ArticlePDF AvailableLiterature Review

Effects of Spaceflight on Human Skin

  • Hautarztpraxis Glattbrugg

Abstract and Figures

During both short- and long-duration spaceflight, several health problems can occur, including those of the skin. Astronauts in space and after returning to earth experience erythematous, burning, itchy, dry, sensitive, and thinning skin. Other skin problems, such as infections, abrasions, lacerations, delayed wound healing, and accelerated skin aging, are also common. Human skin is an ecosystem composed of a wide range of habitats for bacteria, fungi, and viruses called microbiome, which not only show a strong skin site-specific preference but also serve as microbial fingerprints that are highly unique to individuals. These human skin-associated microorganisms make a substantial contribution to the microbial ecosystems that inhabit the closed environments in space. On the other hand, human skin microbiome is also subject to change during spaceflight, which may lead to skin infections or the flare up of skin diseases. This review highlights some of the interactions between the space environment and the skin.
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Review Article
Skin Pharmacol Physiol
Effects of Spaceflight on Human Skin
Árpád Farkas a Gergő Farkas b
aHautarztpraxis Glattbrugg, Glattbrugg, Switzerland; bIndependent researcher, Zurich, Switzerland
Received: December 15, 2020
Accepted: March 5, 2021
Published online: May 31, 2021
Correspondence to:
Árpád Farkas, arpad.farkasmail @
© 2021 S. Karger AG, Basel
DOI: 10.1159/000515963
Spaceflight · International Space Station · Microgravity ·
Astronaut · Skin · Immune system · Microbiome
During both short- and long-duration spaceflight, several
health problems can occur, including those of the skin. As-
tronauts in space and after returning to earth experience er-
ythematous, burning, itchy, dry, sensitive, and thinning skin.
Other skin problems, such as infections, abrasions, lacera-
tions, delayed wound healing, and accelerated skin aging,
are also common. Human skin is an ecosystem composed of
a wide range of habitats for bacteria, fungi, and viruses called
microbiome, which not only show a strong skin site-specific
preference but also serve as microbial fingerprints that are
highly unique to individuals. These human skin-associated
microorganisms make a substantial contribution to the mi-
crobial ecosystems that inhabit the closed environments in
space. On the other hand, human skin microbiome is also
subject to change during spaceflight, which may lead to skin
infections or the flare up of skin diseases. This review high-
lights some of the interactions between the space environ-
ment and the skin. © 2021 S. Karger AG, Basel
The International Space Station (ISS) is a large closed
habitable construct located approximately 400 km above
the earth. Various life support systems sustain conditions
for humans to work productively and safely. Air pressure,
temperature, humidity, and contamination must be kept
under control [1]. The evaluation of the future of both
noncommercial and commercial human spaceflight in
low-Earth orbit, including long-range opportunities for
the ISS and other free-flying structures, is ongoing. Hu-
man missions are planned to return to the surface of the
Moon and to land on Mars. Microgravity environment,
high radiation levels, continuous work and stress aboard
the ISS, other free-flying structures, and spacecrafts are
the main factors affecting human health over a time span
of minutes to months. Spaceflight alters the cardiovascu-
lar, musculoskeletal, respiratory, vestibular, visual, and
immune systems [2]. Simultaneously, astronauts face
neurocognitive and neuropsychological changes [3]. Wa-
ter supplies on the ISS are very limited, and the methods
that astronauts use to maintain good hygiene in micro-
gravity are not the same as on earth. Astronauts, for ex-
ample, are unable to take a bath or a shower; therefore,
they keep their body clean by using wet tissues and they
Skin Pharmacol Physiol
DOI: 10.1159/000515963
wash their hair with a rinseless shampoo. They do not
have a washing machine and they cannot change their
clothes as often as on earth. These and other circumstanc-
es, such as temperature change, microgravity, radiation,
and direct impairing factors, very much affect their skin
health and lead to frequent skin impairments and skin
diseases. The human skin is host to a complex and rich
microbial community, called microbiome. Spaceflight is
associated with strong and specific microbiome altera-
tions. Understanding the nature of skin alterations and of
the microbiome is key to managing astronaut health and
maintenance of the ISS, other free-flying structures, and
spacecraft equipment. In this article, the main factors en-
countered in space and their impact on human skin will
be reviewed.
Human Skin Impairments and Diseases during Space
Based on the medical records it seems that cutaneous
alterations represent a major concern for astronauts. Ery-
thema, peeling, dryness, burning, pruritus, sensitivity,
thinning, and delayed wound healing are frequent skin
problems [4–11]. Space suit, glove, boot, celestial dust,
and lunar soil can cause significant trauma to crew mem-
bers, such as irritation, bruising, and abrasion, and glove-
induced frostbite, ecchymosis, and onycholysis were re-
corded [12–16]. Skin diseases such as psoriasis, seborrhe-
ic dermatitis, atopic dermatitis, contact dermatitis,
folliculitis, rosacea, and acne may flare up [4, 8, 10, 17,
18]. Bacterial, fungal, and viral infections [9, 19–22] may
occur and reactivation of herpesviruses causing herpes
zoster was noted [4, 23] and increased incidence of hyper-
sensitivities and of allergies were documented [9] (Ta-
The National Aeronautics and Space Administration
(NASA) created the Longitudinal Study of Astronaut
Health in 1992 to address a variety of issues, including both
the health of astronauts during spaceflight and the longer
term health issues that might be associated with spaceflight
and flight training including the possibility that increased
exposure to radiation in space might have an impact on
skin cancer cases. The study found 33 cases of basal and
squamous cell carcinomas of the skin among 312 astro-
nauts compared to 27 cases among 912 controls, an almost
3-fold difference in rate, which is statistically significant.
