Palatal Elevation Research Articles

Abstract: Diagnosis, Treatment, and LONG-TERM Speech Outcomes of Occult Submucous Cleft Palate-Associated Velopharyngeal Insufficiency

INTRODUCTION: Overt submucous cleft palate (SMCP) is characterized by Calnan’s triad of bifid uvula, hard palate notch and zona pellucida. Because occult SMCP (OSMCP) lacks this triad, diagnosis is challenging and treatment (if indicated by the presence of velopharyngeal insufficiency [VPI]) is delayed. This study discusses diagnosis, treatment, and long-term outcomes of OSMCP. METHODS: A retrospective chart review was performed for all patients presenting to the Cleft-Craniofacial Center of Children’s Hospital of Pittsburgh who were surgically treated for SMCP between September 2004 to September 2015. Patients with any one of Calnan’s triad were excluded from analysis. The primary outcome was the requirement of secondary speech surgery due to persistent VPI. To evaluate long-term speech outcomes, postoperative follow-up was required to be >3 years for study inclusion. Speech was evaluated over time using Pittsburgh Weighted Speech Scores (PWSS). RESULTS: 317 SMCP patients underwent surgical treatment for VPI, 41 patients were diagnosed with OSMCP (mean age at surgery 6.7 years). Furlow palatoplasty was performed for all patients (mean follow-up: 5.5 years). Diagnostic techniques for OSMCP: 1) intraoral physical examination demonstrating vaulted V-shaped palatal elevation with gag or phonation in 87.8% (36/41) of patients; 2) MRI demonstrating sagittally oriented levator palatini muscles in 19.5% (8/41) of patients; and 3) videofluroscopy to evaluate palatal kinetics in 65.8% (27/41) of patients. Secondary speech surgery was performed on 39.0% (16/41) of patients. 55.6% of patients (5/9) with VCFS underwent secondary surgery (p>0.05). Patients undergoing secondary surgery had a significantly lower change in PWSS (postoperative PWSS minus preoperative PWSS) compared to those who did not (4.4 and 10.0; p=0.022). Using videofluroscopy, patients who required secondary speech surgery had lateral wall motion with 53.6% closure compared to 74.3% closure for those who did not (p=0.11). No oronasal fistulae developed. Posterior pharyngeal flap (PPF) was performed in 87.5% of patients as the secondary speech surgery. Two of these patients (14.2%) developed obstructive sleep apnea (OSA) and required PPF takedown. CONCLUSION: Patients with VPI and no overt signs of SMCP often have delayed diagnosis and incorrect clinical management. Accurate diagnosis of OSMCP is imperative to guide appropriate surgical treatment. Furlow palatoplasty is an important procedure for patients with OSMCP-associated VPI. This shows promising outcomes in patients with OSCMP and limits the risk of PPF-related OSA.

Diagnosing subtle palatal anomalies: Validation of video-analysis and assessment protocol for diagnosing occult submucous cleft palate

IntroductionSubmucous cleft palate (SMCP) classically involves bifid uvula, zona pellucida, and notched hard palate. However, patients may present with more subtle anatomic abnormalities. The ability to detect these abnormalities is important for surgeons managing velopharyngeal dysfunction (VPD) or considering adenoidectomy. ObjectivesValidate an assessment protocol for diagnosis of occult submucous cleft palate (OSMCP) and identify physical examination features present in patients with OSMCP in the relaxed and activated palate positions. MethodsStudy participants included patients referred to a pediatric VPD clinic with concern for hypernasality or SMCP. Using an appropriately encrypted iPod touch, transoral video was obtained for each patient with the palate in the relaxed and activated positions. The videos were reviewed by two otolaryngologists in normal speed and slow-motion, as needed, and a questionnaire was completed by each reviewer pertaining to the anatomy and function of the palate. Results47 patients, with an average age of 4.6 years, were included in the study over a one-year period. Four videos were unusable due to incomplete view of the palate. The most common palatal abnormality noted was OSMCP, diagnosed by each reviewer in 26/43 and 30/43 patients respectively. Using the assessment protocol, agreement on palatal diagnosis was 83.7% (kappa = 0.68), indicating substantial agreement, with the most prevalent anatomic features being vaulted palate elevation (96%) and visible notching of hard palate (75%). ConclusionThe diagnosis of subtle palatal anomalies is difficult and can be subjective. Using the proposed video-analysis method and assessment protocol may improve reliability of diagnosis of OSMCP.

