Microgravity during spaceflight directly affects in vitro osteoclastogenesis and bone resorption.

Area of Science:

• Space biology
• Bone physiology
• Cell biology

Background:

• Space flight leads to significant bone mass loss.
• The precise mechanisms and cellular players, particularly the balance between bone formation and resorption, are not fully understood.

Purpose of the Study:

• To investigate the role of osteoclasts (OCs) and their precursors in microgravity-induced bone loss.
• To determine if OCs are direct targets of microgravity and mechanical forces.

Main Methods:

• Three experiments (OSTEO, OCLAST, PITS) using isolated OCs and precursors were conducted in microgravity aboard the FOTON-M3 mission.
• Cells were cultured on biomaterials (skelite) or bone slices in bioreactors, with ground and centrifuge controls.
• Gene expression and bone resorption markers (collagen telopeptides) were analyzed.

Main Results:

• Microgravity exposure led to a significant increase in gene expression related to osteoclast maturation and activity.
• Bone resorption markers were elevated in microgravity compared to ground and centrifuge controls.
• Osteoclast differentiation and activity were enhanced under microgravity conditions.

Conclusions:

• Osteoclasts and their precursors are directly affected by microgravity and mechanical forces.
• These findings identify OCs as critical targets for mitigating bone loss during space missions.
• Understanding these cellular responses is crucial for developing countermeasures against spaceflight-induced skeletal fragility.