Several factors, including genetic and environmental insults, impede protein folding and secretion in the endoplasmic reticulum (ER). Accumulation of unfolded or mis-folded protein in the ER manifests as ER stress. To cope with this morbid condition of the ER, recent data has suggested that the intracellular event of an unfolded protein response plays a critical role in managing the secretory load and maintaining proteostasis in the ER. Tauroursodeoxycholic acid (TUDCA) is a chemical chaperone and hydrophilic bile acid that is known to inhibit apoptosis by attenuating ER stress. Numerous studies have revealed that TUDCA affects hepatic diseases, obesity, and inflammatory illnesses. Recently, molecular regulation of ER stress in tooth development, especially during the secretory stage, has been studied. Therefore, in this study, we examined the developmental role of ER stress regulation in tooth morphogenesis using in vitro organ cultivation methods with a chemical chaperone treatment, TUDCA. Altered cellular events including proliferation, apoptosis, and dentinogenesis were examined using immunostaining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. In addition, altered localization patterns of the formation of hard tissue matrices related to molecules, including amelogenin and nestin, were examined to assess their morphological changes. Based on our findings, modulating the role of the chemical chaperone TUDCA in tooth morphogenesis, especially through the modulation of cellular proliferation and apoptosis, could be applied as a supporting data for tooth regeneration for future studies.

Introduction
Materials and Methods
    1. Animals
    2. I n vitro organ cultivation, kidney transplantation anddrug treatment
    3. Histology and immunohistochemistry
    4. Terminal deoxynucleotidyl transferase dUTP nickend labeling (TUNEL) assay
Result
    1. ER stress modulated calcified tooth continues tosecrete matrices
    2. ER stress in developing teeth was alleviated aftertreatment of chemical chaperon
    3. Modulation of ER stress promotes the elongation oftooth root
Discussion
Acknowledgements
Conflicts of Interest
References

• Eui-Seon Lee(Department of Biochemistry, School of Dentistry, Kyungpook National University)
• Yam Prasad Aryal(Department of Biochemistry, School of Dentistry, Kyungpook National University)
• Tae-Young Kim(Department of Biochemistry, School of Dentistry, Kyungpook National University)
• Elina Pokharel(Department of Biochemistry, School of Dentistry, Kyungpook National University)
• Harim Kim(Department of Biochemistry, School of Dentistry, Kyungpook National University)
• Shijin Sung(Department of Biochemistry, School of Dentistry, Kyungpook National University)
• Wern-Joo Sohn(Pre-Major of Cosmetics and Pharmaceutics, Daegu Haany University)
• Youngkyun Lee(Department of Biochemistry, School of Dentistry, Kyungpook National University)
• Chang-Hyeon An(Department of Oral and Maxillofacial Radiology, IHBR, School of Dentistry) Correspondence to
• Jae-Young Kim(Department of Biochemistry, School of Dentistry, Kyungpook National University) Correspondence to