Skeletal abnormalities caused by a Connexin43R239Q mutation in a mouse model for autosomal recessive craniometaphyseal dysplasia.

Craniometaphyseal dysplasia (CMD), a rare craniotubular disorder, occurs in an autosomal dominant (AD) or autosomal recessive (AR) form. CMD is characterized by hyperostosis of craniofacial bones and flaring metaphyses of long bones. Many patients with CMD suffer from neurological symptoms. To date, the pathogenesis of CMD is not fully understood. Treatment is limited to decompression surgery. Here, we report a knock in (KI) mouse model for AR CMD carrying a R239Q mutation in CX43. Cx43KI/KI mice replicate many features of AR CMD in craniofacial and long bones. In contrast to Cx43+/+ littermates, Cx43KI/KI mice exhibit periosteal bone deposition and increased osteoclast (OC) numbers in the endosteum of long bones, leading to an expanded bone marrow cavity and increased cortical bone thickness. Although formation of Cx43+/+ and Cx43KI/KI resting OCs are comparable, on bone chips the actively resorbing Cx43KI/KI OCs resorb less bone. Cortical bones of Cx43KI/KI mice have an increase in degenerating osteocytes and empty lacunae. Osteocyte dendrite formation is decreased with reduced expression levels of Fgf23, Sost, Tnf-α, IL-1ß, Esr1, Esr2, and a lower Rankl/Opg ratio. Female Cx43KI/KI mice display a more severe phenotype. Sexual dimorphism in bone becomes more evident as mice age. Our data show that the CX43R239Q mutation results in mislocalization of CX43 protein and impairment of gap junction and hemichannel activity. Different from CX43 ablation mouse models, the CX43R239Q mutation leads to the AR CMD-like phenotype in Cx43KI/KI mice not only by loss-of-function but also via a not yet revealed dominant function.

Characteristics and Risk Factors for the Fracture of One-Piece Implants.

Objective: The one-piece dental implant was originally designed to overcome the structural weaknesses of the two-piece implant. However, a fractured one-piece implant requires removal because the abutment cannot be repaired or replaced to support new prosthetic restorations. The aim of this study was to clarify the features and risk factors for fracture of the one-piece implant. Methods: This study was designed as a retrospective case series research. The subjects were patients who were treated for fractures of the one-piece implant at a clinic in Japan between 2012 and 2021. Fractures of the one-piece implant were diagnosed by cone-beam computed tomography, and the association between age and duration from implant placement to fracture was analyzed by one-way ANOVA followed by the Tukey test. Results: Eighteen patients and 20 one-piece implants (under 39 years: 5 patients and 6 implants; 40-59 years: 7 patients and 7 implants; over 60 years: 6 patients and 7 implants) had fractures in their one-piece implants. Of the fractured implants, 11 had a diameter of 3 mm, and 9 had a diameter of 4 mm. The mean durations up to implant fracture were 662 days in the younger group, 1467 days in the middle group, and 1239 days in older group, and the duration was significantly shorter in the younger group. In addition, 83.3% of fracture implants in the younger group were in the molar region. All fractures of the one-piece implants occurred under the bone margin. Two patients had torus mandibularis, and 1 patient was had bruxism. Conclusions: One-piece implants in younger patients that are located in the lower molar position are the most susceptible to implant fracture, and the fracture occurred under the bone margin in all cases.

Platelet-Rich Fibrin-Conditioned Medium as an Alternative to Fetal Bovine Serum Promotes Osteogenesis of Human Dental Pulp Stem Cells.

Human dental pulp stem cells (DPSCs) exhibit multilineage differentiation capabilities and superior clonogenic and proliferative properties. However, the use of animal-derived components such as FBS raises concerns regarding the clinical application of stem-cell-based therapies. Platelet-rich fibrin (PRF) derived from human blood is rich in fibrin, platelets, and growth factors and acts as a bioactive scaffold for grafting with biomaterials. In this study, we assessed the efficacy of PRF-conditioned medium (CM) in promoting DPSCs proliferation and osteogenic differentiation compared with the standard culture medium supplemented with FBS. A comparison of DPSCs cultured in FBS and PRF-CM revealed no differences in characteristics or morphology. However, cells cultured with PRF-CM exhibited inferior proliferation rates and cell numbers during passage in comparison with those cultured with FBS. In contrast, DPSCs cultured in PRF-CM showed significantly higher levels of calcification, and RT-PCR confirmed that the gene expression levels of markers associated with osteoblast differentiation were significantly increased. The PRF-CM approach offers a convenient, straightforward, and advantageous method for culturing DPSCs, without relying on animal-derived components. In summary, this study introduces a novel application of PRF-CM for enhancing the osteogenesis of DPSCs, which provides an alternative to FBS culture medium and addresses concerns associated with the use of animal-derived components in clinical settings.

