Cellular mechanotransduction of human osteoblasts in microgravity

Area of Science:

• Space biology
• Cellular mechanobiology
• Bone physiology

Background:

• Astronauts experience significant bone loss in microgravity, mimicking accelerated osteoporosis.
• Understanding how zero-gravity affects bone-forming cells is crucial for mitigating health risks during space missions.

Purpose of the Study:

• Investigate the mechanotransduction mechanisms of bone loss in microgravity.
• Examine the impact of microgravity and pressure on human fetal osteoblasts (hFOBs).

Main Methods:

• Deployed automated microfluidic chips and pressure-controlled chambers on the ISS.
• Measured single-cell mechanics (protrusion elongation) and spheroid actin/protein expression (pSMAD1/5/9, YAP).
• Compared spaceflight samples to ground controls.

Main Results:

• Microgravity exposure led to cell softening (elongated protrusions) in hFOBs.
• Reduced filamentous actin levels were observed in hFOB spheroids under microgravity.
• Applied pressure increased pSMAD1/5/9 expression and restored YAP levels, counteracting microgravity effects.

Conclusions:

• Microgravity alters the mechanical properties of bone cells, contributing to bone loss.
• Compressive pressure can modulate key cell signaling pathways (pSMAD1/5/9, YAP) in osteoblasts under spaceflight conditions.
• Findings offer insights into countermeasures for bone loss during space exploration.