Excessive dexamethasone (Dex) administrated into pregnant mice during critical periods of palatal development can produce a high incidence of cleft palate. Its mechanisms remain unknown. Vitamin B 12 has been shown to antagonize the teratogenic effects of Dex, which, however, remains controversial. In this study, we investigated the effects of Dex and vitamin B 12 on murine embryonic palatal shelf fusion using organ culture of murine embryonic shelves. The explanted palatal shelves on embryonic day 14 (E14) were cultured for 24, 48, 72 or 96 h in different concentrations of Dex and/or vitamin B 12 . The palatal shelves were examined histologically for the morphological alterations on the medial edge epithelium (MEE) and fusion rates among different groups. It was found that the palatal shelves were not fused at 72 h or less of culture in Dex group, while they were completely fused in the control and vitamin B 12 -treated groups at 72 and 96 h, respectively. The MEE still existed and proliferated. In Dex+vitamin B 12 group the palatal shelves were fused at each time point in a similar rate to controls. These results may suggest that Dex causes teratogenesis of murine embryonic palatal shelves and vitamin B 12 prevents the teratogenic effect of Dex on palatogenesis on murine embryos in vitro.

Mice models are an important way to understand the relation between the fetus with cleft palate and changes of maternal biofluid. This paper aims to develop a metabonomics approach to analyze dexamethasone-induced cleft palate in pregnant C57BL/6J mice and to study the relationship between the change of endogenous small molecular metabolites in maternal plasma and the incidence of cleft palate. To do so, pregnant mice were randomly divided into two groups. The one group was injected with dexamethasone. On E17.5th day, the incident rates of cleft palate from embryos in two groups were calculated. The 1H-NMR spectra from the metabolites in plasma in two groups was collected at same time. Then the data were analyzed using metabonomics methods (PCA and SIMCA). The results showed that the data from the two groups displayed distinctive characters, and the incidence of cleft palate were significantly different (P < .005). To conclude, this study demonstrates that the metabonomics approach is a powerful and effective method in detecting the abnormal metabolites from mother in the earlier period of embryos, and supports the idea that a change from dexamethasone induced in maternal metabolites plays an important role in the incidence of cleft palate.

B vitamins rescue cleft palate induced by glucocorticoids in rodents; however, the mechanism of this effect remains largely unknown. The objective of our study was to assess the effect of dexamethasone and Vitamin B12 on cell proliferation and apoptosis during palatogenesis. In our study, mesenchymal cell proliferation in mouse embryonic palates decreased when the subjects were administered dexamethasone at embryo day 13.5 (E 13.5). However, mesenchymal cell proliferation was increased after dexamethasone exposure at E 14.0 and E 14.5 in comparison with the control group. After Vitamin B12 treatment, proliferation of mesenchymal cells was restored. No apoptosis was detected until bilaterial palatal shelves adhered and formed a medial epithelium seam in the control group and Vitamin B12-treated group. However, the apoptotic cells were detected under the medial edge epithelium before the palate contacted after dexamethasone treatment. The results suggested that Vitamin B12 restored proliferation, which had been reduced by dexamethasone via a delayed cellular cycle and apoptosis. This study implies that Vitamin B12 may be used to prevent or alleviate cleft palate induced by dexamethasone during embryonic palatogenesis.

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