Private Spaceflight: A New Landscape for Dealing with Medical Risk.

As NASA and other space agencies make plans to proceed with human exploration missions beyond low earth orbit (LEO), the private sector, including Space X, Virgin Galactic, Blue Origin, Space Adventures and others, echo these plans with initiatives of their own to send humans further into space. Development of more sub-orbital flight opportunities, orbital flight opportunities to LEO and even higher risk endeavors will certainly result in exposure to medical risks for an expanding and heterogeneous population of civilians. To date, a handful of "space tourists" have flown to the International Space Station (ISS), at their own expense, ushering in a new era in which anyone with reasonably good health and even those with physical disability may consider becoming space travelers. Indeed, medical and behavioral issues of healthy, professional astronauts, have not been problematic on short orbital flights. However, recent attempts to test the potential limitations in astronauts on extended duration orbital flights in preparation for future missions beyond LEO raise concern about individual differences in ability to tolerate the hazardous spaceflight environment. Given the rapid development of opportunities for non-professionals and the employees of private companies to travel into space, this is an appropriate time to consider the development of selection strategies for non-government space travelers, including the development of genomic and other modern tools to assess susceptibility to spaceflight risk.

Factors limiting the duration of artificially induced torpor in mice.

The possibility of artificial induction of a torpid state in animals that do not naturally do so, as well as in humans, offers a great potential in biomedicine and in human spaceflight. However, the mechanisms of action that provide a coordinated and concomitant downregulation with a safe recovery from this state are poorly understood. In our previous study, we demonstrated that the metabolic rate of mice can be reduced by nearly 94% and can remain stable under hypothermic conditions for a prolonged period of up to 11 h. The present study was carried out in order to test the limitations and identify potential factors that can enable the safe and reversible arousal of non-hibernating mice from deep artificially-induced torpor to an active state. Results demonstrate that the energy budget may be a limiting factor for the prolongation and safe recovery from the hypometabolic state. While the continuation of torpor may be possible for additional hours, we found that a reduction of 40% or more in the plasma glucose level increases the risk of heart fibrillation, which results in death during arousal. Therefore, the plasma glucose level could be a component of the criteria indicating the reversibility of torpor. Another important factor complementing the energetic necessity that may limit the duration of torpor in mice is a gradual reduction in body mass during torpor. Under the conditions of our experiment, body mass declines by nearly 15% after 16 h from the initiation of torpor and may continue to decline if the mice are allowed to remain in torpor longer. Extrapolation of this data suggests that there may be a critical mass relating to animal mortality and thus limiting the duration of torpor. Control and maintenance of the body mass and glucose level in a torpid animal may extend the longevity of torpor and mitigate the risk of cardiac failure during rewarming to the metabolically active state. The cardiac complications that occur during arousal from torpor in many cases could be mitigated and even avoided by applying appropriate temperature-arising kinetics and providing a sufficient dynamic range to maintain cardiac output.

Shallow metabolic depression and human spaceflight: a feasible first step.

Synthetic torpor is an induced state of deep metabolic depression (MD) in an organism that does not naturally employ regulated and reversible MD. If applied to spaceflight crewmembers, this metabolic state may theoretically mitigate numerous biological and logistical challenges of human spaceflight. These benefits have been the focus of numerous recent articles where, invariably, they are discussed in the context of hypothetical deep MD states in which the metabolism of crewmembers is profoundly depressed relative to basal rates. However, inducing these deep MD states in humans, particularly humans aboard spacecraft, is currently impossible. Here, we discuss shallow MD as a feasible first step toward synthetic torpor during spaceflight and summarize perspectives following a recent NASA-hosted workshop. We discuss methods to safely induce shallow MD (e.g., sleep and slow wave enhancement via acoustic and photoperiod stimulation; moderate sedation via dexmedetomidine), which we define as an ~20% depression of metabolic rate relative to basal levels. We also discuss different modes of shallow MD application (e.g., habitual versus targeted, whereby shallow MD is induced routinely throughout a mission or only under certain circumstances, respectively) and different spaceflight scenarios that would benefit from its use. Finally, we propose a multistep development plan toward the application of synthetic torpor to human spaceflight, highlighting shallow MD's role. As space agencies develop missions to send humans further into space than ever before, shallow MD has the potential to confer health benefits for crewmembers, reduce demands on spacecraft capacities, and serve as a testbed for deeper MD technologies.