Application of Dental Pulp Stem Cells for Bone and Neural Tissue Regeneration in Oral and Maxillofacial Region.

In the oral and maxillofacial region, the treatment of severe bone defects, caused by fractures, cancers, congenital abnormalities, etc., remains a great challenge. In addition, neurological disorders are frequently accompanied by these bone defects or the treatments for them. Therefore, novel bone regenerative techniques and methods to repair nerve injury are eagerly sought. Among them, strategies using dental pulp stem cells (DPSCs) are promising options. Human DPSCs can be collected easily from extracted teeth and are now considered a type of mesenchymal stem cell with higher clonogenic and proliferative potential. DPSCs have been getting attention as a cell source for bone and nerve regeneration. In this article, we reviewed the latest studies on osteogenic or neural differentiation of DPSCs as well as bone or neural regeneration methods using DPSCs and discussed the potential of DPSCs for bone and nerve tissue regeneration.

Computed tomography evaluation of risk factors for an undesirable buccal split during sagittal split ramus osteotomy.

Sagittal split ramus osteotomy (SSRO) sometimes induces an irregular split pattern referred to as a bad split. We investigated the risk factors for bad splits in the buccal plate of the ramus during SSRO. Ramus morphology and bad splits in the buccal plate of the ramus were assessed using preoperative and postoperative computed tomography images. Of the 53 rami analyzed, 45 had a successful split, and 8 had a bad split in the buccal plate. Horizontal images at the height of the mandibular foramen showed that there were significant differences in the ratio of the forward thickness to the backward thickness of the ramus between patients with a successful split and those with a bad split. In addition, the distal region of the cortical bone tended to be thicker and the curve of the lateral region of the cortical bone tended to be smaller in the bad split group than in the good split group. These results indicated that a ramus shape in which the width becomes thinner towards the back frequently induces bad splits in the buccal plate of the ramus during SSRO, and more attention should be paid to patients who have rami of these shapes in future surgeries.

VCAM-1 and GFPT-2: Predictive markers of osteoblast differentiation in human dental pulp stem cells.

INTRODUCTION: Dental pulp stem cells (DPSCs) have high proliferative and multilineage differentiation potential in mesenchymal stem cells. However, several studies have indicated that there are individual differences in the potential for osteogenic differentiation of DPSCs, and the factors determining these differences are unknown. OBJECTIVE: To identify the genes responsible for the individual differences in the osteogenic differentiation ability of DPSCs. METHODS: We divided DPSCs into high and low osteogenic differentiation ability groups (HG or LG) with ALP and von Kossa stain, and compared the gene expression patterns using RNA-seq. In addition, genes that may affect osteogenic differentiation were knocked down using small interfering RNA (siRNA) and their effects were investigated. RESULTS: The RNA-seq patterns revealed that VCAM1 and GFPT2 were significantly expressed at higher levels in the HG than in the LG. The results of siRNA analysis showed that VCAM1 and GFPT2 knockdown significantly reduced the expression of osteogenic markers. Furthermore, we analyzed the involvement of these two genes in cell signaling in DPSC differentiation. The results indicated that the VCAM1-mediated Ras-MEK-Erk and PI3K/Akt pathways are involved in the osteogenic differentiation of DPSCs, and that GFPT2-mediated HBP signaling influences the osteogenic differentiation of DPSCs. CONCLUSIONS: These findings indicate that DPSCs that highly express VCAM1 and GFPT2 have a high capacity for osteogenic differentiation. Evaluation of VCAM1 and GFPT2 expression in undifferentiated DPSCs may predict the outcome of bone regenerative therapy using DPSCs. Moreover, the expression levels of VCAM1 and GFPT2 in DPSCs may be useful in setting criteria for selecting donors for allogeneic cell transplantation for bone regeneration.