BMP9-initiated osteogenic/odontogenic differentiation of mouse tooth germ mesenchymal cells (TGMCS) requires Wnt/β-catenin signalling activity

SIRT5 promotes the osteo-inductive potential of BMP9 by stabilizing the HIF-1α protein in mouse embryonic fibroblasts

Bone morphogenetic protein 9 (BMP9) exhibits remarkable osteogenic potential. However, the intricate mechanisms driving this function of BMP9 remain elusive. This study endeavors to investigate the potential role of sirtuin 5 (SIRT5) in enhancing BMP9's osteogenic capacity and decipher the underlying molecular pathways. To achieve this aim, we employed real-time PCR, western blotting, histochemical staining, and a cranial defect repair model to assess the impact of SIRT5 on BMP9-mediated osteogenesis. We utilized real-time PCR, western blotting, immunofluorescent staining, and immunoprecipitation assay to explore the associated mechanisms. Our results revealed that SIRT5 significantly up-regulated BMP9-induced osteogenic markers, while SIRT5 knockdown reduced their expression. Concurrently, hypoxia-inducible factor 1 subunit alpha (HIF-1α) level was increased by SIRT5, but reduced by SIRT5 knockdown. Notably, HIF-1α potentiated the SIRT5's ability to strengthen BMP9's osteogenic potential, whereas HIF-1α silencing reduced this effect, which was confirmed by bone defect repair assay. The acetylation and malonylation levels of HIF-1α were reduced by SIRT5, which may enhance its stability to promote BMP9's osteogenic effect. Conversely, SIRT5 knockdown reversed these effects and promoted the degradation of HIF-1α. Collectively, our results demonstrated that the BMP9's osteogenic potential could be promoted by SIRT5, potentially through stabilizing HIF-1α by reducing its acetylation and malonylation modification. This discovery may offer a novel strategy to accelerate bone tissue engineering by enhancing osteogenic differentiation, and it also sheds light on the possible mechanisms underlying BMP9-mediated osteogenic differentiation.

An Intervertebral Disc (IVD) Regeneration Model Using Human Nucleus Pulposus Cells (iHNPCs) and Annulus Fibrosus Cells (iHAFCs)

Intervertebral disc (IVD) degeneration (IVDD), primarily caused by nucleus pulposus (NP) dehydration, leads to low back pain. While current treatments focus on symptom management or surgical intervention, tissue engineering using IVD-derived cells, biofactors, and scaffolds offers a promising regenerative approach. Here, human NP cells (NPCs) and annulus fibrosus cells (AFCs) are immortalized with human telomerase reverse transcriptase (hTERT), generating immortalized NPCs (iHNPCs) and AFCs (iHAFCs). These cells express NP and AF-specific markers, are reversible via FLP recombinase, and are non-tumorigenic. iHAFCs exhibit osteogenic potential, while iHNPCs show chondrogenic differentiation. A 3D-printed citrate-based scaffold was employed to develop an IVD regeneration model, with BMP9-stimulated iHAFCs in the peripheral region and BMP2-stimulated iHNPCs in the central region. Histological analysis revealed bone formation in the iHAFC region and cartilage formation in the iHNPC region, mimicking the natural IVD structure. Additionally, an ex vivo spine fusion model demonstrated robust bone formation in iHAFC-treated segments. These findings highlight the potential of iHAFCs and iHNPCs as valuable tools for IVD tissue engineering and regeneration.

Establishment of immortalized rabbit bone marrow mesenchymal stem cells and a preliminary study of their osteogenic differentiation capability

BACKGROUND

A stable and standardized source of mesenchymal stem cells is a prerequisite for bone repair tissue engineering research and application. We aimed to establish a stable cell line of bone marrow mesenchymal stem cells from New Zealand rabbits and explore their osteogenic differentiation capacity.

METHODS

Primary rabbit bone marrow mesenchymal stem cells (RBMSCs) were isolated and immortalized via retroviral expression of SV40 Large T antigen (LTA). To assess the osteogenic differentiation capacity of the cells in vitro, we studied the alkaline phosphatase (ALP) expression level and calcium deposition in bone morphogenetic protein 9 (BMP9)-induced immortalized cells using ALP staining and quantification, as well as alizarin red staining. Ectopic bone formation by the cells was assessed using micro-computed tomography (μCT) and histological examination.

