Healthy offspring from freeze-dried mouse spermatozoa held on the International Space Station for 9 months

Abstract

If humans ever start to live permanently in space, assisted reproductive technology using preserved spermatozoa will be important for producing offspring; however, radiation on the International Space Station (ISS) is more than 100 times stronger than that on Earth, and irradiation causes DNA damage in cells and gametes.Here we examined the effect of space radiation on freeze-dried mouse spermatozoa held on the ISS for 9 mo at -95°C, with launch and recovery at room temperature. DNA damage to the spermatozoa and male pronuclei was slightly increased, but the fertilization and birth rates were similar to those of controls. Nextgeneration sequencing showed only minor genomic differences between offspring derived from space-preserved spermatozoa and controls, and all offspring grew to adulthood and had normal fertility. Thus, we demonstrate that although space radiation can damage sperm DNA, it does not affect the production of viable offspring after at least 9 mo of storage on the ISS.International Space Station | preservation | freeze-dry | spermatozoa | fertilization S ince the "space dog" Laika (Лайка) was first placed into orbit in 1957 (1), many humans and animals have been to space or stayed on the International Space Station (ISS) for more than 6 mo. In the future, humans likely will live on largescale space stations or in other space habitats for several years or even over many generations. At that time, assisted reproductive technology (ART) likely will be used to produce humans in space habitats, given that the use of ART by infertile couples has increased year by year and that ART can be performed with cryopreserved spermatozoa or embryos (2, 3). In a similar way, domestic animals likely will be generated by artificial insemination (AI) in space, because many domestic animals are already produced by AI using long-term cryopreserved spermatozoa (4). In addition, genetic diversity is very important for maintaining a species, especially in small colonies, and this could be achieved by cryopreserving a diverse range of gamete cells. The environment in space is very different from that on Earth, however, including high levels of space radiation and microgravity, and the effects of these factors on mammalian reproduction are largely unknown. Although with current technology, producing offspring in such an environment can be difficult or dangerous (5), the study of reproduction in space is a very important subject for our future.So far, the effects of microgravity on early development have been studied using sea urchins, fish, amphibians, and birds (6-12). These studies have concluded that microgravity does not prevent animal reproduction. However, because of the difficulty in maintaining mammals and performing experiments in space, studies of mammal reproduction in space have not progressed as well as in other animals, and only a few papers have been published (13-18). Those studies and our previous study (19) have suggested that mammalian reproduction in space under conditions of microgravity cannot be easil...

Space Radiation Biology for “Living in Space”

“…Japan Aerospace Exploration Agency (JAXA) has conducted a series of monitoring experiments to evaluate the radiation environment inside and outside the Japanese Experiment Module Kibo, which is part of the ISS with Passive Dosimeter for Life-Science and Experiments in Space (PADLES) [9,13,14]: area radiation monitoring in the Japanese Experiment Module "Kibo" of the ISS (Area PADLES) [15]; dose measurements of biological samples exposed to space radiation (Bio PADLES) [16][17][18][19]; radiation dosimetry of Asian astronauts (Crew PADLES); various kinds of international cooperative experiments with ISS partners (Dosimetric-PADLES); measurement of the directional dependence of the radiation dose inside the Kibo module (Exp PADLES) [11,20]; and measurement of outside doses and evaluation of the shielding effect of the ISS Kibo hull (Free-space PAD-LES). Those experiments were initiated in 2008 just after attachment of the Japanese Pressurized Module (JPM) to the ISS.…”

“…We concluded that the characteristics of the space radiation environment in LEO contain the following: (i) a high contribution from high-linear energy transfer (LET) radiation that have a high-quality factor (QF) up to 30; (ii) dose rates have values that are a few hundred times greater than those on the ground; (iii) the directional distribution of space radiation is nearly isotropic; and (iv) radiation effects occur under μG [13,14,19]. Space radiation for LET greater than several keV/μm causes more serious damage to living things than low-LET radiation.…”

“…The machine exposes cultured cells or small fish to γ-rays over the range of 0.3-1,500 mGy/day by combining the radiation source choice and distance. The dose rate of space radiation in the ISS is 0.5 mGy/day [13][14][15][16][17][18][19]. Thus, the instrument at the RBC may provide important information about the health risks to astronauts at the ISS.…”

“…Facilities. Dose rates from cosmic radiation such as SEP and GCR are low at around 0.5 mGy/day as measured inside ISS Kibo [13][14][15][16][17][18][19].…”

Production of mouse offspring from inactivated spermatozoa using horse PLCζ mRNA

“…Blastocyste immunofluorescence staining was performed as described to evaluate the quality of blastocysts derived from mPLCζ or ePLCζ mRNA injected embryos [30]. The primary antibodies used were an anti-CDX2 rabbit monoclonal antibody (1:500; BioGenex, California, CA, USA) to detect the TE cells and an anti-NANOG mouse polyclonal antibody (1:500; Abcam, Cambridge, UK) to detect the ICM cells.…”