time or the blood volume could be reduced to improve the efficiency of analysis for mass casualty scenarios.

RABiT-III: an Automated Micronucleus Assay at a Non-Specialized Biodosimetry Facility

Micronuclei, detected through the cytokinesis-block micronucleus assay, are valuable indicators of ionizing radiation exposure, especially in short-term lymphocyte cultures. The peripheral human blood lymphocyte assay is recognized as a prime candidate for automated biodosimetry. In a prior project at the Columbia University Center for Radiological Research, we automated this assay using the 96-well ANSI/SLAS microplate standard format and relied on established biotech robotic systems named Rapid Automated Biodosimetry Tool (RABiT). In this study, we present the application of a similar automated biotech setup at an external high-throughput facility (RABiT-III) to implement the same automated cytokinesis-block micronucleus assay. Specifically, we employed the Agilent BRAVO liquid-handling system and GE IN Cell Analyzer 6000 imaging system in conjunction with the PerkinElmer Columbus image data storage and analysis system. Notably, this analysis system features an embedded PhenoLOGIC machine learning module, simplifying the creation of cell classification algorithms for CBMN assay image analysis and enabling the generation of radiation dose-response curves. This investigation underscores the adaptability of the RABiT-II CBMN protocol to diverse RABiT-III biotech robotic platforms in non-specialized biodosimetry centers. Furthermore, it highlights the advantages of machine learning in rapidly developing algorithms crucial for the high-throughput automated analysis of RABiT-III images.

Sex and dose rate effects in automated cytogenetics

Testing and validation of biodosimetry assays is routinely performed using conventional dose rate irradiation platforms, at a dose rate of approximately 1 Gy/min. In contrast, the exposures from an improvised nuclear device will be delivered over a large range of dose rates with a prompt irradiation component, delivered in less than 1 μs, and a protracted component delivered over hours and days. We present preliminary data from a large demographic study we have undertaken for investigation of age, sex and dose rate effects on dicentric and micronucleus yields. Our data demonstrate reduced dicentric and micronucleus yields at very high dose rates. Additionally, we have seen small differences between males and females, with males having slightly fewer micronuclei and slightly more dicentrics than females, at high doses.

Improved prediction of breast cancer risk based on phenotypic DNA damage repair capacity in peripheral blood B cells

Background

Standard Breast Cancer (BC) risk prediction models based only on epidemiologic factors generally have quite poor performance, and there have been a number of risk scores proposed to improve them, such as AI-based mammographic information, polygenic risk scores and pathogenic variants. Even with these additions BC risk prediction performance is still at best moderate. In that decreased DNA repair capacity (DRC) is a major risk factor for development of cancer, we investigated the potential to improve BC risk prediction models by including a measured phenotypic DRC assay.

Methods

Using blood samples from the Breast Cancer Family Registry we assessed the performance of phenotypic markers of DRC in 46 matched pairs of individuals, one from each pair with BC (with blood drawn before BC diagnosis) and the other from controls matched by age and time since blood draw. We assessed DRC in thawed cryopreserved peripheral blood mononuclear cells (PBMCs) by measuring γ-H2AX yields (a marker for DNA double-strand breaks) at multiple times from 1 to 20 hrs after a radiation challenge. The studies were performed using surface markers to discriminate between different PBMC subtypes.

Results

The parameter F res , the residual damage signal in PBMC B cells at 20 hrs post challenge, was the strongest predictor of breast cancer with an AUC (Area Under receiver-operator Curve) of 0.89 [95% Confidence Interval: 0.84-0.93] and a BC status prediction accuracy of 0.80. To illustrate the combined use of a phenotypic predictor with standard BC predictors, we combined F res in B cells with age at blood draw, and found that the combination resulted in significantly greater BC predictive power (AUC of 0.97 [95% CI: 0.94-0.99]), an increase of 13 percentage points over age alone.

Conclusions

If replicated in larger studies, these results suggest that inclusion of a fingerstick-based phenotypic DRC blood test has the potential to markedly improve BC risk prediction.

Cross-platform validation of a mouse blood gene signature for quantitative reconstruction of radiation dose

In the search for biological markers after a large-scale exposure of the human population to radiation, gene expression is a sensitive endpoint easily translatable to in-field high throughput applications. Primarily, the ex-vivo irradiated healthy human blood model has been used to generate available gene expression datasets. This model has limitations i.e., lack of signaling from other irradiated tissues and deterioration of blood cells cultures over time. In vivo models are needed; therefore, we present our novel approach to define a gene signature in mouse blood cells that quantitatively correlates with radiation dose (at 1 Gy/min). Starting with available microarray datasets, we selected 30 radiation-responsive genes and performed cross-validation/training–testing data splits to downselect 16 radiation-responsive genes. We then tested these genes in an independent cohort of irradiated adult C57BL/6 mice (50:50 both sexes) and measured mRNA by quantitative RT-PCR in whole blood at 24 h. Dose reconstruction using net signal (difference between geometric means of top 3 positively correlated and top 4 negatively correlated genes with dose), was highly improved over the microarrays, with a root mean square error of ± 1.1 Gy in male and female mice combined. There were no significant sex-specific differences in mRNA or cell counts after irradiation.

