CA1 Modulates the Osteogenic Differentiation of Dental Follicle Stem Cells by Activating the BMP Signaling Pathway In Vitro

BACKGROUND

Carbonic anhydrase 1 (CA1) has been found to be involved in osteogenesis and osteoclast in various human diseases, but the molecular mechanisms are not completely understood. In this study, we aim to use siRNA and lentivirus to reduce or increase the expression of CA1 in Dental follicle stem cells (DFSCs), in order to further elucidate the role and mechanism of CA1 in osteogenesis, and provide better osteogenic growth factors and stem cell selection for the application of bone tissue engineering in alveolar bone fracture transplantation.

METHODS

The study used RNA interference and lentiviral vectors to manipulate the expression of the CA1 gene in DFSCs during in vitro osteogenic induction. The expression of osteogenic marker genes was evaluated and changes in CA1, alkaline phosphatase (ALP), Runt-related transcription factor 2 (RUNX2), and Bone morphogenetic proteins (BMP2) were measured using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting (WB). The osteogenic effect was assessed through Alizarin Red staining.

RESULTS

The mRNA and protein expression levels of CA1, ALP, RUNX2, and BMP2 decreased distinctly in the si-CA1 group than other groups (p < 0.05). In the Lentivirus-CA1 (LV-CA1) group, the mRNA and protein expressions of CA1, ALP, RUNX2, and BMP2 were amplified to varying degrees than other groups (p < 0.05). Apart from CA1, BMP2 (43.01%) and ALP (36.69%) showed significant upregulation (p < 0.05). Alizarin red staining indicated that the LV-CA1 group produced more calcified nodules than other groups, with a higher optical density (p < 0.05), and the osteogenic effect was superior.

CONCLUSIONS

CA1 can impact osteogenic differentiation via BMP related signaling pathways, positioning itself upstream in osteogenic signaling pathways, and closely linked to osteoblast calcification and ossification processes.

Periostin plays a key role in maintaining the osteogenic abilities of dental follicle stem cells in the inflammatory microenvironment

OBJECTIVE

This study aimed to explore the effect of periostin in the osteogenic abilities of dental follicle stem cells (DFSCs) and DFSC sheets in the inflammatory microenvironment.

DESIGN

DFSCs were isolated from dental follicles and identified. A lentiviral vector was used to knock down periostin in DFSCs. 250 ng/ml lipopolysaccharide from Porphyromonas gingivalis (P.g-LPS) was used to construct the inflammatory microenvironment. Osteogenic differentiation was evaluated by alizarin red staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot. The formation of extracellular matrix was assessed by qRT-PCR and immunofluorescence. The expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) were measured by western blot.

RESULTS

Knockdown of periostin inhibited osteogenic differentiation and promoted adipogenic differentiation of DFSCs. In an inflammatory microenvironment, knockdown of periostin attenuated the proliferation and osteogenic differentiation of DFSCs. Knockdown of periostin inhibited the formation of extracellular matrix collagen I (COL-I), fibronectin, and laminin in DFSC sheets, but did not affect the expression of osteogenesis-related markers alkaline phosphatase (ALP) and osteocalcin (OCN). In the inflammatory microenvironment, knocking down periostin inhibited the expression of OCN and OPG in DFSC sheets, and promoted the expression of RANKL.

CONCLUSION

Periostin played a key role in maintaining the osteogenic abilities of DFSCs and DFSC sheets in the inflammatory microenvironment and might be an important molecule in the process of DFSCs coping with inflammatory microenvironment and promoting periodontal tissues regeneration.

