Yongwen Guo

Effect of maxillary incisor labiolingual inclination and anteroposterior position on smiling profile esthetics.

OBJECTIVE To test the null hypothesis that there is no effect of maxillary incisor labiolingual inclination and anteroposterior (AP) position on smiling profile esthetics in young adult females. MATERIALS AND METHODS A facial smiling profile photograph of a Chinese woman with a normal profile, a Class I occlusion, and a Class I skeletal pattern was digitized. The digital image was modified to obtain four series comprising 29 smiling profiles. The sample of individuals rating these pictures comprised 21 orthodontic professionals and 66 undergraduates. Post hoc tests were done with the Student Newman Keuls method to analyze the data. RESULTS Significant differences (P < .001) were detected when each photographs ratings were compared. The smiling profile with the highest score was the one with 5° lingual inclination, while the ones with 15° labial inclination or 4-mm retrusion had lower scores than the others. Maxillary incisor protrusion and lingual inclination were preferable compared with retruded or flared incisors. There was no significant discrepancy between the professional and nonprofessional groups in terms of their assessments. CONCLUSIONS The hypothesis is rejected. Both maxillary incisor labiolingual inclination and AP position play an essential role in the esthetics of the smiling profile. However, when formulating treatment plans, dentists should never underestimate the labiolingual inclinations influence on the smiling profile.

TGF‐β1 and FGF2 Stimulate the Epithelial–Mesenchymal Transition of HERS Cells Through a MEK‐Dependent Mechanism

Hertwig’s epithelial root sheath (HERS) cells participate in cementum formation through epithelial–mesenchymal transition (EMT). Previous studies have shown that transforming growth factor beta 1 (TGF‐β1) and fibroblast growth factor 2 (FGF2) are involved in inducing EMT. However, their involvement in HERS cell transition remains elusive. In this study, we confirmed that HERS cells underwent EMT during the formation of acellular cementum. We found that both TGF‐β1 and FGF2 stimulated the EMT of HERS cells. The TGF‐β1 regulated the differentiation of HERS cells into periodontal ligament fibroblast‐like cells, and FGF2 directed the differentiation of HERS cells into cementoblast‐like cells. Treatment with TGF‐β1 or FGF2 inhibitor could effectively suppress HERS cells differential transition. Combined stimulation with both TGF‐β1 and FGF‐2 did not synergistically accelerate the EMT of HERS. Moreover, TGF‐β1/FGF2‐mediated EMT of HERS cells was reversed by the MEK1/2 inhibitor U0126. These results suggest that TGF‐β1 and FGF2 induce the EMT of HERS through a MAPK/ERK‐dependent signaling pathway. They also exert their different tendency of cellular differentiation during tooth root formation. This study further expands our knowledge of tooth root morphogenesis and provides more evidence for the use of alternative cell sources in clinical treatment of periodontal diseases. J. Cell. Physiol. 229: 1647–1659, 2014.

Response of immortalized murine cementoblast cells to hypoxia in vitro

OBJECTIVES The aim of the study was to investigate the impact of hypoxia on proliferation, apoptosis and mineralization of cementoblast-like cells (OCCM-30) in vitro. METHODS The effects of different periods of hypoxia (2% O2) on proliferation, apoptosis, cementoblastic potential and root cementum resorption capability of OCCM-30 were evaluated, by using MTT, flow cytometry, alkaline phosphatase (ALP) activity assay, reverse transcription-polymerase chain reaction measurement, enzyme-linked immunosorbent assay and mineralization nodule formation assay. RESULTS OCCM-30 viability was significantly inhibited by hypoxia while the apoptosis ratio was enhanced in a time-dependent manner; hypoxia inducible factor-1α and vascular endothelial growth factor mRNA were induced by hypoxia in different manners; temporary hypoxia (<24 h) stimulated cementoblastic function of OCCM-30, while long-term hypoxia inhibited it, manifested by decreased mRNA level or release of ALP, osteocalcin, bone sialoprotein, osteopontin and osteoprotegerin. In addition, hypoxia affected mineralized nodule formation of OCCM-30 in a time-dependent fashion; moreover, root cementum resorption function was also induced by hypoxia, manifested by increased receptor activator of nuclear factor kappa B ligand mRNA and protein expression. CONCLUSION Temporary exposure of OCCM-30 to hypoxia inhibited proliferation, promoted apoptosis and mineralization, while longer duration of hypoxia could inhibit the cementoblast function. The findings may provide theoretical basis for developing novel therapeutics to prevent root resorption during orthodontic treatment.

