Acvr1 deletion in osteoblasts impaired mandibular bone mass through compromised osteoblast differentiation and enhanced sRANKL-induced osteoclastogenesis.

Bone morphogenetic protein (BMP) signaling is well known in bone homeostasis. However, the physiological effects of BMP signaling on mandibles are largely unknown, as the mandible has distinct functions and characteristics from other bones. In this study, we investigated the roles of BMP signaling in bone homeostasis of the mandibles by deleting BMP type I receptor Acvr1 in osteoblast lineage cells with Osterix-Cre. We found mandibular bone loss in conditional knockout mice at the ages of postnatal day 21 and 42 in an age-dependent manner. The decreased bone mass was related to compromised osteoblast differentiation together with enhanced osteoclastogenesis, which was secondary to the changes in osteoblasts in vivo. In vitro study revealed that deletion of Acvr1 in the mandibular bone marrow stromal cells (BMSCs) significantly compromised osteoblast differentiation. When wild type bone marrow macrophages were cocultured with BMSCs lacking Acvr1 both directly and indirectly, both proliferation and differentiation of osteoclasts were induced as evidenced by an increase of multinucleated cells, compared with cocultured with control BMSCs. Furthermore, we demonstrated that the increased osteoclastogenesis in vitro was at least partially due to the secretion of soluble receptor activator of nuclear factor-κB ligand (sRANKL), which is probably the reason for the mandibular bone loss in vivo. Overall, our results proposed that ACVR1 played essential roles in maintaining mandibular bone homeostasis through osteoblast differentiation and osteoblast-osteoclast communication via sRANKL.

A survey of power density of light-curing units used in private dental offices in Changchun City, China.

This study investigated power density and relevant information related to light-curing units used in private dental offices in Changchun City, China. The power density of 196 light-curing units used in private dental offices in Changchun City was measured using a simple random sampling method. Relevant information included the brand, type, years of operation, frequency of use, model numbers and types of light guide, resin buildup on the light guides, damage caused by the light guides, required maintenance of the curing lights, and ratio of the unit and chair number. There were 132 quartz tungsten halogen (QTH) units and 64 light-emitting diode units. The power density range was defined as 0-1,730 mW/cm(2). The mean power density was 453.1 mW/cm(2). The mean years of operation of the light-curing units were 3.96. The majority of dentists never tested the power density of the light-curing units and a considerable number of light guide surfaces showed resin buildup and damage. In Changchun City, the majority of light-curing units were QTH. Some units needed to be replaced due to aging. The majority of dentists were not aware that the light-curing units require periodic testing and maintenance. The data herein indicate the importance of periodic testing of the power density of light-curing units and timely replacement of the components and then guarantee the quality of medical services and their benefits to patients.

Construction of hollow polydopamine nanoparticle based drug sustainable release system and its application in bone regeneration.

Nanomaterial-based drug sustainable release systems have been tentatively applied to bone regeneration. They, however, still face disadvantages of high toxicity, low biocompatibility, and low drug-load capacity. In view of the low toxicity and high biocompatibility of polymer nanomaterials and the excellent load capacity of hollow nanomaterials with high specific surface area, we evaluated the hollow polydopamine nanoparticles (HPDA NPs), in order to find an optimal system to effectively deliver the osteogenic drugs to improve treatment of bone defect. Data demonstrated that the HPDA NPs synthesized herein could efficiently load four types of osteogenic drugs and the drugs can effectively release from the HPDA NPs for a relatively longer time in vitro and in vivo with low toxicity and high biocompatibility. Results of qRT-PCR, ALP, and alizarin red S staining showed that drugs released from the HPDA NPs could promote osteogenic differentiation and proliferation of rat bone marrow mesenchymal stem cells (rBMSCs) in vitro. Image data from micro-CT and H&E staining showed that all four osteogenic drugs released from the HPDA NPs effectively promoted bone regeneration in the defect of tooth extraction fossa in vivo, especially tacrolimus. These results suggest that the HPDA NPs, the biodegradable hollow polymer nanoparticles with high drug load rate and sustainable release ability, have good prospect to treat the bone defect in future clinical practice.

