Tetrachlorodibenzo-p-dioxin-induced cleft palate because of partial loss of cell polarity to interfere with apoptosis during early developmental stage

Abstract

In this study, folic acid (FA) was tested for antiteratogenic effects on Tetrachlorodibenzo-p-dioxin (TCDD)-induced cleft palate in fetal mice. In the present study, pregnant mice were dosed with TCDD 24 µg/kg and with or without FA 5 mg/kg body weight on gestation day 10. Control group mice received sesame oil 50 ml/kg body weight on gestation day(GD)10. The mice were sacrificed on GD12.5, GD13.5, GD14.5, GD15.5 and GD16.5. From each pregnant mouse on GD16.5, embryos were obtained to examine under a dissecting microscope, and routine histology was performed for detection and classification of palatal clefts. The fetuses were prepared for histologic examination, scanning electron microscope and TdT-mediated X-dUTP nick and labeling (TUNEL). On GD12.5, GD13.5, GD14.5 and GD15.5. Meanwhile, real-time (RT)-PCR was employed to detect the mRNA expression levels about arylhydrocarbon receptor (AHR) and transforming growth factor (TGF)β3 in this animal model. Total frequencies of clefts were 70.2% in TCDD group(group B) and 66.3% in TCDD+FA group(group C) in relation to control fetuses(group A). Filopodia disappeared completely at the medial edge epithelia surface on GD15.5 (group A), GD12.5 (group B) and GD14.5 (group C). the RT-PCR results showed that TGF -β3 expression was down-regulated on GD13.5 and GD14.5 compared to the control. It is found that folic acid has no protects agaist 2.3.7.8-TCDD-indued cleft palate in the experiment. Meanwhile, TCDD repressed the TGF-β3 expression during the palatal development. Anormal apoptosis was induced by 2, 3, 7, 8-TCDD at the medial edge epithelia (MEE) during the early development stage.