Microgravity Effects on the Matrisome

Comparative Analysis of Acute Kidney Injury Models and Related Fibrogenic Responses: Convergence on Methylation Patterns Regulated by Cold Shock Protein

BACKGROUND

Fibrosis is characterized by excessive extracellular matrix formation in solid organs, disrupting tissue architecture and function. The Y-box binding protein-1 (YB-1) regulates fibrosis-related genes (e.g., Col1a1, Mmp2, and Tgfβ1) and contributes significantly to disease progression. This study aims to identify fibrogenic signatures and the underlying signaling pathways modulated by YB-1.

METHODS

Transcriptomic changes associated with matrix gene patterns in human chronic kidney diseases and murine acute injury models were analyzed with a focus on known YB-1 targets. Ybx1-knockout mouse strains (Ybx1ΔRosaERT+TX and Ybx1ΔLysM) were subjected to various kidney injury models. Fibrosis patterns were characterized by histopathological staining, transcriptome analysis, qRT-PCR, methylation analysis, zymography, and Western blotting.

RESULTS

Integrative transcriptomic analyses revealed that YB-1 is involved in several fibrogenic signatures related to the matrisome, the WNT, YAP/TAZ, and TGFß pathways, and regulates Klotho expression. Changes in the methylation status of the Klotho promoter by specific methyltransferases (DNMT) are linked to YB-1 expression, extending to other fibrogenic genes. Notably, kidney-resident cells play a significant role in YB-1-modulated fibrogenic signaling, whereas infiltrating myeloid immune cells have a minimal impact.

CONCLUSIONS

YB-1 emerges as a master regulator of fibrogenesis, guiding DNMT1 to fibrosis-related genes. This highlights YB-1 as a potential target for epigenetic therapies interfering in this process.

How are cell and tissue structure and function influenced by gravity and what are the gravity perception mechanisms?

Progress in mechanobiology allowed us to better understand the important role of mechanical forces in the regulation of biological processes. Space research in the field of life sciences clearly showed that gravity plays a crucial role in biological processes. The space environment offers the unique opportunity to carry out experiments without gravity, helping us not only to understand the effects of gravitational alterations on biological systems but also the mechanisms underlying mechanoperception and cell/tissue response to mechanical and gravitational stresses. Despite the progress made so far, for future space exploration programs it is necessary to increase our knowledge on the mechanotransduction processes as well as on the molecular mechanisms underlying microgravity-induced cell and tissue alterations. This white paper reports the suggestions and recommendations of the SciSpacE Science Community for the elaboration of the section of the European Space Agency roadmap "Biology in Space and Analogue Environments" focusing on "How are cells and tissues influenced by gravity and what are the gravity perception mechanisms?" The knowledge gaps that prevent the Science Community from fully answering this question and the activities proposed to fill them are discussed.

Histoarchitecture of stromal collagen fibers in gastrointestinal hollow organs of mice after a 30-day space flight

The digestive organs are highly sensitive to the influence of orbital flight factors and can limit the professional activities of crew members aboard the International Space Station. Connective tissue, as a system-forming matrix of the integrative-buffer metabolic environment, is of particular relevance in space biomedicine, ensuring the functioning of internal organs under an altered gravitational stimulus. However, the adaptive mechanisms of the fibrous extracellular matrix of the gastric and intestinal connective tissue have not been fully investigated under prolonged microgravity weightlessness. Using histochemical techniques, we experimentally studied the state of collagen fibers in the specific tissue microenvironment of the gastric and intestinal membranes in C57BL/6 N mice after a 30-day space flight, subsequent 7-day ground readaptation, and in animals of the relevant control groups. The 30-day stay of laboratory animals aboard the Bion-M 1 biosatellite resulted in a reduction in the fibrous extracellular matrix of connective tissue in the studied digestive organs, excepting the gastric lamina propria. Increased fibrillogenesis was revealed in the gastrointestinal mucous membranes of animals 7 days after biosatellite landing compared with the parameters of animals in the space flight group. During the experiment with ground simulated orbital flight conditions, changes in collagen fibers were not significant compared to the vivarium control group. Thus, the results obtained evidence gravisensitivity of the fibrous extracellular matrix of the intraorgan connective tissue. This fact also highlights the necessity to further improve gastrointestinal tract-related preventive measures for astronauts during orbital flight.