RESULTS

The immortalized cell line we established using SV40 LTA, which we termed iRBMSCs, was non-tumorigenic and maintained long-term proliferative activity. We further discovered that BMP9 (MOI = 30) effectively induced the osteogenic differentiation capacity of iRBMSCs in vitro, and there was a synergy with GelMA hydrogel in inducing osteogenic differentiation of the iRBMSCs in vivo.

CONCLUSION

We confirmed that iRBMSCs are promising as a stable cell line source for bone defect repair engineering.

Establishment and characterization of a rat model of scalp-cranial composite defect for multilayered tissue engineering

Composite cranial defects have individual functional and aesthetic ramifications, as well as societal burden, while posing significant challenges for reconstructive surgeons. Single-stage composite reconstruction of these deformities entail complex surgeries that bear many short- and long-term risks and complications. Current research on composite scalp-cranial defects is sparse and one-dimensional, often focusing solely on bone or skin. Thus, there is an unmet need for a simple, clinically relevant composite defect model in rodents, where there is a challenge in averting healing of the skin component via secondary intention. By utilizing a customizable (3D-printed) wound obturator, the scalp wound can be rendered non-healing for a long period (more than 6 weeks), with the cranial defect patent. The wound obturator shows minimal biotoxicity and will not cause severe endocranium-granulation adhesion. This composite defect model effectively slowed the scalp healing process and preserved the cranial defect, embodying the characteristics of a "chronic composite defect". In parallel, an autologous reconstruction model was established as the positive control. This positive control exhibited reproducible healing of the skin within 3 weeks with variable degrees of osseointegration, consistent with clinical practice. Both models provide a stable platform for subsequent research not only for composite tissue engineering and scaffold design but also for mechanistic studies of composite tissue healing.

Canonical and noncanonical Wnt signaling: Multilayered mediators, signaling mechanisms and major signaling crosstalk

Wnt signaling plays a major role in regulating cell proliferation and differentiation. The Wnt ligands are a family of 19 secreted glycoproteins that mediate their signaling effects via binding to Frizzled receptors and LRP5/6 coreceptors and transducing the signal either through β-catenin in the canonical pathway or through a series of other proteins in the noncanonical pathway. Many of the individual components of both canonical and noncanonical Wnt signaling have additional functions throughout the body, establishing the complex interplay between Wnt signaling and other signaling pathways. This crosstalk between Wnt signaling and other pathways gives Wnt signaling a vital role in many cellular and organ processes. Dysregulation of this system has been implicated in many diseases affecting a wide array of organ systems, including cancer and embryological defects, and can even cause embryonic lethality. The complexity of this system and its interacting proteins have made Wnt signaling a target for many therapeutic treatments. However, both stimulatory and inhibitory treatments come with potential risks that need to be addressed. This review synthesized much of the current knowledge on the Wnt signaling pathway, beginning with the history of Wnt signaling. It thoroughly described the different variants of Wnt signaling, including canonical, noncanonical Wnt/PCP, and the noncanonical Wnt/Ca2+ pathway. Further description involved each of its components and their involvement in other cellular processes. Finally, this review explained the various other pathways and processes that crosstalk with Wnt signaling.

Current Trends, Advances, and Challenges of Tissue Engineering-Based Approaches of Tooth Regeneration: A Review of the Literature

INTRODUCTION

Tooth loss is a significant health issue. Currently, this situation is often treated with the use of synthetic materials such as implants and prostheses. However, these treatment modalities do not fully meet patients' biological and mechanical needs and have limited longevity. Regenerative medicine focuses on the restoration of patients' natural tissues via tissue engineering techniques instead of rehabilitating with artificial appliances. Therefore, a tissue-engineered tooth regeneration strategy seems like a promising option to treat tooth loss.

OBJECTIVE

This review aims to demonstrate recent advances in tooth regeneration strategies and discoveries about underlying mechanisms and pathways of tooth formation.

RESULTS AND DISCUSSION

Whole tooth regeneration, tooth root formation, and dentin-pulp organoid generation have been achieved by using different seed cells and various materials for scaffold production. Bioactive agents are critical elements for the induction of cells into odontoblast or ameloblast lineage. Some substantial pathways enrolled in tooth development have been figured out, helping researchers design their experiments more effectively and aligned with the natural process of tooth formation.

