Fabien Bornert

RSK2 Is a Modulator of Craniofacial Development

Background The RSK2 gene is responsible for Coffin-Lowry syndrome, an X-linked dominant genetic disorder causing mental retardation, skeletal growth delays, with craniofacial and digital abnormalities typically associated with this syndrome. Craniofacial and dental anomalies encountered in this rare disease have been poorly characterized. Methodology/Principal Findings We examined, using X-Ray microtomographic analysis, the variable craniofacial dysmorphism and dental anomalies present in Rsk2 knockout mice, a model of Coffin-Lowry syndrome, as well as in triple Rsk1,2,3 knockout mutants. We report Rsk mutation produces surpernumerary teeth midline/mesial to the first molar. This highly penetrant phenotype recapitulates more ancestral tooth structures lost with evolution. Most likely this leads to a reduction of the maxillary diastema. Abnormalities of molar shape were generally restricted to the mesial part of both upper and lower first molars (M1). Expression analysis of the four Rsk genes (Rsk1, 2, 3 and 4) was performed at various stages of odontogenesis in wild-type (WT) mice. Rsk2 is expressed in the mesenchymal, neural crest-derived compartment, correlating with proliferative areas of the developing teeth. This is consistent with RSK2 functioning in cell cycle control and growth regulation, functions potentially responsible for severe dental phenotypes. To uncover molecular pathways involved in the etiology of these defects, we performed a comparative transcriptomic (DNA microarray) analysis of mandibular wild-type versus Rsk2-/Y molars. We further demonstrated a misregulation of several critical genes, using a Rsk2 shRNA knock-down strategy in molar tooth germs cultured in vitro. Conclusions This study reveals RSK2 regulates craniofacial development including tooth development and patterning via novel transcriptional targets.

MSCT versus CBCT: evaluation of high-resolution acquisition modes for dento-maxillary and skull-base imaging

AbstractObjectivesOur aim was to conduct a quantitative and qualitative evaluation of high-resolution skull-bone imaging for dentistry and otolaryngology using different architectures of recent X-ray computed tomography systems.Material and methodsThree multi-slice computed tomography (MSCT) systems and one Cone-beam computed tomography (CBCT) system were used in this study. All apparatuses were tested with installed acquisition modes and proprietary reconstruction software enabling high-resolution bone imaging. Quantitative analyses were performed with small fields of view with the preclinical vmCT phantom, which permits to measure spatial resolution, geometrical accuracy, linearity and homogeneity. Ten operators performed visual qualitative analyses on the vmCT phantom images, and on dry human skull images.ResultsQuantitative analysis showed no significant differences between protocols in terms of linearity and geometric accuracy. All MSCT systems present a better homogeneity than the CBCT. Both quantitative and visual analyses demonstrate that CBCT acquisitions are not better than the collimated helical MSCT mode.ConclusionOur results demonstrate that current high-resolution MSCT protocols could exceed the performance of a previous generation CBCT system for spatial resolution and image homogeneity.Key Points• Quantitative evaluation is a prerequisite for comparison of imaging equipment. • Bone imaging quality could be objectively assessed with a phantom and dry skull. • The current MSCT shows better image quality than a dental CBCT system. • CBCT remains a work-in-progress technology.

Subtle Morphological Changes in the Mandible of Tabby Mice Revealed by Micro-CT Imaging and Elliptical Fourier Quantification.

X-linked hypohidrotic ectodermal dysplasia (XLHED) is a genetic disorder due to a mutation of the EDA gene and is mainly characterized by an impaired formation of hair, teeth and sweat glands, and craniofacial dysmorphologies. Although tooth abnormalities in Tabby (Ta) mutant mice – the murine model of XLHED – have been extensively studied, characterization of the craniofacial complex, and more specifically the mandibular morphology has received less attention. From 3D micro-CT reconstructions of the left mandible, the mandibular outline observed in lateral view, was quantified using 2D elliptical Fourier analysis. Comparisons between Ta specimens and their wild-type controls were carried out showing significant shape differences between mouse strains enabling a clear distinction between hemizygous Ta specimens and the other mouse groups (WT and heterozygous EdaTa/+ specimens). Morphological differences associated with HED correspond not only to global mandibular features (restrained development of that bone along dorsoventral axis), but also to subtle aspects such as the marked backward projection of the coronoid process or the narrowing of the mandibular condylar neck. These modifications provide for the first time, evidence of a predominant effect of the Ta mutation on the mandibular morphology. These findings parallel the well described abnormalities of jugal tooth row and skeletal defects in Ta mice, and underline the role played by EDA-A in the reciprocal epithelial–mesenchymal interactions that are of critical importance in normal dental and craniofacial development.

