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THE COMPARISON OF TWO VITRO PALATAL ORGAN CULTURE MODELS TO STUDY CELL SIGNALING PATHWAYS DURING PALATOGENESIS
Citation:
TAKACS, M. AND B. D. ABBOTT. THE COMPARISON OF TWO VITRO PALATAL ORGAN CULTURE MODELS TO STUDY CELL SIGNALING PATHWAYS DURING PALATOGENESIS. Presented at Teratology Society Meeting, St. Pete Beach, FL, June 25 - 30, 2005.
Description:
This study was performed to determine the best palatal organ culture model to use in evaluating the role of epidermal growth factor (EGF) signaling in the response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Previous work has shown that TCDD and EGF can induce teratogenic effects in vivo and in vitro in various strains of mice. In this study, C57BL/6J mice were used in a suspended or a supported culture model. In the suspended model, the entire midfacial region of gestation day (GD) 12 fetuses was submerged in a serumless culture medium. Cultures were exposed for 96 hrs to medium containing 0.1% DMSO, 1 x 10-8 M TCDD, and 0 or 2 ng EGF/ml. The stages of palate fusion were classified and all groups were compared. In the supported model, dissected GD12 shelves were placed on a membrane above medium, treatments were as above for 96 hrs. Palatal fusion was determined histologically and all groups were compared. Neither culture model resulted in a significant difference in palatal fusion between control and TCDD-exposed groups. In the suspended model, controls had 95% palatal fusion and 5% touching but not fused by 96 hrs. The TCDD + EGF/ml treatment group had 76% palatal fusion, with 6% of the unfused palates touching. In the supported model, 74% of the controls had complete palatal fusion and 26% partial fusion by 96 hrs. The TCDD + EGF/ml treatment group showed 56% complete palatal fusion and 44% partial fusion. To further examine the variables that affect responsiveness to TCDD in vitro, several parameters were adjusted. Using the supported model, adding 5% FBS or increasing EGF to 5 ng/ml reduced the incidence of palatal fusion in both control and TCDD-exposed palates. In vivo oral dosing with 24 �g TCDD/kg on GD12 caused a 100% incidence of cleft palate on GD18. However, the palates of GD14 fetuses exposed in vivo fused when placed in contact in the supported model. Although previous studies report responsiveness of other mice strains to TCDD in vitro, this study demonstrated that the C57BL/6J strain did not respond in vitro with the expected failure of palates to fuse. This suggests that neither the suspended nor supported culture model is well suited to study the mechanisms of response to TCDD in the C57BL/6J strain. This abstract does not necessarily reflect EPA policy.