Deep learning for virtual orthodontic bracket removal: tool establishment and application.

OBJECTIVE: We aimed to develop a tool for virtual orthodontic bracket removal based on deep learning algorithms for feature extraction from bonded teeth and to demonstrate its application in a bracket position assessment scenario. MATERIALS AND METHODS: Our segmentation network for virtual bracket removal was trained using dataset A, containing 978 bonded teeth, 20 original teeth, and 20 brackets generated by scanners. The accuracy and segmentation time of the network were tested by dataset B, which included an additional 118 bonded teeth without knowing the original tooth morphology. This tool was then applied for bracket position assessment. The clinical crown center, bracket center, and orientations of separated teeth and brackets were extracted for analyzing the linear distribution and angular deviation of bonded brackets. RESULTS: This tool performed virtual bracket removal in 2.9 ms per tooth with accuracies of 98.93% and 97.42% (P < 0.01) in datasets A and B, respectively. The tooth surface and bracket characteristics were extracted and used to evaluate the results of manually bonded brackets by 49 orthodontists. Personal preferences for bracket angulation and bracket distribution were displayed graphically and tabularly. CONCLUSIONS: The tool's efficiency and precision are satisfactory, and it can be operated without original tooth data. It can be used to display the bonding deviation in the bracket position assessment scenario. CLINICAL SIGNIFICANCE: With the aid of this tool, unnecessary bracket removal can be avoided when evaluating bracket positions and modifying treatment plans. It has the potential to produce retainers and orthodontic devices prior to tooth debonding.

Neutrophils are involved in early bone formation during midpalatal expansion.

OBJECTIVE: Midpalatal expansion (MPE) is routinely employed to treat transverse maxillary arch deficiency. Neutrophils are indispensable for recruiting bone marrow stromal cells (BMSCs) at the initial stage of bone regeneration. This study aimed to explore whether neutrophils participate in MPE and how they function during bone formation under mechanical stretching. MATERIALS AND METHODS: The presence and phenotype of neutrophils in the midpalatal suture during expansion were detected by flow cytometry and immunofluorescence staining. The possible mechanism of neutrophil recruitment and polarization was explored in vitro by exposing vascular endothelial cells (VECs) to cyclic tensile strain. RESULTS: The number of neutrophils in the distracted suture peaked on Day 3, and N2-type neutrophils significantly increased on Day 5 after force application. The depletion of circulatory neutrophils reduced bone volume by 43.6% after 7-day expansion. The stretched VECs recruited neutrophils via a CXCR2 mechanism in vitro, which then promoted BMSC osteogenic differentiation through the VEGFA/VEGFR2 axis. Consistently, these neutrophils showed higher expression of canonical N2 phenotype genes, including CD206 and Arg1. CONCLUSIONS: These results suggested that neutrophils participated in early bone formation during MPE. Based on these findings, we propose that stretched VECs recruited and polarized neutrophils, which, in turn, induced BMSC osteogenic differentiation.

The psc-CVM assessment system: A three-stage type system for CVM assessment based on deep learning.

BACKGROUND: Many scholars have proven cervical vertebral maturation (CVM) method can predict the growth and development and assist in choosing the best time for treatment. However, assessing CVM is a complex process. The experience and seniority of the clinicians have an enormous impact on judgment. This study aims to establish a fully automated, high-accuracy CVM assessment system called the psc-CVM assessment system, based on deep learning, to provide valuable reference information for the growth period determination. METHODS: This study used 10,200 lateral cephalograms as the data set (7111 in train set, 1544 in validation set and 1545 in test set) to train the system. The psc-CVM assessment system is designed as three parts with different roles, each operating in a specific order. 1) Position Network for locating the position of cervical vertebrae; 2) Shape Recognition Network for recognizing and extracting the shapes of cervical vertebrae; and 3) CVM Assessment Network for assessing CVM according to the shapes of cervical vertebrae. Statistical analysis was conducted to detect the performance of the system and the agreement of CVM assessment between the system and the expert panel. Heat maps were analyzed to understand better what the system had learned. The area of the third (C3), fourth (C4) cervical vertebrae and the lower edge of second (C2) cervical vertebrae were activated when the system was assessing the images. RESULTS: The system has achieved good performance for CVM assessment with an average AUC (the area under the curve) of 0.94 and total accuracy of 70.42%, as evaluated on the test set. The Cohen's Kappa between the system and the expert panel is 0.645. The weighted Kappa between the system and the expert panel is 0.844. The overall ICC between the psc-CVM assessment system and the expert panel was 0.946. The F1 score rank for the psc-CVM assessment system was: CVS (cervical vertebral maturation stage) 6 > CVS1 > CVS4 > CVS5 > CVS3 > CVS2. CONCLUSIONS: The results showed that the psc-CVM assessment system achieved high accuracy in CVM assessment. The system in this study was significantly consistent with expert panels in CVM assessment, indicating that the system can be used as an efficient, accurate, and stable diagnostic aid to provide a clinical aid for determining growth and developmental stages by CVM.