Clinical application prospects and transformation value of dental follicle stem cells in oral and neurological diseases

Since dental pulp stem cells (DPSCs) were first reported, six types of dental SCs (DSCs) have been isolated and identified. DSCs originating from the craniofacial neural crest exhibit dental-like tissue differentiation potential and neuro-ectodermal features. As a member of DSCs, dental follicle SCs (DFSCs) are the only cell type obtained at the early developing stage of the tooth prior to eruption. Dental follicle tissue has the distinct advantage of large tissue volume compared with other dental tissues, which is a prerequisite for obtaining a sufficient number of cells to meet the needs of clinical applications. Furthermore, DFSCs exhibit a significantly higher cell proliferation rate, higher colony-formation capacity, and more primitive and better anti-inflammatory effects than other DSCs. In this respect, DFSCs have the potential to be of great clinical significance and translational value in oral and neurological diseases, with natural advantages based on their origin. Lastly, cryopreservation preserves the biological properties of DFSCs and enables them to be used as off-shelf products for clinical applications. This review summarizes and comments on the properties, application potential, and clinical transformation value of DFSCs, thereby inspiring novel perspectives in the future treatment of oral and neurological diseases.

N-acetylcysteine regulates dental follicle stem cell osteogenesis and alveolar bone repair via ROS scavenging

Background

Dental follicle stem cells (DFSCs) show mesenchymal stem cell properties with the potential for alveolar bone regeneration. Stem cell properties can be impaired by reactive oxygen species (ROS), prompting us to examine the importance of scavenging ROS for stem cell-based tissue regeneration. This study aimed to investigate the effect and mechanism of N-acetylcysteine (NAC), a promising antioxidant, on the properties of DFSCs and DFSC-based alveolar bone regeneration.

Methods

DFSCs were cultured in media supplemented with different concentrations of NAC (0–10 mM). Cytologic experiments, RNA-sequencing and antioxidant assays were performed in vitro in human DFSCs (hDFSCs). Rat maxillary first molar extraction models were constructed, histological and radiological examinations were performed at day 7 post-surgery to investigate alveolar bone regeneration in tooth extraction sockets after local transplantation of NAC, rat DFSCs (rDFSCs) or NAC-treated rDFSCs.

Results

5 mM NAC-treated hDFSCs exhibited better proliferation, less senescent rate, higher stem cell-specific marker and immune-related factor expression with the strongest osteogenic differentiation; other concentrations were also beneficial for maintaining stem cell properties. RNA-sequencing identified 803 differentially expressed genes between hDFSCs with and without 5 mM NAC. “Developmental process (GO:0032502)” was prominent, bioinformatic analysis of 394 involved genes revealed functional and pathway enrichment of ossification and PI3K/AKT pathway, respectively. Furthermore, after NAC treatment, the reduction of ROS levels (ROS, superoxide, hydrogen peroxide), the induction of antioxidant levels (glutathione, catalase, superoxide dismutase), the upregulation of PI3K/AKT signaling (PI3K-p110, PI3K-p85, AKT, phosphorylated-PI3K-p85, phosphorylated-AKT) and the rebound of ROS level upon PI3K/AKT inhibition were showed. Local transplantation of NAC, rDFSCs or NAC-treated rDFSCs was safe and promoted oral socket bone formation after tooth extraction, with application of NAC-treated rDFSCs possessing the best effect.

Conclusions

The proper concentration of NAC enhances DFSC properties, especially osteogenesis, via PI3K/AKT/ROS signaling, and offers clinical potential for stem cell-based alveolar bone regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03161-y.

Small extracellular vesicles from dental follicle stem cells provide biochemical cues for periodontal tissue regeneration

Background

Treatments based on stem cell-derived small extracellular vesicles (sEVs) have been explored as an alternative to stem cell transplantation-based therapies in periodontal regeneration. Dental follicle stem cells (DFSCs) have shown great potential for regenerative medicine applications. However, it is unclear whether sEVs derived from DFSCs (DFSCs-sEVs) could be used in periodontal regeneration. This study investigates whether DFSCs-sEVs could regenerate damaged periodontal tissue and the potential underlying mechanism.

