Bridging Developmental Biology and Regenerative Endodontics: Postnatal Rat Tooth Germ as A Model for Root Dentinogenesis
DOI:
https://doi.org/10.15517/3aetrn30Keywords:
Rat tooth germ; Root dentinogenesis; Regenerative endodontic treatment; Hertwig's epithelial root sheath; Odontoblast differentiation; Postnatal molar development.Abstract
Regenerative endodontic treatment (RET) aims to promote continued root maturation and restoration of the pulp–dentin complex through tissue-engineering principles. However, conventional infection-based experimental models introduce inflammatory and microbial confounders that may obscure the intrinsic mechanisms of physiological root dentinogenesis. This narrative review evaluates postnatal day 7-19 rat mandibular first molar root tooth germ as a biologically defined developmental model for mechanistic RET research. The literature was searched in PubMed, Scopus and Web of Science using predefined developmental, molecular and regenerative endodontic keywords. Studies addressing root development, Hertwig’s epithelial root sheath (HERS), odontoblast differentiation, dentin matrix protein expression, stem cells of the apical papilla (SCAPs) and inflammatory effects on odontogenic signaling were included. Evidence indicates that the P7-P19 developmental window encompasses sequential HERS elongation, odontoblast differentiation, predentin secretion, dentin mineralization and an early cementogenesis. The model also preserves physiological signaling pathways, including Wnt/β-catenin, BMP and TGF-β networks without the confounding influence of lipopolysaccharide-induced NF-κB activation or matrix metalloproteinase-mediated extracellular matrix degradation. Although translational limitations between rodent and human biology remain, the reviewed evidence supports the value of this normal-tissue developmental model as a reproducible baseline for mechanistic studies in regenerative endodontics.
Downloads
References
Rathee M., Jain P. Embryology, teeth. 2020.
Shokouhinejad N., Razmi H., Farbod M., Alikhasi M., Camilleri J. Coronal tooth discoloration induced by regenerative endodontic treatment using different scaffolds and intracanal coronal barriers: a 6-month ex vivo study. Restor Dent Endod. The Korean Academy of Conservative Dentistry; 2019; 44 (3). DOI: https://doi.org/10.5395/rde.2019.44.e25
Brizuela C., Huang G.T.-J., Diogenes A., Botero T., Khoury M. The four pillars for successful regenerative therapy in endodontics: stem cells, biomaterials, growth factors, and their synergistic interactions. Stem Cells Int. Wiley Online Library; 2022; 2022 (1): 1580842. DOI: https://doi.org/10.1155/2022/1580842
Wei X., Yang M., Yue L., Huang D., Zhou X., Wang X., et al. Expert consensus on regenerative endodontic procedures. Int J Oral Sci. Nature Publishing Group UK London; 2022; 14 (1): 55. DOI: https://doi.org/10.1038/s41368-022-00206-z
Alothman F.A., Hakami L.S., Alnasser A., AlGhamdi F.M., Alamri A.A., Almutairii B.M., et al. Recent advances in regenerative endodontics: a review of current techniques and future directions. Cureus. Cureus; 2024; 16 (11). DOI: https://doi.org/10.7759/cureus.74121
Phumpatrakom P., Srisuwan T. Regenerative capacity of human dental pulp and apical papilla cells after treatment with a 3-antibiotic mixture. J Endod. Elsevier; 2014; 40 (3): 399-405. DOI: https://doi.org/10.1016/j.joen.2013.09.027
Li X-L., Fan W., Fan B. Dental pulp regeneration strategies: A review of status quo and recent advances. Bioact Mater. Elsevier; 2024; 38: 258-75. DOI: https://doi.org/10.1016/j.bioactmat.2024.04.031
