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Hypergravity effects on osteoclasts activity
1National Institute for Advanced Interdisciplinary Research (NAIR), Tsukuba Research Center, Tsukuba, Ibaraki, Japan.
Journal of Gravitational Physiology : a Journal of the International Society for Gravitational Physiology
|April 17, 2003
Summary
Long-term space flight causes bone loss. This study found hypergravity enhances osteoclast enzyme expression, suggesting increased bone resorption activity, not just osteoclast numbers.
Area of Science:
- Space biology
- Bone physiology
- Cellular mechanics
Background:
- Spaceflight leads to bone density loss, but mechanisms remain unclear.
- The specific role of gravity on osteoclasts is not well understood.
- Osteoclasts are crucial for bone resorption and are implicated in spaceflight-induced bone loss.
Purpose of the Study:
- To investigate the gravitational effect on osteoclast function.
- To analyze the mRNA expression of osteoclast marker enzymes under hypergravity.
- To determine if hypergravity influences osteoclast activation or resorption activity.
Main Methods:
- Primary rabbit osteoclasts were isolated and cultured.
- Cells were exposed to hypergravity (30 x g) for 2 or 18 hours.
- Messenger RNA (mRNA) expression of tartrate-resistant acid phosphatase (TRAP) and cathepsin K was analyzed using RT-PCR.
- Actin ring formation in osteoclasts was examined to assess activation.
Main Results:
- Hypergravity differentially enhanced mRNA expression of TRAP and cathepsin K.
- Cathepsin K mRNA expression showed a non-monotonous time course, peaking at 2 hours.
- No significant effect of hypergravity was observed on the number of osteoclasts forming actin rings.
Conclusions:
- Hypergravity may not affect the number of osteoclasts with resorption activity.
- Hypergravity appears to enhance the resorption activity of already activated osteoclasts.
- These findings contribute to understanding bone loss mechanisms during spaceflight.