Methods

DFSCs-sEVs were isolated and identified, and periodontal ligament stem cells (PDLSCs) were cocultured with the isolated sEVs. The effect of DFSCs-sEVs on the biological behaviour of PDLSCs was examined using EdU assay, CCK-8 assay, cell cycle analysis, wound healing, alizarin red staining, qRT-PCR, and western blot analysis. RNA sequencing and functional enrichment analysis were used to detect the signal pathway involved in the effect of DFSCs-sEVs on PDLSCs. PDLSCs were pretreated with ERK1/2 or p38 MAPK inhibitors to investigate the possible involvement of the ERK1/2 and p38 MAPK pathways. Additionally, DFSCs-sEVs were combined with collagen sponges and transplanted into the periodontal defects in SD rats, and then, pathological changes in periodontal tissue were examined using haematoxylin and eosin (HE) staining and micro-CT.

Results

PDLSCs could internalize DFSCs-sEVs, thereby enhancing the proliferation assessed using EdU assay, CCK-8 assay and cell cycle analysis. DFSCs-sEVs significantly enhanced the migration of PDLSCs. DFSCs-sEVs promoted osteogenic differentiation of PDLSCs, showing deep Alizarin red staining, upregulated osteogenic genes (RUNX2, BSP, COL1), and upregulated protein expression (RUNX2, BSP, COL1, ALP). We found that p38 MAPK signalling was activated via phosphorylation. Inhibition of this signalling pathway with a specific inhibitor (SB202190) partially weakened the enhanced proliferation. After DFSCs-sEVs transplantation, new periodontal ligament-like structures and bone formation were observed in the damaged periodontal area in rats. Labelled DFSCs-sEVs were observed in the newly formed periodontal ligament and soft tissue of the defect area.

Conclusions

Our study demonstrated that DFSCs-sEVs promoted periodontal tissue regeneration by promoting the proliferation, migration, and osteogenic differentiation of PDLSCs. The effect of DFSCs-sEVs in promoting PDLSCs proliferation may be partially attributed to the activation of p38 MAPK signalling pathway. DFSCs-sEVs provide us with a novel strategy for periodontal regeneration in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02767-6.

Antidiuretic hormone inhibits osteogenic differentiation of dental follicle stem cells via V1a receptors and the PLC-IP3 pathway

OBJECTIVE

The aim of this study was to elucidate the molecular mechanism by which antidiuretic hormone (ADH) inhibited osteogenesis in dental follicle stem cells.

DESIGN

Rat dental follicle stem cells were cultured in osteogenic differentiation medium supplemented with ADH. Alkaline phosphatase enzyme activity, Alizarin Red S staining, MTT assay and RT-qPCR was used to examine ADH's impact on cell mineralization, viability, and osteogenic gene expression. Real-time calcium imaging analysis was performed to identify the ADH receptor and its mechanism of action.

RESULTS

ADH supplementation to the osteogenic differentiation medium inhibited cell mineralization without compromising cell viability and downregulated the expression of key osteogenic genes: DCN (Decorin), RUNX2 (Runt-related transcription factor 2) and BSP (Bone sialoprotein). Real-time calcium imaging analysis revealed that ADH (1-1000 nM) increased intracellular calcium in a concentration-dependent manner. Pretreatment of cells with V2255, a V1a receptor blocker, inhibited the calcium signals, but not with the V1b (Nelivaptan) or V2 (Tolvaptan). V2255 also reversed the inhibitory effect of ADH on osteogenesis. Furthermore, U73122, a Phospholipase C (PLC) inhibitor, 2-APB, an Inositol Triphosphate (IP₃) receptor blocker, and depletion of endoplasmic reticulum calcium stores abolished the calcium signals by ADH.

CONCLUSIONS

Our results demonstrated that ADH activates V1a receptors and the PLC-IP₃ pathway to stimulate intracellular calcium signals, which inhibits cell mineralization and osteogenic gene expression. These findings uncovered a novel function for ADH as a negative regulator of osteogenesis in dental follicle stem cells. The role of ADH in the pathogenesis of bone diseases remains to be determined.

