Root resorptions induced by genetic disorders: A systematic review.

OBJECTIVES: Root resorption in permanent teeth is a common pathological process that often follows dental trauma or orthodontic treatment. More rarely, root resorption is a feature of genetic disorders and can help with diagnosis. Thus, the present review aims to determine which genetic disorders could induce pathological root resorptions and thus which mutated genes could be associated with them. METHODS: We conducted a systematic review following the PRISMA guidelines. Articles describing root resorptions in patients with genetic disorders were included from PubMed, Embase, Web of Science, and Google Scholar. We synthesized the genetic disorder, the type, severity, and extent of the resorptions, as well as the other systemic and oral symptoms and histological features. RESULTS: The synthetic analysis included 25 studies among 937 identified records. We analyzed 21 case reports, three case series, and one cohort study. Overall, we highlighted 14 different pathologies with described root resorptions. Depending on the pathology, the sites of resorption, their extent, and their severity showed differences. CONCLUSION: With 14 genetic pathologies suspected to induce root resorptions, our findings are significant and enrich a previous classification. Among them, three metabolic disorders, three calcium-phosphorus metabolism disorders, and osteolysis disorders were identified.

MSCs-Derived Decellularised Matrix: Cellular Responses and Regenerative Dentistry.

The decellularised extracellular matrix (dECM) of in vitro cell culture is a naturally derived biomaterial formed by the removal of cellular components. The compositions of molecules in the extracellular matrix (ECM) differ depending on various factors, including the culture conditions. Cell-derived ECM provides a 3-dimensional structure that has a complex influence on cell signalling, which in turn affects cell survival and differentiation. This review describes the effects of dECM derived from mesenchymal stem cells (MSCs) on cell responses, including cell migration, cell proliferation, and cell differentiation in vitro. Published articles were searched in the PubMed databases in 2005 to 2022, with assigned keywords (MSCs and decellularisation and cell culture). The 41 articles were reviewed, with the following criteria. (1) ECM was produced exclusively from MSCs; (2) decellularisation processes were performed; and (3) the dECM production was discussed in terms of culture systems and specific supplementations that are suitable for creating the dECM biomaterials. The dECM derived from MSCs supports cell adhesion, enhances cell proliferation, and promotes cell differentiation. Importantly, dECM derived from dental MSCs shows promise in regenerative dentistry applications. Therefore, the literature strongly supports cell-based dECMs as a promising option for innovative tissue engineering approaches for regenerative medicine.

[Oral mesenchymal cells, a specific niche, from development to regeneration]. / Les cellules mésenchymateuses orales, une niche spécifique, du développement à la régénération.

Oral buccal tissues, including bone and mucosa, have unique properties. Oral mucosal fibroblasts and jaw osteoblasts, both derived from Cranial Neural Crest cells, play a key role in healing and repair. These cells express a specific repertoire of genes with their regenerative properties, but also craniofacial diseases. Understanding these tissues holds clinical promise for tissue regeneration and repair of bone and mucosal defects. These multidisciplinary advances also offer potential for better management of periodontal-related conditions and improved oral health.

Title: Les cellules mésenchymateuses orales, une niche spécifique, du développement à la régénération. Abstract: Les tissus muqueux et osseux oraux présentent des propriétés uniques. Les fibroblastes de la muqueuse orale et les ostéoblastes des mâchoires, issus des crêtes neurales crâniennes, jouent un rôle clé dans la cicatrisation/réparation. Ces cellules expriment un répertoire spécifique de gènes associés à leurs propriétés régénératives, mais aussi liés aux maladies rares crâniofaciales. La connaissance de ces tissus ouvre des perspectives cliniques pour la régénération tissulaire et la réparation des défauts osseux et muqueux. Ces avancées multidisciplinaires ont aussi un impact prometteur sur la prise en charge des maladies liées au parodonte et sur l'amélioration de la santé bucco-dentaire.

Reduced bone dimension in patients affected by oligodontia: A retrospective study on maxillary and mandibular CBCT.

