Expression of Cre recombinase in chondrocytes causes abnormal craniofacial and skeletal development.

The cranial base synchondroses are growth centers that drive cranial and upper facial growth. The intersphenoid synchondrosis (ISS) and the spheno-occipital synchondrosis (SOS) are two major synchondroses located in the middle of the cranial base and are maintained at early developmental stages to sustain cranial base elongation. In this study, we report unexpected premature ossification of ISS and SOS when Cre recombinase is activated in a chondrocyte-specific manner. We used a Cre transgenic line expressing Aggrecan enhancer-driven, Tetracycline-inducible Cre (ATC), of which expression is controlled by a Col2a1 promoter. Neonatal doxycycline injection or doxycycline diet fed to breeders was used to activate Cre recombinase. The premature ossification of ISS and/or SOS led to a reduction in cranial base length and subsequently a dome-shaped skull. Furthermore, the mice carrying either heterozygous or homozygous conditional deletion of Tsc1 or Fip200 using ATC mice developed similar craniofacial abnormalities, indicating that Cre activity itself but not conditional deletion of Tsc1 or Fip200 gene, is the major contributor of this phenotype. In contrast, the Col2a1-Cre mice carrying Cre expression in both perichondrium and chondrocytes and the mice carrying the conditional deletion of Tsc1 or Fip200 using Col2a1-Cre did not manifest the same skull abnormalities. In addition to the defective craniofacial bone development, our data also showed that the Cre activation in chondrocytes significantly compromised bone acquisition in femur. Our data calls for the consideration of the potential in vivo adverse effects caused by Cre expression in chondrocytes and reinforcement of the importance of including Cre-containing controls to facilitate accurate phenotype interpretation in transgenic research.

Interdisciplinary dental management of patient with oligodontia and maxillary hypoplasia: a case report.

BACKGROUND: The craniofacial developmental abnormality can significantly complicate the oral rehabilitation of patients with oligodontia. This case report describes an interdisciplinary approach that took 7 years to successfully treat a young patient with non-syndromic oligodontia and midface deficiency. CASE PRESENTATION: A 14-year-old patient with complex oral and maxillofacial conditions and diagnosis of oligodontia presented to our clinic. In addition to 4 retained deciduous teeth and congenitally missing 10 permanent teeth, dentofacial findings included maxillary and malar deficiency with a concave facial profile, Angle Class III malocclusion, and poor dental esthetics. The interdisciplinary treatment included pre-surgical orthodontic decompensation, high Le Fort I maxillary osteotomy, postsurgical orthodontic therapy, osseous ridge augmentation using recombinant human bone morphogenetic protein-2 (rhBMP-2), interim removable partial denture, dental implant installation, interim implant prostheses, and final prosthetic rehabilitation. CONCLUSIONS: The successful treatment of patients with oligodontia and complex dentofacial abnormalities requires the close and orderly collaboration among orthodontist, oral maxillofacial surgeon, and prosthodontist. Within the limitations of this case report, presented interdisciplinary approaches may optimize the oral rehabilitation outcome in patients with similar clinical challenges. A prospective clinical investigation is desired to verify the benefit of presented interdisciplinary approach.

Chondrocyte Tsc1 controls cranial base bone development by restraining the premature differentiation of synchondroses.

Cranial base bones are formed through endochondral ossification. Synchondroses are growth plates located between cranial base bones that facilitate anterior-posterior growth of the skull. Coordinated proliferation and differentiation of chondrocytes in cranial base synchondroses is essential for cranial base bone growth. Herein, we report that constitutive activation of the mechanistic target of rapamycin complex 1 (mTORC1) signaling via Tsc1 (Tuberous sclerosis 1) deletion in chondrocytes causes abnormal skull development with decreased size and rounded shape. In contrast to decreased anterior-posterior growth of the cranial base, mutant mice also exhibited significant expansion of cranial base synchondroses including the intersphenoid synchondrosis (ISS) and the spheno-occipital synchondrosis (SOS). Cranial base synchondrosis expansion in TSC1-deficient mice was accounted for by an expansion of the resting zone due to increased cell number and size without alteration in cell proliferation. Furthermore, our data showed that mTORC1 activity is inhibited in the resting and proliferating zone chondrocytes of wild type mice, and Tsc1 deletion activated mTORC1 signaling of the chondrocytes in the resting zone area. Consequently, the chondrocytes in the resting zone of TSC1-deficient mice acquired characteristics generally attributed to pre-hypertrophic chondrocytes including high mTORC1 activity, increased cell size, and increased expression level of PTH1R (Parathyroid hormone 1 receptor) and IHH (Indian hedgehog). Lastly, treatment with rapamycin, an inhibitor of mTORC1, rescued the abnormality in synchondroses. Our results established an important role for TSC1-mTORC1 signaling in regulating cranial base bone development and showed that chondrocytes in the resting zone of synchondroses are maintained in an mTORC1-inhibitory environment.

A Technique to Simultaneously Fabricate Multiple Custom Impression Posts for Implant-Supported Restorations in the Esthetic Zone.

Peri-implant transmucosal tissue, an essential element of peri-implant esthetics, is critical to the success of prostheses in the esthetic zone. The optimal transmucosal tissue profile can be transferred to the master cast with the aid of custom impression posts. In this clinical technique, the initial cast used to fabricate provisional prostheses was conveniently used to aid in the time-efficient fabrication of multiple custom impression posts simultaneously using self-cured acrylic resin. This technique also applies to single restorations. In addition, the use of an initial cast as holder makes it easy to transfer custom impression posts to the mouth accurately and efficiently.

Oral Care Program for Successful Long-Term Full Mouth Habilitation of Patients with Hypohidrotic Ectodermal Dysplasia.

Hypohidrotic ectodermal dysplasia (HED) is a rare congenital disorder that associates with dental manifestations of anodontia, hypodontia, and atrophic alveolar ridges. Although the disorder does not affect the life expectancy of the patient, it poses tremendous challenges on the patient's physical and psychosocial development. Early and multidisciplinary dental care can benefit HED children's development and improve their quality of life. This study presents two cases addressing the dental management continuously for 10 to 13 years in the dental school clinics. The keys to long-term success of the oral care program for HED patients at different age phases are reviewed and discussed, which can be summarized as early intervention, multidisciplinary collaborative care, and continuous recall.

Nitrogen removal from wastewater using a double-biofilm reactor with a continuous-flow method.

Wastewater microorganisms of nitrification and denitrification were cultivated to compose two biofilm modules, termed the permeable support bioreactor (PSB) and the membrane feeding substrate bioreactor (MFSB). PSB and MFSB were combined in a single tank to develop a double-biofilm reactor, which was used to treat nitrogen contaminants in wastewater. With a membrane supplement of substrates (O(2) and CH(3)OH), the D.O. and COD levels were at a low value in the bulk solution thus inhibitive effects between nitrification and denitrification were minimized. Simultaneous nitrification/denitrification was conducted in the reactor and the double-biofilm reactor achieved high nitrification and denitrification efficiency, of 96.5% and 82%, respectively.