Lane K. Christenson

Spaceflight profoundly impacts cardiovascular physiology. To gain insight into the underlying molecular adaptations, we examined the female cardiac proteome during spaceflight and recovery. We hypothesized that spaceflight remodels the cardiac proteome, including mitochondrial bioenergetics and redox homeostasis pathways, during both flight and recovery, altering cardiovascular health risk. Proteomic analysis was performed on hearts from female C57BL/6J mice flown aboard the International Space Station (ISS) for 55 to 60 days as part of the NASA Rodent Research-20 (RR-20) study and a recovery cohort returned to Earth after 42 days, with sampling occurring five days after landing, and corresponding ground controls. Consistent with our hypothesis, spaceflight enriched mitochondrial bioenergetic pathways relative to ground controls, including cellular respiration, the tricarboxylic acid cycle, and oxidative phosphorylation. These changes occurred alongside the remodeling of antioxidant pathways, suggesting altered redox regulation during flight and increased susceptibility to reactive oxygen species (ROS) accumulation in the heart versus controls. Postflight recovery was characterized by distinct metabolic, redox, and structural remodeling signatures, including pathways associated with sarcomere organization, contractile function, and extracellular matrix regulation. These findings reveal cardiac proteomic remodeling during and after spaceflight and provide molecular insights relevant to cardiovascular risk assessment and countermeasure development for exploration missions.

Spaceflight presents unique gravitational, radiation, and isolation hazards for human exploration of the Moon, Mars, and beyond, yet its impact on the female reproductive system and successive generations has been largely unassessed. In the NASA Rodent Research 20 mission, we examined the impact of a 42-d spaceflight on the female reproductive axis including ovulatory capacity, implantation rate, and fecundity as well as behavioral, metabolic, and functional outcomes in F1 and F2 offspring. Females bred 5 d after return to Earth became pregnant but only exhibited a slight decline in fecundity compared to ground controls. In contrast, F1 offspring from spaceflight dams exhibited marked growth, functional, and behavioral differences compared to F1 offspring from control dams. Moreover, F1 female offspring from spaceflight dams exhibited decreased ovarian reserves as evidenced by reduced anti-Mullerian hormone levels early in life (21 d of age) and premature ovarian failure or an early loss in fertility, as indicated by reduced numbers of litters and total number of pups born to females over a 9-mo period. Strikingly, transgenerational metabolic and reproductive disturbances were also observed in F2 pups of spaceflight granddams, including persistent reductions in ovarian reserve, suggesting germline-level effects. Together these findings reveal significant short- and long-term impacts of spaceflight on the female reproductive system and on their offspring across generations, demonstrating biological transmission of reproductive vulnerability following maternal spaceflight exposure, and raising concerns for space travelers and colonization missions.

Circular RNAs (circRNAs) emerge as alternate regulators of gene expression. CircRNAs are generated by back-splicing processes, are highly conserved, and are resistant to degradation. Recent advances in sequencing and computational tools have led to the discovery of the critical regulatory roles of these molecules in different physiological and pathological processes. Different functions of circRNAs in many physiological processes have been reported in the past few years, such as miRNA sponge activity, protein decoy/sponge/recruiter activity, deviation from parental gene expression, and encoding proteins/peptides. Additionally, circRNAs are being used clinically as biomarkers. Technological advances in molecular biology over the past few years have led to the development of various techniques for detecting, quantifying, manipulating, and analyzing the functions of circRNAs. This article summarizes different wet lab techniques for preparing, detecting, validating, localizing, and interacting with circRNAs, as well as determining miRNA sponge activity and functional analysis.

Oocytes from women of advanced reproductive age exhibit diminished developmental potential, but the underlying mechanisms remain incompletely defined. Oocyte maturation depends on translational control of maternal mRNA synthesized during growth. We performed a computational analysis on human oocytes from women <30 versus ≥40 years and observed that mRNA GC content correlates negatively with half-life in oocytes from young (40 yr) women. In young oocytes, longer mRNA half-life is associated with lower protein abundance, whereas in aged oocytes GC content correlates positively with protein abundance. During the GV-to-MII transition, codon composition stratifies stability: codons that support rapid translation (optimal) stabilize mRNA, while slow-translating codons (non-optimal) promote decay. With reproductive aging, GC-containing codons become more optimal and align with increased protein abundance. These findings indicate that reproductive aging remodels codon-optimality-linked, translation-coupled mRNA decay, stabilizing a subset of GC-rich maternal mRNA that may be prone to excess translation during maturation. Our analysis is explicitly within human reproductive aging; it does not revisit cross-species stability rules. Instead, it shows that sequence–stability relations are reprogrammed with age within human oocytes, including an inversion of the GC–stability association during GV-to-MII transition. Disruption of the normal mRNA clearance program in aged oocytes may compromise oocyte competence and alter maternal mRNA dosage, with downstream consequences for early embryonic development.