All these cases of basal and squamous cell carcinomas of
the skin were excluded from the analysis of the astronaut
group and of the comparison group. The reason for this
deletion is that astronauts spend significant time outdoors
for both training and recreational purposes; therefore,
these results have to be interpreted carefully [24].
Skin Physiology in Microgravity: Dermal Atrophy,
Cutaneous Muscle, Hair Follicle, and Metabolic
During the SkinCare experiment, skin surface, epider-
mis, and dermis were analyzed preflight, in-flight, and
postflight of an ISS astronaut. One measuring field of the
2 inner forearms was treated with a skincare emulsion. It
seemed that after a prolonged stay in weightlessness, the
skin underwent an accelerated aging with a thinner, more
structured, coarser epidermis and a loss of skin elasticity.
These changes appeared to be reversible because after a
year the skin’s condition returned to normal [5].
Later the Skin-B project was launched to validate the
results of the SkinCare study on 6 astronauts. In orbit,
skin hydration, skin barrier function, and surface evalua-
tion of the living skin (SELS; VisioScan® VC98 camera)
were measured. On the ground, skin elasticity, skin den-
sity, skin thickness, and skin microcirculation were eval-
uated. An improvement was seen in skin hydration and
skin barrier function. No changes or improvement was
observed in the appearance of the skin surface. Skin den-
sity, skin thickness, and skin elasticity values were un-
Table 1. In-flight skin-related clinical symptoms and medical
conditions which may occur, flare up, or worsen on board the ISS
Clinical symptoms Medical conditions
Erythema Psoriasis
Burning Seborrheic dermatitis
Pruritus Atopic dermatitis
Peeling Contact dermatitis
Dryness Folliculitis
Sensitivity Rosacea
Irritation Acne
Thinning Bacterial infections
Abrasions Viral infections
Bruising Fungal infections
Fluid shift Hypersensitivities
Ecchymosis Allergies
Delayed wound healing
Skin cancer
ISS, International Space Station.
Skin in Spaceflight
Skin Pharmacol Physiol
DOI: 10.1159/000515963
changed from preflight values. These findings correspond
to some reports from other astronauts after returning
from flight. Quicker skin healing, decreased skin cracking
over the course of the mission, and use of a lower amount
of skin lotion than on earth was documented. The authors
of the Skin-B investigation explain these differences by
improved space conditions such as the use of better exer-
cise devices and better nutrition on board the ISS [25].
During the Skin-B project, the authors measured the skin
surface profile by means of SELS and after interpreting
their results they concluded that it is necessary to take a
closer look at the fluid shift phenomenon when an in-
creased volume of fluid travels toward the upper regions
of the body, making them look swollen. They found that
only the parameter skin volume leads to meaningful data
under microgravity and the formulas for the SELS param-
eters, such as roughness, scaling, and wrinkles, need to be
reevaluated [26]. These observations highlight the impor-
tance of carefully selecting and adapting the experimental
methods during microgravity studies.
A rodent study which involved 3 mice having spent 3
months in orbit showed a significant reduction in dermal
thickness accompanied by increased newly synthetized
procollagen. Transcriptomic data suggested that the der-
mal atrophy might be related to an early degradation of
defective newly formed procollagen molecules. Many
hair follicles in the growing anagen phase were observed,
validated by an increased expression of specific hair fol-
licle genes. Additionally the analysis of whole thickness
skin showed that a large proportion of the upregulated
transcripts encoded proteins related to striated muscle
homeostasis [27].
In summary, data from the Skin-B study contradicted
the SkinCare results. During the SkinCare experiment, a
reduction in skin density, a loss of skin elasticity, and re-
duced skin thickness were observed. These skin physiol-
ogy parameters remained unchanged during the Skin-B
study and skin hydration and skin barrier function even
changed for the better. The above mentioned rodent
study confirmed the reduced skin thickness in agreement
with the data obtained in the SkinCare experiment. How-
ever, these changes should be the subject of further inves-
Another study which analyzed the hair follicles of 10
astronauts showed that genes related to hair growth, such
as Homo sapiens fibroblast growth factor 18, Homo sapi-
ens angiopoietin-like 7, and Homo sapiens cartilage oligo-
meric matrix protein, were upregulated during flight,
suggesting that spaceflight inhibits cell proliferation in
hair follicles [28].
A mouse study during a Space Shuttle Atlantis (STS-
135) mission showed that in the flight group many genes
responsible for regulating production and metabolism of
reactive oxygen species were significantly altered with
1.5-fold changes compared to controls. For extracellular
matrix profile, several genes encoding matrix and metal-
loproteinases involved in extracellular matrix remodeling
were significantly up-/downregulated. Of 332 biochemi-
cal markers, 19 differed significantly, with 12 upregulated
and 7 downregulated including altered amino acid, car-
bohydrate metabolism, cell signaling, and transmethyl-
ation pathways. The data demonstrated that spaceflight
condition leads to a shift in biological and metabolic ho-
meostasis as a consequence of increased regulation in cel-
lular antioxidants, reactive oxygen species production,
and tissue remodeling [29].
