PROBLEM: TGFβs are among the main immunoregulatory molecules contributing to successful embryonic development. Besides, our and other studies revealed that maternal immunopotentiation has a potential to increase the resistance of the embryo to the teratogenic insult. This work was designed to evaluate: (1) whether the formation of teratogen-induced anomalies is accompanied by an altered pattern of TGFβ2 expression in embryonic cells and (2) whether maternal immunopotentiation modifies the pattern of TGFβ2 expression in embryos responding to the teratogenic insult.
METHOD OF STUDY: Experiments were performed in embryos of ICR mice exposed to 15 and 40 mg/kg of a reference teratogen, cyclophosphamide (CP) on day 12 of gestation. A group of mice was immunopotentiated with xenogeneic rat splenocytes 21 hr before the beginning of mating. Embryos were examined for the occurrence of gross structural anomalies 24 and 72 hr after CP treatment. Then, immunohistohemistry and in situ hybrydization assays were used to evaluate the expression of TGFβ2 protein and mRNA in the brain, face, limbs and liver of these embryos.
RESULTS: No external anomalies were observed in embryos examined 24 hr after CP treatment. Embryos examined 72 hr after CP treatment at 40mg/kg exhibited agnathia, micrognathia, kinky tail, phocomelia, but no signs of dismorphogenesis were observed in the liver at the organ level. A significant increase in the expression of TGFβ2 mRNA was observed in cells, residing in the brain, face and limbs but not in the liver of CP-exposed embryos tested 24 hr after CP injection in both doses. The level of TGFβ2 protein in these embryos did not differ from that of controls. In embryos tested 72 hr after CP injection in the high dose both TGFβ2 protein and mRNA expression were found to be elevated. Maternal immunopotentiation while enhancing the embryo's resistance to CP practically abolished an elevated expression of the TGFβ2 mRNA detected in tested organ structures of embryos of non-immunopotentiated CP treated mice 24 hr after CP injection in both the low and the high doses. Also, a significant decrease in the level of TGFβ2 mRNA expression was observed in embryos of immunopotentiated mice examined 72 hr after CP treatment.
CONCLUSIONS: The results of this work show a possible involvement of TGFβ2 in the formation of teratogen-induced structural anomalies and suggest that the stimulation of the maternal immune system may realize its protective effect by normalizing the level of TGFβ2 expression in teratogen-targeted embryonic structures.