This study explores the histological features and Bmp4 expression patterns in the replaced tooth germ of Xenopus laevis . Tooth germ formation starts from the dental placode through epithelial-mesenchymal interactions, involving various signaling pathways such as Fgf, Shh, Bmp, and Wnt. In mice, Bmp4 expression in the dental placode inhibits Pax9 expression in the dental mesenchyme. Although absent in the presumptive dental lamina of birds and toothless mammals, Bmp4 remains conserved in reptiles and fish owing to gene duplication. However, its expression in amphibian tooth germs is poorly understood. Three-month-old X. laevis were employed in this study. Initially, samples underwent paraffin embedding and were sectioned into 5 or 12 μm ribbons for H&E staining and in situ hybridization, respectively. Results revealed teeth appearing in two maxillary rows: the labial side, with prefunctional and functional teeth, and the lingual side, with replaced tooth germs behind functional teeth. Enameloid was observed between the inner dental epithelium and dental mesenchyme at the cap or early bell stages, whereas enamel and dentin formed during the late bell or mineralization stages from the replaced tooth germ. Bmp4 expression was evident in the inner dental epithelium (ameloblasts), dental papilla (odontoblasts), stellate reticulum, and Hertwig’s epithelial root sheath. Overall, these findings highlight the conservation of Bmp4 expression in X. laevis tooth development.

Introduction
Materials and Methods
    1. 실험동물 및 조직표본 제작
    2. H&E 염색
    3. cRNA probe 제작 및 in situ hybridization
Results
    1. 조직학적 관찰
    2. Bmp4 의 발현
Discussion
Funding
Acknowledgements
Conflicts of Interest
References

• Young-Hoon Lee(Department of Oral Anatomy, School of Dentistry, and Institute of Oral Biosciences, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Renming Guo(Department of Oral Anatomy, School of Dentistry, and Institute of Oral Biosciences, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Yibo Li(Department of Oral Anatomy, School of Dentistry, and Institute of Oral Biosciences, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Byung Keon Park(Department of Oral Anatomy, School of Dentistry, and Institute of Oral Biosciences, Jeonbuk National University, Jeonju 54896, Republic of Korea) Corresponding author