The Effects of Hyperthermia on FGF-8 and BMP-4 Expression during Early Odontogenesis in Hsp70 Knock-out Mice Fetuses / 체질인류학회지

During early tooth development, multiple signaling molecules are expressed in the dental lamina and induce the dental mesenchyme. One signal, FGF-8, is expressed in the early dental epithelium, another one, BMP-4, has been shown to induce morphologic changes in dental mesenchyme. Meanwhile, hyperthermic exposure during pregnancy, as one of teratogens, is known to disturbe normal development and induce several congenital anomalies. This study is aimed to investigate the effects of maternal hyperthermia on the expressions of FGF-8 and BMP-4 in early odontogenesis. The pregnant Hsp70 knock-out at gestational day 8 were immersed in 43degrees C water bath until their body core temperature reached at 43degrees C. Thereafter, pregnant mice were given more 5 minutes hyperthermic exposure. Heat-untreated Hsp70 KO mice fetuses were used as the control group. Fetuses were collected at embryonic day (ED) 13, 15 and 17. Developing tooth in the mandible was processed for immunohistochemical study. Tissue sections were immunostained for FGF-8 and BMP-4 and observed with light microscope. The obtained results were as follows: Tooth development in the heat shocked (HS) group is delayed rather than the control group in the given developmental period. FGF-8 immunolocalization in control group at ED 13 was gradually decreased compared to the HS group which showed continuously positive immunoreaction. BMP-4 immunolocalization was detected in dental mesenchyme, however, there was no positive immunoreaction found in HS group. These results suggest that maternal hyperthermia should induce the early odontogenesis, delay the expression of FGF-8 in dental epithelium, and disturbe the expression of BMP-4 in dental mesenchyme. Consequently, hyperthermic exposure during pregnancy affects epithelial-mesenchymal interactions.

Immunohistochemical Study on Early Odontogenesis in Hsp70 Knock-out Mice Fetuses Exposed by Maternal Hyperthermia / 대한해부학회지

To investigate the effects of maternal hyperthermia on early odontogenesis,pregnant Hsp70 knock-out and wild type mice at embryonic day (ED)8.5 were immersed in a 43 degrees C water bath until their core body temperature reached that temperature,and then given a further 5 min of hyperthermia.Untreated Hsp70 WT mice fetuses were used as the control group.Fetuses were collected at EDs 13.5,15.5 and 17.5.Developing teeth in the mandible were processed for histological and immunohistochemical studies.Tissue sections were immunostained for FGF-8 and FGF -4 and observed using light microscopy.In the controls, FGF-8 immunolocalization was observed in cells within the dental lamina and in apically located dental epithelium at ED 13.5.However,a few cells were immunopositive in the heat shocked (HS)group.At EDs 15.5 and 17.5 of the control group,the basal lamina adjacent to the dental pulp showed positive immunostaining.In contrast,most of the dental epithelium was immunopositive at ED 15.5 in the HS group and inner and outer dental epithelial cells were continuously immunopositive by ED 17.5.FGF-4 immunolocalization was found in apical dental epithelium at ED 13.3 in the control group,but no such positive reaction was observed in the HS group.At ED 15.5 in the controls,basal lamina and dental epithelium near the cervical loop were immunopositive.In contrast,early cap-stage teeth had cells near the mouth of the dental bud and cervical loop that were immunopositive to FGF-4 in the HS group.In controls at ED 17.5,cells near the future secondary enamel knot were immunopositive,whereas most of the dental epithelium except for cells in the mouth of the dental lamina was negative in the HS group.Thus,maternal hyperthermia may inhibit normal odontogenesis through sustained production of FGF-8 and downregulation of FGF-4.