CONCLUSION

According to current knowledge, tooth regeneration is possible in case of proper selection of stem cells, appropriate design and manufacturing of a biocompatible scaffold, and meticulous application of bioactive agents for odontogenic induction. Understanding innate odontogenesis pathways play a crucial role in accurately planning regenerative therapeutic interventions in order to reproduce teeth.

Immortalized cell lines derived from dental/odontogenic tissue

Stem cells derived from dental/odontogenic tissue have the property of multiple differentiation and are prospective in tooth regenerative medicine and cellular and molecular studies. However, in the face of cellular senescence soon in vitro, the proliferation ability of the cells is limited, so studies are hindered to some extent. Fortunately, immortalization strategies are expected to solve the above issues. Cellular immortalization is that cells are immortalized by introducing oncogenes, human telomerase reverse transcriptase genes (hTERT), or miscellaneous immortalization genes to get unlimited proliferation. At present, a variety of immortalized stem cells from dental/odontogenic tissue has been successfully generated, such as dental pulp stem cells (DPSCs), periodontal ligament cells (PDLs), stem cells from human exfoliated deciduous teeth (SHEDs), dental papilla cells (DPCs), and tooth germ mesenchymal cells (TGMCs). This review summarized establishment and applications of immortalized stem cells from dental/odontogenic tissues and then discussed the advantages and challenges of immortalization.

METTL3-Mediated lncSNHG7 m6A Modification in the Osteogenic/Odontogenic Differentiation of Human Dental Stem Cells

Background: Human dental pulp stem cells (hDPSCs) play an important role in endodontic regeneration. N6-methyladenosine (m⁶A) is the most common RNA modification, and noncoding RNAs have also been demonstrated to have regulatory roles in the expression of m⁶A regulatory proteins. However, the study on m⁶A modification in hDPSCs has not yet been conducted. Methods: Single base site PCR (MazF) was used to detect the m⁶A modification site of lncSNHG7 before and after mineralization of hDPSCs to screen the target m⁶A modification protein, and bioinformatics analysis was used to analyze the related pathways rich in lncSNHG7. After knockdown and overexpression of lncSNHG7 and METTL3, the osteogenic/odontogenic ability was detected. After METTL3 knockdown, the m⁶A modification level and its expression of lncSNHG7 were detected by MazF, and their binding was confirmed. Finally, the effects of lncSNHG7 and METTL3 on the Wnt/β-catenin pathway were detected. Results: MazF experiments revealed that lncSNHG7 had a m⁶A modification before and after mineralization of hDPSCs, and the occurrence site was 2081. METTL3 was most significantly upregulated after mineralization of hDPSCs. Knockdown/ overexpression of lncSNHG7 and METTL3 inhibited/promoted the osteogenic/odontogenic differentiation of hDPSCs. The m⁶A modification and expression of lncSNHG7 were both regulated by METTL3. Subsequently, lncSNHG7 and METTL3 were found to regulate the Wnt/β-catenin signaling pathway. Conclusion: These results revealed that METTL3 can activate the Wnt/β-catenin signaling pathway by regulating the m⁶A modification and expression of lncSNHG7 in hDPSCs to enhance the osteogenic/odontogenic differentiation of hDPSCs. Our study provides new insight into stem cell-based tissue engineering.

Modeling lung diseases using reversibly immortalized mouse pulmonary alveolar type 2 cells (imPAC2)

BACKGROUND

A healthy alveolar epithelium is critical to the gas exchange function of the lungs. As the major cell type of alveolar epithelium, alveolar type 2 (AT2) cells play a critical role in maintaining pulmonary homeostasis by serving as alveolar progenitors during lung injury, inflammation, and repair. Dysregulation of AT2 cells may lead to the development of acute and chronic lung diseases and cancer. The lack of clinically relevant AT2 cell models hampers our ability to understand pulmonary diseases. Here, we sought to establish reversibly immortalized mouse pulmonary alveolar type 2 cells (imPAC2) and investigate their potential in forming alveolar organoids to model pulmonary diseases.

METHODS

Primary mouse pulmonary alveolar cells (mPACs) were isolated and immortalized with a retroviral expression of SV40 Large T antigen (LTA). Cell proliferation and survival was assessed by crystal violet staining and WST-1 assays. Marker gene expression was assessed by qPCR, Western blotting, and/or immunostaining. Alveolar organoids were generated by using matrigel. Ad-TGF-β1 was used to transiently express TGF-β1. Stable silencing β-catenin or overexpression of mutant KRAS and TP53 was accomplished by using retroviral vectors. Subcutaneous cell implantations were carried out in athymic nude mice. The retrieved tissue masses were subjected to H & E histologic evaluation.