Inhibition of the miR-17-92 Cluster Separates Stages of Palatogenesis

The role that noncoding regions of the genome play in the etiology of cleft palate is not well studied. A novel method of microRNA (miR) inhibition that allows for specific miR knockdown in vivo has been developed by our laboratory. To further understand the role of miRs in palatogenesis, we used a new mouse model to inhibit specific miRs within the miR-17-92 cluster. Transgenic mice expressing inhibitory complexes for miR-17 and miR-18 manifested a clefting phenotype that was distinct from that observed in mice carrying inhibitory complexes for miR-17, miR-18, miR-19, and miR-92. An in silico candidate gene analysis and bioinformatics review led us to identify TGFBR2 as a likely target of miR-17 and miR-19 family members. Reverse transcription polymerase chain reaction (RT-PCR) experiments showed that TGFBR1 and TGFBR2 expression levels were elevated in the palates of these miR transgenic embryos at embryonic day 15.5. RT-PCR data also showed that the expression of mature miRs from the miR-17-92 cluster was significantly decreased in the transgenic embryos. Decreased expression of TGFB pathway signaling ligands was also observed. Experiments in cells showed that inhibition of miR-17 and miR-18 was sufficient to induce increases in expression of TGFB receptors, while a concomitant decrease in TGFB signaling ligands was not observed. RT-PCR of mature miR-17-92 in cells demonstrated the selectivity and specificity of inhibitory complexes. While this study builds on previous studies that have implicated miR-17-92 in the regulation of important molecular components of the TGFB signaling pathway, it is likely that interactions remain to be elucidated between miR-17-92 and as-of-yet unidentified molecules important for the control of palatogenesis. The differential regulation of palatogenesis by members of the miR-17-92 cluster indicates that several gene combinations regulate palate elevation and extension during development.

In Vivo Inhibition of microRNA (miR) Using a Novel miR Inhibitor System Reveals a Role for miR‐17‐92 in Palate Elevation and/or Extension

MicroRNAs (miRs) are short non‐coding RNA molecules approximately 22 nucleotides long. miRs bind to complementary targets on the 3′ untranslated region (UTR) of messenger RNAs (mRNAs), attenuating mRNA translation via either mRNA strand degradation or sequestration. Given their redundancy throughout the genome, conventional knockout strategies are difficult to employ when studying miRs. To circumvent this difficulty, we have developed a novel method of miR inhibition, the Plasmid‐Based miRNA Inhibition System (PMIS), to allow for the simultaneous knockdown of homologous miRs. Short hairpin structures that flank the anti‐sense miR target site on the PMIS inhibitor complex (PMIS‐IC) dramatically increase miR inhibition by associating with RISC complex factors. The PMIS‐IC is composed of native, unmodified nucleic acids and can be stably integrated into the genome. In this study, we employ this strategy to analyze the effects of inhibition of mature miRs in the miR‐17‐92 cluster. Here we show how the PMIS system can be used to inhibit miRs from the miR‐17‐92 cluster and associated family members in stable cell lines and transgenic mice. We also show how inhibition of the miR‐17‐92 cluster can lead to differences in the point of palate formation arrest in mice carrying PMIS‐ICs for miR‐17‐92. These results demonstrate the effectiveness of this novel miR inhibition strategy and indicate new roles for miR‐17‐92 in palatogenesis.Support or Funding InformationUniversity of Iowa Carver College of MedicineUniversity of Iowa College of DentistryUniversity of Iowa Research FoundationNational Institutes of Health (National Institute for Dental and Craniofacial Research)

Transferrin receptor facilitates TGF-β and BMP signaling activation to control craniofacial morphogenesis.