AIM: Oligodontia (OD) is a rare developmental condition characterized by the absence of six or more teeth. Dental implant placement may be challenging due to anatomical factors. This study aims to evaluate the alveolar bone dimensions in OD patients compared with controls. MATERIALS AND METHODS: On maxillary and mandibular cone-beam computed tomography (CBCT), bone height and width were measured at every tooth and edentulous site. The distance to the inferior alveolar nerve was also measured. Fifty-three OD patients (40 maxillary and 32 mandibular CBCT) and 82 controls (51 maxillary and 31 mandibular CBCT) were compared using mixed models. RESULTS: Compared with those in OD patients, maxillary permanent teeth and edentulous sites showed significantly higher mean height in control patients (incisive-canine site height: +2.12 mm; edentulous incisive-canine site height: +4.46 mm [p > .001]). For the mandibular permanent teeth, mean height was higher in controls than in OD patients at the incisive-canine (+3.82 mm [p > .001]) and premolar areas (+2.06 mm [p > .001]). Only edentulous incisive-canine sites were significantly different between controls and OD patients (mean: +0.52 mm [p > .001]). Changes in alveolar nerve position were observed in case of molar agenesis. CONCLUSION: Maxillary and mandibular bone dimensions are reduced in OD patients compared with controls both in sites with permanent teeth and in edentulous areas.

Role of periosteum during healing of alveolar critical size bone defects in the mandible: a pilot study.

OBJECTIVES: Minipigs present advantages for studying oral bone regeneration; however, standardized critical size defects (CSD) for alveolar bone have not been validated yet. The objectives of this study are to develop a CSD in the mandibular alveolar bone in Aachen minipigs and to further investigate the specific role of periosteum. MATERIALS AND METHODS: Three female Aachen minipigs aged 17, 24, and 84 months were used. For each minipig, a split-mouth design was performed: an osteotomy (2 cm height × 2.5 cm length) was performed; the periosteum was preserved on the left side and removed on the right side. Macroscopic, cone beam computed tomography (CBCT), microcomputed tomography (µCT), and histological analyses were performed to evaluate the bone defects and bone healing. RESULTS: In both groups, spontaneous healing was insufficient to restore initial bone volume. The macroscopic pictures and the CBCT results showed a larger bone defect without periosteum. µCT results revealed that BMD, BV/TV, and Tb.Th were significantly lower without periosteum. The histological analyses showed (i) an increased osteoid apposition in the crestal area when periosteum was removed and (ii) an ossification process in the mandibular canal area in response to the surgical that seemed to increase when periosteum was removed. CONCLUSIONS: A robust model of CSD model was developed in the alveolar bone of minipigs that mimics human mandibular bone defects. This model allows to further investigate the bone healing process and potential factors impacting healing such as periosteum. CLINICAL RELEVANCE: This model may be relevant for testing different bone reconstruction strategies for preclinical investigations.

The Role of GH/IGF Axis in Dento-Alveolar Complex from Development to Aging and Therapeutics: A Narrative Review.

The GH/IGF axis is a major regulator of bone formation and resorption and is essential to the achievement of normal skeleton growth and homeostasis. Beyond its key role in bone physiology, the GH/IGF axis has also major pleiotropic endocrine and autocrine/paracrine effects on mineralized tissues throughout life. This article aims to review the literature on GH, IGFs, IGF binding proteins, and their respective receptors in dental tissues, both epithelium (enamel) and mesenchyme (dentin, pulp, and tooth-supporting periodontium). The present review re-examines and refines the expression of the elements of the GH/IGF axis in oral tissues and their in vivo and in vitro mechanisms of action in different mineralizing cell types of the dento-alveolar complex including ameloblasts, odontoblasts, pulp cells, cementoblasts, periodontal ligament cells, and jaw osteoblasts focusing on cell-specific activities. Together, these data emphasize the determinant role of the GH/IGF axis in physiological and pathological development, morphometry, and aging of the teeth, the periodontium, and oral bones in humans, rodents, and other vertebrates. These advancements in oral biology have elicited an enormous interest among investigators to translate the fundamental discoveries on the GH/IGF axis into innovative strategies for targeted oral tissue therapies with local treatments, associated or not with materials, for orthodontics and the repair and regeneration of the dento-alveolar complex and oral bones.

Head to Knee: Cranial Neural Crest-Derived Cells as Promising Candidates for Human Cartilage Repair.