RESULTS

We immortalized primary mPACs with SV40 LTA to yield the imPACs that were non-tumorigenic and maintained long-term proliferative activity that was reversible by FLP-mediated removal of SV40 LTA. The EpCAM+ AT2-enriched subpopulation (i.e., imPAC2) was sorted out from the imPACs, and was shown to express AT2 markers and form alveolar organoids. Functionally, silencing β-catenin decreased the expression of AT2 markers in imPAC2 cells, while TGF-β1 induced fibrosis-like response by regulating the expression of epithelial-mesenchymal transition markers in the imPAC2 cells. Lastly, concurrent expression of oncogenic KRAS and mutant TP53 rendered the imPAC2 cells a tumor-like phenotype and activated lung cancer-associated pathways. Collectively, our results suggest that the imPAC2 cells may faithfully represent AT2 populations that can be further explored to model pulmonary diseases.

Carboxymethyl chitosan prolongs adenovirus-mediated expression of IL-10 and ameliorates hepatic fibrosis in a mouse model

Effective and safe liver-directed gene therapy has great promise in treating a broad range of liver diseases. While adenoviral (Ad) vectors have been widely used for efficacious in vivo gene delivery, their translational utilities are severely limited due to the short duration of transgene expression and solicitation of host immune response. Used as a promising polymeric vehicle for drug release and nucleic acid delivery, carboxymethyl chitosan (CMC) is biocompatible, biodegradable, anti-microbial, inexpensive, and easy accessible. Here, by exploiting its biocompatibility, controlled release capability and anti-inflammatory activity, we investigated whether CMC can overcome the shortcomings of Ad-mediated gene delivery, hence improving the prospect of Ad applications in gene therapy. We demonstrated that in the presence of optimal concentrations of CMC, Ad-mediated transgene expression lasted up to 50 days after subcutaneous injection, and at least 7 days after intrahepatic injection. Histologic evaluation and immunohistochemical analysis revealed that CMC effectively alleviated Ad-induced host immune response. In our proof-of-principle experiment using the CCl4-induced experimental mouse model of chronic liver damage, we demonstrated that repeated intrahepatic administrations of Ad-IL10 mixed with CMC effectively mitigated the development of hepatic fibrosis. Collectively, these results indicate that CMC can improve the prospect of Ad-mediated gene therapy by diminishing the host immune response while allowing readministration and sustained transgene expression.

Downregulation of DNA methyltransferase-3a ameliorates the osteogenic differentiation ability of adipose-derived stem cells in diabetic osteoporosis via Wnt/β-catenin signaling pathway

Background

Diabetes-related osteoporosis (DOP) is a chronic disease caused by the high glucose environment that induces a metabolic disorder of osteocytes and osteoblast-associated mesenchymal stem cells. The processes of bone defect repair and regeneration become extremely difficult with DOP. Adipose-derived stem cells (ASCs), as seed cells in bone tissue engineering technology, provide a promising therapeutic approach for bone regeneration in DOP patients. The osteogenic ability of ASCs is lower in a DOP model than that of control ASCs. DNA methylation, as a mechanism of epigenetic regulation, may be involved in DNA methylation of various genes, thereby participating in biological behaviors of various cells. Emerging evidence suggests that increased DNA methylation levels are associated with activation of Wnt/β-catenin signaling pathway. The purpose of this study was to investigate the influence of the diabetic environment on the osteogenic potential of ASCs, to explore the role of DNA methylation on osteogenic differentiation of DOP-ASCs via Wnt/β-catenin signaling pathway, and to improve the osteogenic differentiation ability of ASCs with DOP.