Aubeux D., Renard E., Pérez F., Tessier S., Geoffroy V., Gaudin A. Review of animal models to study pulp inflammation. Front Dent Med. Frontiers Media SA; 2021; 2: 673552. DOI: https://doi.org/10.3389/fdmed.2021.673552
Li J., Zhao Y.-N., Wang Y.-H., Chen Y., Hou J.-L., Wang D.-Y., et al. Animal models of oral infectious diseases. Front Oral Heal. Frontiers Media SA; 2025; 6: 1571492. DOI: https://doi.org/10.3389/froh.2025.1571492
Chen M., Lin X., Zhang L., Hu X. Effects of nuclear factor-κB signaling pathway on periodontal ligament stem cells under lipopolysaccharide-induced inflammation. Bioengineered. Taylor & Francis; 2022; 13 (3): 7951-61. DOI: https://doi.org/10.1080/21655979.2022.2051690
Yang Y., Deng K., Jiang S., Guo X., Zhong Y., Wu B., et al. Punicalagin ameliorates lipopolysaccharide-induced inflammatory response in dental pulp cells via inhibition of the NF-κB/Wnt5a-ROR2 pathway. Immunopharmacol Immunotoxicol. Taylor & Francis; 2025; 47 (3): 317-27. DOI: https://doi.org/10.1080/08923973.2025.2470343
Sonmez Kaplan S., Sazak Ovecoglu H., Genc D., Akkoc T. TNF-α, IL-1B and IL-6 affect the differentiation ability of dental pulp stem cells. BMC Oral Health. Springer; 2023; 23 (1): 555. DOI: https://doi.org/10.1186/s12903-023-03288-1
Chaussain C., Boukpessi T., Khaddam M., Tjaderhane L., George A., Menashi S. Dentin matrix degradation by host matrix metalloproteinases: inhibition and clinical perspectives toward regeneration. Front Physiol. Frontiers Media SA; 2013; 4: 308. DOI: https://doi.org/10.3389/fphys.2013.00308
Baethge C., Goldbeck-Wood S., Mertens S. SANRA—a scale for the quality assessment of narrative review articles. Res Integr peer Rev. Springer; 2019; 4 (1): 5. DOI: https://doi.org/10.1186/s41073-019-0064-8
Christensen M. On the developmental basis of scaling crown size in mammalian teeth. Helsingin yliopisto; 2024.
Lungová V., Radlanski R.J., Tucker A.S., Renz H., Míšek I., Matalová E. Tooth-bone morphogenesis during postnatal stages of mouse first molar development. J Anat. Wiley Online Library; 2011; 218 (6): 699-716. DOI: https://doi.org/10.1111/j.1469-7580.2011.01367.x
Huang X.-F., Chai Y. Molecular regulatory mechanism of tooth root development. Int J Oral Sci. Nature Publishing Group; 2012; 4 (4): 177-81. DOI: https://doi.org/10.1038/ijos.2012.61
Jing J., Feng J., Yuan Y., Guo T., Lei J., Pei F., et al. Spatiotemporal single-cell regulatory atlas reveals neural crest lineage diversification and cellular function during tooth morphogenesis. Nat Commun. Nature Publishing Group UK London; 2022; 13 (1): 4803. DOI: https://doi.org/10.1038/s41467-022-32490-y
Rao P., Jing J., Fan Y., Zhou C. Spatiotemporal cellular dynamics and molecular regulation of tooth root ontogeny. Int J Oral Sci. Nature Publishing Group UK London; 2023; 15 (1): 50. DOI: https://doi.org/10.1038/s41368-023-00258-9
Balzano R., Stellini E., Mucignat-Caretta C. Cell differentiation and replication during postnatal development of the murine first molar. Biology (Basel). MDPI; 2021; 10 (8): 776. DOI: https://doi.org/10.3390/biology10080776
Baba O., Qin C., Brunn J.C., Wygant J.N., McIntyre B.W., Butler W.T. Colocalization of dentin matrix protein 1 and dentin sialoprotein at late stages of rat molar development. Matrix Biol. Elsevier; 2004; 23 (6): 371-9. DOI: https://doi.org/10.1016/j.matbio.2004.07.008
Li H., Hu X., Zen A., Chen Y., Yang M., Zhang J., et al. Transcriptomic network regulation of rat tooth germ from bell differentiation stage to secretory stage: MAPK signaling pathway is crucial to extracellular matrix remodeling. Biomed Res Int. Wiley Online Library; 2023; 2023 (1): 4038278. DOI: https://doi.org/10.1155/2023/4038278