The Pierre Robin Sequence (PRS), consisting of cleft palate, glossoptosis and micrognathia, is a common human birth defect. However, how this abnormality occurs remains largely unknown. Here we report that neural crest cell (NCC)-specific knockout of transferrin receptor (Tfrc), a well known transferrin transporter protein, caused micrognathia, cleft palate, severe respiratory distress and inability to suckle in mice, which highly resemble human PRS. Histological and anatomical analysis revealed that the cleft palate is due to the failure of palatal shelves elevation that resulted from a retarded extension of Meckel's cartilage. Interestingly, Tfrc deletion dramatically suppressed both transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) signaling in cranial NCCs-derived mandibular tissues, suggesting that Tfrc may act as a facilitator of these two signaling pathways during craniofacial morphogenesis. Together, our study uncovers an unknown function of Tfrc in craniofacial development and provides novel insight into the etiology of PRS.

Bone morphogenetic protein type I receptor inhibition induces cleft palate associated with micrognathia and cleft lower lip in mice.

Gain-of- and loss-of-function studies have demonstrated that changes in bone morphogenetic protein (BMP) signaling during embryo development cause craniofacial malformations, including cleft palate. It remains uncertain whether BMP signaling could be targeted pharmacologically to affect craniofacial morphogenesis. Pregnant C57Bl/6J mice were treated with the BMP type I receptor inhibitor LDN-193189 at the dose of 3, 6, or 9 mg/kg twice a day by intraperitoneal injection from embryonic day 10.5 (E10.5) to E15.5. At E16.5, embryos were investigated by facial measurement analysis and histology to determine the optimal concentration for malformation. Subsequent embryonic phenotypes were analyzed in detail by histology, whole-mount skeletal staining, micro-computed tomography, and palatal organic culture. We further used immunohistochemistry to analyze protein expression of the BMP-mediated canonical and noncanonical signaling components. The optimal concentration of LDN-193189 was determined to be 6 mg/kg. In utero, LDN-193189 exposures induced partial clefting of the anterior palate or complete cleft palate, which was attributed to a reduced cell proliferation rate in the secondary palate, and delayed palatal elevation caused by micrognathia. Analysis of signal transduction in palatal shelves at E12.5 and E13.5 identified a significant reduction of BMP/Smad signaling (p-Smad1/5/8) and unchanged BMP noncanonical signaling (p-p38, p-Erk1/2) after treatment with LDN-193189. The results of this study indicate that LDN-193189 can be used to manipulate BMP signaling by selectively targeting the BMP/Smad signaling pathway to affect palatal morphogenesis and produce phenotypes mimicking those caused by genetic mutations. This work established a novel mouse model for teratogen-induced cleft palate. Birth Defects Research (Part A) 106:612-623, 2016. © 2016 Wiley Periodicals, Inc.

Surgical anatomy and physiology of swallowing

Deglutition, the act of swallowing, is an extremely complex process involving approximately 50 pairs of muscles and nerves that are responsible for preparing and transferring food and liquids from the mouth to the stomach. A problem with any of these structures can lead to dysphagia and a decrease in the quality of life in patients suffering from it. To successfully diagnose and treat dysphagia, a thorough understanding of deglutition is essential. The anatomy and physiology of the swallowing process is reviewed as it pertains to operative approach and technique.

Functional neurological treatment approach for chronic dizziness in an adult female patient.

Functional neurological treatment approach for chronic dizziness in an adult female patient.

The Effect of the Cervical Orthosis on Swallowing Physiology and Cervical Spine Motion During Swallowing.