Proteomic profiling of various human dental stem cells - a systematic review

BACKGROUND

The proteomic signature or profile best describes the functional component of a cell during its routine metabolic and survival activities. Additional complexity in differentiation and maturation is observed in stem/progenitor cells. The role of functional proteins at the cellular level has long been attributed to anatomical niches, and stem cells do not deflect from this attribution. Human dental stem cells (hDSCs), on the whole, are a combination of mesenchymal and epithelial coordinates observed throughout craniofacial bones to pulp.

AIM

To specify the proteomic profile and compare each type of hDSC with other mesenchymal stem cells (MSCs) of various niches. Furthermore, we analyzed the characteristics of the microenvironment and preconditioning changes associated with the proteomic profile of hDSCs and their influence on committed lineage differentiation.

METHODS

Literature searches were performed in PubMed, EMBASE, Scopus, and Web of Science databases, from January 1990 to December 2018. An extra inquiry of the grey literature was completed on Google Scholar, ProQuest, and OpenGrey. Relevant MeSH terms (PubMed) and keywords related to dental stem cells were used independently and in combination.

RESULTS

The initial search resulted in 134 articles. Of the 134 full-texts assessed, 96 articles were excluded and 38 articles that met the eligibility criteria were reviewed. The overall assessment of hDSCs and other MSCs suggests that differences in the proteomic profile can be due to stem cellular complexity acquired from varied tissue sources during embryonic development. However, our comparison of the proteomic profile suffered inconsistencies due to the heterogeneity of various hDSCs. We believe that the existence of a heterogeneous population of stem cells at a given niche determines the modalities of regeneration or tissue repair. Added prominences to the differences present between various hDSCs have been reasoned out.

CONCLUSION

Systematic review on proteomic studies of various hDSCs are promising as an eye-opener for revisiting the proteomic profile and in-depth analysis to elucidate more refined mechanisms of hDSC functionalities.

Dental follicle stem cells rescue the regenerative capacity of inflamed rat dental pulp through a paracrine pathway

Background

Pulpitis is a common dental disease characterized by sustained inflammation and impaired pulp self-repair. Mesenchymal stem cell-based minimally invasive vital pulp therapy (MSC-miVPT) is a potential treatment method, but its application is limited by the difficulty in acquiring MSCs. We recently revealed the immunomodulatory effects of rat dental follicle stem cells (rDFSCs) on acute lung injury. The present study focused on the paracrine effects of rDFSCs on the inflammation and regeneration of rat injured dental pulp to detect whether DFSCs are a potential candidate for MSC-miVPT.

Methods

Conditioned medium from rDFSCs (rDFSC-CM) was applied to lipopolysaccharide (LPS)-induced inflammatory rat dental pulp cells (rDPCs). The inflammation and regeneration of rDPCs were detected by RT-qPCR, Western blotting, immunofluorescence staining, Cell Counting Kit-8 (CCK-8) assay, flow cytometry, wound-healing assay, and Masson’s staining. The effects of rDFSC-CM on inflamed rat dental pulp were further evaluated by hematoxylin-eosin and immunohistochemical staining.

Results

rDFSC-CM downregulated the ERK1/2 and NF-κB signaling pathways, which resulted in suppression of the expression of IL-1β, IL-6, and TNF-α and promotion of the expression of IL-4 and TGF-β, and these findings lead to the attenuation of rDPC inflammation. rDFSC-CM enhanced the in vitro proliferation, migration, and odontogenic differentiation of inflammatory rDPCs and their in vivo ectopic dentinogenesis. Furthermore, rDFSC-CM inhibited inflammatory cell infiltration in rat pulpitis and triggered Runx2 expression in some of the odontoblast-like cells surrounding the injured site, and these effects were conducive to the repair of inflamed dental pulp.

Conclusions

rDFSC-CM exhibits therapeutic potential by rescuing the regeneration of the inflamed rat dental pulp through an immunomodulatory mechanism, indicating the application prospects of DFSCs in biological regenerative endodontics.

