Abstract
Microgravity is well-known to induce Osteopenia. However, the combined effects of microgravity and radiation that commonly exist in space have not been broadly elucidated. This research investigates the combined effects on MC3T3-E1 cells and rat femurs. In MC3T3-E1 cells, simulated microgravity and X-ray radiation, alone or combination, show decreased cell activity, increased apoptosis rates by flow cytometric analysis, and decreased Runx2 and increased Caspase-3 mRNA and protein expressions. In rat femurs, simulated microgravity and X-ray radiation, alone or combination, show increased bone loss by micro-CT test and Masson staining, decreased serum BALP levels and Runx2 mRNA expressions, and increased serum CTX-1 levels and Caspase-3 mRNA expressions. The strongest effect is observed in the combined group in MC3T3-E1 cells and rat femurs. These findings suggest that the combination of microgravity and radiation exacerbates the effects of either treatment alone on MC3T3-E1 cells and rat femurs.
Highlights
Space programs have been clearly shifted toward long-term space missions[1,2,3]
Studies have demonstrated that the balance of bone tissue depends on the balance of osteogenesis and bone resorption, which is mediated by osteoblasts and osteoclasts[7,8]
The present study demonstrates that the combination of MG and X-ray RA has a synergistic effect on the activity of MC3T3-E1 cells and on bone loss in rat femurs
Summary
Space programs have been clearly shifted toward long-term space missions[1,2,3]. Severe bone loss in astronauts is still an important medical concern. Studies have demonstrated that the balance of bone tissue depends on the balance of osteogenesis and bone resorption, which is mediated by osteoblasts and osteoclasts[7,8]. 1 Gy protons[14] or 2 Gy X-rays[15] could simulate the space radiation that causes a significant and long-term loss of trabecular microstructure. Many studies have been designed to investigate clinical radiotherapy in tumors[18] These studies indicated that RA causes direct damage to bone tissue, causing growth disturbances, osteopenia, and incomplete fracture healing[19]. There are many studies on the bone loss induced by MG or RA, the actual phenomenon and mechanism of the combined effects of these two factors are still not clear, and relevant research is extremely limited. It is necessary to furtherly examine the combined effects to obtain deep insight into the effects of space and to develop effective preventative measures
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