Environmental Biocontamination on Board the ISS
and Skin Microbiome
Diverse bacteria, fungi, and viruses inhabit the human
skin. These microorganisms have an individual pattern
and vary between different skin sites. Some microbes join
the ISS when new crew members or payload arrives and
some were inhabitants from the very beginning when the
station was assembled.
The initial colonization of surfaces on board the Rus-
sian segment of the ISS was dominated by Gram-positive
members of the genera Staphylococcus, Micrococcus, Ba-
cillus, and Streptococcus showing that the skin of crew
members was the primary source of early contamination.
Gram-negative bacteria and fungi were also present [30].
Predominant bacteria belonged to the members of the
Staphylococcus genus, isolated from 84% of air and sur-
face samples [31, 32]. In air samples, Aspergillus and Pen-
icillium were the dominant fungi, while on the surface
samples, Aspergillus and Cladosporium dominated [32,
33]. Similar observations have been made after sampling
of NASA’s Destiny Laboratory [34, 35] and Japan Aero-
space Exploration Agency’s Kibo facility aboard the ISS,
where earlier Alternaria and Malassezia species were also
detected [35–37].
Staphylococcus species isolated from ISS air and crew
members were resistant to at least 1 antibiotic used aboard
the ISS and most were capable of surface colonization and
subsequent biofilm formation [38]. Rifampicin resistance
due to higher mutation frequencies of Staphylococcus epi-
dermidis cultivated in the ISS compared to ground con-
trols was confirmed during an investigation as part of the
Skin Pharmacol Physiol
DOI: 10.1159/000515963
SpaceX-3 resupply mission showing that the human
spaceflight environment leads to changes in bacterial mu-
tagenic potential [39]. Many other studies were per-
formed, which analyzed ISS surface and air samples to
assess the succession and persistence of microbial com-
munities, their antimicrobial resistance profiles, and vir-
ulence properties. These investigations revealed the rich-
ness of microbial diversity inside the ISS and confirmed
previous results showing that skin-associated bacterial
and fungal species play an important role. Some of them
belong to risk group microorganisms showing antimicro-
bial resistance signatures associated with β-lactam, cat-
ionic antimicrobial peptide, and vancomycin. Prominent
virulence factors were cobalt-zinc-cadmium resistance
and multidrug resistance efflux pumps [40–50]. Table2
summarizes the most important skin-related microbial
species, which play a role on board the ISS.
One study has investigated the microbiome changes of
9 astronauts who spent 6–12 months in the ISS [51]. The
ISS environment differentially influenced the forehead
and forearm skin microbiota. Alpha diversity and rich-
ness increased or decreased, depending upon the indi-
vidual, but was consistent between the forehead and fore-
arm skin. In spite of the bimodal variance amongst astro-
naut skin microbiomes, there was a common shift in the
microbial composition of all crew members. These chang-
es involved a significant in-flight reduction of Proteobac-
teria, mostly Gammaproteobacteria and Betaproteobacte-
ria, with a concomitant increase in Firmicutes, including
staphylococcal and streptococcal species. Different fac-
tors may contribute to the decreased amount of Gamma-
proteobacteria and Betaproteobacteria abundance such as
the lack of a “green” natural environment plus the con-
stant filtration of air and the alteration of the skin struc-
ture during spaceflight. The reduction of skin Gamma-
proteobacteria might then contribute to the high frequen-
cy of skin hypersensitivity reactions/rashes and skin
infections. The change in skin structure might also facili-
tate the establishment of skin infections by opportunistic
pathogens such as the staphylococcal and streptococcal
species [51].
Human spaceflight activities in low-Earth orbit are in
transition as governments in the future become only one
of the possible customers for commercial services. There
is an emerging industry that is close to becoming a reality:
space tourism. In the near future, lunar surface opera-
tions and missions beyond cislunar space will help the
return of astronauts to the surface of the Moon and capa-
bilities are being developed for human missions to Mars
and other destinations.
Therefore, it is getting more important to better un-
derstand human health issues during these missions and
optimize healthcare in space, which includes optimal
body cleaning methods and the use of moisturizers, and
to address improper space suit, glove, and boot fit-in-
duced skin breakdown [15, 16]. In microgravity, desic-
cated skin particles or foot calluses simply float; therefore,
the station’s ventilation system should work properly.
The use of the NASA imaging systems facilitates the
diagnosis of health-related conditions and the crew’s sur-
geons periodically discuss all health issues of each crew
member to initiate a treatment with proper medication.
Telemedicine may function well for the astronauts on the
ISS, but as they get further away from Earth they will have
an increased communication delay so the approach to
medical care will need to change. Crews need to be more
autonomous and there needs to be a physician on board.
Skin cancer prevention studies have to be implement-
ed and the relationship between radiation and micrograv-
ity has to be further investigated. Common stick insect
(Carausius morosus) experiments showed abnormal dif-
ferentiation under space microgravity and recessive lethal
mutations were induced by space radiation in the prog-
eny of fruit flies showing that microgravity and space ra-
diation may together elevate mutation frequencies. It was
suggested that DNA damage repair inhibition and stress-
related protein accumulation were involved. On the con-
trary, some space experiments have shown that mutation
Table 2. Skin-related microbial species which play a role on board
the ISS
Bacterial species Fungal species
Staphylococcus Malassezia
Corynebacterium Cladosporium
Micrococcus Cyberlindnera
Propionibacterium Candida
Streptococcus Trichosporon
Sporosarcina Cryptococcus
Actinomyces Penicillium
Rothia Saccharomyces
Haemophilus Aspergillus
Pseudomonas Alternaria
ISS, International Space Station.
