Objective: To find out the molecular mechanisms of togenesis, especially neural tube defects (NTDs) caused by hyperglycemia and thiadiazole.
Methods: Mice were raised with a ratio of 2:1 between females and males. Forty-five pregnant female mice were randomly divided into 5 groups: blank control group (without any treatment), high-glucose group (treated with subcutaneous injection of 25% glucose), glucose-control group (n = 12, treated with subcutaneous injection of 5% glucose), thiadiazole group (treated with gastric perfusion of thiadiazole), and thiadiazole-control group (n = 11, treated with the solvent of thiadiazole). The blood sugar was examined among the mice of the first three groups on the 8th gestational day. All of the mice were killed on the 15th gestational day and the embryos were taken. The existence of teras was observed. RT-PCR was used to detect the expression of Pax3 and of Cx43 genes and immunohistochemistry was used to examine the Pax3 and Cx43 proteins in the embryos.
Results: The blood sugar of the pregnant mice in the high-glucose group was 13.4 mmol/L +/- 0.8 mmol/L, significantly higher than those in the 2 control groups (4.9 mmol/L +/- 0.4 mmol/L and 4.8 mmol/L +/- 0.4 mmol/L respectively, both P < 0.01). The teras rate, absorbed embryo rate and still embryo rate in high-glucose group were significantly higher than those in the 2 control groups (all P < 0.01). The embryo weight of the high-glucose group was significantly lower. The expression of Pax3 in the hyperglycemia group was significantly lower than those in the 2 control groups (both P < 0.01), while the expression of Cx43 in high-glucose group was significantly higher than those in the 2 control groups (both P < 0.01). In the thiadiazole group, the expression of Pax3 was not significantly different from, and the expression of Cx43 was significantly higher than those in the 2 control groups.
Conclusion: Hyperglycemia is induced in nondiabetic pregnant mice by subcutaneous glucose injection, and elevated glucose appears to be critical in the diabetic embryopathy. Hyperglycemic episodes disturb the essential embryonic control genes: decrease the expression of Pax3 gene and increase the expression of Cx43 gene, thus causing congenital defects. Thiadiazole induces NTDs by increasing the expression of Cx43.