A large array of therapeutic procedures is available to treat cartilage disorders caused by trauma or inflammatory disease. Most are invasive and may result in treatment failure or development of osteoarthritis due to extensive cartilage damage from repeated surgery. Despite encouraging results of early cell therapy trials that used chondrocytes collected during arthroscopic surgery, these approaches have serious disadvantages, including morbidity associated with cell harvesting and low predictive clinical outcomes. To overcome these limitations, adult stem cells derived from bone marrow and subsequently from other tissues are now considered as preferred sources of cells for cartilage regeneration. Moreover, with new evidence showing that the choice of cell source is one of the most important factors for successful cell therapy, there is growing interest in neural crest-derived cells in both the research and clinical communities. Neural crest-derived cells such as nasal chondrocytes and oral stem cells that exhibit chondrocyte-like properties seem particularly promising in cartilage repair. Here, we review the types of cells currently available for cartilage cell therapy, including articular chondrocytes and various mesenchymal stem cells, and then highlight recent developments in the use of neural crest-derived chondrocytes and oral stem cells for repair of cartilage lesions.

Involvement of neural crest and paraxial mesoderm in oral mucosal development and healing.

Tissue engineering therapies using adult stem cells derived from neural crest have sought accessible tissue sources of these cells because of their potential pluripotency. In this study, the gingiva and oral mucosa and their associated stem cells were investigated. Biopsies of these tissues produce neither scarring nor functional problems and are relatively painless, and fresh tissue can be obtained readily during different chairside dental procedures. However, the embryonic origin of these cells needs to be clarified, as does their evolution from the perinatal period to adulthood. In this study, the embryonic origin of gingival fibroblasts were determined, including gingival stem cells. To do this, transgenic mouse models were used to track neural crest derivatives as well as cells derived from paraxial mesoderm, spanning from embryogenesis to adulthood. These cells were compared with ones derived from abdominal dermis and facial dermis. Our results showed that gingival fibroblasts are derived from neural crest, and that paraxial mesoderm is involved in the vasculogenesis of oral tissues during development. Our in vitro studies revealed that the neuroectodermal origin of gingival fibroblasts (or gingival stem cells) endows them with multipotential properties as well as a specific migratory and contractile phenotype which may participate to the scar-free properties of the oral mucosa. Together, these results illustrate the high regenerative potential of neural crest-derived stem cells of the oral mucosa, including the gingiva, and strongly support their use in cell therapy to regenerate tissues with impaired healing.

In vitro effects of two silicate-based materials, Biodentine and BioRoot RCS, on dental pulp stem cells in models of reactionary and reparative dentinogenesis.

BACKGROUND: Calcium silicate-based cements are biomaterials with calcium oxide and carbonate filler additives. Their properties are close to those of dentin, making them useful in restorative dentistry and endodontics. The aim of this study was to evaluate the in vitro biological effects of two such calcium silicate cements, Biodentine (BD) and Bioroot (BR), on dental stem cells in both direct and indirect contact models. The two models used aimed to mimic reparative dentin formation (direct contact) and reactionary dentin formation (indirect contact). An original aspect of this study is the use of an interposed thin agarose gel layer to assess the effects of diffusible components from the materials. RESULTS: The two biomaterials were compared and did not modify dental pulp stem cell (DPSC) proliferation. BD and BR showed no significant cytotoxicity, although some cell death occurred in direct contact. No apoptosis or inflammation induction was detected. A striking increase of mineralization induction was observed in the presence of BD and BR, and this effect was greater in direct contact. Surprisingly, biomineralization occurred even in the absence of mineralization medium. This differentiation was accompanied by expression of odontoblast-associated genes. Exposure by indirect contact did not stimulate the induction to such a level. CONCLUSION: These two biomaterials both seem to be bioactive and biocompatible, preserving DPSC proliferation, migration and adhesion. The observed strong mineralization induction through direct contact highlights the potential of these biomaterials for clinical application in dentin-pulp complex regeneration.

Validation of Housekeeping Genes to Study Human Gingival Stem Cells and Their In Vitro Osteogenic Differentiation Using Real-Time RT-qPCR.

