Targeting fibroblast growth factor receptors causes severe craniofacial malformations in zebrafish larvae

Background and Objective

A key pathway controlling skeletal development is fibroblast growth factor (FGF) and FGF receptor (FGFR) signaling. Major regulatory functions of FGF signaling are chondrogenesis, endochondral and intramembranous bone development. In this study we focus on fgfr2, as mutations in this gene are found in patients with craniofacial malformations. The high degree of conservation between FGF signaling of human and zebrafish (Danio rerio) tempted us to investigate effects of the mutated fgfr2 ^sa10729 allele in zebrafish on cartilage and bone formation.

Methods

We stained cartilage and bone in 5 days post fertilization (dpf) zebrafish larvae and compared mutants with wildtypes. We also determined the expression of genes related to these processes. We further investigated whether pharmacological blocking of all FGFRs with the inhibitor BGJ398, during 0-12 and 24-36 h post fertilization (hpf), affected craniofacial structure development at 5 dpf.

Results

We found only subtle differences in craniofacial morphology between wildtypes and mutants, likely because of receptor redundancy. After exposure to BGJ398, we found dose-dependent cartilage and bone malformations, with more severe defects in fish exposed during 0-12 hpf. These results suggest impairment of cranial neural crest cell survival and/or differentiation by FGFR inhibition. Compensatory reactions by upregulation of fgfr1a, fgfr1b, fgfr4, sp7 and dlx2a were found in the 0-12 hpf group, while in the 24-36 hpf group only upregulation of fgf3 was found together with downregulation of fgfr1a and fgfr2.

Conclusions

Pharmacological targeting of FGFR1-4 kinase signaling causes severe craniofacial malformations, whereas abrogation of FGFR2 kinase signaling alone does not induce craniofacial skeletal abnormalities. These findings enhance our understanding of the role of FGFRs in the etiology of craniofacial malformations.

Curcumin-induced heme oxygenase-1 expression prevents H2O2-induced cell death in wild type and heme oxygenase-2 knockout adipose-derived mesenchymal stem cells

Mesenchymal stem cell (MSC) administration is a promising adjuvant therapy to treat tissue injury. However, MSC survival after administration is often hampered by oxidative stress at the site of injury. Heme oxygenase (HO) generates the cytoprotective effector molecules biliverdin/bilirubin, carbon monoxide (CO) and iron/ferritin by breaking down heme. Since HO-activity mediates anti-apoptotic, anti-inflammatory, and anti-oxidative effects, we hypothesized that modulation of the HO-system affects MSC survival. Adipose-derived MSCs (ASCs) from wild type (WT) and HO-2 knockout (KO) mice were isolated and characterized with respect to ASC marker expression. In order to analyze potential modulatory effects of the HO-system on ASC survival, WT and HO-2 KO ASCs were pre-treated with HO-activity modulators, or downstream effector molecules biliverdin, bilirubin, and CO before co-exposure of ASCs to a toxic dose of H₂O₂. Surprisingly, sensitivity to H₂O₂-mediated cell death was similar in WT and HO-2 KO ASCs. However, pre-induction of HO-1 expression using curcumin increased ASC survival after H₂O₂ exposure in both WT and HO-2 KO ASCs. Simultaneous inhibition of HO-activity resulted in loss of curcumin-mediated protection. Co-treatment with glutathione precursor N-Acetylcysteine promoted ASC survival. However, co-incubation with HO-effector molecules bilirubin and biliverdin did not rescue from H₂O₂-mediated cell death, whereas co-exposure to CO-releasing molecules-2 (CORM-2) significantly increased cell survival, independently from HO-2 expression. Summarizing, our results show that curcumin protects via an HO-1 dependent mechanism against H₂O₂-mediated apoptosis, and likely through the generation of CO. HO-1 pre-induction or administration of CORMs may thus form an attractive strategy to improve MSC therapy.

Delayed cutaneous wound closure in HO-2 deficient mice despite normal HO-1 expression

Impaired wound healing can lead to scarring, and aesthetical and functional problems. The cytoprotective haem oxygenase (HO) enzymes degrade haem into iron, biliverdin and carbon monoxide. HO-1 deficient mice suffer from chronic inflammatory stress and delayed cutaneous wound healing, while corneal wound healing in HO-2 deficient mice is impaired with exorbitant inflammation and absence of HO-1 expression. This study addresses the role of HO-2 in cutaneous excisional wound healing using HO-2 knockout (KO) mice. Here, we show that HO-2 deficiency also delays cutaneous wound closure compared to WT controls. In addition, we detected reduced collagen deposition and vessel density in the wounds of HO-2 KO mice compared to WT controls. Surprisingly, wound closure in HO-2 KO mice was accompanied by an inflammatory response comparable to WT mice. HO-1 induction in HO-2 deficient skin was also similar to WT controls and may explain this protection against exaggerated cutaneous inflammation but not the delayed wound closure. Proliferation and myofibroblast differentiation were similar in both two genotypes. Next, we screened for candidate genes to explain the observed delayed wound closure, and detected delayed gene and protein expression profiles of the chemokine (C-X-C) ligand-11 (CXCL-11) in wounds of HO-2 KO mice. Abnormal regulation of CXCL-11 has been linked to delayed wound healing and disturbed angiogenesis. However, whether aberrant CXCL-11 expression in HO-2 KO mice is caused by or is causing delayed wound healing needs to be further investigated.