Yamamoto T., Yamada T., Yamamoto T., Hasegawa T., Hongo H., Oda K., et al. Hertwig’s Epithelial Root Sheath Fate during Initial Cellular Cementogenesis in Rat Molars. ACTA Histochem Cytochem. 2015; 48 (3): 95-101. DOI: https://doi.org/10.1267/ahc.15006
Jeong J.-K., Kim T.-H., Choi H., Cho E.-S. Impaired breakdown of Herwig’s epithelial root sheath disturbs tooth root development. Dev Dyn. 2024; 253 (4): 423-34. DOI: https://doi.org/10.1002/dvdy.667
Yang S., Choi H., Kim T.-H., Jeong J.-K., Liu Y., Harada H., et al. Cell dynamics in Hertwig’s epithelial root sheath are regulated by β-catenin activity during tooth root development. J Cell Physiol. 2021; 236 (7): 5387-98. DOI: https://doi.org/10.1002/jcp.30243
Sun K., Yu M., Wang J., Zhao H., Liu H., Feng H., et al. A Wnt10a-Notch signaling axis controls Hertwig’s epithelial root sheath cell behaviors during root furcation patterning. Int J Oral Sci. Nature Publishing Group UK London; 2024;16 (1): 25. DOI: https://doi.org/10.1038/s41368-024-00288-x
Liu M.M., Li W.T., Xia X.M., Wang F., MacDougall M., Chen S. Dentine sialophosphoprotein signal in dentineogenesis and dentine regeneration. Eur Cell Mater. 2021; 42: 43. DOI: https://doi.org/10.22203/eCM.v042a04
Alwan M.H. Comparative morphogenesis of mouse and rat mandibular first molars (M1): a review of developmental timing, structure, and signaling pathways. Anat Cell Biol. 2026. DOI: https://doi.org/10.5115/acb.25.354
Guo Y., Guo W., Chen J., Chen G., Tian W., Bai D. Are Hertwig’s epithelial root sheath cells necessary for periodontal formation by dental follicle cells? Arch Oral Biol. 2018; 94: 1-9. DOI: https://doi.org/10.1016/j.archoralbio.2018.06.014
Mu H., Liu X., Geng S., Su D., Chang H., Li L., et al. Epithelial Bone Morphogenic Protein 2 and 4 Are Indispensable for Tooth Development. Front Physiol. 2021;12. DOI: https://doi.org/10.3389/fphys.2021.660644
Jing Y., Wu J., Liu Y., Liu X., Ma C. Novel Roles of Nestin in Postnatal Root Formation. Dent J. 2025; 13 (3). DOI: https://doi.org/10.3390/dj13030113
He W., Zhang J., Niu Z., Yu Q., Wang Z., Zhang R., et al. Regulatory interplay between NFIC and TGF-β1 in apical papilla-derived stem cells. J Dent Res. SAGE Publications Sage CA: Los Angeles, CA; 2014; 93 (5): 496-501. DOI: https://doi.org/10.1177/0022034514525200
Amri N., Djole S.X., Petit S., Babajko S., Coudert A.E., Castaneda B., et al. Distorted Patterns of Dentinogenesis and Eruption in Msx2 Null Mutants Involvement of Sost/Sclerostin. Am J Pathol. 2016; 186 (10): 2577-87. DOI: https://doi.org/10.1016/j.ajpath.2016.06.013
Braut A., Kollar E.J., Mina M. Analysis of the odontogenic and osteogenic potentials of dental pulp in vivo using a Col1a1-2.3-GFP transgene. Int J Dev Biol. 2003; 47 (4): 281-92. DOI: https://doi.org/10.1387/ijdb.12755333
Andujar M.B., Hartmann D.J., Emonard H., Magloire H. Distribution and synthesis of type I and type III collagens in developing mouse molar tooth root. Histochemistry. Springer; 1988; 88 (2): 131-40. DOI: https://doi.org/10.1007/BF00493295
Wang X., Gu L., Zhang P., Zhou Y. MFAP5 Activates ITGA5 to Drive Tooth Germ Mineralization Through the MAPK/ERK Pathway: Insights from Single-Cell Transcriptomics. Int J Mol Sci. MDPI; 2025; 27 (1): 394. DOI: https://doi.org/10.3390/ijms27010394
Saito M., Iwase M., Maslan S., Nozaki N., Yamauchi M., Handa K., et al. Expression of cementum-derived attachment protein in bovine tooth germ during cementogenesis. Bone. Elsevier; 2001; 29 (3): 242-8. DOI: https://doi.org/10.1016/S8756-3282(01)00573-7