Gingival stem cells (GSCs) are recently isolated multipotent cells. Their osteogenic capacity has been validated in vitro and may be transferred to human cell therapy for maxillary large bone defects, as they share a neural crest cell origin with jaw bone cells. RT-qPCR is a widely used technique to study gene expression and may help us to follow osteoblast differentiation of GSCs. For accurate results, the choice of reliable housekeeping genes (HKGs) is crucial. The aim of this study was to select the most reliable HKGs for GSCs study and their osteogenic differentiation (dGSCs). The analysis was performed with ten selected HKGs using four algorithms: ΔCt comparative method, GeNorm, BestKeeper, and NormFinder. This study demonstrated that three HKGs, SDHA, ACTB, and B2M, were the most stable to study GSC, whereas TBP, SDHA, and ALAS1 were the most reliable to study dGSCs. The comparison to stem cells of mesenchymal origin (ASCs) showed that SDHA/HPRT1 were the most appropriate for ASCs study. The choice of suitable HKGs for GSCs is important as it gave access to an accurate analysis of osteogenic differentiation. It will allow further study of this interesting stem cells source for future human therapy.

Comparative Physicochemical Analysis of Pulp Stone and Dentin.

INTRODUCTION: Odontoblasts are responsible for the synthesis of dentin throughout the life of the tooth. Tooth pulp tissue may undergo a pathologic process of mineralization, resulting in formation of pulp stones. Although the prevalence of pulp stones in dental caries is significant, their development and histopathology are poorly understood, and their precise composition has never been established. The aim of the present study was to investigate the physicochemical properties of the mineralized tissues of teeth to elucidate the pathologic origin of pulp stones. METHODS: Areas of carious and healthy dentin of 8 decayed teeth intended for extraction were analyzed and compared. In addition, 6 pulp stones were recovered from 5 teeth requiring root canal treatment. The samples were embedded in resin, sectioned, and observed by scanning electron microscopy and energy-dispersive spectroscopy. X-ray diffraction was performed to identify phases and crystallinity. X-ray fluorescence provided information on the elemental composition of the samples. RESULTS: Pulp stones showed heterogeneous structure and chemical composition. X-ray diffraction revealed partially carbonated apatite. X-ray fluorescence identified P, Ca, Cu, Zn, and Sr within dentin and pulp stones. Zn and Cu concentrations were higher in pulp stones and carious dentin compared with healthy dentin. CONCLUSIONS: Pulpal cells produce unstructured apatitic mineralizations containing abnormally high Zn and Cu levels.

Ameloblastin as a putative marker of specific bone compartments.

Ameloblastin (AMBN), a member of the enamel matrix protein family, has been recently identified as integral part of the skeleton beyond the enamel. However, the specific role of endogenous AMBN in bone tissue is not fully elucidated. This study aims at investigating mRNA expression of AMBN in wild-type mice in different bone sites from early embryonic to adult stages. AMBN mRNA expression started at pre-dental stages in mouse embryos (E10.5) in both head and body parts. Using laser capture microdissection on 3-day-old mice, we showed an unambiguous mRNA expression of AMBN in extra-dental tissue (mandible bone). Screening of AMBN mRNA expression in adult mice (15-week-old) revealed that mRNA expression of AMBN varied according to the bone site; a higher mRNA levels in mandibular and frontal bone compartments were observed when compared to tibia and occipital bones. These results strongly suggest that AMBN expression may be regulated in a site-specific manner and identify AMBN as a putative in vivo marker of the site-specific fingerprint of bone organs.

Tracking endogenous amelogenin and ameloblastin in vivo.

Research on enamel matrix proteins (EMPs) is centered on understanding their role in enamel biomineralization and their bioactivity for tissue engineering. While therapeutic application of EMPs has been widely documented, their expression and biological function in non-enamel tissues is unclear. Our first aim was to screen for amelogenin (AMELX) and ameloblastin (AMBN) gene expression in mandibular bones and soft tissues isolated from adult mice (15 weeks old). Using RT-PCR, we showed mRNA expression of AMELX and AMBN in mandibular alveolar and basal bones and, at low levels, in several soft tissues; eyes and ovaries were RNA-positive for AMELX and eyes, tongues and testicles for AMBN. Moreover, in mandibular tissues AMELX and AMBN mRNA levels varied according to two parameters: 1) ontogenic stage (decreasing with age), and 2) tissue-type (e.g. higher level in dental epithelial cells and alveolar bone when compared to basal bone and dental mesenchymal cells in 1 week old mice). In situ hybridization and immunohistodetection were performed in mandibular tissues using AMELX KO mice as controls. We identified AMELX-producing (RNA-positive) cells lining the adjacent alveolar bone and AMBN and AMELX proteins in the microenvironment surrounding EMPs-producing cells. Western blotting of proteins extracted by non-dissociative means revealed that AMELX and AMBN are not exclusive to mineralized matrix; they are present to some degree in a solubilized state in mandibular bone and presumably have some capacity to diffuse. Our data support the notion that AMELX and AMBN may function as growth factor-like molecules solubilized in the aqueous microenvironment. In jaws, they might play some role in bone physiology through autocrine/paracrine pathways, particularly during development and stress-induced remodeling.

