Background

Energetic primary and secondary particles pose a health risk to astronauts in extended International Space Station (ISS) and future Lunar and Mars missions. High-LET radiation is much more effective than low-LET radiation in the induction of various biological effects, including cell inactivation, genetic mutations, cataracts and cancer. Most of these biological endpoints are closely correlated to chromosomal damage, which can be utilized as a biomarker for radiation insult.

Solution

USRA researchers, working in collaboration with NASA, have applied new cytogenetic techniques that allow for the simultaneous measurement of inter- and intra- chromosome aberrations to assess radiation effects.

Specifically, the study aims to analyze low- and high-LET induced chromosomal aberrations in human lymphocytes and human epithelial cells using varying state of the art techniques, including two novel tools, multicolor fluorescent in situ hybridization (mFISH) and multicolor banding in situ hybridization (mBAND), known to provide advantageous benefits over other cytogenetic techniques. These two techniques are capable of identifying complex chromosomal aberrations and stable intrachromosomal aberrations, respectively. mFISH analysis will provide the true complexity of chromosomal damage in all human chromosomes, whilst the use of mBAND may allow us to identify longer-lived biomarkers for high-LET exposure.

Results

USRA researchers exposed human epithelial cells in vitro to 137Cs g rays, Fe ions (600 MeV/nucleon) at NASA Space Radiation Laboratory or secondary neutrons at Los Alamos Nuclear Center whose spectrum is similar to that measured inside the Space Station. Chromosomes were collected using a premature chromosome condensation technique, and aberrations in chromosome 3 were analyzed using mBAND probes. Results of the study confirmed the observation of higher incidence of inversions for high-LET irradiation. However, detailed analysis of the inversion type revealed that all of the three radiation types in the study induced a low incidence of simple inversions. Half of the inversions observed in the low-LET irradiated samples were accompanied by other types of intrachromosome aberrations, but few inversions were accompanied by interchromosome aberrations. In contrast, Fe ions induced a significant fraction of inversions that involved complex rearrangements of both the inter- and intrachromosome exchanges.

These cytogenetic techniques are helping to identify complex cellular damage caused by exposure to space radiation. Understanding the effects of high energy particle radiation on human physiology can lead to the development of countermeasures that could address astronaut health and safety during missions to the Moon and Mars.