Skin in Spaceflight
Skin Pharmacol Physiol
DOI: 10.1159/000515963
frequencies and DNA repair activity were not affected by
microgravity in Escherichia coli, Bacillus subtilis, Dictyo-
stelium discoideum, Saccharomyces cerevisiae, and hu-
man cells. Measurements of space radiation in the Shut-
tle-Mir mission 9 showed that doses differed between tis-
sues and organs of the human body with effective doses
varying by 10% or more. There was a tendency to have a
high dose on the surface of the body (skin) and protrud-
ing near surface elements (e.g., bone surfaces correspond-
ing to the shoulder) and to have low doses in internal re-
gions (e.g., bone marrow and colon). These data highlight
the importance of radiation protection systems for travel
in space [52].
The dysregulation of the human immune system in
space includes altered leukocyte, monocyte, and granulo-
cyte function, altered cytokine production patterns, abro-
gated bone marrow responsiveness to colony-stimulating
factors, altered T-cell intracellular signaling, persistent
hypersensitivity reactions, inhibition of natural killer cell
activity, and apparent T helper 2 potential bias shift. This
means that astronauts are more susceptible to infections.
Interventions for reducing the risk of infections prior to
space journeys include vaccinations. Because of the pos-
sible reactivation of herpesviruses, varicella zoster virus
vaccine should be given to mention one. Screening of as-
tronauts for both methicillin-susceptible and methicillin-
resistant Staphylococcus aureus is worth considering and
Staphylococcus aureus carriers may be decolonized. Re-
cent research has demonstrated that colonizing the skin
and nares with extracellular serine protease-producing
Staphylococcus epidermidis selectively inhibits Staphylo-
coccus aureus nasal colonization and biofilm formation.
As such, a somewhat far reaching countermeasure could
involve colonizing astronauts’ skin and nares prior to
travel with extracellular serine protease-producing Staph-
ylococcus epidermidis [53, 54].
To mimic spaceflight conditions ground-based habi-
tats have been built such as the Antarctic Concordia Sta-
tion and isolation facilities like an inflated lunar/Mars
analog habitat, the Hawai’i Space Exploration Analog and
Simulation isolation habitat, and the Mars500 facility.
The Mars500 project simulated a crewed 520-day-long
return flight to Mars. Cultivation assays revealed a Staph-
ylococcus- and Bacillus-dominated microbial community
on various surfaces, with a microbial load that did not
exceed the allowed limits for ISS in-flight requirements.
Mainly the crew was responsible for microbial dispersal.
Opportunistic pathogens, stress-tolerant or potentially
mobile element-bearing microorganisms were prevalent,
while the overall microbial diversity dropped significant-
ly over time [55]. It is therefore important for the ad-
vancement of spaceflight activities to properly govern mi-
crobial communities. Data from these ground-based fa-
cilities may help to estimate future risk of crewed
spaceflight, could facilitate the design of a more optimal
spacecraft mission, and can promote to choose appropri-
ate microbial monitoring methods and potential counter-
measures to ensure a microbiologically safe spaceflight
A recent NASA study, which compared the impact of
the spaceflight environment on a pair of monozygotic
(identical) twin astronauts, highlights the importance of
the measurement of the same variables in an astronaut
and in his Earth-bound twin, because previous studies
could not integrate simultaneous effects on multiple sys-
tems and data types in the same subject. One of the previ-
ous observations confirmed by this study was that some
physiological adaptations, such as headward fluid shift,
are rapid and reach a new steady state within days [56].
However, this fluid shift has an impact during measure-
ments on the parameter volume, skin roughness, skin
scaling, and skin wrinkles. This has to be taken into con-
sideration when methods such as SELS are being used
Further and ongoing tests on more subjects are needed
to minimize space-induced skin impairments. The pos-
sible lessons learned with space exploration will also have
an impact on human health on Earth. In fact, this is a pro-
ductive, cross-fertilized, endeavor in which studies per-
formed on Earth yield countermeasures for protection of
space crew health and space research is translated into
health measures for the Earth-bound population.
Conflict of Interest Statement
The authors have no conflicts of interest to declare.
Funding Sources
The authors did not receive any funding.
Author Contributions
Árpád Farkas performed a comprehensive literature search in
the databases, contacted experts, and wrote the article. Gergő Far-
kas suggested the structure of the article and corrected the article.
Skin Pharmacol Physiol
DOI: 10.1159/000515963
Data Availability Statement
The authors provided a systematic critical digest of English ar-
ticles using MEDLINE search (2000–2020). Additional informa-
tion, articles, publications, and abstracts were identified by reading
previously published reviews, by searching NASA databases and
using ResearchGate (1974–2020). Experts in the field were also
contacted. Search terms included space, spaceflight, astronaut, mi-
crogravity, international space station, ISS, skin, dermatology, mi-
crobiome, immune system, telemedicine, and teledermatology.
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... Wounding can happen during Space exploration (Gontcharov et al., 2005;Tronnier et al., 2008;Crucian et al., 2016;Farkas and Farkas, 2021). Astronauts are exposed to skin erythema, peeling, dryness, burning, pruritus, sensitivity, thinning, therefore the physiology of the healing process of cutaneous injuries is hence affected (Farahani and DiPietro, 2008;Cubo-Mateo and Gelinsky, 2021). ...