Methods

DOP-ASCs and control ASCs were isolated from DOP C57BL/6 and control mice, respectively. The multipotency of DOP-ASCs was confirmed by Alizarin Red-S, Oil Red-O, and Alcian blue staining. Real-time polymerase chain reaction (RT-PCR), immunofluorescence, and western blotting were used to analyze changes in markers of osteogenic differentiation, DNA methylation, and Wnt/β-catenin signaling. Alizarin Red-S staining was also used to confirm changes in the osteogenic ability. DNMT small interfering RNA (siRNA), shRNA-Dnmt3a, and LVRNA-Dnmt3a were used to assess the role of Dnmt3a in osteogenic differentiation of control ASCs and DOP-ASCs. Micro-computed tomography, hematoxylin and eosin staining, and Masson staining were used to analyze changes in the osteogenic capability while downregulating Dnmt3a with lentivirus in DOP mice in vivo.

Results

The proliferative ability of DOP-ASCs was lower than that of control ASCs. DOP-ASCs showed a decrease in osteogenic differentiation capacity, lower Wnt/β-catenin signaling pathway activity, and a higher level of Dnmt3a than control ASCs. When Dnmt3a was downregulated by siRNA and shRNA, osteogenic-related factors Runt-related transcription factor 2 and osteopontin, and activity of Wnt/β-catenin signaling pathway were increased, which rescued the poor osteogenic potential of DOP-ASCs. When Dnmt3a was upregulated by LVRNA-Dnmt3a, the osteogenic ability was inhibited. The same results were obtained in vivo.

Conclusions

Dnmt3a silencing rescues the negative effects of DOP on ASCs and provides a possible approach for bone tissue regeneration in patients with diabetic osteoporosis.

Reversely immortalized mouse salivary gland cells presented a promising metabolic and fibrotic response upon BMP9/Gdf2 stimulation

The submandibular gland (SMG) and the sublingual gland (SLG) are two of the three major salivary glands in mammals. In mice, they are adjacent to each other and open into the oral cavity, producing saliva to lubricate the mouth and aid in food digestion. Though salivary gland dysfunction accompanied with fibrosis and metabolic disturbance is common in clinic, in-depth mechanistic research is lacking. Currently, research on how to rescue salivary function is challenging, as it must resort to using terminally differentiated acinar cells or precursor acinar cells with unknown differentiation. In this study, we established reversely immortalized mouse primary SMG cells (iSMGCs) and SLG cells (iSLGCs) on the first postnatal day (P0). The iSMGCs and iSLGCs grew well, exhibited many salivary gland characteristics, and retained the metabolism-related genes derived from the original tissue as demonstrated using transcriptome sequencing (RNA-seq) analysis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of these two cell lines, which overlapped with those of the SMG and SLG, were enriched in cysteine and methionine metabolism. Furthermore, we investigated the role of bone morphogenetic protein 9 (BMP9), also known as growth differentiation factor 2(Gdf2), on metabolic and fibrotic functions in the SMG and SLG. We demonstrated that iSMGCs and iSLGCs presented promising adipogenic and fibrotic responses upon BMP9/Gdf2 stimulation. Thus, our findings indicate that iSMGCs and iSLGCs faithfully reproduce characteristics of SMG and SLG cells and present a promising prospect for use in future study of salivary gland metabolism and fibrosis upon BMP9/Gdf2 stimulation.

Reversibly immortalized keratinocytes (iKera) facilitate re-epithelization and skin wound healing: Potential applications in cell-based skin tissue engineering

Skin injury is repaired through a multi-phase wound healing process of tissue granulation and re-epithelialization. Any failure in the healing process may lead to chronic non-healing wounds or abnormal scar formation. Although significant progress has been made in developing novel scaffolds and/or cell-based therapeutic strategies to promote wound healing, effective management of large chronic skin wounds remains a clinical challenge. Keratinocytes are critical to re-epithelialization and wound healing. Here, we investigated whether exogenous keratinocytes, in combination with a citrate-based scaffold, enhanced skin wound healing. We first established reversibly immortalized mouse keratinocytes (iKera), and confirmed that the iKera cells expressed keratinocyte markers, and were responsive to UVB treatment, and were non-tumorigenic. In a proof-of-principle experiment, we demonstrated that iKera cells embedded in citrate-based scaffold PPCN provided more effective re-epithelialization and cutaneous wound healing than that of either PPCN or iKera cells alone, in a mouse skin wound model. Thus, these results demonstrate that iKera cells may serve as a valuable skin epithelial source when, combining with appropriate biocompatible scaffolds, to investigate cutaneous wound healing and skin regeneration.

