Transgenic Tissue-Equivalents as Enhanced Biosensors for Assessment of Environmental Space Radiation Risk to Astronauts

摘要

Risk assessment for the biological effects of high-energy charged particles, ranging from protons to iron and heavier nuclei, encountered in space is essential for the success of long-term space exploration. While prokaryotic and eukaryotic cell models, developed in our lab and others, have advanced our understanding of many aspects of genotoxicity, there is a need for biosensors to assess the risk to humans from environmental insults that are representative of the cellular interactions present in tissues and capable of quantifying genotoxic damage. The objective of this study is to examine the effect of the localized microenvironment of cells, either cultured as 2- dimensional monolayers (2D) or 3-dimensional aggregates (3D), on the rate and type of genotoxic damage, and to examine those effects after the normal cell repair processes. The 3D multi-cellular tissue-like aggregate model was developed using NASA-designed bioreactors by the culture of mammalian cells on collagen-coated Cytodex microspheres. A transgenic cell line containing 50-70 copies of the transgene was utilized to provide the enhanced sensitivity required to enable the identification and quantification of the types of mutational events incurred and specifically, to assess the mutational frequency and type from exposure to high-energy iron charged particles which makes up a significant portion of Space radiation. The samples were exposed to high-LET iron charged particles at Brookhaven National Laboratory's Alternating Gradient Synchrotron facility at a dose rate of 1 Gy/min for a total dose of 0, 0.1, 0.25, 0.5, 1.0, and 2.0Gy and recovered after 0, 1, and 7 days of tissue culture post-irradiation. The mutational frequency was found to be greater for the 3D samples when compared to the 2D samples at all doses. In addition, there was increased mutational frequency with 7 days culture post irradiation when compared to samples analyzed immediately after exposure. This study represents a significant contribution to the advancement of the understanding of the biological effects of Space- associated genotoxic damage and enables the development of strategies to minimize or eliminate these harmful effects.