Cervical orthosis is used to immobilize the neck in various disorders such as trauma and post-operation. However, it is still uncertain how cervical orthosis restricts the degree of movement of the cervical spine during swallowing and how they affect swallowing physiology. The purpose of this study was to evaluate these issues using the Philadelphia(®) Collar. We conducted videofluorography of swallowing in 39 healthy subjects (23 men, 16 women; mean age of 34.3years) with and without cervical orthosis. To compare the two conditions regarding the cervical spine motion, we determined the angular and positional changes of the occipital bone (C0) and each cervical vertebra (C1-C7) from the oral phase to the pharyngeal phase. Similarly, to compare swallowing physiology, we assessed the start and end times and the durations of soft palate elevation, rapid hyoid anterosuperior movement, epiglottis inversion, closure of the laryngeal vestibule, and pharyngoesophageal segment (PES) opening. Finally, we compared the transit times of contrast agent in the two conditions. The respective extensions of C1, C2, and C3 were 0.31°, 0.07°, and 0.05° (mean) with cervical orthosis, and the respective flexions of C1, C2, and C3 were 0.98°, 1.42°, and 0.85° (mean) without. These results suggested that cervical orthosis restricted the flexion of C1-C3. Analysis of swallowing physiology revealed that the average durations of hyoid anterosuperior elevation, epiglottic inversion, and PES opening were prolonged by 0.09, 0.19, and 0.05s, respectively. In conclusion, the cervical orthosis restricted the movement of the cervical spine during swallowing and changed swallowing physiology.

Correlation analysis of hearing level and soft palate movement after palatoplasty

To explore the relationship between hearing level and soft palate movement after palatoplasty and to verify the importance of recovery of soft palate movement function for improving the middle ear function as well as reducing the hearing loss. A total of 64 non-syndromic cleft palate patients were selected and the lateral cephalometric radiographs were taken. The patients hearing level was evaluated by the pure tone hearing threshold examination. This study also analyzed the correlation between hearing threshold of the patients after palatoplasty and the soft palate elevation angle and velopharyngeal rate respectively. Kendall correlation analysis revealed that the correlation coefficient between hearing threshold and the soft palate elevation angle after palatoplasty was -0.339 (r = -0.339, P < 0.01).The correlation showed a negative correlation. The hearing threshold decreased as the soft palate elevation angle increased. After palatoplasty, the correlation coefficient between the hearing threshold and the rate of velopharyngeal closure was -0.277 (r = -0.277, P < 0.01). The correlation showed a negative correlation. While, The hearing threshold decreased with the increase of velopharyngeal closure rate. The hearing threshold was correlated with soft palate elevation angle and velpharyngeal closure rate. The movement of soft palate and velopharyngeal closure function after palatoplasty both have impact on patient hearing level. In terms of the influence level, the movement of soft palate has a higher level of impact on patient hearing level than velopharygeal closure function.

Swallowing outcomes following primary surgical resection and primary free flap reconstruction for oral and oropharyngeal squamous cell carcinomas: a systematic review protocol

Swallowing outcomes following primary surgical resection and primary free flap reconstruction for oral and oropharyngeal squamous cell carcinomas: a systematic review protocol

Quantitative description of eustachian tube movements during swallowing as visualized by transnasal videoendoscopy.