Matrix mechanics regulate the polarization state of bone marrow-derived neutrophils through the JAK1/STAT3 signaling pathway.

Matrix mechanics regulate essential cell behaviors through mechanotransduction, and as one of its most important elements, substrate stiffness was reported to regulate cell functions such as viability, communication, migration, and differentiation. Neutrophils (Neus) predominate the early inflammatory response and initiate regeneration. The activation of Neus can be regulated by physical cues; however, the functional alterations of Neus by substrate stiffness remain unknown, which is critical in determining the outcomes of engineered tissue mimics. Herein, a three-dimensional (3D) culture system made of hydrogels was developed to explore the effects of varying stiffnesses (1.5, 2.6, and 5.7 kPa) on the states of Neus. Neus showed better cell integrity and viability in the 3D system. Moreover, it was shown that the stiffer matrix tended to induce Neus toward an anti-inflammatory phenotype (N2) with less adhesion molecule expression, less reactive oxygen species (ROS) production, and more anti-inflammatory cytokine secretion. Additionally, the aortic ring assay indicated that Neus cultured in a stiffer matrix significantly increased vascular sprouting. RNA sequencing showed that a stiffer matrix could significantly activate JAK1/STAT3 signaling in Neus and the inhibition of JAK1 ablated the stiffness-dependent increase in the expression of CD182 (an N2 marker). Taken together, these results demonstrate that a stiffer matrix promotes Neus to shift to the N2 phenotype, which was regulated by JAK1/STAT3 pathway. This study lays the groundwork for further research on fabricating engineered tissue mimics, which may provide more treatment options for ischemic diseases and bone defects. STATEMENT OF SIGNIFICANCE.

Evaluation of optimal single-photon emission computed tomography reference value and three-dimensional mandibular growth pattern in 54 Chinese unilateral condylar hyperplasia patients.

BACKGROUND: The research aimed to evaluate the optimal Single-Photon Emission Computed Tomography (SPECT) cut-off value in differentiating condylar growth activeness, to observe 3-dimensional (3D) mandibular growth pattern, and to explore the potential correlation between 3D measurement parameters and SPECT uptake ratios in Chinese unilateral condylar hyperplasia (UCH) patients. METHODS:  Data of fifty-four Chinese UCH patients were analyzed retrospectively. All patients underwent SPECT within 1 month before or after the first CT examination (CT1); and received a second CT examination at least 12 months later (CT2). Data from CT scans were analyzed by comparing bilateral differences between CT1 and CT2. The sensitivity and specificity of SPECT were calculated by the receiver operating characteristic (ROC) curve. Pearson's correlation analysis was performed to investigate whether the mandibular growth was correlated with SPECT value. RESULTS: SPECT had a sensitivity of 68.00% and a specificity of 72.41%, with an area under the ROC curve being 0.709. The optimal SPECT cut-off value for evaluating condylar activity has been determined to be 13%. In patients with an active growing condyle, there was a significant increase in Co-Gn and Co-Go, but not in Go-Gn, Go-MF, or MF-Gn. Pearson's correlation analysis revealed no correlation between 3D measurement parameters and differences in relative condylar uptake ratios. CONCLUSION: SPECT showed good diagnostic performance in UCH with the cut-off value of 13%. For those with an active growing condyle, the mandible grows diagonally and vertically, while the relative condylar uptake ratio was not directly related to mandibular growth.

Biomimetic Hydroxyapatite Nanorods Promote Bone Regeneration via Accelerating Osteogenesis of BMSCs through T Cell-Derived IL-22.