... Space missions occur in non-sterile, extreme confined environments, where air pressure, temperature, humidity, limited water supply are kept under strict control (Gentry and Cover, 2015). In this environment, astronauts are not able to take proper shower keeping their body clean by using wet tissues, using rinseless shampoo, and they do not change their clothes often (Farkas and Farkas, 2021). It is therefore important to understand the astronauts' skin microbiomes and their fluctuation over time. ...
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Wound healing is slowed in Space. Microgravity and possible physical factors associated with Space affect alterations in fibroblast, matrix formation, dysregulation in apoptosis and inflammation. The microbial populations settled on skin, space modules, in space suits, are also playing a pivotal role, as wound healing is also affected by the microbial community. We propose a perspective that includes four domines for the application of human skin microbiota for wound healing in Space: The natural antimicrobial properties of the skin microbiota, the crosstalk of the skin microbiota with the immune system during wound healing, the contribution of the microbiota in precision medicine, and the role of gut-skin and gut-brain axes. A stronger understanding of the connections and metabolic network among bacteria, fungi, the host’s immune system and the host metabolism will support the basis for a better wound healing in Space.
... Although the effects of microgravity and its similarities on microorganisms have been studied for more than 60 years, diverse results and plausible conflicts have been reported in different experiments, especially with respect to their phenotypes and metabolisms (Tirumalai et al. 2017;Huang et al. 2018;Siddiqui et al. 2021;Domnin et al. 2022). During spaceflight, astronauts were in a state of weightlessness and immunocompromised, in which they were more vulnerable to disease by conditional pathogenic bacteria in vivo (Mermel 2013;Farkas and Farkas 2021). In addition, microorganisms can produce many specific metabolites that may be harmful to humans. ...
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This study aimed to investigate the differences in the effects of spaceflight and ground environment on the metabolites of the tobramycin-resistant mutant strain of Escherichia coli (T1_13). A spaceflight-exposed tobramycin-resistant Escherichia coli strain (T1_13) in outer space for 64 days was labeled as the ST5, and the ground test group (GT5) was cultivated under the same conditions except for spaceflight. The metabolites in culture supernatant and precipitate of the ST5 and GT5 were identified by liquid chromatography-mass spectrometry (LC–MS). Compared with the GT5, a total of 83 different metabolites were identified in the supernatant of the ST5 (p < 0.05, FC ≥ 2 or p ≤ 0.5, VIP > 1), and 80 different metabolites were additionally identified in the precipitate of the ST5 (p < 0.05, FC ≥ 2 or p ≤ 0.5, VIP > 1). The results showed that spaceflight had a significant impact on different metabolic pathways. KEGG enrichment analysis indicated that the significantly enriched in the supernatant (S) were nicotinate and nicotinamide metabolism, aminobenzoate degradation, ABC transporters, metabolic pathways, and microbial metabolism in diverse environments. In addition, in the precipitate (C), toluene degradation, glycine, serine and threonine metabolism, pentose and glucuronate interconversions, cysteine and methionine metabolism, benzoate degradation, aminobenzoate degradation, microbial metabolism in diverse environments, 2-Oxocarboxylic acid metabolism and degradation of aromatic compounds were significantly enriched. Exploring metabolism characters of Escherichia coli would be helpful to further understand the physiological characteristics of tobramycin-resistant mutagenesis of Escherichia coli in outer space. This research will provide a basis for astronaut safety during spaceflight exposed to pathogenic bacteria.
... On that basis, surveillance of the microbiota structure may be crucial to counteract significant health risks during long-term flight and to guide medical treatment. Moreover, since astronaut skin is the primary source of spacecraft surface contamination, monitoring skin alterations and alterations in the skin-associated microbiome is key to managing astronaut health as well as in the maintenance of space stations, spaceships and spacecraft equipment [121]. ...
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During space missions, astronauts are faced with a variety of challenges that are unique to spaceflight and that have been known to cause physiological changes in humans over a period of time. Several of these changes occur at the microbiome level, a complex ensemble of microbial communities residing in various anatomic sites of the human body, with a pivotal role in regulating the health and behavior of the host. The microbiome is essential for day-to-day physiological activities, and alterations in microbiome composition and function have been linked to various human diseases. For these reasons, understanding the impact of spaceflight and space conditions on the microbiome of astronauts is important to assess significant health risks that can emerge during long-term missions and to develop countermeasures. Here, we review various conditions that are caused by longterm space exploration and discuss the role of the microbiome in promoting or ameliorating these conditions, as well as space-related factors that impact microbiome composition. The topics explored pertain to microgravity, radiation, immunity, bone health, cognitive function, gender differences and pharmacomicrobiomics. Connections are made between the trifecta of spaceflight, the host and the microbiome, and the significance of these interactions for successful long-term space missions.
... Since the beginning of the age of space travel in the 1960s, the question of if and how microgravity (µg) influences whole organisms and cells has been one major focus in the field of space medicine and related disciplines. Over the years, it has become clear that µg can induce a multitude of health risks in astronauts, including bone loss, muscle atrophy, cardiac atrophy, visual impairment, increased intracranial pressure, cardiovascular complications, skin problems, increased infection risk, impaired immune system, motion sickness, and orientation problems (besides the radiation-induced effects during space travel, such as an increased risk for cancer or cataracts) [1][2][3][4][5][6][7][8]. ...