Eustachian tube (ET) dysfunction predisposes ears to otitis media, tympanic membrane retraction, retraction pocket and perforation, or cholesteatoma. To develop a method to quantitatively measure the eustachian tube (ET) component movements and their interactions captured by transnasal videoendoscopy of the ET during swallowing. A blinded analysis of ET mechanics in 33 adults, aged 18 to 54 years, with no middle ear disease at present but without (group 1 [n = 16]) or with (group 2 [n = 17]) history of disease, conducted at a clinical research laboratory. Videoendoscopy of the ET orifice at the nasopharynx. Eustachian tube component translations and structural interactions during a swallow and the between-group differences in those variables. After topical anesthesia of the nose, a 45° telescope was introduced unilaterally and focused on the ipsilateral ET orifice. A video recording of ET component movements was made during 3 swallows. Swallow and ET opening durations and times to selected events were calculated. Images at 3 time points were analyzed by measuring the apex angle, the medial-lateral luminal width, and the medial angles between a frame-normal horizontal line through the apex and fixed points on the torus and medial and lateral luminal walls. Linear and angular variables during a swallow were expressed as change from baseline. Luminal opening was driven by soft palate elevation-related medial rotation of the torus and medial wall, coupled with lateral wall fixedness. The magnitude of the change from baseline for most variables was statistically greater than 0. Swallow time, palatal elevation time, time interval between maximum palatal elevation, and maximum eustachian tube opening time were not different between groups 1 and 2. Opening time was longer (mean [SD], 0.49 [0.28] vs 0.67 [0.51] seconds; P = .03) in group 2. Higher magnitude of torus rotation (mean [SD], 36.05° [12.96°] vs 27.72° [9.45°]; P = .002) with maximum soft palate elevation in group 1 resulted in greater degree of eustachian tube orifice widening (mean [SD], 0.34% [0.47%] vs -0.02% [0.49%]; P = .001) compared with the resting position in that group. This methodology has application in developing quantitative descriptions of ET mechanics in groups of persons without and with history or suspected ET dysfunction. A lesser degree of soft palate elevation during swallow that derives the ET medial lamina rotation and widening of the ET orifice may be associated with poor ET function and higher risk for otitis media. Videoendoscopic evaluation of the ET orifice may assist in diagnosing presence and mechanism of ET dysfunction.

MULTIMODAL NEUROREHABILITATION IMPROVES PATIENT WITH DEVELOPMENTAL DYSLEXIA

Event Abstract Back to Event MULTIMODAL NEUROREHABILITATION IMPROVES PATIENT WITH DEVELOPMENTAL DYSLEXIA David J. Traster1* and Kelsey Brenner1* 1 Carrick Institute, United States Background: We describe a 20 year old male who presents with developmental dyslexia, ADHD and visual tracking problems. Methods: Comprehensive neurologic examination demonstrated a left yaw and left roll head positioning with a left correctasia. Decrease palate elevation bilaterally, decrease of left peripheral visual field upon confrontation testing, bilateral decrease of arm swing upon gait examination with left Lateropulsion during dual task, left percussion myotonia of the thumb and a positive Myerson’s/glabellar sign. Oculomotor examination revealed large amplitude saccadic intrusions contaminating the smooth visual pursuits in all directions. Three days of a neurorehabilitation program was administered consisting of specific oculomotor rehabilitation, off-vertical-axis-rotation vestibular rehabilitation, interactive metronome and repetitive peripheral somatosensory stimulation of the tongue bilaterally. Results: Patient reported improvement in focus and reading ability. Initial saccadic intrusions were completely resolved during pursuit testing in all directions. Conclusion: This case showed significant improvements in a patient with developmental dyslexia. The authors suggest further investigation concerning a multimodal neurorehabilitation strategy in the management of developmental dyslexia. Keywords: Dyslexia, devleopmental dyslexia, Neurorehabilitation, ADHD, visual tracking disorder, reading comprehension Conference: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration, Orlando, Florida, United States, 10 Dec - 14 Dec, 2015. Presentation Type: Poster Presentation Topic: Case Reports for Poster Presentation Citation: Traster DJ and Brenner K (2015). MULTIMODAL NEUROREHABILITATION IMPROVES PATIENT WITH DEVELOPMENTAL DYSLEXIA. Front. Neurol. Conference Abstract: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration. doi: 10.3389/conf.fneur.2015.58.00111 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Sep 2015; Published Online: 02 Nov 2015. * Correspondence: Dr. David J Traster, Carrick Institute, Cape Canaveral, United States, dtraster3@gmail.com Dr. Kelsey Brenner, Carrick Institute, Cape Canaveral, United States, kelseyjoanbrenner@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers David J Traster Kelsey Brenner Google David J Traster Kelsey Brenner Google Scholar David J Traster Kelsey Brenner PubMed David J Traster Kelsey Brenner Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Obstructive sleep apnea syndrome in children with 22q11.2 deletion syndrome after operative intervention for velopharyngeal insufficiency.