Manipulations of morphological properties of nanobiomaterials have been demonstrated to modulate the outcome of osteoimmunomodulation and eventually osteogenesis through innate immune response. However, the functions and mechanisms of adaptive immune cells in the process of nanobiomaterials-mediated bone regeneration have remained unknown. Herein, we developed bone-mimicking hydroxyapatite (HAp) nanorods with different aspect ratios as model materials to investigate the impacts of the nanoshape features on osteogenesis and to explore the underlying mechanisms focusing on the functions of T cells and T cell-derived cytokines. HAp nanorods with different aspect ratios (HAp-0, HAp-30, and HAp-100) were implanted into mouse mandibular defect models. Micro-CT and hematoxylin and eosin staining demonstrated that HAp-100 had the best osteogenic effects. Flow cytometry analysis revealed that HAp-100 increased the percentage of T cells in injured mandibles. The osteogenic effects of HAp-100 were significantly blunted in injured mandibles of TCRß-/- mice. The Luminex xMAP assay and ELISA showed that HAp-100 induced a marked increase of interleukin (IL)-22 in injured mandibles. In cultured T cells, HAp-100 manifested the best capacity to induce the production of IL-22. Conditioned media from HAp-100-primed T cells promoted osteogenesis and JAK1/STAT3 activation in bone marrow stromal cells, all of which were abolished by neutralizing antibodies against IL-22. In summary, bone-mimicking HAp nanorods with different aspect ratios could regulate osteogenesis through modulation of T cells and IL-22 in the bone regeneration process. These findings provided insights for mediation of the immune response of T cells by nanomaterials on osteogenesis and strategies for designing biomaterials with osteoimmunomodulative functions.

Aberrant Fluid Shear Stress Contributes to Articular Cartilage Pathogenesis via Epigenetic Regulation of ZBTB20 by H3K4me3.

PURPOSE: Osteoarthritis (OA) is a common disease for human beings, characterized by severe inflammation, cartilage degradation, and subchondral bone destruction. However, current therapies are limited to relieving pain or joint replacement and no effective treatment methods have been discovered to improve degenerative changes. Currently, a variety of evidences have indicated that aberrant mechanical stimuli is closely associated with articular joint pathogenesis, while the detailed underlying mechanism remains unelucidated. In the present study, we determined to investigate the impact of excessive high fluid shear stress (FSS) on primary chondrocytes and the underlying epigenetic mechanisms. MATERIALS AND METHODS: Phalloidin staining and EdU staining were used to evaluate cell morphology and viability. The mRNA level and protein level of genes were determined by qPCR, Western blot assay, and immunofluorescence staining. Mechanistic investigation was performed through RNA-sequencing and CUT&Tag sequencing. In vivo, we adopted unilateral anterior crossbites (UAC) mice model to investigate the expression of H3K4me3 and ZBTB20 in aberrant force-related cartilage pathogenesis. RESULTS: The results demonstrated that FSS greatly disrupts cell morphology and significantly decreased chondrocyte viability. Aberrant FSS induces remarkable inflammatory mediators production, leading to cartilage degeneration and degradation. In depth mechanistic study showed that FSS results in more than 10-fold upregulation of H3K4me3, and the modulatory effect of H3K4me3 on cartilage was obtained by directly targeting ZBTB20. Furthermore, Wnt signaling was strongly activated in high FSS-induced OA pathogenesis, and the negative impact of ZBTB20 on chondrocytes was also achieved through activating Wnt signaling pathway. Moreover, pharmacological inhibition of H3K4me3 activation by MM-102 or treatment with Wnt pathway inhibitor LF3 could effectively alleviate the destructive effect of FSS on chondrocytes. In vivo UAC mice model validated the dysregulation of H3K4me3 and ZBTB20 in aberrant force-induced cartilage pathogenesis. CONCLUSION: Through the combination of in vitro FSS model and in vivo UAC model, KMT2B-H3K4me3-ZBTB20 axis was first identified in aberrant FSS-induced cartilage pathogenesis, which may provide evidences for epigenetic-based therapy in the future.

Stimulating Factors and Origins of Precursor Cells in Traumatic Heterotopic Ossification Around the Temporomandibular Joint in Mice.