Spaceflight presents unique microgravity, hypergravity, radiation, and isolation hazards for astronauts. Notably, spaceflight impacts on many life sustaining physiologic systems (e.g., cardiac, musculoskeletal) are known, while impacts on the reproductive systems and progeny of space travelers are largely unassessed. This study analyzes behavioral, metabolic, and functional outcomes in F1 and F2 offspring of female mice following a 42-day spaceflight on the International Space Station. Progeny from the spaceflight dams that were bred following return to earth exhibited growth, functional and behavioral differences compared to control offspring. Introduction of a secondary stressor (feeding a Western diet) revealed a transgenerational inheritance pattern in F2 pups of spaceflight granddams. This study demonstrates spaceflight can impact subsequent generations, pointing to the importance of further study to protect future astronauts’ children.

Exposure to cosmic ionizing radiation is an innate risk of the spaceflight environment that can cause DNA damage and altered cellular function. In astronauts, longitudinal monitoring of physiological systems and interactions between these systems are important to consider for mitigation strategies. In addition, assessments of sex-specific biological responses in the unique environment of spaceflight are vital to support future exploration missions that include both females and males. Here we assessed sex-specific, multi-system immune and endocrine responses to simulated cosmic radiation. For this, 24-week-old, male and female C57Bl/6J mice were exposed to simplified five-ion, space-relevant galactic cosmic ray (GCRsim) radiation at 15 and 50 cGy, to simulate predicted radiation exposures that would be experienced during lunar and Martian missions, respectively. Blood and adrenal tissues were collected at 3- and 14-days post-irradiation for analysis of immune and endocrine biosignatures and pathways. Sexually dimorphic adrenal gland weights and morphology, differential total RNA expression with corresponding gene ontology, and unique immune phenotypes were altered by GCRsim. In brief, this study offers new insights into sexually dimorphic immune and endocrine kinetics following simulated cosmic radiation exposure and highlights the necessity for personalized translational approaches for astronauts during exploration missions.

Ovarian follicles undergo a series of dynamic changes following the ovulatory surge of luteinizing hormone including cumulus expansion, oocyte maturation, ovulation, and luteinization. Post-transcriptional gene regulatory events are critical for mediating LH follicular responses, and among all RNA isoforms, circular RNA (circRNA) is one of the most abundant forms present in cells, yet they remain the least studied. Functionally, circRNA can act as miRNA sponges, protein sponges/decoys, and regulators of transcription and translation. In the context of ovarian follicular development, the identity and roles of circRNA are relatively unknown. In the present study, high throughput RNA sequencing of granulosa cells immediately prior to and 4-h after the LH/hCG surge identified 42,381 circRNA originating from 7712 genes. A total of 54 circRNA were identified as differentially expressed between 0-h and 4-h time points (Fold Change ± 1.5, FDR ≤ 0.1), among them 42 circRNA were upregulated and 12 circRNA were downregulated. All differentially expressed circRNA between the 0-h and 4-h groups were subjected to circinteractome analysis and identified networks of circRNA-protein and circRNA-miRNA were further subjected to “micro-RNA target filter analysis” in Ingenuity Pathway Analyses, which resulted in the identification of miRNA targeted mRNAs. A comparison of these circRNA target mRNAs with LH-induced mRNAs identified Runx2, Egfr, Areg, Sult1el, Cyp19a1, Cyp11a1, and Hsd17b1 as targets of circKif2, circVcan, circMast4, and circMIIt10. These newly identified LH/hCG-induced circRNA, their target miRNA and protein networks provide new insights into the complex interactions associated with periovulatory follicular development.