Three-Dimensional Spheroid Formation of Cryopreserved Human Dental Follicle-Derived Stem Cells Enhances Pluripotency and Osteogenic Induction Properties

Background

Enhancement and maintenance of the stemness of mesenchymal stem cells (MSCs) is one of the most important factors contributing to the successful in vivo therapeutic application of these cells. In this regard, three-dimensional (3D) spheroid formation has been developed as reliable method for increasing the pluripotency of MSCs. Moreover, using a new protocol, we have previously shown that dental tissues of extracted wisdom teeth can be effectively cryopreserved for subsequent use as a source of autologous stem cells. The main purpose of this study is to analyze the stemness and in vitro osteogenic differentiation potential of 3D spheroid dental MSCs compared with conventional mono-layer cultured MSCs.

Methods

In this study, MSC-characterized stem cells were isolated and cultured from long-term cryopreserved dental follicles (hDFSCs), and then 2D hDFSCs were cultured under 3D spheroid-forming conditions using a newly designed microchip dish. The spheroids (3D hDFSCs) thus produced were investigated and characterized with respect to stemness, MSC marker expression, apoptosis, cell cycle analysis, extracellular matrix (ECM) production, and osteogenic and adipogenic differentiation properties.

Results

In terms of MSC and senescence markers, spheroid cells showed no difference when compared with 2D hDFSCs; however, 3D hDFSCs were observed to have a higher proportion of cell cycle arrest and a larger number of apoptotic cells. Moreover, spheroids showed substantially increased levels of pluripotency marker (early transcription factors) and ECM protein expression. Compared with 2D hDFSCs, there was also a notable enhancement in the osteogenic induction potential of spheroids, although no differences were observed with respect to in vitro adipogenesis.

Conclusion

To the best of our knowledge, this is the first study to demonstrate the application of a spheroid culture system for dental follicle-derived stem cells using a microchip dish. Although further studies are needed, including in vivo transplantation, the results obtained in this study indicate that spheroid hDFSCs derived from cryopreserved dental follicle tissues could be used as a valuable source of autologous stem cells for bone tissue regeneration.

Dental Follicle Stem Cells Ameliorate Lipopolysaccharide-Induced Inflammation by Secreting TGF-β3 and TSP-1 to Elicit Macrophage M2 Polarization

BACKGROUND/AIMS

Increasing evidence has demonstrated the novel roles of mesenchymal stem cells (MSCs) in immunotherapy. However, difficulty in acquiring these cells and possible ethical issues limited their application. Recently, we have isolated a unique MSC population from dental follicles with potent stem cell-like properties. This study focused on the effects of dental follicle stem cells (DFSCs) on macrophage activation and polarization to determine their role in immunomodulation and to test if DFSCs are a promising cell source for MSC-based immunotherapy.

METHODS

Rat acute lung injury (ALI) models induced by Lipopolysaccharide (LPS) were applied to test the immune-modulatory effects of DFSC/DFSC-CM in vivo. The pulmonary permeability was determined by the dry / wet weight ratios of the left upper lung lobe. The lung histopathological damage was graded on a 0 to 4+ scale. And the inflammatory cytokines in bronchoalveolar lavage fluid (BALF) were tested by ELISA. Then we established LPS-induced inflamed macrophage models in vitro. Inflammatory cytokine production and polarization marker expression were measured by RT-qPCR, ELISA, western blot and flow cytometric analysis in macrophages following DFSC-CM treatment. The paracrine factors in DFSC-CM were revealed by a RayBiotech Protein Array. Thereafter, neutralization studies were performed to confirm the potential immune regulators in DFSC-CM.