Kruzynska-Frejtag A., Wang J., Maeda M., Rogers R., Krug E., Hoffman S., et al. Periostin is expressed within the developing teeth at the sites of epithelial–mesenchymal interaction. Dev Dyn an Off Publ Am Assoc Anat. Wiley Online Library; 2004; 229 (4): 857-68. DOI: https://doi.org/10.1002/dvdy.10453
Choi H., Jin H., Kim J.-Y., Lim K.-T., Choung H.-W., Park J.-Y., et al. Hypoxia Promotes CEMP1 Expression and Induces Cementoblastic Differentiation of Human Dental Stem Cells in an HIF-1-Dependent Manner. TISSUE Eng PART A. 2014; 20 (1-2): 410-23. DOI: https://doi.org/10.1089/ten.tea.2013.0132
Novacescu D., Dumitru C.S., Zara F., Raica M., Suciu C.S., Barb A.C., et al. The Morphogenesis, Pathogenesis, and Molecular Regulation of Human Tooth Development—A Histological Review. Int J Mol Sci. MDPI; 2025; 26 (13): 6209. DOI: https://doi.org/10.3390/ijms26136209
Zhang S., Li X., Wang S., Yang Y., Guo W., Chen G., et al. Immortalized Hertwig’s epithelial root sheath cell line works as model for epithelial-mesenchymal interaction during tooth root formation. J Cell Physiol. 2020; 235 (3): 2698-709. DOI: https://doi.org/10.1002/jcp.29174
Nakatomi M., Ida-Yonemochi H., Ohshima H. Lymphoid Enhancer-binding Factor 1 Expression Precedes Dentin Sialophosphoprotein Expression during Rat Odontoblast Differentiation and Regeneration. J Endod. 2013; 39 (5): 612-8. DOI: https://doi.org/10.1016/j.joen.2012.12.016
Ono W., Sakagami N., Nishimori S., Ono N., Kronenberg H.M. Parathyroid hormone receptor signalling in osterix-expressing mesenchymal progenitors is essential for tooth root formation. Nat Commun. 2016; 7. DOI: https://doi.org/10.1038/ncomms11277
Zhang R., Yang G., Wu X., Xie J., Yang X., Li T. Disruption of Wnt/β-catenin signaling in odontoblasts and cementoblasts arrests tooth root development in postnatal mouse teeth. Int J Biol Sci. 2013; 9 (3): 228. DOI: https://doi.org/10.7150/ijbs.5476
Oh H.-J., Lee H.-K., Park S.-J., Cho Y.-S., Bae H.-S., Cho M.-I., et al. Zinc balance is critical for NFI-C mediated regulation of odontoblast differentiation. J Cell Biochem. 2012; 113 (3): 877-87. DOI: https://doi.org/10.1002/jcb.23421
Wu S., Xu X., Gao S., Huo S., Wan M., Zhou X., et al. MicroRNA-93-5p regulates odontogenic differentiation and dentin formation via KDM6B. J Transl Med. Springer; 2024; 22 (1): 54. DOI: https://doi.org/10.1186/s12967-024-04862-z
Kim T.H., Bae C.H., Lee J.C., Kim J.E., Yang X., de Crombrugghe B., et al. Osterix Regulates Tooth Root Formation in a Site-specific Manner. J Dent Res. 2015; 94 (3): 430-8. DOI: https://doi.org/10.1177/0022034514565647
Zhang H., Jiang Y., Qin C., Liu Y., Ho S.P., Feng J.Q. Essential Role of Osterix for Tooth Root but not Crown Dentin Formation. J BONE Miner Res. 2015; 30 (4): 742-6. DOI: https://doi.org/10.1002/jbmr.2391
Hosoya A., Kim J.-Y., Cho S.-W., Jung H.-S. BMP4 signaling regulates formation of Hertwig’s epithelial root sheath during tooth root development. Cell Tissue Res. 2008; 333 (3): 503-9. DOI: https://doi.org/10.1007/s00441-008-0655-z
Wang J., Ran S., Liu B., Gu S. Monitoring of canonical BMP and Wnt activities during postnatal stages of mouse first molar root formation. J Appl Oral Sci. SciELO Brasil; 2021; 29: e20210281. DOI: https://doi.org/10.1590/1678-7757-2021-0281
Liu Q., Gao Y., He J. Stem Cells from the Apical Papilla (SCAPs): Past, Present, Prospects, and Challenges. BIOMEDICINES. 2023; 11 (7). DOI: https://doi.org/10.3390/biomedicines11072047