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Cancer is a disease exhibiting uncontrollable cell growth and spreading to other parts of the organism. It is a heavy, worldwide burden for mankind with high morbidity and mortality. Therefore, groundbreaking research and innovations are necessary. Research in space under microgravity (µg) conditions is a novel approach with the potential to fight cancer and develop future cancer therapies. Space travel is accompanied by adverse effects on our health, and there is a need to counteract these health problems. On the cellular level, studies have shown that real (r-) and simulated (s-) µg impact survival, apoptosis, proliferation, migration, and adhesion as well as the cytoskeleton, the extracellular matrix, focal adhesion, and growth factors in cancer cells. Moreover, the µg-environment induces in vitro 3D tumor models (multicellular spheroids and organoids) with a high potential for preclinical drug targeting, cancer drug development, and studying the processes of cancer progression and metastasis on a molecular level. This review focuses on the effects of r- and s-µg on different types of cells deriving from thyroid, breast, lung, skin, and prostate cancer, as well as tumors of the gastrointestinal tract. In addition, we summarize the current knowledge of the impact of µg on cancerous stem cells. The information demonstrates that µg has become an important new technology for increasing current knowledge of cancer biology.
... Therefore, attempts have been made to better comprehend the changes undergone by the skin and to find possible countermeasures to maintain healthy skin. One recent publication summarizes the spaceflight-induced skin alterations observed in astronauts [11]. However, in this review, we intend to give an overview of the research performed in space as well as on Earth, and summarize these findings that have helped to better understand the skin's reaction to the space environment in response to the different stressors encountered in space. ...
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Traveling to space puts astronauts at risk of developing serious health problems. Of particular interest is the skin, which is vitally important in protecting the body from harmful environmental factors. Although data obtained from long-duration spaceflight studies are inconsistent, there have been indications of increased skin sensitivity and signs of dermal atrophy in astronauts. To better understand the effects of spaceflight stressors including microgravity, ionizing radiation and psychological stress on the skin, researchers have turned to in vitro and in vivo simulation models mimicking certain aspects of the spaceflight environment. In this review, we provide an overview of these simulation models and highlight studies that have improved our understanding on the effect of simulation spaceflight stressors on skin function. Data show that all aforementioned spaceflight stressors can affect skin health. Nevertheless, there remains a knowledge gap regarding how different spaceflight stressors in combination may interact and affect skin health. In future, efforts should be made to better simulate the spaceflight environment and reduce uncertainties related to long-duration spaceflight health effects.
... The weakened immune system may result in a reactivation of latent infections with viruses, such as herpes viruses [18,19] or cytomegaloviruses [20] as well as in an increased susceptibility to infections. Astronauts often suffer from skin diseases, partially caused by infections [21]. Additionally, the potential risk of microbial infections is aggravated by two more factors: (1) increased growth of microorganisms in space crafts and (2) increased virulence of potentially pathogenic bacteria and fungi. ...
Introduction : A long-term stay of humans in space causes a large number of well-known health problems and changes in protists and plants. Deep space exploration will increase the time humans or rodents will spend in microgravity (µg). Moreover, they are exposed to cosmic radiation, hypodynamia, and isolation. OMICS investigations will increase our knowledge of the underlying mechanisms of µg-induced alterations in vivo and in vitro. Areas covered : We summarize the findings over the recent 3 years on µg-induced changes in the proteome of protists, plants, rodent and human cells. Considering the thematic orientation of microgravity-related publications in that time frame, we focus on medicine-associated findings such as the µg-induced antibiotic resistance of bacteria, the myocardial consequences of µg-induced calpain activation and the role of MMP13 in osteoarthritis. All these point to the fact that µg is an extreme stressor that could not be evolutionarily addressed on Earth. Expert Commentary : In conclusion, when interpreting µg-experiments, the direct, mostly unspecific stress response, must be distinguished from specific µg-effects. For this reason, recent studies often do not consider single protein findings but place them in the context of protein-protein interactions. This enables an estimation of functional relationships, especially if these are supported by epigenetic and transcriptional data (multi-omics).
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The International Space Station (ISS) is a complex built environment physically isolated from Earth. Assessing the interplay between the microbial community of the ISS and its crew is important for preventing biomedical and structural complications for long term human spaceflight missions. In this study, we describe one crewmember's microbial profile from body swabs of mouth, nose, ear, skin and saliva that were collected at eight different time points pre-, during and post-flight. Additionally, environmental surface samples from eight different habitable locations in the ISS were collected from two flights. Environmental samples from one flight were collected by the crewmember and samples from the next flight were collected after the crewmember departed. The microbial composition in both environment and crewmember samples was measured using shotgun metagenomic sequencing and processed using the Livermore Metagenomics Analysis Toolkit. Ordination of sample to sample distances showed that of the eight crew body sites analyzed, skin, nostril, and ear samples are more similar in microbial composition to the ISS surfaces than mouth and saliva samples; and that the microbial composition of the crewmember's skin samples are more closely related to the ISS surface samples collected by the crewmember on the same flight than ISS surface samples collected by other crewmembers on different flights. In these collections , species alpha diversity in saliva samples appears to decrease during flight and rebound after returning to Earth. This is the first study to compare the ISS microbiome to a crewmember's microbiome via shotgun metagenomic sequencing. We observed that the microbiome of the surfaces inside the ISS resemble those of the crew's skin. These data support future crew and ISS microbial surveillance efforts and the design of preventive measures to maintain crew habitat onboard spacecraft destined for long term space travel.