In vivo impact of Dlx3 conditional inactivation in neural crest-derived craniofacial bones.

Mutations in DLX3 in humans lead to defects in craniofacial and appendicular bones, yet the in vivo activities related to Dlx3 function during normal skeletal development have not been fully elucidated. Here we used a conditional knockout approach to analyze the effects of neural crest deletion of Dlx3 on craniofacial bones development. At birth, mutant mice exhibit a normal overall positioning of the skull bones, but a change in the shape of the calvaria was observed. Molecular analysis of the genes affected in the frontal bones and mandibles from these mice identified several bone markers known to affect bone development, with a strong prediction for increased bone formation and mineralization in vivo. Interestingly, while a subset of these genes were similarly affected in frontal bones and mandibles (Sost, Mepe, Bglap, Alp, Ibsp, Agt), several genes, including Lect1 and Calca, were specifically affected in frontal bones. Consistent with these molecular alterations, cells isolated from the frontal bone of mutant mice exhibited increased differentiation and mineralization capacities ex vivo, supporting cell autonomous defects in neural crest cells. However, adult mutant animals exhibited decreased bone mineral density in both mandibles and calvaria, as well as a significant increase in bone porosity. Together, these observations suggest that mature osteoblasts in the adult respond to signals that regulate adult bone mass and remodeling. This study provides new downstream targets for Dlx3 in craniofacial bone, and gives additional evidence of the complex regulation of bone formation and homeostasis in the adult skeleton.

The effect of globin scaffold on osteoblast adhesion and phenotype expression in vitro.

PURPOSE: Different synthetic and natural biomaterials have been used in bone tissue regeneration. However, several limitations are associated with the use of synthetic as well as allogenous or xenogenous natural materials. This study evaluated, in an in vitro model, the behavior of rat osteoblastic cells cultured on a human globin scaffold. MATERIALS AND METHODS: Rat osteoblastic cells were isolated from the calvaria of 21-day-old fetal Sprague-Dawley rats. They were then grown in the presence of globin. Real-time polymerase chain reaction (RT-PCR) was performed to study the expression of cyclin D1, integrin Β1, Msx2, Dlx5, Runx2, and osteocalcin on days 1, 5, and 9. Moreover, alkaline phosphatase activity was measured on days 1, 3, 5, and 7. Alizarin red staining was performed on day 9 to observe calcium deposition. RESULTS: Cells were able to adhere, proliferate, and differentiate on globin scaffolds. Moreover, RT-PCR showed that globin may stimulate some key genes of osteoblastic differentiation (Runx2, osteocalcin, Dlx5). Globin had an inhibitory effect on alkaline phosphatase activity. Calcium deposits were seen after 9 days of culture. CONCLUSIONS: These results indicate that purified human globin might be a suitable scaffold for bone tissue regeneration.

Neural crest deletion of Dlx3 leads to major dentin defects through down-regulation of Dspp.

During development, Dlx3 is expressed in ectodermal appendages such as hair and teeth. Thus far, the evidence that Dlx3 plays a crucial role in tooth development comes from reports showing that autosomal dominant mutations in DLX3 result in severe enamel and dentin defects leading to abscesses and infections. However, the normal function of DLX3 in odontogenesis remains unknown. Here, we use a mouse model to demonstrate that the absence of Dlx3 in the neural crest results in major impairment of odontoblast differentiation and dentin production. Mutant mice develop brittle teeth with hypoplastic dentin and molars with an enlarged pulp chamber and underdeveloped roots. Using this mouse model, we found that dentin sialophosphoprotein (Dspp), a major component of the dentin matrix, is strongly down-regulated in odontoblasts lacking Dlx3. Using ChIP-seq, we further demonstrate the direct binding of Dlx3 to the Dspp promoter in vivo. Luciferase reporter assays determined that Dlx3 positively regulates Dspp expression. This establishes a regulatory pathway where the transcription factor Dlx3 is essential in dentin formation by directly regulating a crucial matrix protein.