Active Nanomaterials to Meet the Challenge of Dental Pulp Regeneration

The vitality of the pulp is fundamental to the functional life of the tooth. For this aim, active and living biomaterials are required to avoid the current drastic treatment, which is the removal of all the cellular and molecular content regardless of its regenerative potential. The regeneration of the pulp tissue is the dream of many generations of dental surgeons and will revolutionize clinical practices. Recently, the potential of the regenerative medicine field suggests that it would be possible to achieve such complex regeneration. Indeed, three crucial steps are needed: the control of infection and inflammation and the regeneration of lost pulp tissues. For regenerative medicine, in particular for dental pulp regeneration, the use of nano-structured biomaterials becomes decisive. Nano-designed materials allow the concentration of many different functions in a small volume, the increase in the quality of targeting, as well as the control of cost and delivery of active molecules. Nanomaterials based on extracellular mimetic nanostructure and functionalized with multi-active therapeutics appear essential to reverse infection and inflammation and concomitantly to orchestrate pulp cell colonization and differentiation. This novel generation of nanomaterials seems very promising to meet the challenge of the complex dental pulp regeneration.

Combining 2D angiogenesis and 3D osteosarcoma microtissues to improve vascularization

Abstract Angiogenesis is now well known for being involved in tumor progression, aggressiveness, emergence of metastases, and also resistance to cancer therapies. In this study, to better mimic tumor angiogenesis encountered in vivo, we used 3D culture of osteosarcoma cells (MG‐63) that we deposited on 2D endothelial cells (HUVEC) grown in monolayer. We report that endothelial cells combined with tumor cells were able to form a well‐organized network, and that tubule‐like structures corresponding to new vessels infiltrate tumor spheroids. These vessels presented a lumen and expressed specific markers as CD31 and collagen IV. The combination of 2D endothelial cells and 3D microtissues of tumor cells also increased expression of angiogenic factors as VEGF, CXCR4 and ICAM1. The cell environment is the key point to develop tumor vascularization in vitro and to be closer to tumor encountered in vivo. Graphical abstract Figure. No caption available. HighlightsCombining 2D endothelial cells/3D tumor cells leads to a well‐organized network.This network consists of tubule‐like structures able to infiltrate 3D tumor.These vessels present a lumen and express specific marker as CD31 and Collagen IV.Combined 2D/3D strategy allows to an increased expression of angiogenic factors.

Temporomandibular Joint Regenerative Medicine

The temporomandibular joint (TMJ) is an articulation formed between the temporal bone and the mandibular condyle which is commonly affected. These affections are often so painful during fundamental oral activities that patients have lower quality of life. Limitations of therapeutics for severe TMJ diseases have led to increased interest in regenerative strategies combining stem cells, implantable scaffolds and well-targeting bioactive molecules. To succeed in functional and structural regeneration of TMJ is very challenging. Innovative strategies and biomaterials are absolutely crucial because TMJ can be considered as one of the most difficult tissues to regenerate due to its limited healing capacity, its unique histological and structural properties and the necessity for long-term prevention of its ossified or fibrous adhesions. The ideal approach for TMJ regeneration is a unique scaffold functionalized with an osteochondral molecular gradient containing a single stem cell population able to undergo osteogenic and chondrogenic differentiation such as BMSCs, ADSCs or DPSCs. The key for this complex regeneration is the functionalization with active molecules such as IGF-1, TGF-β1 or bFGF. This regeneration can be optimized by nano/micro-assisted functionalization and by spatiotemporal drug delivery systems orchestrating the 3D formation of TMJ tissues.

Bone substitutes: a review of their characteristics, clinical use, and perspectives for large bone defects management:

Bone replacement might have been practiced for centuries with various materials of natural origin, but had rarely met success until the late 19th century. Nowadays, many different bone substitutes can be used. They can be either derived from biological products such as demineralized bone matrix, platelet-rich plasma, hydroxyapatite, adjunction of growth factors (like bone morphogenetic protein) or synthetic such as calcium sulfate, tri-calcium phosphate ceramics, bioactive glasses, or polymer-based substitutes. All these substitutes are not suitable for every clinical use, and they have to be chosen selectively depending on their purpose. Thus, this review aims to highlight the principal characteristics of the most commonly used bone substitutes and to give some directions concerning their clinical use, as spine fusion, open-wedge tibial osteotomy, long bone fracture, oral and maxillofacial surgery, or periodontal treatments. However, the main limitations to bone substitutes use remain the management of large defects and the lack of vascularization in their central part, which is likely to appear following their utilization. In the field of bone tissue engineering, developing porous synthetic substitutes able to support a faster and a wider vascularization within their structure seems to be a promising way of research.