Introduction: Surgical treatment of velopharyngeal insufficiency (VPI) in 22q11.2 deletion syndrome is often warranted. In this patient population, VPI is characterized by poor palatal elevation and muscular hypotonia with an intact palate. We hypothesize that 22q11.2 deletion patients are at greater risk of obstructive sleep apnea (OSA) after surgical correction of VPI, due, in part, to their functional hypotonia, large velopharyngeal gap size, and the need to surgically obstruct the velopharynx.Methods: We performed a retrospective analysis of patients with 22q11.2 deletion syndrome treated at a tertiary pediatric hospital between the years of 2002 and 2012. The incidence of VPI, need for surgery, post-operative polysomnogram, post-operative VPI assessment, and OSA treatments were evaluated.Results: Forty-three patients (18 males, 25 females, ages 1–14 years) fitting the inclusion criteria were identified. Twenty-eight patients were evaluated by speech pathology due to hypernasality. Twenty-one patients had insufficient velopharyngeal function and required surgery. Fifteen underwent pharyngeal flap surgery, three underwent sphincter pharyngoplasty, two underwent Furlow palatoplasty, and one underwent combined sphincter pharyngoplasty with Furlow palatoplasty. Of these, eight had post-operative snoring. Six of these underwent polysomnography (five underwent pharyngeal flap surgeries and one underwent sphincter pharyngoplasty). Four patients were found to have OSA based on the results of the polysomnography (average apnea/hypopnea index of 4.9 events/h, median = 5.1, SD = 2.1). Two required continuous positive airway pressure (CPAP) due to moderate OSA.Conclusion: Surgery is often necessary to correct VPI in patients with 22q11.2 deletion syndrome. Monitoring for OSA should be considered after surgical correction of VPI due to a high occurrence in this population. Furthermore, families should be counseled of the risk of OSA after surgery and the potential need for treatment with CPAP.

Marchiafava-Bignami disease mimics motor neuron disease: case report

BackgroundMarchiafava-Bignami disease (MBD) is a rare neurologic complication of chronic alcohol consumption that is characterized by callosal lesions involving demyelination and necrosis. Various reversible neurologic symptoms are found in patients with MBD. Dysarthria and dysphagia are found in various neurological diseases.Case presentationWe report a 51-year-old man with chronic alcoholism and malnutrition who progressively developed dysarthria and dysphagia. On admission, the patient was alert with mild cognitive dysfunction. The facial expression was flat, and there was weakness of the orbicularis oris bilaterally. The patient’s speech was slurred, there was difficulty swallowing, and the gag reflex and palate elevation were poor. The jaw jerk reflex was brisk and the snout reflex was positive. Neither tongue atrophy nor fasciculation were found. Bilateral upper and lower limb weakness with increased bilateral upper limb reflexes and Babinski reflexes were found. Because he had progressive dysarthria and dysphagia with upper and lower motor neuron signs, the initial diagnosis was motor neuron disease. However, electrophysiological analysis was normal. The vitamin B1 level was 14 ng/mL (normal: >24 ng/mL), and MRI revealed hyperintense lesions in the splenium of the corpus callosum and the primary motor cortices bilaterally. After vitamin B therapy for 17 days, the neurological disorders alleviated concurrently with disappearance of the lesions on MRI, which led to the definitive diagnosis of MBD.ConclusionsMBD presenting with these lesions can mimic motor neuron disease clinically.