Platelet-poor plasma stimulates the proliferation but inhibits the differentiation of rat osteoblastic cells in vitro.

INTRODUCTION: Recent studies have shown that the use of platelet preparations in bone and implant surgery might stimulate bone formation. However, the biological mechanisms are not well understood. Moreover, few studies have attempted to evaluate the effect of platelet-poor plasma (PPP), which is a product of the platelet-rich plasma preparation process. OBJECTIVE: Thus, this study investigated the behavior of osteoblasts isolated from fetal rat calvaria cultivated in the presence of homologous PPP. MATERIAL AND METHODS: PPP was obtained by centrifugation of the rat mother's blood and used in replacement of fetal calf serum, which is classically used in primary culture procedures. Proliferation was measured by an MTT assay at 24, 48, and 72 h. Real-time PCR was performed to study the expression of Runx2, Dlx5, and osteocalcin (OC) on days 0 (4 h), 1, 3, 7, and 12. RESULTS: Alkaline phosphatase (ALP) biochemical activity was evaluated on days 0 (4 h), 1, 3, 7, and 12. Observations by phase-contrast microscopy showed that osteoblasts were able to differentiate until the mineralization of the matrix in the presence of PPP. PPP enhanced the proliferation significantly compared with the control group (P< or =0.001). PCR results showed that Runx2, Dlx5, and OC were expressed by cells in the experimental group at lower levels compared with the control group. Biochemical assay of ALP showed a lower activity in the experimental group compared with the control group (P<0.001). CONCLUSION: These results suggest that, in the presence of homologous PPP, rat osteoblastic cells are able to maintain their phenotype, with a higher rate of proliferation. However, PPP seems to inhibit osteoblastic differentiation.

Bone-like tissue formation on a biomimetic titanium surface in an explant model of osteoconduction.

The clinical use of titanium in dental and orthopedic applications is limited. Over recent years, implant surfaces have undergone numerous modifications to enhance bone integration. In this study, we experimented a bioactive titanium using a simple chemical and moderate heat treatment that led to the formation of a bone-like apatite layer on its surface in simulated body fluids. We used a bone explant model to demonstrate that cells can migrate from the explants and subsequently differentiate to form a mineralized nodular structure. Furthermore, these cells expressed alkaline phosphatase, bone sialoprotein, osteocalcin and the transcription factor, Runx2. Using this model of osteoconduction, we showed that bioactive titanium bonds directly to bone, while pure titanium cannot. These findings show the importance of implant surface composition in promoting osteogenic cell differentiation and subsequent apposition of the bone matrix, allowing strong bonds to form. This model could be particularly beneficial to closely mimic bone formation adjacent to endosseous implants.

beta-TCP microporosity decreases the viability and osteoblast differentiation of human bone marrow stromal cells.

Association of osteoprogenitor cells to calcium phosphate ceramics is currently under intense investigation, for its considered ability to induce bone formation and therefore to allow the successful repair of large bone defects. However, if the first experimental and clinical studies provided promising results, lack of new bone formation has been reported in a large number of animal experiments. In this context and since it has been reported that in some conditions, calcium phosphate ceramic microstructure induces ectopic bone formation, we investigated the effects of ceramic microporosity on the behavior of osteoprogenitor cells for the development of hybrid materials. Human bone marrow stromal cells (BMSCs) were seeded on beta-tricalcium phosphate (TCP) ceramics with 0, 25, or 45% microporosity and cell adhesion, viability, and osteoblastic differentiation have been studied for three weeks. Cell counts, measurement of MTS conversion, and LDH activity indicated that microporosity decreased the viability of BMSCs in a time and rate-dependent manner. In addition, microporosity inhibited osteoblastic differentiation as compared with nonmicroporous ceramics, as revealed by decreased alkaline phosphatase activity and osteocalcin secretion. Results of this in vitro study therefore highlight a negative role for beta-TCP microporosity in the behavior of human osteoprogenitor cells.