In space, man encounters many strange and potentially harmful environmental factors. Cosmic radiation and microgravity are limiting for long duration space flights. Humans and whole animals' responses to microgravity have already been studied in depth.
For mammalian cells many microgravity dependent alterations have been reported. In addition to microgravity, cosmic radiation affects cells in space as revealed by cell inactivation, mutation induction and chromosomal aberrations. It is hypothesised, that alterations in the expression of cell cycle regulatory proteins may represent important early events in the process of oncogenic transformation in vitro. Basic types of DNA damages lead to altered gene expression patterns of mammalian cells.
The working group of Cellular Biodiagnostic develops mammalian cell based bioassays which will be used to investigate human response to space flight conditions already on a cellular level. Bioassays to be developed relay on the receptor-reporter principle well known for many bacterial assays. The sensing systems consist of specially designed plasmids or vectors, where promoters, which is dependent on certain environmental conditions, act as a sensing receptor. Fluorescent proteins, such as green fluorescent protein from the jellyfish Aequorea victoria or DsRed from Discosoma sp, are valuable tools for reporter components. Receptor-reporter constructs stably transfected to mammalian cells (preferably of human origin) transfer the sensing capacity coded by the vector to the cell. So far we have constructed different reporter vectors for screening of constitutive expressed house-keeping genes and of NF- B activation in human cell systems. Another sensing system which is being developed will detect the activity of the ribonucleotide reductase (RNR) system, which supplies mammalian cells with deoxyribonucleotides for DNA synthesis. Recombinant cells as hosts for the reporter vectors are human embryonic kidney cells (HEK), mamma Carcinoma cells (MCF7) and murine bone cells of various differentiation levels.
The space experiment Cellular Responses to Radiation in Space (CERASP), to be performed on the International Space Station (ISS) will supply basic information on the cellular response to radiation applied in microgravity. One of the biological end-points under investigation will be gene activation by space flight conditions in mammalian cells, based on fluorescent promoter reporter systems using green fluorescent protein.