Targeting the redox balance in inflammatory skin conditions

Reactive oxygen species (ROS) can be both beneficial and deleterious. Under normal physiological conditions, ROS production is tightly regulated, and ROS participate in both pathogen defense and cellular signaling. However, insufficient ROS detoxification or ROS overproduction generates oxidative stress, resulting in cellular damage. Oxidative stress has been linked to various inflammatory diseases. Inflammation is an essential response in the protection against injurious insults and thus important at the onset of wound healing. However, hampered resolution of inflammation can result in a chronic, exaggerated response with additional tissue damage. In the pathogenesis of several inflammatory skin conditions, e.g., sunburn and psoriasis, inflammatory-mediated tissue damage is central. The prolonged release of excess ROS in the skin can aggravate inflammatory injury and promote chronic inflammation. The cellular redox balance is therefore tightly regulated by several (enzymatic) antioxidants and pro-oxidants; however, in case of chronic inflammation, the antioxidant system may be depleted, and prolonged oxidative stress occurs. Due to the central role of ROS in inflammatory pathologies, restoring the redox balance forms an innovative therapeutic target in the development of new strategies for treating inflammatory skin conditions. Nevertheless, the clinical use of antioxidant-related therapies is still in its infancy.

[Dental tours de force 6. Autotransplantation in case of agenesis or traumatic tooth loss]

Autotransplantation of a tooth is probably the most natural method to replace a missing or lost tooth. This treatment has been performed successfully already for more than twenty years. The prognosis of a transplanted tooth is determined by tooth type, stage of root formation at the time of transplantation, surgical technique used, and duration and way of splinting. Determining the optimal stage of root formation of the tooth is very important in planning the autotransplantation. If the transplantation is carried out successfully, the transplanted tooth behaves at its new location just like before: it erupts, the root formation is continuing, it shows physiological mobility and it can be displaced by orthodontic forces. Most cases of autotransplantation require teamwork between oral surgeon, orthodontist, and dentist.

[Permanent retention: yes or no?]

The (in)stability of orthodontic treatment is a daily problem in orthodontics. This implies that retention--in whatever way--also remains an actual subject. There is however scarce valid scientific evidence on the topic of retention.

[Developments in fixed orthodontic appliances]

The Edgewise system and the Begg technique were until the early 1970's two of the most familiar and well-known fixed appliance techniques in orthodontics. During the following years they both underwent some slight adaptations that were generally based on more straightforward biomechanics. These changes have led to what in recent years is called the 'Straight Wire technique'. The latter claims to be the treatment option of choice based on preadjusted appliances and preformed arch wires. Besides biomechanics, treatment tools also concentrated on esthetics. It resulted in the development of smaller brackets as well as tooth coloured ones made from polycarbonates or ceramics. Finally lingual orthodontics starts to play a more important role in the orthodontic treatment options for the new millennium.

Interdisciplinary treatment planning for orthodontic-prosthetic implant anchorage in a partially edentulous patient

Successful orthodontic treatment is characterized by optimal anchorage control. Teeth or groups of teeth are united to counteract biomechanical reactive forces during orthodontic treatment. These classic anchorage control mechanisms are less efficient or even non-existent in partially edentulous patients who are missing multiple posterior teeth. However, osseointegrated oral implants ad modum Brånemark can provide optimal anchorage control for orthodontic tooth alignment and rehabilitation of occlusion through prosthetic implant restorations. Careful multidisciplinary planning based on complex diagnostic wax setup casts to determine exact implant location and orientation in line with future orthodontic tooth displacements and prosthetic implant crown restorations is the most important step in the overall treatment planning.

[Facial growth: men and women differ]

In the craniofacial complex there appears to be a sexual dimorphism: men and women not only differ during the 'active growth' period for the timing, amount and localization of growth, but also in the non-active phase thereafter gender differences in facial morphology remain present. In the active growth phase, girls reach their final facial dimensions earlier than boys and boys have larger final facial dimensions than girls. The specific differences in the lateral view of the face are situated in the eminent supraorbital sinus and nose, a larger occipital condyle and mastoid process. In the frontal view, boys show a larger prominence of the zygomatic bones and the gonial region than girls. As far as the 'non-active growth' changes in adulthood are concerned, the differences between men and women are smaller, but consistent and significant. Women have smaller faces (5-9% difference) but there are now configurational differences that appear in the pattern of growth. While men maintain their vertical growth pattern from puberty, women change from a horizontal to a vertical growth pattern during adulthood.