Expression analysis of α-smooth muscle actin and tenascin-C in the periodontal ligament under orthodontic loading or in vitro culture

α-smooth muscle actin (α-SMA) and tenascin-C are stress-induced phenotypic features of myofibroblasts. The expression levels of these two proteins closely correlate with the extracellular mechanical microenvironment. We investigated how the expression of α-SMA and tenascin-C was altered in the periodontal ligament (PDL) under orthodontic loading to indirectly reveal the intrinsic mechanical microenvironment in the PDL. In this study, we demonstrated the synergistic effects of transforming growth factor-β1 (TGF-β1) and mechanical tensile or compressive stress on myofibroblast differentiation from human periodontal ligament cells (hPDLCs). The hPDLCs under higher tensile or compressive stress significantly increased their levels of α-SMA and tenascin-C compared with those under lower tensile or compressive stress. A similar trend was observed in the tension and compression areas of the PDL under continuous light or heavy orthodontic load in rats. During the time-course analysis of expression, we observed that an increase in α-SMA levels was matched by an increase in tenascin-C levels in the PDL under orthodontic load in vivo. The time-dependent variation of α-SMA and tenascin-C expression in the PDL may indicate the time-dependent variation of intrinsic stress under constant extrinsic loading.

Hemiarthroplasty of the Shoulder Joint Using a Custom-Designed High-Density Nano-Hydroxyapatite/Polyamide Prosthesis With a Polyvinyl Alcohol Hydrogel Humeral Head Surface in Rabbits

In this study, a novel custom-designed high-density nano-hydroxyapatite/polyamide (n-HA/PA) prosthesis with a polyvinyl alcohol (PVA) hydrogel humeral head surface was employed to repair the shoulder joint head for hemiarthroplasty in rabbits. The prosthesis was fabricated using three-dimensional computed tomography and computer-aided design and computer-aided manufacturing systems for perfect fitting. Sixteen New Zealand white rabbits underwent humeral head excision, and received the composite prostheses for hemiarthroplasty. The implant sites were free from suppuration and necrosis at all periods. The X-ray results showed that there was a clear space between the prosthesis head and the glenoid surface, and the joint capsules and surfaces of the glenoid and PVA were well preserved without any damage during the whole inspection period. A high density of bone was observed around the firmware part of the prosthesis. Histological results revealed that significant osteogenesis was surrounding the firmware part, and the joint space was clear and the cartilage of the upper joint surface was basically intact. There was no visible absorption of the joint surfaces even after 3 months of continuous functional motions. The maximum tensile strength between the prosthesis and host bone reached 2.63 MPa at the 12th week postimplantation. In conclusion, the customized prosthesis by combination of PVA and high-density n-HA/PA has excellent biocompatibility and biological fixation, and offers a promising substitute for both the cartilage and the bone of the humeral head in a rabbit model as level V evidence.

The role of odontogenic genes and proteins in tooth epithelial cells and their niche cells during rat tooth root development

OBJECTIVES The rodent incisor cervical loop and molar Hertwigs epithelial root sheath (HERS) are common models used for investigating tooth root generation. The purpose of the present study was to gain a better understanding of the molecular mechanisms mediating root development by determining the distinctive gene and protein expression profiles of each during different stages of development. METHODS In this study, we used quantitative real time reverse transcription-PCR and immunohistochemistry to analyse the expression levels of high mobility group AT-hook 2, ameloblastin, amelogenin, dentine sialoprotein, dentine matrix protein 1, osteocalcin, and bone sialoprotein in rat epithelial and mesenchymal cells isolated at postnatal days 4 and 8. RESULTS Results showed that the expression of these genes and proteins was up-regulated in cervical loop epithelial cells, but decreased or unchanged in other cells during development. This increase in expression in the incisor cervical loop may be due to the interaction of the inner incisor dental papilla cells, which are the niche cells of cervical loop epithelial cells and demonstrated up-regulated expression of the corresponding proteins, revealing a complex and dynamic interplay of these molecules during neonatal tooth development. CONCLUSION These findings provide novel insights into the molecular processes underlying crown development of rodent incisors, and contribute to our overall understanding of the pathogenic processes of tooth root dysontogenesis.

