Mouth breathing induces condylar remodelling and chondrocyte apoptosis via both the extrinsic and mitochondrial pathways in male adolescent rats

The prevalence of mouth breathing is high in children and adolescents. It causes various changes to the respiratory tract and, consequently, craniofacial growth deformities. However, the underlying mechanisms contributing to these effects are obscure. Herein, we aimed to study the effects of mouth breathing on chondrocyte proliferation and death in the condylar cartilage and morphological changes in the mandible and condyle. Additionally, we aimed to elucidate the mechanisms underlying chondrocyte apoptosis and investigate any variations in the related pathways. Subchondral bone resorption and decreased condylar cartilage thickness were observed in mouth-breathing rats; further, mRNA expression levels of Collagen II, Aggrecan, and Sox 9 were lower in the mouth breathing group, while those of matrix metalloproteinase 9 increased. TdT-mediated dUTP nick end labelling staining and immunohistochemistry analyses showed that apoptosis occurred in the proliferative and hypertrophic layers of cartilage in the mouth breathing group. TNF, BAX, cytochrome c, and cleaved-caspase-3 were highly expressed in the condylar cartilage of the mouth-breathing rats. These results suggest that mouth breathing leads to subchondral bone resorption, cartilage layer thinning, and cartilage matrix destruction, inducing chondrocyte apoptosis via both the extrinsic and mitochondrial apoptosis pathways.

Hemifacial hypertrophy - Report of 2 cases

Hemifacial hyperplasia (HH) is a rare congenital condition involving enlargement of one or more tissues of the face. The treatment is surgically challenging and requires expertise. This manuscript aims to report two similar appearing HH but warranting different surgical treatment. A 19-year-old female and a 14-year-old boy presented with right facial asymmetry since birth and sought correction of the same. Surgical treatment was planned. Based on clinical history, diagnosis and imaging, HH was diagnosed. The first case was entirely a soft tissue abnormality that was treated with debulking while the second case had involvement of facial bones, necessitating surgical recontouring. The facial asymmetry was addressed. Healing was uneventful. Though the aesthetical concern and appearance of the two cases of HH were same, the treatment vastly differed. This was based on the source of asymmetry. Proper diagnosis and informed decision are a key for successful surgical outcome.

Complex craniosynostosis in the context of Carpenter's syndrome

Carpenter's syndrome or acrocephalopolysyndactyly type II is a rare genetic autosomal recessive disease, with an incidence estimated at 1 per 1 million births. Common findings of a brachydactyly, polysyndactyly, and a trefoil-like skull with extreme brachycephaly due to fusion of the bilateral coronal, sagittal and lambdoid sutures. We report a 12-month-old male who was referred to our care for evaluation of a craniofacial deformity-a trefoil-like skull, flattened and receding forehead, bulging of temporal bones, hypertelorism, exorbitism, and polysyndactyly in the upper and lower limbs and psychomotor delay. Head computed tomography (CT) with 3D reconstruction revealed craniosynostosis with fusion of the coronal, metopic, and sagittal sutures. Correction of the craniofacial deformity was performed with satisfactory aesthesis of the craniofacial bones at 2 years of follow-up. Early correction of craniofacial deformity in Carpenter's syndrome is usually safe within 6 to 12 months. Venous drainage abnormalities and ectatic emissary veins can lead to significant bleeding and may be detected on MR angiography. Significant skull weakening may lead to bony fragmentation while creating cranial flaps and is best evaluated with 3D CT imaging. Taking these pitfalls into consideration decreases the chances of aborting the surgery and may lead to better overall outcomes.

Mir24-2-5p suppresses the osteogenic differentiation with Gnai3 inhibition presenting a direct target via inactivating JNK-p38 MAPK signaling axis

Background: Congenital anomalies are increasingly becoming a global pediatric health concern, which requires immediate attention to its early diagnosis, preventive strategies, and efficient treatments. Guanine nucleotide binding protein, alpha inhibiting activity polypeptide 3 (Gnai3) gene mutation has been demonstrated to cause congenital small jaw deformity, but the functions of Gnai3 in the disease-specific microRNA (miRNA) upregulations and their downstream signaling pathways during osteogenesis have not yet been reported. Our previous studies found that the expression of Mir24-2-5p was significantly downregulated in the serum of young people with overgrowing mandibular, and bioinformatics analysis suggested possible binding sites of Mir24-2-5p in the Gnai3 3'UTR region. Therefore, this study was designed to investigate the mechanism of Mir24-2-5p-mediated regulation of Gnai3 gene expression and explore the possibility of potential treatment strategies for bone defects.

Methods: Synthetic miRNA mimics and inhibitors were transduced into osteoblast precursor cells to regulate Mir24-2-5p expression. Dual-luciferase reporter assay was utilized to identify the direct binding of Gnai3 and its regulator Mir24-2-5p. Gnai3 levels in osteoblast precursor cells were downregulated by shRNA (shGnai3). Agomir, Morpholino Oligo (MO), and mRNA were microinjected into zebrafish embryos to control mir24-2-5p and gnai3 expression. Relevant expression levels were determined by the qRT-PCR and Western blotting. CCK-8 assay, flow cytometry, and transwell migration assays were performed to assess cell proliferation, apoptosis, and migration. ALP, ARS and Von Kossa staining were performed to observe osteogenic differentiation. Alcian blue staining and calcein immersions were performed to evaluate the embryonic development and calcification of zebrafish.

