Microgravity Signal Ensnarls Cell Adhesion, Cytoskeleton, and Matrix Proteins of Rat Osteoblasts

Abstract

Rat osteoblasts were cultured for 4 or 5 days aboard the Space Shuttle and solubilized during spaceflight. Post-flight analyses by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) determined the relative mRNA levels of matrix proteins, adhesion molecules, and cytoskeletal proteins including osteopontin (OP), osteonectin (ON), CD44, alpha-tubulin, actin, vimentin, fibronectin (FN), and beta1-integrin. The mRNA levels of OP and alpha-tubulin in the flight cultures were decreased by 30% and 50% on day 4 and day 5 of flight, as compared to the ground controls. In contrast, the CD44 mRNA levels in the flight cultures increased by 280% and 570% of the ground controls on day 4 and day 5. The mRNA levels of ON and FN in the flight cultures were slightly increased as compared to ground controls. The mRNA levels of actin, vimentin, or beta1-integrin did not change in spaceflight conditions. The matrix proteins, adhesion molecules, and cytoskeletal proteins may form dynamic network complexity with signaling molecules as an adaptive response to perturbation of mechanical stress under microgravity.