Comparative study on differentiation of cervical-loop cells and Hertwig’s epithelial root sheath cells under the induction of dental follicle cells in rat

Cervical loop cells (CLC) and Hertwig’s epithelial root sheath (HERS) cells are believed to play critical roles in distinct developmental patterns between rodent incisors and molars, respectively. However, the differences in differentiation between CLC and HERS cells, and their response to inductions from dental follicle cells, remain largely unknown. In present study, CLC and HERS cells, as well as incisor dental follicle (IF) cells and molar dental follicle (MF) cells were isolated from post-natal 7-day rats. IF and MF cell derived conditioned medium (CM) was obtained for induction of CLC and HERS cells. In vitro experiments, we found that, under the induction of dental follicle cell derived CM, CLC cells maintained the epithelial polygonal-shapes and formed massive minerals, while part of HERS cells underwent shape transformation and generated granular minerals. CLC cells expressed higher enamel-forming and mineralization related genes, while HERS cells showed opposite expression patterns of BMP2, BMP4, AMBN and AMGN. In vivo, CLC cells generated enamel-like tissues while HERS cells formed cementum-periodontal ligament-like structures. Taken together, CLC and HERS cells present distinct differentiation patterns under the inductions from dental follicle cells.

YAP regulates periodontal ligament cell differentiation into myofibroblast interacted with RhoA/ROCK pathway: HE et al.

During orthodontic tooth movement (OTM), periodontal ligament cells (PDLCs) receive the mechanical stimuli and transform it into myofibroblasts (Mfbs). Indeed, previous studies have demonstrated that mechanical stimuli can promote the expression of Mfb marker α-smooth muscle actin (α-SMA) in PDLCs. Transforming growth factor β1 (TGF-β1), as the target gene of yes-associated protein (YAP), has been proven to be involved in this process. Here, we sought to assess the role of YAP in Mfbs differentiation from PDLCs. The time-course expression of YAP and α-SMA was manifested in OTM model in vivo as well as under tensional stimuli in vitro. Inhibition of RhoA/Rho-associated kinase (ROCK) pathway using Y27632 significantly reduced tension-induced Mfb differentiation and YAP expression. Moreover, overexpression of YAP with lentiviral transfection in PDLCs rescued the repression effect of Mfb differentiation induced by Y27632. These data together suggest a crucial role of YAP in regulating tension-induced Mfb differentiation from PDLC interacted with RhoA/ROCK pathway.

Are Hertwig’s epithelial root sheath cells necessary for periodontal formation by dental follicle cells?

OBJECTIVE The role of Hertwigs epithelial root sheath (HERS) cells in periodontal formation has been controversial. This study aimed to further clarify whether HERS cells participate in formation of the periodontium, and the necessity of HERS cells in differentiation of dental follicle cells (DFCs) for periodontal regeneration. DESIGN HERS cells and DFCs were isolated and identified from post-natal 7-day Sprauge-Dawley rats. In vitro, direct co-culture of HERS cells and DFCs as well as the individual culture of HERS and DFCs were performed and followed by alizarin red staining and the quantitative real-time polymerase chain reaction analysis. For in vivo evaluation, the inactivated dentin matrix (iTDM) was fabricated. HERS cells and DFCs were seeded in combination or alone on iTDM and then transplanted into the rat omentum. Scanning electron microscope and further histological analysis were carried out. RESULTS In vitro, mineral-like nodules were found in the culture of HERS cells alone or HERS + DFCs either by alizarin red staining or scanning electronic microscope. The mineralization and fiber-forming relevant mRNA expressions, such as bone sialoprotein, osteopontin, collagen I and collagen III in HERS + DFCs were significantly higher than that of the HERS or DFCs alone group. After transplantation in vivo, cementum and periodontal ligament-like tissues were formed in groups of HERS + DFCs and HERS alone, while no evident hard tissues and attached fibers were found in DFCs alone. CONCLUSIONS Hertwigs epithelial root sheath cells directly participate in the formation of the periodontium, and they are essential for the differentiation of dental follicle cells to form periodontal structures. The combination use of Hertwigs epithelial root sheath cells and dental follicle cells is a promising approach for periodontal regeneration.