Involvement of Runx2 in the differentiation process of osteoblastic precursor cells after radiation exposure

Abstract

Astronauts on exploratory space missions will experience a complex environment that includes microgravity and radiation. While the deleterious effects of unloading on bone are well established, fewer studies have focused on the effects of radiation. Space radiation produces distinct biological damages which, up to now, little is known about the correlation between radiation exposure and bone tissue. In our study we used osteoblastic precursor cells to investigate the radiation response of bone cells. Effects of radiation on differentiation were investigated by their ability to deposit extracellular matrices that mineralize under in vitro culture conditions using the histochemical Alizarin Red Staining (ARS). Calcium precipitation was detected in a bright red color already ten days after exposure to X-rays for doses up to 10 Gy. Notably, our results indicate that exposure to higher radiation doses could be correlated to a pronounced staining of the extracellular matrix. In order to gain more detailed insights into the osteoblast specific mineralization process, the transcriptional expression level of Runx2 was analysed. Our studies suggest that space relevant radiation significantly modulates the mineralization process and effectively modulates the gene expression levels of Runx2 involved in the differentiation of osteoblasts. In conclusion, the presented data allow the suggestion that exposure to ionizing radiation interferes with bone formation at the level of cellular differentiation.