Augmented BMPRIA-Mediated BMP Signaling in Cranial Neural Crest Lineage Leads to Cleft Palate Formation and Delayed Tooth Differentiation

The importance of BMP receptor Ia (BMPRIa) mediated signaling in the development of craniofacial organs, including the tooth and palate, has been well illuminated in several mouse models of loss of function, and by its mutations associated with juvenile polyposis syndrome and facial defects in humans. In this study, we took a gain-of-function approach to further address the role of BMPR-IA-mediated signaling in the mesenchymal compartment during tooth and palate development. We generated transgenic mice expressing a constitutively active form of BmprIa (caBmprIa) in cranial neural crest (CNC) cells that contributes to the dental and palatal mesenchyme. Mice bearing enhanced BMPRIa-mediated signaling in CNC cells exhibit complete cleft palate and delayed odontogenic differentiation. We showed that the cleft palate defect in the transgenic animals is attributed to an altered cell proliferation rate in the anterior palatal mesenchyme and to the delayed palatal elevation in the posterior portion associated with ectopic cartilage formation. Despite enhanced activity of BMP signaling in the dental mesenchyme, tooth development and patterning in transgenic mice appeared normal except delayed odontogenic differentiation. These data support the hypothesis that a finely tuned level of BMPRIa-mediated signaling is essential for normal palate and tooth development.

Transforming growth factor‐β activates c‐Myc to promote palatal growth

During palatogenesis, the palatal mesenchyme undergoes increased cell proliferation resulting in palatal growth, elevation and fusion of the two palatal shelves. Interestingly, the palatal mesenchyme expresses all three transforming growth factor (TGF) β isoforms (1, 2, and 3) throughout these steps of palatogenesis. However, the role of TGFβ in promoting proliferation of palatal mesenchymal cells has never been explored. The purpose of this study was to identify the effect of TGFβ on human embryonic palatal mesenchymal (HEPM) cell proliferation. Our results showed that all isoforms of TGFβ, especially TGFβ3, increased HEPM cell proliferation by up-regulating the expression of cyclins and cyclin-dependent kinases as well as c-Myc oncogene. TGFβ activated both Smad-dependent and Smad-independent pathways to induce c-Myc gene expression. Furthermore, TBE1 is the only functional Smad binding element (SBE) in the c-Myc promoter and Smad4, activated by TGFβ, binds to the TBE1 to induce c-Myc gene activity. We conclude that HEPM proliferation is manifested by the induction of c-Myc in response to TGFβ signaling, which is essential for complete palatal confluency. Our data highlights the potential role of TGFβ as a therapeutic molecule to correct cleft palate by promoting growth.

Width and elevation of the palatal shelves in unoperated unilateral and bilateral cleft lip and palate patients in the permanent dentition

Patients with cleft left lip and palate (CLP) normally require extensive surgery from an early age up to the end of adolescence. These surgeries affect the growth of the maxillofacial complex. The degree to which the cleft itself affects growth of the maxillofacial complex remains poorly understood. By analysing the width and elevation of the palatal shelves in unoperated adolescents and adults with unilateral and bilateral cleft lip and palate (UCLP and BCLP, respectively) and a non-cleft control group, it is possible to gain more insight into the real intrinsic growth potential of the maxillary structures. In this study, dental casts of the full permanent dentition of individuals with unrepaired UCLP (n = 68) and BCLP (n = 13) and non-cleft controls (n = 24) from the same area of Indonesia were digitized three-dimensionally. Maxillary arch width in the canine, premolar and molar regions, and the width and elevation of the palatal shelves were measured. Results showed that in patients with UCLP, the width of the palatal shelves on the cleft side in all regions, and on the non-cleft side in the canine/first premolar region, was significantly smaller compared with the control group. BCLP subjects showed similar deviations. In the UCLP group, the palatal shelves were rotated cranially and positioned more vertically. In the BCLP group, the palatal shelves were inclined by almost 10 ° more than the control group. The width of the palatal shelf and width of the maxillary arch positively correlated in the canine and first premolar regions for both the cleft and non-cleft side in patients with UCLP, and in the canine region for patients with BCLP. This means that the wider the palatal shelf, the wider the maxillary arch. The elevation of palatal shelves correlated with the maxillary arch width in all regions in patients with UCLP, and only in the premolar region in the control group. Thus, the wider the arch width, the smaller the elevation angle (the maxillary shelves are less vertical). No correlations between palatal shelf elevation and maxillary arch width were found in the BCLP group. This shows that the intrinsic growth potential in patients with UCLP and BCLP is affected by a smaller palatal shelf width and larger elevation of the shelves. These deviations may result in a wider cleft.