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Background: In space, due to fluid shift a 45% decrease in the skin topography parameter volume (mm3 ) was seen using the VisioScan® camera. Simultaneously, the parameters roughness, scaling and wrinkles changed dramatically as well. Thus, the present study has the objective to understand the relationship between the SELS parameters under extreme conditions and their application by addressing scientific-dermatological questions. Material and methods: SELS measurements were performed on the volar forearms of six astronauts. The Pearson correlation coefficient was used to determine the association between the variables. Results: A significant correlation was found between the skin topography parameter volume and the skin parameters roughness, scaling and wrinkles. A closer look at each astronaut revealed a significant correlation for all astronauts for the parameters volume and roughness and for more than 65% of the astronauts for the parameters volume and scaling and volume and wrinkles. However, no correlation could be found between the parameters skin hydration and roughness and scaling, respectively. Conclusion: Only the parameter skin volume leads to meaningful data under microgravity. Physiological changes observed by fluid shift are comparable to the skin condition edema on earth. Based on the obtained data, we can conclude that the formulas for the SELS parameters roughness, scaling and wrinkles for this special skin condition need to be reviewed.
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Over the course of a mission to the International Space Station (ISS) crew members are exposed to a number of stressors that can potentially alter the composition of their microbiomes and may have a negative impact on astronauts’ health. Here we investigated the impact of long-term space exploration on the microbiome of nine astronauts that spent six to twelve months in the ISS. We present evidence showing that the microbial communities of the gastrointestinal tract, skin, nose and tongue change during the space mission. The composition of the intestinal microbiota became more similar across astronauts in space, mostly due to a drop in the abundance of a few bacterial taxa, some of which were also correlated with changes in the cytokine profile of crewmembers. Alterations in the skin microbiome that might contribute to the high frequency of skin rashes/hypersensitivity episodes experienced by astronauts in space were also observed. The results from this study demonstrate that the composition of the astronauts’ microbiome is altered during space travel. The impact of those changes on crew health warrants further investigation before humans embark on long-duration voyages into outer space.
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Background The International Space Station (ISS) is a closed system inhabited by microorganisms originating from life support systems, cargo, and crew that are exposed to unique selective pressures such as microgravity. To date, mandatory microbial monitoring and observational studies of spacecraft and space stations have been conducted by traditional culture methods, although it is known that many microbes cannot be cultured with standard techniques. To fully appreciate the true number and diversity of microbes that survive in the ISS, molecular and culture-based methods were used to assess microbial communities on ISS surfaces. Samples were taken at eight pre-defined locations during three flight missions spanning 14 months and analyzed upon return to Earth. Results The cultivable bacterial and fungal population ranged from 10⁴ to 10⁹ CFU/m² depending on location and consisted of various bacterial (Actinobacteria, Firmicutes, and Proteobacteria) and fungal (Ascomycota and Basidiomycota) phyla. Amplicon sequencing detected more bacterial phyla when compared to the culture-based analyses, but both methods identified similar numbers of fungal phyla. Changes in bacterial and fungal load (by culture and qPCR) were observed over time but not across locations. Bacterial community composition changed over time, but not across locations, while fungal community remained the same between samplings and locations. There were no significant differences in community composition and richness after propidium monoazide sample treatment, suggesting that the analyzed DNA was extracted from intact/viable organisms. Moreover, approximately 46% of intact/viable bacteria and 40% of intact/viable fungi could be cultured. Conclusions The results reveal a diverse population of bacteria and fungi on ISS environmental surfaces that changed over time but remained similar between locations. The dominant organisms are associated with the human microbiome and may include opportunistic pathogens. This study provides the first comprehensive catalog of both total and intact/viable bacteria and fungi found on surfaces in closed space systems and can be used to help develop safety measures that meet NASA requirements for deep space human habitation. The results of this study can have significant impact on our understanding of other confined built environments on the Earth such as clean rooms used in the pharmaceutical and medical industries. Electronic supplementary material The online version of this article (10.1186/s40168-019-0666-x) contains supplementary material, which is available to authorized users.
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To understand the health impact of long-duration spaceflight, one identical twin astronaut was monitored before, during, and after a 1-year mission onboard the International Space Station; his twin served as a genetically matched ground control. Longitudinal assessments identified spaceflight-specific changes, including decreased body mass, telomere elongation, genome instability, carotid artery distension and increased intimamedia thickness, altered ocular structure, transcriptional and metabolic changes, DNA methylation changes in immune and oxidative stress–related pathways, gastrointestinal microbiota alterations, and some cognitive decline postflight. Although average telomere length, global gene expression, and microbiome changes returned to near preflight levels within 6 months after return to Earth, increased numbers of short telomeres were observed and expression of some genes was still disrupted. These multiomic, molecular, physiological, and behavioral datasets provide a valuable roadmap of the putative health risks for future human spaceflight.
