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.

Extracellular Matrix and Integrin Interactions in the Skeletal Responses to Mechanical Loading and Unloading

“…Although there are complications to the use of these devices such as the potential for hypoxia [93], careful control of the bioreactor environment can lead to a stimulation of osteogenesis in rat calvarial osteoblasts [94] and in human palatal mesenchymal cells [95]. In contrast, growth of human mesenchymal stem cells under osteogenic conditions in a rotating cell culture system leads to disruption of actin stress fibers, decreased integrin signaling through FAK [96,97] and impaired osteoblastogenesis; these latter responses are consistent with the expectation that modeled microgravity exerts effects that are simply opposite to those of increased mechanical loading by hypergravity [98][99][100][101].…”

Differential Gene Regulation under Altered Gravity Conditions in Follicular Thyroid Cancer Cells: Relationship between the Extracellular Matrix and the Cytoskeleton

“…Acridine orange/ethidium bromide staining and Hoechst 33342 staining revealed no increase in apoptosis or necrosis after 31 parabolas. In contrast, Kumei et al [36] reported a decrease in OPN gene expression, but they also found an increase in fibronectin gene expression in rat osteoblasts when cultured for a longer period of 4 or 5 days aboard the Space Shuttle [36]. The mRNA levels of actin, vimentin, or 1 -integrin (ITGB1) did not change under space flight conditions.…”

“…Cytoskeletal changes occur in a variety of cell types including lymphocytes [35], thyrocytes [3], glial cells [33], chondrocytes [6], endothelial cells [4] and osteoblasts [36,37] during real microgravity and various simulation approaches. The external signals (altered gravity conditions) might be transduced into intracellular signals through the extracellular matrix, adhesion molecules, and the cytoskeletal structure.…”

Effects of simulated weightlessness on cellular morphology and biological characteristics of cell lines SGC-7901 and HFE-145

“…These physical phenomena can influence cell shape, metabolism, movement, and exocrine and signal conduction, either directly or indirectly (Freed and Vunjak-Novakovic, 2002). Previous studies have suggested that cytoskeleton and membrane structural changes occur when cells are subjected to weightlessness (Ingber, 1999;Infanger et al, 2004Infanger et al, , 2006aKumei et al, 2006). A corresponding redistribution of the cell structure occurs to maintain balance.…”