Automatic reagent handling and assay processing of human biospecimens inside a transportation container for a medical disaster response against radiation

Biological materials can be shipped off-site for diagnostic, therapeutic and research purposes. They usually are kept in certain environments for their final application during transportation. However, active reagent handling during transportation from a collection site to a laboratory or biorepository has not been reported yet. In this paper, we show the application of a micro-controlled centrifugal microfluidic system inside a shipping container that can add reagent to an actively cultured human blood sample during transportation to ensure a rapid biodosimetry of cytokinesis-block micronucleus (CBMN) assay. The newly demonstrated concept could have a significant impact on rapid biodosimetry triage for medical countermeasure in a radiological disaster. It also opens a new capability in accelerated sample processing during transportation for biomedical and healthcare applications.

MicroRNA-149 suppresses osteogenic differentiation of mesenchymal stem cells via inhibition of AKT1-dependent Twist1 phosphorylation

Osteogenic differentiation is a vital process for growth, repair, and remodeling of bones. Accumulating evidence have suggested that microRNAs (miRNAs or miRs) play a crucial role in osteogenic differentiation of mesenchymal stem cells (MSCs). Hence, the current study set out to elucidate the role of miR-149 in osteogenic differentiation of MSCs and the underlying mechanism. First, rat models of bone differentiation were established using the Masquelet-induced membrane technique, and MSCs were isolated. The expression of miR-149 and AKT1 in the rats and cells was detected with RT-qPCR and western blot analysis. The relationships among miR-149, AKT1, and Twist1 were further predicted by online bioinformatics prediction and verified using dual luciferase reporter gene assay. Alteration of miR-149, AKT1, or Twist1 was performed to further explore their effect on osteogenic differentiation of MSCs. miR-149 was poorly expressed in the process of osteogenic differentiation of MSCs, while AKT1 was highly expressed. miR-149 negatively regulated the expression of AKT1, which in turn diminished the protein levels of Twist1 and promoted the phosphorylation levels of Twist1. Lastly, miR-149 acted as an inhibitor of osteogenic differentiation of MSCs, which could be reversed by AKT1. To sum up, miR-149 silencing promoted osteogenic differentiation of MSCs by enhancing Twist1 degradation through AKT1 upregulation, representing a new method for bone repair treatment.

Cytogenetic biological dosimetry assays: recent developments and updates

Biological dosimetry is the measurement of radiation-induced changes in the human to measure short and long-term health risks. Biodosimetry offers an independent means of obtaining dose information and also provides diagnostic information on the potential for "partial-body" exposure information using biological indicators and otherwise based on computer modeling, dose reconstruction, and physical dosimetry. A variety of biodosimetry tools are available and some features make some more valuable than others. Among the available biodosimetry tool, cytogenetic biodosimetry methods occupy an exclusive and advantageous position. The cytogenetic analysis can complement physical dosimetry by confirming or ruling out an accidental radiological exposure or overexposures. We are discussing the recent developments and adaptability of currently available cytogenetic biological dosimetry assays.

Whole blood gene expression within days after total-body irradiation predicts long term survival in Gottingen minipigs

Gottingen minipigs mirror the physiological radiation response observed in humans and hence make an ideal candidate model for studying radiation biodosimetry for both limited-sized and mass casualty incidents. We examined the whole blood gene expression profiles starting one day after total-body irradiation with increasing doses of gamma-rays. The minipigs were monitored for up to 45 days or time to euthanasia necessitated by radiation effects. We successfully identified dose- and time-agnostic (over a 1-7 day period after radiation), survival-predictive gene expression signatures derived using machine-learning algorithms with high sensitivity and specificity. These survival-predictive signatures fare better than an optimally performing dose-differentiating signature or blood cellular profiles. These findings suggest that prediction of survival is a much more useful parameter for making triage, resource-utilization and treatment decisions in a resource-constrained environment compared to predictions of total dose received. It should hopefully be possible to build such classifiers for humans in the future.

