Abstract
PurposeTo study the outcomes of mouse preimplantation embryos irradiated with low doses of X-rays (≤ 1 Gy) and investigate apoptosis and pluripotency of the irradiated embryos.MethodsMouse embryos at the 2-cell stage were collected for in vitro culture. After reaching the 8-cell stage, embryos were irradiated with various low doses of X-rays (0–1 Gy). Blastocysts with a normal appearance were transferred into a pseudopregnant uterus. The developmental rate to blastocysts and the survival rate following embryo transfer were examined. Expression levels of p21, Smad2, Foxo1, Cdx2, Oct4, and Nanog genes were measured by RT-PCR. Apoptotic cells in mouse blastocysts were examined immunofluorescently by staining for cleaved caspase-3.ResultsMore than 90% of non-irradiated and low-dose X-ray-irradiated preimplantation embryos developed to morphologically normal blastocysts that could be implanted and survive in the uterus. However, embryos irradiated with X-rays had more apoptotic cells in a dose-dependent manner. Expression of p21, Smad2, and Foxo1 genes in X-ray-irradiated embryos was increased significantly, while expression of Cdx2, Oct4, and Nanog genes was maintained in comparison with non-irradiated embryos.ConclusionsAlthough irradiated embryos contained apoptotic cells, the low doses of irradiation did not disturb development of 8-cell stage embryos to blastocysts or their survival in utero. The underlying mechanisms might involve anti-apoptotic systems, including the Smad-p21 pathway, and preservation of pluripotency.
Highlights
Radiation is indispensable for the diagnosis of diseases
Using 8-cell stage mouse embryos irradiated with a low dose (0.1–1.0 Gy), we aimed to (1) observe the developmental rate and survival rate after embryo transfer, (2) investigate the apoptotic process including the Smad-p21 pathway, and (3) evaluate the pluripotency of the inner cell mass (ICM) and trophectoderm (TE)
Forty-eight hours after pregnant mare serum gonadotropin (PMSG) injection, the mice were injected with 6.7 IU human chorionic gonadotrophin
Summary
Radiation is indispensable for the diagnosis of diseases. Imaging techniques, such as X-rays, computed tomographic. Irradiated preimplantation embryos either die or survive without any detectable malformation [4], and the effect of irradiation on an embryo depends on both the embryo stage and exposure dose [5]. When the fetal radiation dose is less than 0.05 Gy, non-carcinogenic risk such as abortion and malformation is negligible. The effect of a fetal dose of less than 0.1 Gy will be clinically not detectable [6] It has been suggested that minimal threshold of the central nervous system may be 0.06–0.3 Gy [7]. Excess of 1-Gy exposure during embryogenesis will result in clinically significant fetal
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