Smooth Muscle Actin as a Criterion for Gravisensitivity of Stomach and Jejunum in Laboratory Rodents

Smooth muscle tissue (SMT) is one of the main structural components of visceral organs, acting as a key factor in the development of adaptive and pathological conditions. Despite the crucial part of SMT in the gastrointestinal tract activity, the mechanisms of its gravisensitivity are still insufficiently studied. The study evaluated the content of smooth muscle actin (α-SMA) in the membranes of the gastric fundus and jejunum in C57BL/6N mice (30-day space flight), in Mongolian gerbils Meriones unguiculatus (12-day orbital flight) and after anti-orthostatic suspension according to E.R. Morey-Holton. A morphometric analysis of α-SMA in the muscularis externa of the stomach and jejunum of mice and Mongolian gerbils from space flight groups revealed a decreased area of the immunopositive regions, a fact indicating a weakening of the SMT functional activity. Gravisensitivity of the contractile structures of the digestive system may be due to changes in the myofilament structural components of the smooth myocytes or myofibroblast actin. A simulated antiorthostatic suspension revealed no significant changes in the content of the α-SMA expression level, a fact supporting an alteration in the functional properties of the muscularis externa of the digestive hollow organs under weightless environment. The data obtained contribute to the novel mechanisms of the SMT contractile apparatus remodeling during orbital flights and can be used to improve preventive measures in space biomedicine.

Microgravity Effects and Aging Physiology: Similar Changes or Common Mechanisms?

Despite the use of countermeasures (including intense physical activity), cosmonauts and astronauts develop muscle atony and atrophy, cardiovascular system failure, osteopenia, etc. All these changes, reminiscent of age-related physiological changes, occur in a healthy person in microgravity quite quickly - within a few months. Adaptation to the lost of gravity leads to the symptoms of aging, which are compensated after returning to Earth. The prospect of interplanetary flights raises the question of gravity thresholds, below which the main physiological systems will decrease their functional potential, similar to aging, and affect life expectancy. An important role in the aging process belongs to the body's cellular reserve - progenitor cells, which are involved in physiological remodeling and regenerative/reparative processes of all physiological systems. With age, progenitor cell count and their regenerative potential decreases. Moreover, their paracrine profile becomes pro-inflammatory during replicative senescence, disrupting tissue homeostasis. Mesenchymal stem/stromal cells (MSCs) are mechanosensitive, and therefore deprivation of gravitational stimulus causes serious changes in their functional status. The review compares the cellular effects of microgravity and changes developing in senescent cells, including stromal precursors.

Heterotypic Cell Culture from Mouse Bone Marrow under Simulated Microgravity: Lessons for Stromal Lineage Functions

Muscle and skeleton structures are considered most susceptible to negative factors of spaceflights, namely microgravity. Three-dimensional clinorotation is a ground-based simulation of microgravity. It provides an opportunity to elucidate the effects of microgravity at the cellular level. The extracellular matrix (ECM) content, transcriptional profiles of genes encoding ECM and remodelling molecules, and secretory profiles were investigated in a heterotypic primary culture of bone marrow cells after 14 days of 3D clinorotation. Simulated microgravity negatively affected stromal lineage cells, responsible for bone tissue formation. This was evidenced by the reduced ECM volume and stromal cell numbers, including multipotent mesenchymal stromal cells (MSCs). ECM genes encoding proteins responsible for matrix stiffness and cell-ECM contacts were downregulated. In a heterotypic population of bone marrow cells, the upregulation of genes encoding ECM degrading molecules and the formation of a paracrine profile that can stimulate ECM degradation, may be mechanisms of osteodegenerative events that develop in real spaceflight.

The Remodeling of Dermal Collagen Fibrous Structures in Mice under Zero Gravity: The Role of Mast Cells

Mechanisms of adaptive rearrangements of the fibrous extracellular matrix of connective tissues under microgravity practically remain unexplored, despite the most essential functions of the stroma existing to ensure the physiological activity of internal organs. Here we analyzed the biomaterial (the skin dermis) of C57BL/6J mice from the Rodent Research-4 experiment after a long stay in space flight. The biomaterial was fixed onboard the International Space Station. It was found that weightlessness resulted in a relative increase in type III collagen-rich fibers compared to other fibrous collagens in the skin. The number of mast cells in the skin did not change, but their secretory activity increased. At the same time, co-localization of mast cells with fibroblasts, as well as impregnated fibers, was reduced. Potential molecular-cellular causes of changes in the activity of fibrillogenesis under zero-gravity conditions and the slowdown of the polymerization of tropocollagen molecules into supramolecular fibrous structures, as well as a relative decrease in the number of fibrous structures with a predominant content of type-I collagen, are discussed. The data obtained evidence of the different sensitivity levels of the fibrous and cellular components of a specific tissue microenvironment of the skin to zero-gravity conditions. The obtained data should be taken into account in the systematic planning of long-term space missions in order to improve the prevention of undesirable effects of weightlessness.