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Latent herpes virus reactivation has been demonstrated in astronauts during shuttle (10–16 days) and International Space Station (≥180 days) flights. Following reactivation, viruses are shed in the body fluids of astronauts. Typically, shedding of viral DNA is asymptomatic in astronauts regardless of mission duration; however, in some cases, live/infectious virus was recovered by tissue culture that was associated with atopic-dermatitis or skin lesions during and after spaceflight. Hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal-medullary (SAM) axes activation during spaceflight occurs as indicated by increased levels of stress hormones including cortisol, dehydroepiandrosterone, epinephrine, and norepinephrine. These changes, along with a decreased cell mediated immunity, contribute to the reactivation of latent herpes viruses in astronauts. Currently, 47/89 (53%) astronauts from shuttle-flights and 14/23 (61%) astronauts from ISS missions shed one or more herpes viruses in saliva/urine samples. Astronauts shed Epstein–Barr virus (EBV), varicella-zoster virus (VZV), and herpes-simplex-1 (HSV-1) in saliva and cytomegalovirus (CMV) in urine. Larger quantities and increased frequencies for these viruses were found during spaceflight as compared to before or after flight samples and their matched healthy controls. The shedding did not abate during the longer ISS missions, but rather increased in frequency and amplitude. These findings coincided with the immune system dysregulation observed in astronauts from shuttle and ISS missions. VZV shedding increased from 41% in space shuttle to 65% in ISS missions, EBV increased 82 to 96%, and CMV increased 47 to 61%. In addition, VZV/CMV shed ≤30 days after ISS in contrast to shuttle where VZV/CMV shed up to 5 and 3 days after flight respectively. Continued shedding of infectious-virus post-flight may pose a potential risk for crew who may encounter newborn infants, sero-negative adults or any immunocompromised individuals on Earth. Therefore, developing spaceflight countermeasures to prevent viral reactivation is essential. Our spaceflight-developed technologies for saliva collection/rapid viral detection have been extended to include clinical applications including zoster patients, chicken pox, post-herpetic neuralgia, multiple sclerosis, and various neurological disorders. These protocols are employed in various clinics and hospitals including the CDC and Columbia University in New York, as well as overseas in Switzerland and Israel.
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Following publication of the original article [1], the authors reported a typographic error in scientific notation in the number of reads, the text should read as:
The International Space Station (ISS) is a confined and closed habitat with unique conditions such as cosmic radiation, and microgravity. These conditions have a strong effect on the human and spacecraft microflora. They can affect the immune response of the crew-members, thus posing a threat to their health. Microbial diversity and abundance of microorganisms from surfaces, air filters and air samples on the ISS have been studied. Enterobacteriaceae, Bacillus spp., Propionibacterium spp., Corynebacterium spp., and Staphylococcus spp. were among the most frequently isolated bacteria. Microbial growth, biofilm formation, stress response, and pathogenicity are affected by microgravity. Increased resistance to antibiotics in bacteria isolated from the ISS has often been reported. Enterococcus faecalis and Staphylococcus spp. isolates from the ISS have been shown to harbor plasmid-encoded transfer genes. These genes facilitate the dissemination of antibiotic resistances. These features of ISS-pathogens call for novel approaches including highly effective antimicrobials which can be easily used on the ISS. A promising material is the antimicrobial surface coating AGXX®, a self-recycling material consisting of two noble metals. It drastically reduced microbial growth of multi-resistant human pathogens, such as staphylococci and enterococci. Further novel approaches include the application of cold atmospheric plasma for the sterilization of spacecrafts.
Background: One of the most challenging and important factors of manned space missions is to keep astronauts healthy on orbit. In a study on 46 ISS crew members who were on 6-month (average) missions, skin rashes were the most self-reported event. Furthermore, among notable events, 40% were classified as skin rashes/hypersensitivities. Thus, especially skin conditions during space travel are of major clinical interest and require further research. Aims: The aim of the study was to determine skin conditions in space flight among US and European astronauts, especially taking into account the terrestrial skin conditions as well as on-orbit skin care habits. Methods: A preflight questionnaire was given to the astronauts asking about their terrestrial skin care habits and skin conditions/atopy before launch. In addition, they were asked to fill out a postflight questionnaire asking about their on-orbit skin care routine and whether any special observations regarding the skin were made during flight. Results: A total of 23 skin symptoms were recorded by 8 nonatopic astronauts (mean age: 41 years) during the mission. The symptoms were peeling (21.74%), rash (17.39%), dryness (13.04%), severe dryness (8.70%), reddening (8.70%), itchiness (8.70%), bruising (4.35%), skin sensitivity (4.34%), bumps (4.35%), acne (4.35%) and slow healing of contusions and lacerations (4.35%). Especially the hands and feet were affected by skin problems. As a result of this examination, it was shown that the skin symptoms correlate with poor hygiene on orbit, whereas the factor “environment” on the ISS plays a minor role. Surprisingly, 2 astronauts even experienced positive effects on their skin. Conclusion: Based on these preliminary data, it is important to pay more attention to skin hygiene and maintenance in space.
Background: Skin reaction to spaceflight has not really been studied yet, although the skin has a very important barrier function to protect the body and can contribute to a more general understanding of physiology. It is proposed here to make a more thorough investigation of the skin during long-term spaceflight, using noninvasive techniques. Aims: The aim of the present Skin-B study is to investigate the kinetics and range of possible skin modifications during long-duration spaceflights and their recovery. Methods: In order to investigate the effect on skin physiological parameters during spaceflight, measurements were carried out on 6 astronauts with respect to skin hydration, transepidermal water loss/barrier function, and surface evaluation of the living skin in orbit. Additional measured parameters on the ground were skin elasticity, skin density and thickness, as well as microcirculation. Results: Data from the Skin-B subjects (n = 6) contradict the results obtained in the previous pilot study SkinCare (n = 1 subject). In the present study, no deterioration of the skin was found but rather an improvement in skin hydration and skin barrier function, and no changes or improvement in the appearance of the skin surface. Furthermore, the skin density and skin thickness as well as skin elasticity values were unchanged from pre-flight values. Conclusion: In conclusion, we found that spaceflight under present conditions has no negative impact on skin physiological parameters.