Impact of the Microgravity Environment in a Three–dimensional Clinostat on Osteoblast- and Osteoclast-like Cells

Makihira Seicho

Kawahara Yumi

Yuge Louis

Mine Yuichi

Nikawa Hiroki

Cell Biology International

Mechanical unloading conditions result in decreases in bone mineral density and quantity, which may be partly attributed to an imbalance in bone formation and resorption. To investigate the effect of mechanical unloading on osteoblast and osteoclast differentiation, and the expression of RANKL and OPG genes in osteoblasts, we used a three-dimensional (3D) clinostat system simulating microgravity to culture MC3T3-E1 and RAW264.7 cells. Long-term exposure (7 days) of MC3T3-E1 cells to microgravity in the 3D clinostat inhibited the expression of Runx2, Osterix, type I collagen αI chain, RANKL and OPG genes. Similarly, 3D clinostat exposure inhibited the enhancement of β3-integrin gene expression, which normally induced by sRANKL stimulation in RAW264.7 cells. These results, taken together, demonstrate that long-term 3D clinostat exposure inhibits the differentiation of MC3T3-E1 cells together with suppression of RANKL and OPG gene expression, as well as the RANKL-dependent cellular fusion of RAW264.7 cells, suggesting that long-term mechanical unloading suppresses bone formation and resorption.

Osteoblast cells

Osteoclast cells

3D clinostat

Microgravity

RANKL

OPG

Medical sciences [ 490 ]

eng

Academic Press Inc.

Elsevier Science

Copyright (c) 2008 International Federation for Cell Biology Published by Elsevier Ltd.

[ISSN] 1065-6995

[DOI] 10.1016/j.cellbi.2008.04.027

[NCID] AA10882014

[DOI] http://dx.doi.org/10.1016/j.cellbi.2008.04.027