[Polarity of ameloblasts and odontoblasts and their related regulators].

The polarity of ameloblasts and odontoblasts is crucial for their differentiation and function. Polarity-related molecules play an important role in this process. This review summarizes the process of polarity formation of ameloblasts and odontoblasts and their related regulators.

Distinctive role of ACVR1 in dentin formation: requirement for dentin thickness in molars and prevention of osteodentin formation in incisors of mice.

Dentin is a major component of teeth that protects dental pulp and maintains tooth health. Bone morphogenetic protein (BMP) signaling is required for the formation of dentin. Mice lacking a BMP type I receptor, activin A receptor type 1 (ACVR1), in the neural crest display a deformed mandible. Acvr1 is known to be expressed in the dental mesenchyme. However, little is known about how BMP signaling mediated by ACVR1 regulates dentinogenesis. To explore the role of ACVR1 in dentin formation in molars and incisors in mice, Acvr1 was conditionally disrupted in Osterix-expressing cells (designated as cKO). We found that loss of Acvr1 in the dental mesenchyme led to dentin dysplasia in molars and osteodentin formation in incisors. Specifically, the cKO mice exhibited remarkable tooth phenotypes characterized by thinner dentin and thicker predentin, as well as compromised differentiation of odontoblasts in molars. We also found osteodentin formation in the coronal part of the cKO mandibular incisors, which was associated with a reduction in the expression of odontogenic gene Dsp and an increase in the expression of osteogenic gene Bsp, leading to an alteration of cell fate from odontoblasts to osteoblasts. In addition, the expressions of WNT antagonists, Dkk1 and Sost, were downregulated and B-catenin was up-regulated in the cKO incisors, while the expression levels were not changed in the cKO molars, compared with the corresponding controls. Our results indicate the distinct and critical roles of ACVR1 between incisors and molars, which is associated with alterations in the WNT signaling related molecules. This study demonstrates for the first time the physiological roles of ACVR1 during dentinogenesis.

[The role of bone morphogenetic protein signaling pathway in tooth root development].

The bone morphogenetic protein (BMP) family is an important factor in the regulation of cell ular life activities and in the development of almost all tissues. BMP-mediated signaling plays an important role in tooth root development, which is a part of tooth development. Epithelial and mesenchymal interactions are involved in tooth root development, but the BMP signaling pathway has a different effect on tooth root development in epithelial and mesenchymal. This review summarizes the advances of BMP signaling in tooth root development.

[A survey of power density of clinical curing-light units used in Changchun].

OBJECTIVES: To investigate the power density and other relevant data of clinical curing-light units used in Changchun, and to provide practice recommendations to clinical dentists about maintaining of cuing-light units. METHODS: Stomatology hospitals, departments of stomatology in general hospitals, and private dental offices in Changchun were randomly selected to participate in the Survey. The investigation analyzed 270 curing-light units. The following data of curing-light units were gathered: brand, type, operation ages, numbers and types of light guide, resin build-ups on light guides, damages of light guides, use frequency, monitor and maintenance of curing lights, and unit numbers/chair numbers. RESULTS: There were 174 QTH and 96 LED units. The distribution of power density was from 0 to 1702 mW/cm(2). The mean power density was 413.2 mW/cm(2). The power densities of 73 lights were less than 200 mW/cm(2) and could not polymerize resin composites adequately. The mean number of operation age of the light units was 4.74 years. Most of clinical dentists didn't monitor the light-curing units and the situation of build-up from composite resin or damages on light guides was very severe. CONCLUSIONS: Most of the light-curing units used in Changchun were QTH. Some QTH units degenerate severely and need to be replaced with the new ones. Most of the clinical doctors lack the knowledge of how to properly monitor and maintain the light-curing units.