Researchers at the Guangzhou Institutes of Biomedicine and Health have developed a novel culture medium that preserves the tooth-forming capacity of mouse dental mesenchymal cells for up to 14 days, a significant extension beyond the 24-hour limit of traditional systems. Published in Cell Regeneration, the study demonstrates that this optimized N2B27-based medium allows cells to maintain their odontogenic potential even after passaging, offering a robust platform for studying tooth development and generating cell sources for bioengineered dental tissues. The work addresses a critical bottleneck in regenerative dentistry, where current culture systems fail to sustain the functionality of dental mesenchymal cells (DMCs) beyond short-term periods, thereby limiting their utility for tissue engineering applications.
The study, led by Jinglei Cai and colleagues, focused on the challenge of maintaining the odontogenic potential of mouse DMCs in vitro. Traditional culture media containing fetal bovine serum (FBS) or serum-free media with Knockout Serum Replacement (KSR) have historically maintained this potential for only 24 to 48 hours. The researchers aimed to bridge this gap by developing a culture system that could extend the maintenance of odontogenic potential to at least 14 days, even after the cells were passaged. This approach was designed to achieve a high tooth induction rate, which the study reports as 40.74% under specific conditions, providing a stable environment for mechanistic studies of tooth development.
To assess the impact of the new culture conditions, the team isolated mDMCs from E14.5 dental mesenchyme and compared their behavior in the novel N2B27 medium against a traditional FBS-based control. In the FBS medium, cells exhibited strong adherence and a pronounced three-dimensional morphology initially, but by day 4, most cells displayed large, flat cell bodies. In contrast, mDMCs cultured in the N2B27 medium showed lower adherence after 24 hours, with elongated cell bodies and multiple pseudopods.
Cell viability and proliferation were evaluated using a cell counting kit-8 assay and flow cytometry. Cells maintained in FBS medium following the first passage exhibited significantly reduced viability compared to the other treatment groups. Conversely, the N2B27 groups demonstrated consistently higher viability over the initial five-day period. Flow cytometry analysis revealed that the DNA content profiles of cultured mDMCs in both media were characteristic of a healthy, actively cycling cell population, with clear definition of the G0/G1, S, and G2/M peaks.
The odontogenic potential of the cultured cells was evaluated through classical tissue recombination assays using non-odontogenic dental epithelium. In the FBS group, tooth-like structures were generated only from mDMCs cultured for 24 hours, with a formation rate of 71.79%. Cells cultured for four or seven days in FBS formed only cysts upon recombination. In stark contrast, the N2B27 groups exhibited tooth-like structure formation from cultured mDMCs at both the pre-passage and post-passage stages. The tooth formation rates in the N2B27 group were 83.33% at day 1, 72.73% at day 4, and 79.37% at day 7 for the pre-passage cells. After the first passage, the rates were 40.74% at day 1, 47.92% at day 4, and 42.86% at day 7, demonstrating the medium’s ability to sustain regenerative capacity through cell division.
Transcriptome profiling using bulk RNA-seq and single-cell RNA sequencing (scRNA-seq) revealed distinct gene expression patterns between the two culture systems. The analysis identified specific gene clusters activated in N2B27-cultured mDMCs, including those related to epithelial proliferation regulation, neurogenesis, and odontogenesis. A cluster of genes associated with ossification and biomineralization, such as Spp1 (osteopontin), was specifically expressed in the N2B27-cultured cells. Conversely, a cluster of genes specifically activated in FBS-cultured mDMCs was enriched for negative regulators of BMP signaling. These findings suggest that the N2B27 medium fosters a molecular environment conducive to odontogenesis by activating biomineralization genes while suppressing inhibitory signaling pathways.
The role of BMP signaling in regulating odontogenic potential was further investigated through recombination experiments. Inhibition of BMP type I receptors with dorsomorphin partially rescued the odontogenic potential of cultured cells in the FBS group. Conversely, the over-activation of BMP signaling by adding BMP4 completely blocked the odontogenic potential in the N2B27 group. These results indicate that sustained high expression of Bmp4 suppresses the odontogenic potential of mDMCs in vitro. The scRNA-seq data supported this, showing that Bmp4 was highly expressed in the non-odontogenic cell path but not in the odontogenic path, suggesting that BMP signaling inhibits the regenerative potential under FBS culture conditions.
The study also examined the roles of osteopontin (OPN) and all-trans retinoic acid (ATRA) in maintaining odontogenic potential. Supplementation with recombinant OPN or ATRA partially restored the tooth-forming capacity in suboptimal FBS cultures. Specifically, a tooth-like structure was detected in 1 out of 14 recombinants when OPN was added to FBS-cultured cells, and in 1 out of 12 when ATRA was added. qPCR analysis showed that OPN treatment significantly upregulated Dmp1 and Dlx2, while ATRA treatment led to marked increases in Dmp1, Dlx2, and Spp1 expression. These molecular changes confirm the activation of tooth development-related and mineralization-related pathways, highlighting the importance of balanced BMP4 activity and high OPN levels in maintaining DMC functionality.
