Delayed Long Bone Formation in Hyperthermia-exposed Mouse Embryos

Oh, Soon Keum; Choi, Ji Eun; Lee, Jin; Kim, Won Kyu

Abstract

Maternal hyperthermia, which is currently confirmed as one of major causative factors inducing growth retardation, congenital anomalies and abortion, is known to influence normal development of CNS and various organ system. In addition, maternal hyperthermia could induce severe developmental defects including development of the limb. However, it is not clearly identified how maternal hyperthermia affects the expression of chondrogenesis-related proteins in developing limb of mouse. Thus, this study is aimed to investigate the effects of the maternal hyperthermia on the expression of a various proteins in developing upper limb. To elucidate it, ICR mice were used in this study, and the animals were divided into control and heat shock groups. The heat shock treatment was given to embryonic day (ED) 8. The animals were sacrificed on ED 11, 13, 15 and 17, and the humerus were removed. Chondrogenesis-related factors such as FGF8, SOX9 and collagen II were detected on ED 11, 13 and 15 using western blot and immunohistochemistry. Developing humerus on ED 17 was stained with alizarin red S and alcian blue. The expression of FGF8 of heat shock groups was continued even though the development was succeeded. SOX9 expression in heat shock groups was significantly elevated on ED 13 compared to the control embryos. In addition, collagen II expression of heat groups was significantly higher than that of the control group on ED 13 and 15. The results of this study suggest that hyperthermia causes delayed endochondral ossification in long bone through continuous expression of FGF8, SOX9 and collagen II proteins even though the endochondral ossification is succeeded.