The contributing factors and the origins of precursor cells in traumatic heterotopic ossification around the temporomandibular joint (THO-TMJ), which causes obvious restriction of mouth opening and maxillofacial malformation, remain unclear. In this study, our findings demonstrated that injured chondrocytes in the condylar cartilage, but not osteoblasts in the injured subchondral bone, played definite roles in the development of THO-TMJ in mice. Injured condylar chondrocytes without articular disc reserves might secrete growth factors, such as IGF1 and TGFß2, that stimulate precursor cells, such as endothelial cells and muscle-derived cells, to differentiate into chondrocytes or osteoblasts and induce THO-TMJ. Preserved articular discs can alleviate the pressure on the injured cartilage and inhibit the development of THO-TMJ by inhibiting the secretion of these growth factors from injured chondrocytes. However, the exact molecular relationships among trauma, the injured condylar cartilage, growth factors such as TGFß2, and pressure need to be explored in detail in the future.

The Transcription Factor Foxc1 Promotes Osteogenesis by Directly Regulating Runx2 in Response of Intermittent Parathyroid Hormone (1-34) Treatment.

Parathyroid hormone (PTH) is crucial for bone remodeling. Intermittent PTH (1-34) administration stimulates osteogenesis and promotes bone formation; however, the possible targets and underlying mechanisms still remain unclear. In this study, functional links between PTH and Foxc1, a transcription factor reported to be predominant in skeletal development and formation, were indicated. We determined the impacts of Foxc1 on in vitro osteogenic differentiation and in vivo bone regeneration under intermittent PTH induction, and further explored its possible targets. We found that the expression level of Foxc1 was upregulated during osteogenic induction by intermittent PTH treatment, and the elevated expression of Foxc1 induced by PTH was inhibited by PTH1R silencing, while rescued by intermittent PTH supplement. By gain- and loss-of-function strategies targeting Foxc1 in MC3T3-E1 cells, we demonstrated that Foxc1 could promote in vitro osteogenic differentiation by intermittent PTH induction. Moreover, immunofluorescence analysis indicated the nuclear co-localization of Foxc1 with Runx2. Luciferase-reporter and chromatin immunoprecipitation analysis further confirmed that Foxc1 could bind to the P1 promoter region of Runx2 directly, which plays an indispensable part in osteogenic differentiation and bone mineralization. Meanwhile, we also revealed that Foxc1 could promote bone regeneration induced by intermittent PTH treatment in vivo. Taken together, this study revealed the role and mechanism of Foxc1 on in vitro osteogenic differentiation and in vivo bone regeneration in response of intermittent PTH treatment.

Cytochalasin D Promotes Osteogenic Differentiation of MC3T3-E1 Cells via p38-MAPK Signaling Pathway.

BACKGROUND: Bone defect caused by trauma, tumor resection, infection or congenital malformation is a common clinical disease. Bone tissue engineering is regarded as a promising way of bone defect reconstruction. Thus, agents that can promote osteogenesis have received great attention. Cytochalasin D (Cyto D), a metabolite derived from molds, proves to be able to modify actin, reorganize cytoskeleton, and then promote the osteogenic differentiation. OBJECTIVE: The purpose of this study was to explore the effect and mechanism of Cyto D on osteogenic differentiation of mouse pre-osteoblast MC3T3-E1 cells. METHODS: The optimum concentration of Cyto D was explored. The osteogenic differentiation of MC3T3-E1 cells induced by Cyto D was assessed by alkaline phosphatase (ALP) staining, Alizarin Red S (ARS) staining, western blotting and quantitative real-time polymerase chain reaction (RT-qPCR). In addition, a specific pathway inhibitor was utilized to explore whether MAPK pathways were involved in this process. RESULTS: The results showed that the optimized concentration of action was 10-2µg/ml. The expression of Runx2, OCN and OSX was up-regulated by the supplement of Cyto D. ALP activity, calcium deposition, and phosphorylation level of p38 protein were also improved. Inhibition of the pathway significantly reduced the activation of p38, and the expression of osteogenic-related genes. CONCLUSION: Cyto D can promote the osteogenic differentiation of MC3T3 cells via the p38-MAPK signaling pathway, but not the ERK1/2 or JNK, and it is a potential agent to improve the osteogenesis of MC3T3 cells.

Development process of traumatic heterotopic ossification of the temporomandibular joint in mice.

