Abstract
Aims:The Mice Drawer System (MDS) Tissue Sharing program was the longest rodent space mission ever performed. It provided 20 research teams with organs and tissues collected from mice having spent 3 months on the International Space Station (ISS). Our participation to this experiment aimed at investigating the impact of such prolonged exposure to extreme space conditions on mouse skin physiology.Methods:Mice were maintained in the MDS for 91 days aboard ISS (space group (S)). Skin specimens were collected shortly after landing for morphometric, biochemical, and transcriptomic analyses. An exact replicate of the experiment in the MDS was performed on ground (ground group (G)).Results:A significant reduction of dermal thickness (−15%, P=0.05) was observed in S mice accompanied by an increased newly synthetized procollagen (+42%, P=0.03), likely reflecting an increased collagen turnover. Transcriptomic data suggested that the dermal atrophy might be related to an early degradation of defective newly formed procollagen molecules. Interestingly, numerous hair follicles in growing anagen phase were observed in the three S mice, validated by a high expression of specific hair follicles genes, while only one mouse in the G controls showed growing hairs. By microarray analysis of whole thickness skin, we observed a significant modulation of 434 genes in S versus G mice. A large proportion of the upregulated transcripts encoded proteins related to striated muscle homeostasis.Conclusions:These data suggest that a prolonged exposure to space conditions may induce skin atrophy, deregulate hair follicle cycle, and markedly affect the transcriptomic repertoire of the cutaneous striated muscle panniculus carnosus.
Highlights
Weightlessness, as experienced by astronauts during space flights, affects physiological functions of the human organism that has evolved, like other organisms living on Earth, through continuous adaptation to the permanent gravitational field
The Mice Drawer System (MDS) experiment was approved by the American Institutional Animal Care and Use Committee (IACUC protocol n° FLT-09-070-KSC) and performed in accordance with the principles expressed in the NIH ‘Guide for the care and use of laboratory animals’ and following recommendations reported in European Communities Council Directive of 24 November 1986
Immunostaining of blood vessels was performed with anti-CD31 antibody (#DIA310, Dianova GmbH, Hamburg, Germany) and revealed with a rabbit anti-rat biotinylated conjugated secondary antibody (#E0468) and streptavidin/horse radish peroxidase (#P0397) both purchased from Dako (Golstrup, Denmark)
Summary
Weightlessness, as experienced by astronauts during space flights, affects physiological functions of the human organism that has evolved, like other organisms living on Earth, through continuous adaptation to the permanent gravitational field. During long-term missions, astronauts suffer from osteopenia due to an increased osteoclasts-mediated bone resorption and decreased formation.[1] Muscles are strongly affected by reduced loading demands in weightlessness.[2] Similar bone loss and muscle atrophy have been observed in rodents maintained in microgravity,[3] making an acceptable animal model for investigating the mechanisms underlying the space-related health alterations in human. The most significant change was a thinning of the dermal matrix appearing as low-echo zones on ultrasound images to the skin atrophy observed in aging on Earth. These observations were, limited to one test subject. The number of available mice for this study was small, significant alterations affecting the dermal, hair follicles, and muscular compartments of the skin were observed in these mice as compared with replicate ground experiment
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