In vitro peel/shear bond strength of orthodontic adhesives

OBJECTIVES

The purpose of this study was to evaluate the in vitro peel/shear bond strength of a selection of orthodontic bracket adhesives to human premolar teeth.

METHODS

Twenty-two commercially available bracket adhesives were used to bond the same bracket type (Miniature Twin, 3M Unitek, Monrovia, CA. USA) on 264 intact human premolar teeth and then adhesively tested to failure. Peel/shear bond strength values were calculated in newtons and megapascals. The site of bond failure was scored according to the Adhesive Remnant Index. Statistics included one-way analysis of variance and Tukey's Studentized Range test together with Weibull analysis. The latter is a survival analysis able to describe the performance of a material.

RESULTS

The mean bond strengths varied from 9.9 MPa for Concise to 4.1 MPa for Heliosit Orthodontic. The overall F-test showed a significant difference (P < 0.0001). No significant differences in bond strength were found between Concise, AccuBond, Imperva Dual, Transbond XT, Kurasper and Spectrum.

CONCLUSION

Concise and AccuBond are among the materials of choice for bonding fixed orthodontic appliances to teeth. These materials combine high bond strength with a reliable bond that is easily and quickly debonded.

In vitro peel/shear bond strength evaluation of orthodontic bracket base design

OBJECTIVES

The adhesive capacity of 17 different bracket types was evaluated in an in vitro peel/shear test.

METHODS

Silane-treated metal bars were used as substrates with all bonding being performed using the orthodontic adhesive Concise. The effect of aluminium oxide air abrasion on the bonding performance of recycled metal bracket bases was evaluated. Morphological examination of the bracket bases was carried out under scanning electron microscopy. Statistics analysis included one-way ANOVA with Tukey's Studentized Range Test, two-way ANOVA and Weibull analysis.

RESULTS

Mean peel/shear bond strength values range from 13.9 MPa for Allure Accu Arch, a ceramic bracket type, to 1.6 MPa for the plastic bracket CeramaFlex Advant Edge. Allure Accu Arch performed the best of all the ceramic brackets. However, bracket wing fracture was observed. The metal brackets Mini masters and Omni Arch showed no significant difference in bond strength compared with the ceramic bracket Allure Accu Arch (P < 0.01).

CONCLUSION

The type of the bracket base determines its adhesive capacity. Sandblasting the base of recycled metal brackets had no uniform effect.

An evaluation of a light-curing composite for bracket placement

In this study the clinical usefulness of a light-curing (Heliosit) and a chemically-curing composite (Concise) for orthodontic bracket bonding were compared. A sample of 37 patients to be treated with full Edgewise (FE) appliance in one or both arches (in total 52 dental arches) were randomly selected to have brackets on the left or right side of the dental arch bonded either with Concise or with Heliosit. In 12 patients, two teeth were extracted before orthodontic treatment and 25 patients were treated non-extraction. Impressions (Impregum) of the tooth surface and the bracket were made immediately after bracket loss. Frequency scores of bracket loss were noted for both composites and scanning microscopic evaluation of the tooth/composite surface was performed. Significant differences in bracket loss could be demonstrated between the two composites as a whole, and between the anterior and posterior parts of the dentition. For Heliosit bracket loss was observed predominantly in the posterior region, while for Concise it was distributed more equally over the dental arches. It was, however, demonstrated that in the clinical situation of bracket bonding the chemically-cured Concise failed significantly less than Heliosit in the overall frequency score.

[Autotransplantation of teeth]

Autotransplantation of teeth has become a common procedure in oral surgery. The most usual procedures are autotransplantation of premolars, canines and third molars. The method can be performed on young patients in combination with orthodontic treatment, creating optimal occlusal relationship. Indication, selection and timing in connection with the surgical procedure are of paramount importance for optimal results.

Age reference charts of tooth length in Dutch children

The lengths of molar, premolar and canine teeth were determined from orthopantomograms collected in the Nymegen Growth Study. In this Mixed-Longitudinal Interdisciplinary Investigation orthopantomograms were taken every six months from 486 children, covering the age range 4-14 years. A statistically relevant number of mixed-longitudinal data were found for the canines and premolars in the maxilla and for the canines, premolars and molars (except third molars) in the mandible. These data on tooth formation expressed in age reference charts provide useful information for research purposes as well as for orthodontic diagnosis and treatment planning.

[Expert systems in orthodontics]

A review and concept is given of possible applications of expert and other information systems in orthodontics. The key to success probably lies in the fact that all relevant problems can be expressed in a formal system. Informatization projects can be an exciting and useful aspect in the field of orthodontics, if one proceeds with a modular approach.