PURPOSE: The exact development process underlying traumatic heterotopic ossification of the temporomandibular joint (THO-TMJ) is largely unclear. In this study, we try to explore the histological development process of THO-TMJ. MATERIALS AND METHODS: Condylar cartilage of one-month-old male mice was partially removed from the left joint with small scissors to induce THO-TMJ. The phenotypes were observed using gross observation, microcomputed tomography (micro-CT) scans and histological examination from one month to six months after surgery. RESULTS: The micro-CT examination results showed that the injured condyle integrated with ectopic bone tissue to form an osteophyte and that the volume and density of the osteophyte grew exponentially with time. Hematoxylin and eosin (H&E), safranin O and fast green staining of the THO-TMJ specimens revealed that the ectopic bone tissue was mainly nonmineralized fibrous tissue 1 month after surgery. This tissue gradually transformed into cartilage 3 months after surgery. Finally, the tissues transformed into mature bone tissue 6 months after surgery. Immunofluorescence staining showed VEGF-α expression in the heterotopic tissue 1 month after surgery, and the expression of Sox9 in the heterotopic tissue was obvious 3 months after surgery. Furthermore, OCN expression was evident in most of the heterotopic tissue 6 months after surgery. The results also showed clear hypoxia-inducible factor 1-alpha (Hif-1α) expression in the injured chondrocytes of the condyle, especially in the articular proliferative zone and fibrocartilaginous zone. CONCLUSIONS: The THO-TMJ imaging characteristics indicated an exponential change with time. Histologically, the development process of THO-TMJ is an endochondral ossification process and includes three stages, fibroproliferative, chondrogenic and osteogenic stage. In addition, Hif-1α, which was expressed in some of the injured chondrocytes, may play an essential role in the initial THO-TMJ.

Effects of a single condylar neck fracture without condylar cartilage injury on traumatic heterotopic ossification around the temporomandibular joint in mice.

OBJECTIVES: In this study, we tried to explore the effects of a single condylar neck fracture without condylar cartilage injury during the pathogenesis process of traumatic heterotopic ossification around the temporomandibular joint (THO-TMJ). STUDY DESIGN: One-month-old C57 BL/6 J male mice were divided into 2 groups. In group 1, condylar cartilage was partially removed in the right joint to induce THO. In group 2, a single fracture on the condylar neck was created using small scissors. The condylar head was repositioned to its original place if any displacement occurred. The phenotypes were observed using gross observation, micro-computed tomography, and histologic examination. RESULTS: The results showed obvious hyperplasia in the right condyle in group 1, with ectopic bones and cartilage in the periarticular region. In group 2, the surface of condyle was smooth, but the size of the right condylar head became smaller. CONCLUSIONS: Taking these findings together, we concluded that it is condylar cartilage injury, and not a single condylar neck fracture without condylar cartilage injury, that contributes to the development of THO-TMJ.

Mechanical strain promotes osteogenic differentiation of bone mesenchymal stem cells from ovariectomized rats via the phosphoinositide 3­kinase/Akt signaling pathway.

Osteoporosis has become an overwhelming public health problem worldwide. As an elementary physiological factor to regulate bone formation and regeneration, mechanical strain may be used as a non­invasive intervention in osteoporosis prevention and treatment. However, little is known regarding the underlying mechanism. The aim of the current study was to investigate the effect of continuous mechanical strain (CMS) on osteogenic differentiation of bone mesenchymal stem cells (BMSCs) from ovariectomized rats (OVX BMSCs). In addition, involvement of the phosphatidylinositol 3­kinase (PI3K)/Akt signaling pathway in biomechanical signal transduction and its function were evaluated. The results demonstrated that OVX BMSCs subjected to CMS exhibited higher alkaline phosphatase (ALP) activity and deeper staining at 24 and 48 h. In addition, CMS upregulated the mRNA expression levels of ALP, collagen type I, runt related transcription factor 2 (Runx2), as well as the protein expression level of Runx2 in a time­dependent manner. The PI3K/Akt signaling pathway was rapidly activated by CMS, with its phosphorylation level reaching its maximum in a short duration and a large quantity of phosphorylated­Akt remaining in the nucleus. Pre­treatment with a selective blocker significantly blocked the strain­induced activation of PI3K/Akt and reduced the commitment of OVX BMSCs into osteoblasts, demonstrating a dominated regulative effect of PI3K/Akt signaling in strain­induced osteogenesis. These results indicated that CMS induced the early differentiation of OVX BMSCs towards an osteogenic phenotype by activating the PI3K/Akt signaling pathway.

Dental and periodontal phenotypes of Dlx2 overexpression in mice.