Results: The expression of Mir24-2-5p was reduced throughout the mineralization process of osteoblast precursor cells. miRNA inhibitors and mimics were transfected into osteoblast precursor cells. Cell proliferation, migration, osteogenic differentiation, and mineralization processes were measured, which showed a reverse correlation with the expression of Mir24-2-5p. Dual-luciferase reporter gene detection assay confirmed the direct interaction between Mir24-2-5p and Gnai3 mRNA. Moreover, in osteoblast precursor cells treated with Mir24-2-5p inhibitor, the expression of Gnai3 gene was increased, suggesting that Mir24-2-5p negatively targeted Gnai3. Silencing of Gnai3 inhibited osteoblast precursor cells proliferation, migration, osteogenic differentiation, and mineralization. Promoting effects of osteoblast precursor cells proliferation, migration, osteogenic differentiation, and mineralization by low expression of Mir24-2-5p was partially rescued upon silencing of Gnai3. In vivo, mir24-2-5p Agomir microinjection into zebrafish embryo resulted in shorter body length, smaller and retruded mandible, decreased cartilage development, and vertebral calcification, which was partially rescued by microinjecting gnai3 mRNA. Notably, quite similar phenotypic outcomes were observed in gnai3 MO embryos, which were also partially rescued by mir24-2-5p MO. Besides, the expression of phospho-JNK (p-JNK) and p-p38 were increased upon Mir24-2-5p inhibitor treatment and decreased upon shGnai3-mediated Gnai3 downregulation in osteoblast precursor cells. Osteogenic differentiation and mineralization abilities of shGnai3-treated osteoblast precursor cells were promoted by p-JNK and p-p38 pathway activators, suggesting that Gnai3 might regulate the differentiation and mineralization processes in osteoblast precursor cells through the MAPK signaling pathway.

Conclusions: In this study, we investigated the regulatory mechanism of Mir24-2-5p on Gnai3 expression regulation in osteoblast precursor cells and provided a new idea of improving the prevention and treatment strategies for congenital mandibular defects and mandibular protrusion.

Prenatal diagnosis of auriculocondylar syndrome with a novel missense variant of GNAI3: a case report

BACKGROUND

Auriculocondylar syndrome (ACS) is a rare disorder characterized by micrognathia, mandibular condyle hypoplasia, and auricular abnormalities. Only 6 pathogenic variants of GNAI3 have been identified associated with ACS so far. Here, we report a case of prenatal genetic diagnosis of ACS carrying a novel GNAI3 variant.

CASE PRESENTATION

A woman with 30 weeks of gestation was referred to genetic counseling for polyhydramnios and fetal craniofacial anomaly. Severe micrognathia and mandibular hypoplasia were identified on ultrasonography. The mandibular length was 2.4 cm, which was markedly smaller than the 95th percentile. The ears were low-set with no cleft or notching between the lobe and helix. The face was round with prominent cheeks. Whole-exome sequencing identified a novel de novo missense variant of c.140G > A in the GNAI3 gene. This mutation caused an amino acid substitution of p.Ser47Asn in the highly conserved G1 motif, which was predicted to impair the guanine nucleotide-binding function. All ACS cases with GNAI3 mutations were literature reviewed, revealing female-dominated severe cases and right-side-prone deformities.

CONCLUSION

Severe micrognathia and mandibular hypoplasia accompanied by polyhydramnios are prenatal indicators of ACS. We expanded the mutation spectrum of GNAI3 and summarized clinical features to promote awareness of ACS.

The perioral muscle continuum affects premaxillary development in Wistar rats

Craniofacial deformities involve soft tissue and skeletal abnormalities. Facial bone growth is based on congenital defects and iatrogenic factors, in which muscle activity is important. Understanding the effects of muscle function on facial bone growth may help us in clinical treatment. Although there have been some studies, fewer have focused on the effects of perioral muscle continuity on maxillary development, which needs further research. In our study, mimic perioral muscle surgeries were performed in twenty 3-day Wistar rats, which were divided into four equal groups, including five untreated rats as control (Ctrl), five rats by unilateral perioral muscle incision (MI), five rats by unilateral perioral muscle incision combined with muscle stripping (MIMS) and five rats treated by unilateral perioral muscle incision combined with periosteal stripping (MIPS). After six weeks, skulls were imaged and measured by micro-CT scan and hematoxylin-eosin staining. Differences in the rats' premaxilla were analyzed with self-contrasted and group-control studies. Compared with Ctrl group, there were significant premaxillary developmental defects in the affected side of the rats in all three surgical groups. In the affected side, both the width and the length of the premaxilla were less than the unaffected side, particularly in MIMS and MIPS groups. Group-control study showed that the ratio of premaxillary length of affected side to unaffected side had significant differences between MI and MIMS. The conclusion was that complete perioral muscle continuity with intact muscle attachment on the premaxilla is the driving force for the premaxillary development.