Roadmap for translating results from the micronucleus assay into clinical practice: From observational studies to randomized controlled trials

According to the definition delivred by the WHO, a biomarker, independently from its role that may be indicative of exposure, response or effect, is inevitably linked to a clinical outcome or to a disease. The presence of a continuum from early biological events to therapy, and prognosis is the unifying mechanism that justifies this conclusion. Traditionally, the technical and inter-individual variability of the assays, together with the long duration between early pathogenetic events and the disease, prevented clinical applications to these biomarkers. These limitations became less important with the emerging of personalized preventive medicine because of the focus on disease prediction and prevention, and the recommended use of all data concerning measurable patient's features. Several papers have been published on the best validation procedures for translating biomarkers to real life. The history of cholesterol concentration is extensively discussed as a reliable example of a biomarker that - after a long and controversial validation process - is currently used in clinical practice. The frequency of micronucleated cells is a reliable biomarker for the pathogenesis of cancer and other non-communicable diseases, and the link with clinical outcomes is substantiated by epidemiological evidence and strong mechanistic basis. Available literature concerning the use of the micronucleus assay in clinical studies is discussed, and a suitable three-levels road-map driving this biomarker towards clinical practice is presented. Under the perspective of personalized medicine, the use of the micronucleus assays can play a decisive role in addressing preventive and therapeutic strategies of chronic diseases. In many cases the MN assay is either currently used in clinical practice or classified as adequate to consider translation into practice. The roadmap to clinical validation of the micronucleus assay finds inspiration from the history of biomarkers such as cholesterol, which clearly showed that the evidence from prospective studies or RCTs is critical to achieve the required level of trust from the healthcare profession. (307 words).

Transportation container for pre-processing cytogenetic assays in radiation accidents

We report a shipping container that enables a disruptive logistics for cytogenetic biodosimetry for radiation countermeasures through pre-processing cell culture during transportation. The container showed precise temperature control (< 0.01 °C) with uniform sample temperature (< 0.1 °C) to meet the biodosimetry assay requirements. Using an existing insulated shipping box and long shelf life alkaline batteries makes it ideal for national stockpile. Dose curve of cytogenetic biodosimetry assay using the shipping container showed clear dose response and high linear correlation with the control dose curve using a laboratory incubator (Pearson’s correlation coefficient: 0.992). The container’s ability of pre-processing biological samples during transportation could have a significant impact on radiation countermeasure, as well as potential impacts in other applications such as biobanking, novel molecular or cell-based assays or therapies.

Gene Expression Profiles from Heart, Lung and Liver Samples of Total-Body-Irradiated Minipigs: Implications for Predicting Radiation-Induced Tissue Toxicity

In the event of a major accidental or intentional radiation exposure incident, the affected population could suffer from total- or partial-body exposures to ionizing radiation with acute exposure to organs that would produce life-threatening injury. Therefore, it is necessary to identify markers capable of predicting organ-specific damage so that appropriate directed or encompassing therapies can be applied. In the current work, gene expression changes in response to total-body irradiation (TBI) were identified in heart, lungs and liver tissue of Göttingen minipigs. Animals received 1.7, 1.9, 2.1 or 2.3 Gy TBI and were followed for 45 days. Organ samples were collected at the end of day 45 or sooner if the animal displayed morbidity necessitating euthanasia. Our findings indicate that different organs respond to TBI in a very specific and distinct manner. We also found that the liver was the most affected organ in terms of gene expression changes, and that lipid metabolic pathways were the most deregulated in the liver samples of non-survivors (survival time <45 days). We identified organ-specific gene expression signatures that accurately differentiated non-survivors from survivors and control animals, irrespective of dose and time postirradiation. At what point did these radiation-induced injury markers manifest and how this information could be used for applying intervention therapies are under investigation.

The use of a centrifuge-free RABiT-II system for high-throughput micronucleus analysis

The cytokinesis-block micronucleus (CBMN) assay is considered to be the most suitable biodosimetry method for automation. Previously, we automated this assay on a commercial robotic biotech high-throughput system (RABiT-II) adopting both a traditional and an accelerated micronucleus protocol, using centrifugation steps for both lymphocyte harvesting and washing, after whole blood culturing. Here we describe further development of our accelerated CBMN assay protocol for use on high-throughput/high content screening (HTS/HCS) robotic systems without a centrifuge. This opens the way for implementation of the CBMN assay on a wider range of commercial automated HTS/HCS systems and thus increases the potential capacity for dose estimates following a mass-casualty radiological event.

Development of an integrated fingerstick blood self-collection device for radiation countermeasures

We report the development of system for packaging critical components of the traditional collection kit to make an integrated fingerstick blood collector for self-collecting blood samples of 100 μl or more for radiation countermeasures. A miniaturized vacuum tube system (VacuStor system) has been developed to facilitate liquid reagent storage, simple operation and reduced sample contamination. Vacuum shelf life of the VacuStor tube has been analyzed by the ideal gas law and gas permeation theory, and multiple ways to extend vacuum shelf life beyond one year have been demonstrated, including low temperature storage, Parylene barrier coating and container vacuum bag sealing. Self-collection was also demonstrated by healthy donors without any previous fingerstick collection experience. The collected blood samples showed similar behavior in terms of gene expression and cytogenetic biodosimetry assays comparing to the traditionally collected samples. The integrated collector may alleviate the sample collection bottleneck for radiation countermeasures following a large-scale nuclear event, and may be useful in other applications with its self-collection and liquid reagent sample preprocessing capabilities.