Distal-less homeobox 2 (Dlx2) is a member of the homeodomain family of transcription factors and is important for the development of cranial neural crest cells (CNCCs)­derived craniofacial tissues. Previous studies revealed that Dlx2 was expressed in the cementum and a targeted null mutation disrupted tooth development in mice. However, whether Dlx2 overexpression may impair in vivo tooth morphogenesis remains to be elucidated. The present study used a transgenic mouse model to specifically overexpress Dlx2 in neural crest cells in order to identify the dental phenotypes in mice by observation, micro­computed tomography and histological examination. The Dlx2­overexpressed mice exhibited tooth abnormalities including incisor cross­bite, shortened tooth roots, increased cementum deposition, periodontal ligament disorganization and osteoporotic alveolar bone. Therefore, Dlx2 overexpression may alter the alveolar bone, cementum and periodontal ligament (PDL) phenotypes in mice.

Subcutaneous C Shape Muscular Flap for Correcting the Depression of Alar Base in Affected Side in Patients With Unilateral Complete Cleft Lip/Palate During Primary Surgery.

PURPOSE: The depression of alar base in affected side in patients with unilateral complete cleft lip/palate (CL/P) is one of common clinical features. In this study, the authors try to explore the effect of subcutaneous C shape muscular flap for correcting the depression of alar base in affected side in patients with unilateral complete CL/P during primary surgery. METHODS: A total of 30 patients with unilateral complete CL/P who received primary correction of the lip nose deformity were included in this study. The C flap was used to drop and lengthen the height of upper lip in unaffected side, and the subcutaneous muscular flap was dissected from the C flap and positioned at the alar base in the affected side of upper lip to correct the depression. Then the surgical effect was evaluated based on clinical examination during follow-up. RESULTS: Alar base symmetry was obtained in 26 patients of this case series, and 4 patients showed slight improvement in alar base symmetry. No major complications such as flap necrosis, infection, or hypertrophic scars were observed during surgery and follow-up. No additional incisions and operative time were necessary. CONCLUSION: The subcutaneous C shape muscular flap described in this article could offer enough muscular support and markedly correct the depression of nostril and alar base in affected side in primary lip nose repair with no additional incisions and operative time for patients with unilateral complete CL/P.

[The effect of Foxc2 overexpression on the osteogenic properties of C3H10T1/2 cells].

PURPOSE: To investigate the effect of Foxc2 overexpression on osteogenic and adipogenic differentiation of C3H10T1/2 cells. METHODS: C3H10T1/2 cells were transfected with plenti-Foxc2 and selected with puromycin for stable clones. The expression of Foxc2 was determined by real-time PCR and Western blot. Cell proliferation was detected by CCK-8 kit. Cell cycle and apoptosis were detected by flow cytometry. The level of osteogenic biomarkers Runx2, OPN, OCN and adipogenic biomarker PPARγ were quantified by real-time PCR and Western blot. Alkaline phosphatase (ALP) staining and oil red staining were conducted to evaluate the effect of Foxc2 overexpression on osteogenic and adipogenic differentiation. Statistical analysis was performed using SPSS 17.0 software package. RESULTS: C3H10T1/2-Foxc2 cell line was successfully constructed and verified by direct sequencing and Foxc2 overexpression in vitro. Cell proliferation was reduced and cell cycle was blocked in G1/G0 phase. Enhanced ALP staining and reduced oil red staining were observed in C3H10T1/2-Foxc2 cells as compared with the control. Foxc2 overexpression up-regulated Runx2, OPN, OCN during osteogenic differentiation and down-regulated PPARγduring adipogenic differentiation. CONCLUSIONS: C3H10T1/2 cell line stably expressing Foxc2 gene was successfully established, cell proliferation was reduced, osteogenesis biomarkers were up-regulated during the osteogenesis by overexpression Foxc2, PPARγwas down-regulated during adipogenesis.

Overexpression of Dlx2 leads to postnatal condyle degradation.

Distal-less homeobox 2 (Dlx2), a member of the Dlx family of transcription factors, is important for the development of craniofacial tissues. Previous studies based on knock­out mutant mice revealed that Dlx2 primarily disturbed the development of tissues from maxillary arch. The present study used a transgenic mouse model to specifically overexpress Dlx2 in neural crest cells in order to investigate the role of Dlx2 overexpression in post­natal condyle in mice. The model was constructed and the phenotype observed using gross observation, micro­CT scan and histological examination. The model determined that overexpression of Dlx2 may lead to postnatal condyle malformation, subchondral bone degradation and irregular histological structure of the condylar cartilage. In addition, the expression of osteocalcin in the condyle region was markedly downregulated, whereas expression of msh homeobox 2 was upregulated. The results of the present study suggest that Dlx2 overexpression in cranial neural crest cells would disrupt the development of post­natal condyle, which demonstrates that the expression level and the spatiotemporal expression patterns of Dlx2 may be important in regulating the development of post-natal condyle in mice, and also offered a possible temporal­mandibular joint osteoarthritis model animal for future studies.