RESULTS

The DFSC/DFSC-CM not only attenuated histopathological damage and pulmonary permeability, but also downregulated pro-inflammatory cytokines MCP-1, IL-1, IL-6 and TNF-α, and upregulated anti-inflammatory cytokine IL-10 in BALF. Immunofluorescence staining revealed the increased expression of macrophage M2 marker Arg-1. Further in vitro study revealed that macrophages switched to an anti-inflammatory M2 phenotype when co-cultured with DFSC-CM, characterized by suppressed production of pro-inflammatory cytokines MCP-1, IL-1, IL-6, TNF-α and M1-polarizing markers iNOS and CD86; and increased expression of the anti-inflammatory cytokine IL-10 and the M2-polarizing markers Arg-1 and CD163. A RayBiotech Protein Array revealed 42 differentially expressed (> 2-fold) paracrine factors in DFSC-CM compared with the serum-free Ham's F-12K medium, among which TGF-β3 and Thrombospondin-1 (TSP-1) were upregulated by 18- and 105-fold, respectively. Neutralization studies confirmed the immunoregulatory roles of TGF-β3 and TSP-1 in macrophage activation and polarization.

CONCLUSION

These results indicated that DFSCs can reprogram macrophages into the anti-inflammatory M2 phenotype, the paracrine factors TGF-β3 and TSP-1 may be one of the underlying mechanisms. This study supports the hypothesis that DFSCs are promising for MSC-based immunotherapy.

The role of dentin matrix protein 1 (DMP1) in regulation of osteogenic differentiation of rat dental follicle stem cells (DFSCs)

OBJECTIVES

Primary isolated dental follicle stem cells (DFSCs) possess a strong osteogenesis capability, and such capability is reduced during in vitro culture. Because dentin matrix protein 1 (DMP1) is essential in the maturation of osteoblasts, our objectives were to determine (1) the expression of DMP1 in the DFSCs, (2) the correlation between DMP1 expression and osteogenic capability of DFSCs, and (3) the ability of DMP1 to promote osteogenic differentiation of DFSCs.

METHODS

DFSCs and their non-stem cell counterpart dental follicle cells (DFC) were established from postnatal rat pups. Expression of DMP1 in the DFSCs and DFC was determined using real-time RT-PCR and western blotting. Different passages of DFSCs were subjected to osteogenic induction. The correlation between osteogenesis and DMP1 expression was analyzed. Then, expression of DMP1 in the DFSCs was knocked-down using siRNA, followed by osteogenic induction to evaluate the effect of DMP1-knockdown. Finally, the late passage DFSCs with reduced DMP1 expression and osteogenic capability were cultured in osteogenic induction medium containing mouse recombinant DMP1 (mrDMP1) to determine if DMP1 can restore osteogenesis of DFSCs.

RESULTS

DFSCs expressed much higher levels of DMP1 than did DFC. DMP1 expression was correlated with the osteogenic capability of DFSCs. Knockdown of DMP1 expression markedly decreased the osteogenesis and osteogenic gene expression in the DFSCs whereas adding mrDMP1 protein to the osteogenic induction medium enhanced osteogenesis.

CONCLUSIONS

DMP1 is highly expressed in the DFSCs, but minimally expressed in non-stem cell DFC. DMP1 appears to play an important role for osteogenic differentiation of the DFSCs.

Bone morphogenetic protein-9 induces osteogenic differentiation of rat dental follicle stem cells in P38 and ERK1/2 MAPK dependent manner

Dental follicle stem cells are a group of cells possessing osteogenic, adipogenetic and neurogenic differentiations, but the specific mechanism underlying the multilineage differentiation remains still unclear. Great attention has been paid to bone morphogenetic protein-9 (BMP-9) due to its potent osteogenic activity. In the present study, rat dental follicle stem cells were isolated and purified, and cells of passage 3 underwent adenovirus mediated BMP-9 gene transfection to prepare dental follicle stem cells with stable BMP-9 expression. Detection of alkaline phosphatase (ALP) and calcium deposition showed dental follicle stem cells transfected with BMP-9 gene could significantly promote the osteogenesis. In addition, SB203580 and PD98059 were employed to block the p38 mitogen-activated protein kinase (p38MAPK) and extracellular signal-regulated kinase (ERK1/2), respectively. Detection of ALP and calcium deposition revealed the BMP-9 induced osteogenic differentiation of dental follicle stem cells depended on MAPK signaling pathway.