Putative functions of extracellular matrix glycoproteins in secondary palate morphogenesis

Cleft palate is a common birth defect in humans. Elevation and fusion of paired palatal shelves are coordinated by growth and transcription factors, and mutations in these can cause malformations. Among the effector genes for growth factor signaling are extracellular matrix (ECM) glycoproteins. These provide substrates for cell adhesion (e.g., fibronectin, tenascins), but also regulate growth factor availability (e.g., fibrillins). Cleft palate in Bmp7 null mouse embryos is caused by a delay in palatal shelf elevation. In contrast, palatal shelves of Tgf-β3 knockout mice elevate normally, but a cleft develops due to their failure to fuse. However, nothing is known about a possible functional interaction between specific ECM proteins and Tgf-β/Bmp family members in palatogenesis. To start addressing this question, we studied the mRNA and protein distribution of relevant ECM components during secondary palate development, and compared it to growth factor expression in wildtypewild type and mutant mice. We found that fibrillin-2 (but not fibrillin-1) mRNA appeared in the mesenchyme of elevated palatal shelves adjacent to the midline epithelial cells, which were positive for Tgf-β3 mRNA. Moreover, midline epithelial cells started expressing fibronectin upon contact of the two palatal shelves. These findings support the hypothesis that fibrillin-2 and fibronectin are involved in regulating the activity of Tgf-β3 at the fusing midline. In addition, we observed that tenascin-W (but not tenascin-C) was misexpressed in palatal shelves of Bmp7-deficient mouse embryos. In contrast to tenascin-C, tenascin-W secretion was strongly induced by Bmp7 in embryonic cranial fibroblasts in vitro. These results are consistent with a putative function for tenascin-W as a target of Bmp7 signaling during palate elevation. Our results indicate that distinct ECM proteins are important for morphogenesis of the secondary palate, both as downstream effectors and as regulators of Tgf-β/Bmp activity.

Epithelial integrity in palatal shelf elevation

The palate is the ceiling of the oral cavity that separates the nasal and oral cavities in mammals. Anterior two-thirds of the palate that has the bone and the rugae on the oral surface is the hard palate, and the posterior one-third of the palate lacks bone and is referred to as the soft palate. Palate development involves a sequential process of outgrowth, elevation, and fusion of palatal shelves. When these steps are interrupted or compromised, cleft palate, one of the most frequent human congenital anomalies, develops. In particular, during the elevation process, sufficient proliferation of palatal mesenchymal cells and concomitant synthesis of extracellular matrix (ECM) are required, and these are referred to as intrinsic factors. One of major extrinsic factors for this process is the functional maturation of masticatory muscles that are responsible for movement of the mandible and lingual muscles, such that the tongue can descend and sufficient space for shelf elevation is provided. In addition to these factors, recent findings have suggested that a third factor, epithelial integrity, may be an essential component for successful shelf elevation. For example, disruption of epithelial integrity can result in ectopic epithelial fusion between the palate and the mandible, or tongue, which anchors the palatal shelf to inhibit its elevation. Although most histological and molecular aspects of palatal elevation have been well reviewed, those of epithelial integrity have not been thoroughly elucidated. Therefore, in this review, features of epithelial integrity, and its contributing molecules, are described in relation to palatal shelf elevation in mice.