A one-step construction of adenovirus (OSCA) system using the Gibson DNA Assembly technology

Adenovirus (Ad) is a non-enveloped linear double-stranded DNA virus with >50 serotypes in humans. Ad vectors have been used as gene delivery vehicles to express transgenes, small interfering RNAs (siRNAs) for gene silencing, or CRISPR/Cas and designer nucleases for genome editing. Although several methods are used to generate Ad vectors, the Ad-making process remains technically challenging and time consuming. Moreover, the Ad-making techniques have not been improved for the past two decades. Gibson DNA Assembly (GDA) technology allows one-step isothermal DNA assembly of multiple overlapping fragments. Here, we developed a one-step construction of Ad (OSCA) system using GDA technology. Specifically, we first engineered several adenoviral recipient vectors that contain the ccdB suicide gene flanked with two 20-bp unique sequences, which serve as universal sites for GDA reactions in the Ad genome ΔE1 region. In two proof-of-principle experiments, we demonstrated that the GDA reactions were highly efficient and that the resulting Ad plasmids could be effectively packaged into Ads. Ad-mediated expression of mouse BMP9 in mesenchymal stem cells was shown to effectively induce osteogenic differentiation both in vitro and in vivo. Collectively, our results demonstrate that the OSCA system drastically streamlines the Ad-making process and should facilitate Ad-based applications in basic, translational, and clinical research.

A functional autophagy pathway is essential for BMP9-induced osteogenic differentiation of mesenchymal stem cells (MSCs)

Mesenchymal stem cells (MSCs) are capable of differentiating into bone, cartilage and adipose tissues. We identified BMP9 as the most potent osteoinductive BMP although detailed mechanism underlying BMP9-regulated osteogenesis of MSCs is indeterminate. Emerging evidence indicates that autophagy plays a critical role in regulating bone homeostasis. We investigated the possible role of autophagy in osteogenic differentiation induced by BMP9. We showed that BMP9 upregulated the expression of multiple autophagy-related genes in MSCs. Autophagy inhibitor chloroquine (CQ) inhibited the osteogenic activity induced by BMP9 in MSCs. While overexpression of ATG5 or ATG7 did not enhance osteogenic activity induced by BMP9, silencing Atg5 expression in MSCs effectively diminished BMP9 osteogenic signaling activity and blocked the expression of the osteogenic regulator Runx2 and the late marker osteopontin induced by BMP9. Stem cell implantation study revealed that silencing Atg5 in MSCs profoundly inhibited ectopic bone regeneration and bone matrix mineralization induced by BMP9. Collectively, our results strongly suggest a functional autophagy pathway may play an essential role in regulating osteogenic differentiation induced by BMP9 in MSCs. Thus, restoration of dysregulated autophagic activity in MSCs may be exploited to treat fracture healing, bone defects or osteoporosis.

BMP9-initiated osteogenic/odontogenic differentiation of mouse tooth germ mesenchymal cells (TGMCS) requires Wnt/β-catenin signalling activity

Teeth arise from the tooth germ through sequential and reciprocal interactions between immature epithelium and mesenchyme during development. However, the detailed mechanism underlying tooth development from tooth germ mesenchymal cells (TGMCs) remains to be fully understood. Here, we investigate the role of Wnt/β‐catenin signalling in BMP9‐induced osteogenic/odontogenic differentiation of TGMCs. We first established the reversibly immortalized TGMCs (iTGMCs) derived from young mouse mandibular molar tooth germs using a retroviral vector expressing SV40 T antigen flanked with the FRT sites. We demonstrated that BMP9 effectively induced expression of osteogenic markers alkaline phosphatase, collagen A1 and osteocalcin in iTGMCs, as well as in vitro matrix mineralization, which could be remarkably blunted by knocking down β‐catenin expression. In vivo implantation assay revealed that while BMP9‐stimulated iTGMCs induced robust formation of ectopic bone, knocking down β‐catenin expression in iTGMCs remarkably diminished BMP9‐initiated osteogenic/odontogenic differentiation potential of these cells. Taken together, these discoveries strongly demonstrate that reversibly immortalized iTGMCs retained osteogenic/odontogenic ability upon BMP9 stimulation, but this process required the participation of canonical Wnt signalling both in vitro and in vivo. Therefore, BMP9 has a potential to be applied as an efficacious bio‐factor in osteo/odontogenic regeneration and tooth engineering. Furthermore, the iTGMCs may serve as an important resource for translational studies in tooth tissue engineering.