Diagnosis and Innovative Multidisciplinary Management of Hallermann-Streiff Syndrome: 20-Year Follow-Up of a Patient

Hallermann-Streiff syndrome (HSS) is a rare congenital disorder that mainly affects head and face development. We described the different patterns of the disease throughout the whole growth period and provided innovative treatment steps. Indeed, early genioplasty and dental implantation before growth completion were performed. These steps allowed to improve facial growth and to provide orthodontic anchorage, respectively. Complementary orthognathic surgery achieved satisfactory occlusion and refined aesthetics. We believe such an approach could be considered as a relevant treatment modality to complete multidisciplinary care in patients with HSS.

Periodontal Tissues, Maxillary Jaw Bone, and Tooth Regeneration Approaches: From Animal Models Analyses to Clinical Applications

This review encompasses different pre-clinical bioengineering approaches for periodontal tissues, maxillary jaw bone, and the entire tooth. Moreover, it sheds light on their potential clinical therapeutic applications in the field of regenerative medicine. Herein, the electrospinning method for the synthesis of polycaprolactone (PCL) membranes, that are capable of mimicking the extracellular matrix (ECM), has been described. Furthermore, their functionalization with cyclosporine A (CsA), bone morphogenetic protein-2 (BMP-2), or anti-inflammatory drugs’ nanoreservoirs has been demonstrated to induce a localized and targeted action of these molecules after implantation in the maxillary jaw bone. Firstly, periodontal wound healing has been studied in an induced periodontal lesion in mice using an ibuprofen-functionalized PCL membrane. Thereafter, the kinetics of maxillary bone regeneration in a pre-clinical mouse model of surgical bone lesion treated with BMP-2 or BMP-2/Ibuprofen functionalized PCL membranes have been analyzed by histology, immunology, and micro-computed tomography (micro-CT). Furthermore, the achievement of innervation in bioengineered teeth has also been demonstrated after the co-implantation of cultured dental cell reassociations with a trigeminal ganglia (TG) and the cyclosporine A (CsA)-loaded poly(lactic-co-glycolic acid) (PLGA) scaffold in the jaw bone. The prospective clinical applications of these different tissue engineering approaches could be instrumental in the treatment of various periodontal diseases, congenital dental or cranio-facial bone anomalies, and post-surgical complications.

Follicular Lymphomas of Oral Region Treated by Rituximab Monotherapy: About Two Cases

Lymphomas represent the second most common malignant lesions of the head and neck. Among them, follicular lymphomas (FLs) are the second most frequent B-cell non-Hodgkin’s lymphomas. However, their incidence is rare in the oral cavity. We describe here two cases of FL with initial intra-oral presentation. The first patient was 81 years old and presented a palatal hyperplasia, covering the posterior edge of her dental removable prosthesis. After surgical excision of the lesion, the pathological diagnosis was an extra-nodal low-grade follicular lymphoma. Medical imaging assessment found a widespread but non-bulky involvement. The second patient was 38 years old and referred for asymptomatic swelling of the lower vestibule evolving for 4 months. Surgical exploration revealed a cheek lymphadenopathy infiltrated by a grade 3 FL; this patient did not have any other localization. Both patients were treated by a rituximab monotherapy with excellent response after 2 years of follow-up. Most of the time, FL affecting the oral cavity presenting as unspecific swelling, can mimic other frequent and benign oral lesions. In the absence of biopsy, both diagnosis and proper onco-hematological management may be delayed. The introduction of monoclonal antibody rituximab represents a major advance in the management of FL: it can be used as monotherapy or may be combined with chemo-immunotherapy according to histological grading, initial staging (extent, tumor mass or bulk), age and co-morbidities. These two observations show the importance of an early diagnosis regarding a chronic lesion in the oral cavity. Painless lymphadenopathy, asymptomatic swelling, aspecific mucosal lesions, or subprosthetic lesions should draw attention of any oral specialist.