Lei S., Liu X.-M., Liu Y., Bi J., Zhu S., Chen X. Lipopolysaccharide downregulates the osteo-/odontogenic differentiation of stem cells from apical papilla by inducing autophagy. J Endod. Elsevier; 2020; 46 (4): 502-8. DOI: https://doi.org/10.1016/j.joen.2020.01.009
Takimoto K., Widbiller M., Diogenes A. Expression of toll-like receptors in stem cells of the apical papilla and its implication for regenerative endodontics. Cells. MDPI; 2023; 12 (20): 2502. DOI: https://doi.org/10.3390/cells12202502
Brodzikowska A., Ciechanowska M., Kopka M., Stachura A., Włodarski P.K. Role of lipopolysaccharide, derived from various bacterial species, in pulpitis—a systematic review. Biomolecules. MDPI; 2022; 12 (1): 138. DOI: https://doi.org/10.3390/biom12010138
Chen Z., Lang G., Xu X., Liang X., Han Y., Han Y. The role of NF-kappaB in the inflammatory processes related to dental caries, pulpitis, apical periodontitis, and periodontitis–a narrative review. PeerJ. PeerJ Inc.; 2024; 12: e17953. DOI: https://doi.org/10.7717/peerj.17953
Lorencetti-Silva F., Sales L.S., Lamarque G. de C.C., Caixeta G.A., Arnez M.F.M., Faccioli L.H., et al. Effects of inflammation in dental pulp cell differentiation and reparative response. Front Dent Med. Frontiers Media SA; 2022; 3: 942714. DOI: https://doi.org/10.3389/fdmed.2022.942714
Arora S., Cooper P.R., Friedlander L.T., Seo B., Rizwan S.B., Rich A.M., et al. Potentiality and inflammatory marker expression are maintained in dental pulp cell cultures from carious teeth. Int J Mol Sci. Mdpi; 2022; 23 (16): 9425. DOI: https://doi.org/10.3390/ijms23169425
Irfan M., Kim J.H., Sreekumar S., Chung S. Gene expression profiles identify key factors in inflammatory odontoblastic dental pulp stem cell differentiation via TNFα/C5L2. Front Genet. Frontiers Media SA; 2025; 16: 1592599. DOI: https://doi.org/10.3389/fgene.2025.1592599
Kim S.G. Infection and pulp regeneration. Dent J. MDPI; 2016; 4 (1): 4. DOI: https://doi.org/10.3390/dj4010004
Iranmanesh P., Torabinejad M., Saatchi M., Toghraie D., Razavi S.M., Khademi A. Effect of duration of root canal infection on the ability of dentin-pulp complex regeneration of immature permanent teeth: an animal study. J Endod. Elsevier; 2022; 48 (10): 1301-7. DOI: https://doi.org/10.1016/j.joen.2022.07.007
Kamilov K.P., Taylakova D.I., Nikolskaya I.A. Embryonal and postnatal histogenesis of teeth in rats under conditions of the environment. Russ Med. 2019; 25 (4): 230-3. DOI: https://doi.org/10.18821/0869-2106-2019-25-4-230-233
Fry D., Smith A., Storey J., Bate S., Ritskes-Hoitinga M. Design of procedures and projects. In: Practical Handbook on the 3Rs in the Context of the Directive 2010/63/EU. Elsevier; 2022. p. 279-317. DOI: https://doi.org/10.1016/B978-0-12-821180-9.00002-7
Würbel H. More than 3Rs: the importance of scientific validity for harm-benefit analysis of animal research. Lab Anim (NY). Nature Publishing Group; 2017; 46 (4): 164-6. DOI: https://doi.org/10.1038/laban.1220
Published
Issue
Section
License
Copyright (c) 2026 Maryam Hameed Alwan, Jwan Arkan M. Saeed.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
ODOVTOS - Int. J. Dent. Sc. endorses CC BY-NC-SA
This license enables reusers to distribute, remix, adapt, and build upon the material in any medium or format for noncommercial purposes only, and only so long as attribution is given to the creator. If you remix, adapt, or build upon the material, you must license the modified material under identical terms. CC BY-NC-SA includes the following elements:
BY: credit must be given to the creator.
NC: Only noncommercial uses of the work are permitted.
SA: Adaptations must be shared under the same terms.