The researchers noted that the N2B27 medium, originally designed for neural stem cells, may serendipitously provide a cocktail of factors that repress inhibitory signals like excessive BMP4 and activate promotive pathways like OPN and RA signaling. This effectively preserves a regenerative niche in vitro. The ability of N2B27-cultured mDMCs to induce tooth formation when combined with non-odontogenic epithelial components indicates that these cells retain the capacity to initiate and guide the epithelial-mesenchymal interactions crucial for tooth development. The study provides key insights into the features of a regenerative tooth germ and its odontogenic microenvironment, offering a foundation for future translational applications in tooth regeneration.
Despite these advances, the study acknowledges limitations in the current culture system. Even in N2B27 medium, mDMCs undergo progressive differentiation with passaging and exhibit a concomitant decline in odontogenic competence. This likely reflects the inability of conventional two-dimensional systems to recapitulate the signaling homeostasis and epithelial-mesenchymal crosstalk that stabilize embryonic dental mesenchyme. The researchers envision future strategies involving chemically defined media, biomimetic three-dimensional microenvironments, and the restoration of epithelial cues to further extend the durability of odontogenic capacity. Validating this culture system in human cells remains a critical next step for translating these findings into clinical applications.
This work represents a significant advance in the field of tooth regeneration by providing a reliable method to maintain the odontogenic potential of DMCs in vitro. By identifying the molecular mechanisms underlying this extended maintenance, the study opens new avenues for investigating tooth development and testing regenerative strategies. The findings highlight the potential of using optimized culture conditions to generate clinically relevant cell sources for bioengineered dental tissues, moving the field closer to the goal of whole-tooth regeneration.
The study utilized mouse dental mesenchymal cells isolated from E14.5 embryos, a stage corresponding to the post-bud phase of tooth development. The research team employed a combination of bulk RNA sequencing and single-cell RNA sequencing to profile the transcriptomic changes occurring in these cells under different culture conditions. A total of 69,867 cells passed quality control for the single-cell analysis, allowing for a high-resolution examination of cellular trajectories. The data revealed two distinct paths: an odontogenic path characterized by the activation of genes such as Dmp1, Spp1, and Traf2b, and a non-odontogenic path associated with the expression of Hcfc1r1 and Acta2. This divergence highlights the molecular shifts that occur as cells either retain or lose their capacity to form tooth structures, providing a detailed map of the cellular states involved in regenerative potential.
Functional validation of the culture system involved transplanting recombinants beneath the renal capsule of adult male ICR mice. Approximately eight recombinants were transplanted per kidney, and the animals were sacrificed after three weeks to harvest the kidneys and assess tissue formation. The resulting structures were analyzed using bright field imaging and hematoxylin–eosin staining to identify dental features. Most of the tooth-like structures generated from the N2B27-cultured cells contained typical dental components, including an enamel-secreting ameloblast layer, dentin, and dental pulp, often surrounded by bone. This in vivo confirmation demonstrates that the cells cultured in the optimized medium retain the ability to instruct non-dental epithelium to form hard tissues, a critical requirement for whole-tooth regeneration.
The statistical analysis of the sequencing data was performed using Python and R, with specific packages such as DESeq2 for bulk RNA-seq and Scanpy for single-cell data. Differential expression was assessed using a negative binomial distribution model for bulk data and the Wilcoxon rank sum test for single-cell data. Significance was defined by a false discovery rate of 0.05 for sequencing data and a p-value of less than 0.05 for quantitative PCR assays. The experiments were repeated at least three times to ensure robustness, although the study notes that animal experiments were not conducted in a blinded manner.
Subject of Research: In vitro maintenance of odontogenic potential in mouse dental mesenchymal cells using N2B27 medium
Article Title: Regenerative teeth induced by in vitro mesenchymal cells in mice via repressing BMP4 and activating retinoic acid/osteopontin
Article References: Chen, S., Zhao, Y., Chu, H., Mo, Q., Zhang, J., Chen, X., Zhang, Y., Li, X., Wu, D., Liu, P., Feng, B., Qin, D., Wang, Y., Pei, D., & Cai, J. (2025). Regenerative teeth induced by in vitro mesenchymal cells in mice via repressing BMP4 and activating retinoic acid/osteopontin. Cell Regeneration, 14(1), Article 51. https://doi.org/10.1186/s13619-025-00271-9
Image Credits: AI Generated
DOI: 10.1186/s13619-025-00271-9
Keywords: tooth regeneration, dental mesenchymal cells, N2B27 medium, BMP4 signaling, osteopontin, retinoic acid, tissue engineering, scRNA-seq, odontogenesis, cell culture, Regenerative, teeth
News Source: Gregory Coleman. (November 12, 2026). New Medium Keeps Mouse Tooth Cells Regenerative for 14 Days. Scienmag.