Changes in Differential Expression of Genes in Normal and Metabolically Suppressed Mice in Response to Radiation.

Differential gene expression profiles of mice in active and metabolically suppressed states were evaluated in response to a sublethal dose of gamma radiation to identify the beneficial protective effects of suspended animation. Results demonstrated that nearly 90% suppression of metabolic functions in mice lead to significant changes in gene expression profile of different metabolic pathways responsible for adaptation and maintenance of homeostasis in the new physiological state of suspended animation. This state was found sustainable during 18 hrs of experiment and can be reversed back to the normal active state without any visible effects on physiological and behavioral functions of mice. Gene expression during induced states was gathered via Illumina microarray methods. Further analysis of differential gene expressions yielded a result that a hypometabolic state may be responsible for short term and long-term radioprotection.

Synthetic torpor: A method for safely and practically transporting experimental animals aboard spaceflight missions to deep space.

Animal research aboard the Space Shuttle and International Space Station has provided vital information on the physiological, cellular, and molecular effects of spaceflight. The relevance of this information to human spaceflight is enhanced when it is coupled with information gleaned from human-based research. As NASA and other space agencies initiate plans for human exploration missions beyond low Earth orbit (LEO), incorporating animal research into these missions is vitally important to understanding the biological impacts of deep space. However, new technologies will be required to integrate experimental animals into spacecraft design and transport them beyond LEO in a safe and practical way. In this communication, we propose the use of metabolic control technologies to reversibly depress the metabolic rates of experimental animals while in transit aboard the spacecraft. Compared to holding experimental animals in active metabolic states, the advantages of artificially inducing regulated, depressed metabolic states (called synthetic torpor) include significantly reduced mass, volume, and power requirements within the spacecraft owing to reduced life support requirements, and mitigated radiation- and microgravity-induced negative health effects on the animals owing to intrinsic physiological properties of torpor. In addition to directly benefitting animal research, synthetic torpor-inducing systems will also serve as test beds for systems that may eventually hold human crewmembers in similar metabolic states on long-duration missions. The technologies for inducing synthetic torpor, which we discuss, are at relatively early stages of development, but there is ample evidence to show that this is a viable idea and one with very real benefits to spaceflight programs. The increasingly ambitious goals of world's many spaceflight programs will be most quickly and safely achieved with the help of animal research systems transported beyond LEO; synthetic torpor may enable this to be done as practically and inexpensively as possible.

Effect of gamma irradiation on the structural stability and functional activity of plasma-derived IgG.

Plasma-originated commercial intravenous immunoglobulin, which is used for a variety of clinical purposes, has been studied to determine the effect of virus-inactivating doses of gamma irradiation on the structural-functional characteristics of the protein. A detailed analysis has been performed in response to a concern that the use of conventional gamma irradiation may damage biologically active proteins. The results demonstrate that although gamma irradiation of the IgG may have some impact on protein structure, the damage can be reduced or even prevented by appropriate irradiation conditions. At the virucidal dose of gamma irradiation (50 kGy) and a temperature of -80 °C, the integrity of the polypeptide chain of immunoglobulin and the secondary structure of IgG can be completely protected, while conformational changes in tertiary structure are significantly minimized to a level that preserves functional activity. The irradiated IgG retains specific antigen-binding properties and F(c)-binding activity, indicating that the conformational integrity of the most important structural regions is not affected by γ-irradiation. These results present strong evidence that gamma irradiation treatment can be effectively implemented for inactivation of pathogens in IgG solutions that are used for intravenous injection.

