A comparative study on the dose-effect of low-dose radiation based on microdosimetric analysis and single-cell sequencing technology

Abstract

The biological mechanisms triggered by low-dose exposure still need to be explored in depth. In this study, the potential mechanisms of low-dose radiation when irradiating the BEAS-2B cell lines with a Cs-137 gamma-ray source were investigated through simulations and experiments. Monolayer cell population models were constructed for simulating and analyzing distributions of nucleus-specific energy within cell populations combined with the Monte Carlo method and microdosimetric analysis. Furthermore, the 10 × Genomics single-cell sequencing technology was employed to capture the heterogeneity of individual cell responses to low-dose radiation in the same irradiated sample. The numerical uncertainties can be found both in the specific energy distribution in microdosimetry and in differential gene expressions in radiation cytogenetics. Subsequently, the distribution of nucleus-specific energy was compared with the distribution of differential gene expressions to guide the selection of differential genes bioinformatics analysis. Dose inhomogeneity is pronounced at low doses, where an increase in dose corresponds to a decrease in the dispersion of cellular-specific energy distribution. Multiple screening of differential genes by microdosimetric features and statistical analysis indicate a number of potential pathways induced by low-dose exposure. It also provides a novel perspective on the selection of sensitive biomarkers that respond to low-dose radiation.

Keywords: Low dose radiation; Mesh-type cell model; Microdosimetry; Monte Carlo; Single-cell sequencing.

Figure 1

The schematic diagram of the simulation and experimental workflow. Part 1 outlines the process of constructing a monolayer cell population model. (A) is an overhead view of the monolayer cell population model along with an enlarged detail. (B) and (C) represent schematic illustrations of Monte Carlo simulations for irradiation scenarios in circular and square culture dishes containing the monolayer cell population model (the gray planes indicate the monoenergetic photon external irradiation source). Part 2 illustrates the workflow for cell irradiation and single-cell sequencing. A connection is established between these two categories of distributions obtained through Part 1 and Part 2. The Monte Carlo simulations from Part 1 provide the specific energy distribution within cell nucleus, while the sequencing results from Part 2 reveal the distribution of gene expression differences.

Figure 2

Specific energy distributions of cell nucleus in the monolayer cell population model for monoenergic photons with incident energies of 0.1 MeV (A), 0.2 MeV (B), 0.5 MeV (C), and 1 MeV (D) at the macroscopic dose level of 5 mGy. The mesh-type (black) and geometric-type (red) models are considered. The solid lines represent the actual specific energy distributions, while the dashed lines represent the normal distributions by the mean and standard deviation of the specific energy distribution obtained from MC simulations. Panel E provides a comparison of the dispersion of specific energy distributions obtained from two types of cell population models.

Figure 3

Specific energy distributions of cell nucleus in a monolayer geometric-type cell population model for monoenergetic photons with an incident energy of 0.5 MeV at cumulative macroscopic dose levels of 5 mGy (A), 25 mGy (B), 50 mGy (C), 100 mGy (D), 200 mGy (E), and 500 mGy (F). The red line represents the specific energy distribution obtained by MC simulations. Brown lines represent specific energy distributions obtained through convolution with different times, starting from the specific energy distribution of cell nucleus at a cumulative dose of 5 mGy, which was obtained through MC simulation. Black lines represent normal distributions by the mean and standard deviation of the specific energy distribution obtained from MC simulations.

Figure 4

Expression distributions (bar charts) of selected differential genes in BEAS-2B cells irradiated with low doses (10 mGy and 100 mGy) following single-cell sequencing analysis. Normal distributions were obtained by their mean value and standard deviation of expression distributions (solid lines).

Figure 5

Summary of bioinformatics analysis results. (A) Heatmap of dose-dependent transcriptomes among different irradiated groups. (B) Top 10 GO analysis results for the combined differential genes from different clusters. (C) Interaction network of hub genes obtained through two different methods. (D) Chord diagram depicting the top 5 enriched GO pathways and KEGG pathways for the merged 13 genes^–.