Project description:Astronauts experience significant and rapid bone loss as a result of an extended stay in space, making the International Space Station (ISS) the perfect laboratory for studying osteoporosis due to the accelerated nature of bone loss on the ISS. This prompts the question, how does the lack of load due to zero-gravity propagate to bone-forming cells, human fetal osteoblasts (hFOBs), altering their maturation to mineralization? Here, we aim to study the mechanotransduction mechanisms by which bone loss occurs in microgravity. Two automated experiments, microfluidic chips capable of measuring single-cell mechanics via aspiration and cell spheroids incubated in pressure-controlled chambers, were each integrated into a CubeLab deployed to the ISS National Laboratory. For the first experiment, we report protrusion measurements of aspirated cells after exposure to microgravity at the ISS and compare these results to ground control conducted inside the CubeLab. We found slightly elongated protrusions for space samples compared to ground samples indicating softening of hFOB cells in microgravity. In the second experiment, we encapsulated osteoblast spheroids in collagen gel and incubated the samples in pressure-controlled chambers. We found that microgravity significantly reduced filamentous actin levels in the hFOB spheroids. When subjected to pressure, the spheroids exhibited increased pSMAD1/5/9 expression, regardless of the microgravity condition. Moreover, microgravity reduced YAP expression, while pressure increased YAP levels, thus restoring YAP expression for spheroids in microgravity. Our study provides insights into the influence of microgravity on the mechanical properties of bone cells and the impact of compressive pressure on cell signaling in space.
Project description:Astronauts experience significant and rapid bone loss as a result of an extended stay in space, making the International Space Station (ISS) the perfect laboratory for studying osteoporosis due to the accelerated nature of bone loss on the ISS. This prompts the question, how does the lack of load due to zero-gravity propagate to bone-forming cells, human fetal osteoblasts (hFOBs), altering their maturation to mineralization? Here, we aim to study the mechanotransduction mechanisms by which bone loss occurs in microgravity. Two automated experiments, 4 microfluidic chips capable of measuring single-cell mechanics of hFOBs via aspiration and cell spheroids incubated in pressure-controlled chambers, were each integrated into a CubeLab deployed to the ISS National Laboratory. For the first experiment, we report protrusion measurements of aspirated cells after exposure to microgravity at the ISS and compare these results to ground control conducted inside the CubeLab. Our analysis revealed slightly elongated protrusions for space samples compared to ground samples indicating softening of hFOB cells in microgravity. In the second experiment, we encapsulated osteoblast spheroids in collagen gel and incubated the samples in pressure-controlled chambers. We found that microgravity significantly reduced filamentous actin levels in the hFOB spheroids. When subjected to pressure, the spheroids exhibited increased pSMAD1/5/9 expression, regardless of the microgravity condition. Moreover, microgravity reduced YAP expression, while pressure increased YAP levels, thus restoring YAP expression for spheroids in microgravity. Our study provides insights into the influence of microgravity on the mechanical properties of bone cells and the impact of compressive pressure on cell behavior and signaling in space.
Project description:Decreased mechanical loading on bones, such as prolonged bed rest and microgravity during space flights, leads to the development of an osteoporotic-like phenotype. Although osteoblast hypo-functionality is reported to be involved in the progression of bone pathological conditions, the cellular mechanisms of this process remain largely unknown. The combined application of mass spectrometry "-omics" and histochemical and ultrastructural approaches have been employed to investigate the effects of the gravitational unloading on human bone-cell biology. Here we show, ex vivo, that simulated microgravity (Sμg) on human primary osteoblasts (hpOB) induces an alteration of pro-osteogenic determinants (i.e., cell morphology and deposit of hydroxyapatite crystals), accompanied by a downregulation of adhesive proteins and bone differentiation markers (e.g., integrin beta-1, protein folding Crystallin Alpha B (CRYα-B), runt-related transcription factor 2 (RUNX-2), bone morphogenic protein-2 (BMP-2), and receptor activator of nuclear factor kappa-B ligand (RANK-L)), indicating an impairment of osteogenesis. Further, we observed for the first time that Sμg can trigger a transition toward a mesenchymal-like phenotype, in which a mature osteoblast displays an hampered vitamin A metabolism, loses adhesive molecules, gains mesenchymal components (e.g., pre-osteoblast state marker CD44), morphological protrusions (filopodium-like), enhances GTPase activities, which in turn allows it to acquire migrating properties. Although this phenotypic conversion is not complete and can be reversible, Sμg environment proves a plasticity potential hidden on Earth. Overall, our results suggest that Sμg can be a powerful physical cue for triggering ex vivo a dedifferentiation impulse on hpOBs, opening a new scenario of possible innovative therapeutical biomechanical strategies for the treatment of osteo-degenerative diseases.