Adaptation of organisms by resonance of RNA transcription with the cellular redox cycle.

Sequence variation in organisms differs across the genome and the majority of mutations are caused by oxidation, yet its origin is not fully understood. It has also been shown that the reduction-oxidation reaction cycle is the fundamental biochemical cycle that coordinates the timing of all biochemical processes in the cell, including energy production, DNA replication, and RNA transcription. We show that the temporal resonance of transcriptome biosynthesis with the oscillating binary state of the reduction-oxidation reaction cycle serves as a basis for non-random sequence variation at specific genome-wide coordinates that change faster than by accumulation of chance mutations. This work demonstrates evidence for a universal, persistent and iterative feedback mechanism between the environment and heredity, whereby acquired variation between cell divisions can outweigh inherited variation.

Hypothermia postpones DNA damage repair in irradiated cells and protects against cell killing.

Hibernation is an established strategy used by some homeothermic organisms to survive cold environments. In true hibernation, the core body temperature of an animal may drop to below 0°C and metabolic activity almost cease. The phenomenon of hibernation in humans is receiving renewed interest since several cases of victims exhibiting core body temperatures as low as 13.7°C have been revived with minimal lasting deficits. In addition, local cooling during radiotherapy has resulted in normal tissue protection. The experiments described in this paper were prompted by the results of a very limited pilot study, which showed a suppressed DNA repair response of mouse lymphocytes collected from animals subjected to 7-Gy total body irradiation under hypothermic (13°C) conditions, compared to normothermic controls. Here we report that human BJ-hTERT cells exhibited a pronounced radioprotective effect on clonogenic survival when cooled to 13°C during and 12h after irradiation. Mild hypothermia at 20 and 30°C also resulted in some radioprotection. The neutral comet assay revealed an apparent lack on double strand break (DSB) rejoining at 13°C. Extension of the mouse lymphocyte study to ex vivo-irradiated human lymphocytes confirmed lower levels of induced phosphorylated H2AX (γ-H2AX) and persistence of the lesions at hypothermia compared to the normal temperature. Parallel studies of radiation-induced oxidatively clustered DNA lesions (OCDLs) revealed partial repair at 13°C compared to the rapid repair at 37°C. For both γ-H2AX foci and OCDLs, the return of lymphocytes to 37°C resulted in the resumption of normal repair kinetics. These results, as well as observations made by others and reviewed in this study, have implications for understanding the radiobiology and protective mechanisms underlying hypothermia and potential opportunities for exploitation in terms of protecting normal tissues against radiation.

Functional integrity of intravenous immunoglobulin following irradiation with a virucidal dose of gamma radiation.

Although intravenous immunoglobulins (IVIG) and other plasma therapeutics have had a relatively good safety record, improved methods for viral clearance are constantly being evaluated and incorporated into new manufacturing processes. Gamma irradiation has been used routinely to assure sterility of healthcare products and medical devices, but it has not been applied successfully as a viral inactivation method for biologics. We examine whether virucidal doses of gamma irradiation (50 kGy) can be delivered to a manufacturing intermediate form of IVIG, a fractionated plasma paste, with negligible effect on structural and functional integrity of purified IgG product. Immunoglobulins from paste were examined for radiation-induced damage by SDS-PAGE and ELISAs utilizing viral antigens specific for rubella, CMV and mumps. Fc domain integrity was assessed by immunoblotting, quantitatively comparing the binding of irradiated and non-irradiated materials to cell surface Fcgamma receptors, and by employing quantitative RT-PCR to study the kinetics of accumulation of mRNA for the immune modulatory cytokines IL-1alpha, IL-1beta, IL-4, IL-8, IFNgamma, and TNFalpha. The results demonstrate that Fab and Fc domains of IVIG remain essentially intact and functional after gamma irradiation to virucidal doses, suggesting that this method could be used to enhance the safety of IVIG products.