Injured condylar cartilage leads to traumatic temporomandibular joint ankylosis.

PURPOSE: The exact mechanisms of traumatic temporomandibular joint ankylosis (TTMJA) are largely unknown. In this study, we explore the role of injured condylar cartilage in the development of TTMJA. MATERIAL AND METHODS: One-month-old male mice were divided into two groups. In group 1, condylar cartilage was partially removed in the right joint using a small scissors to induce ankylosis. In group 2, condylar cartilage was completely removed in the same right joint using a small scissors to induce ankylosis. The phenotypes were observed using gross observation, micro-computed tomography scans and histological examination. RESULTS: The results revealed a great deal of ectopic cartilage and bone formation in the right periarticular region in all mice in group 1, whereas there was only a small amount of ectopic cartilage present in 26.7% of the mice in group 2. Additionally, there was stronger expression of FGF9 and weaker expression of OPN in the right temporomandibular joint region in group 2 at 7 days after surgery. CONCLUSIONS: These results suggest that the injured cartilage, not the injured bone, plays a crucial role in the development of TTMJA. In addition, it offers a useful TTMJA animal model to study the molecular mechanisms of TTMJA based on the gene manipulation technology, such as gene knock-out and knock-in as well as transgenic or gene mutation.

[The effect of estrogen on adipogenic differentiation of rat bone mesenchymal stem cells].

PURPOSE: In this study, 10⁻9 mol/L 17 ß-estradiol (E2) was applied in the adipogenic differentiation of rat bone mesenchymal stem cells (rBMSCs) and the effect of E2 was explored. METHODS: Rat BMSCs were obtained from the femurs and tibias of SD rats. 10⁻9 mol/L E2 was involved in the adipogenic differentiation of rBMSCs. Oil red staining, real time PCR and Western blot were carried out to detect the effect of 10⁻9 mol/L E2 on adipogenic differentiation of rBMSCs. The data was statistically analyzed using SPSS 19.0 software package. RESULTS: The use of 10⁻9 mol/L E2 decreased the amount of lipid droplets in rBMSCs and weakened the expression of adipogenic related genes and proteins like C/EBP α, C/EBP ß, PPAR γ, aP2, and ARDP, which were significantly lower than the adipogenic induced group. CONCLUSIONS: The use of 10⁻9 mol/L E2 inhibited adipogenic differentiation of rBMSCs significantly in vitro.

[Changes of the microarchitecture of alveolar bone due to different duration of ovariectomy: a Micro-CT study in rats].

PURPOSE: To study the changes of microarchitecture of alveolar bone due to different duration of ovariectomy in rats. METHODS: Twenty-four virgin Sprague-Dawley rats were randomly assigned to ovariectomy group (OVX) or sham-ovariectomy group (sham). OVX rats were subjected to bilateral ovariectomy and sham-ovariectomy was conducted in sham rats. Six rats of each group were sacrificed respectively 3 months and 6 months after surgery. The right semi-maxilla of all rats were scanned by Micro-CT, and the inter-radicular alveolar bone of the maxillary first molar was analyzed. Statistical analysis was carried out with SPSS 16.0 software package. RESULTS: Two-dimensional and three-dimensional reconstructed images of the alveolar bone showed porotic changes in rats both 3 months and 6 months after ovariectomy, including thinner, looser trabeculae and expanded bone marrow. When compared with corresponding sham rats, BMD, BV/TV and Tb.Th of alveolar bone significantly decreased in OVX rats both 3 months and 6 months after ovariectomy (P<0.05). Tb.N and Tb.Sp significantly increased in both OVX groups (P<0.05). When compared with 3 months after ovariectomy, the rats 6 months after ovaroectomy shared deceased BMD, BV/TV and Tb.Th (P<0.05) and increased Tb.N (P<0.05). CONCLUSIONS: Bone loss and deterioration of trabeculae of alveolar bone aggravates with the extended duration of ovariectomy in OVX rats.