Developmental changes in craniofacial morphology in subjects with Duchenne muscular dystrophy

Jak2 and Jaw Muscles Are Required for Buccopharyngeal Membrane Perforation during Mouth Development

The mouth is a central feature of our face, without which we could not eat, breathe, or communicate. A critical and early event in mouth formation is the creation of a "hole" which connects the digestive system and the external environment. This hole, which has also been called the primary or embryonic mouth in vertebrates, is initially covered by a 1-2 cell layer thick structure called the buccopharyngeal membrane. When the buccopharyngeal membrane does not rupture, it impairs early mouth functions and may also lead to further craniofacial malformations. Using a chemical screen in an animal model (Xenopus laevis) and genetic data from humans, we determined that Janus kinase 2 (Jak2) has a role in buccopharyngeal membrane rupture. We have determined that decreased Jak2 function, using antisense morpholinos or a pharmacological antagonist, caused a persistent buccopharyngeal membrane as well as the loss of jaw muscles. Surprisingly, we observed that the jaw muscle compartments were connected to the oral epithelium that is continuous with the buccopharyngeal membrane. Severing such connections resulted in buccopharyngeal membrane buckling and persistence. We also noted puncta accumulation of F-actin, an indicator of tension, in the buccopharyngeal membrane during perforation. Taken together, the data has led us to a hypothesis that muscles are required to exert tension across the buccopharyngeal membrane, and such tension is necessary for its perforation.

Influence of botulinum toxin A on craniofacial morphology after injection into the right masseter muscle of dystrophin deficient (mdx-) mice

BACKGROUND

Severe craniofacial and dental abnormalities, typical for patients with progressive Duchenne muscular dystrophy (DMD), are an exellcent demonstration of Melvin L. Moss "functional matrix theory", highlighting the influence of muscle tissue on craniofacial growth and morphology. However, the currently best approved animal model for investigation of this interplay is the mdx-mouse, which offers only a limited time window for research, due to the ability of muscle regeneration, in contrast to the human course of the disease. The aim of this study was to evaluate craniofacial morphology after BTX-A induced muscle paralysis in C57Bl- and mdx-mice, to prove the suitability of BTX-A intervention to inhibit muscle regeneration in mdx-mice and thus, mimicking the human course of the DMD disease.

METHODS

Paralysis of the right masseter muscle was induced in 100 days old C57Bl- and mdx-mice by a single specific intramuscular BTX-A injection. Mice skulls were obtained at 21 days and 42 days after BTX-A injection and 3D radiological evaluation was performed in order to measure various craniofacial dimensions in the sagittal, transversal and vertical plane. Statstical analysis were performed using SigmaStat®Version 3.5. In case of normal distribution, unpaired t-test and otherwise the Mann-Whitney-U test was applied. A statistical significance was given in case of p ≤ 0.05.

RESULTS

In contrast to C57Bl-mice, in mdx-mice, three weeks after BTX-A treatment a significant decrease of skull dimensions was noted in most of the measurements followed by a significant increase at the second investigation period.

CONCLUSIONS

BTX-A can induce changes in craniofacial morphology and presumably partially inhibit muscle regeneration in mdx-mice, but cannot completely intensify craniofacial effects elicited by dystrophy. Further research is necessary in order to fully understand muscle-bone interplay after BTX-A injection into dystrophic muscles.

FACEts of mechanical regulation in the morphogenesis of craniofacial structures

During embryonic development, organs undergo distinct and programmed morphological changes as they develop into their functional forms. While genetics and biochemical signals are well recognized regulators of morphogenesis, mechanical forces and the physical properties of tissues are now emerging as integral parts of this process as well. These physical factors drive coordinated cell movements and reorganizations, shape and size changes, proliferation and differentiation, as well as gene expression changes, and ultimately sculpt any developing structure by guiding correct cellular architectures and compositions. In this review we focus on several craniofacial structures, including the tooth, the mandible, the palate, and the cranium. We discuss the spatiotemporal regulation of different mechanical cues at both the cellular and tissue scales during craniofacial development and examine how tissue mechanics control various aspects of cell biology and signaling to shape a developing craniofacial organ.

Growing patients with Duchenne muscular dystrophy: longitudinal changes in their dentofacial morphology and orofacial functional capacities

Aim

The aim of this study was to describe the longitudinal changes in facial morphology, dental arch alterations and oral functional capacities that occur in growing patients with Duchenne muscular dystrophy (DMD) in order to identify the effects of the progression of the disease.

Subjects and Methods

Twelve DMD patients (6.5-17.5 years of age) and 12 matched controls were screened on two different occasions (T1 and T2), 2 years apart. Dental casts, lateral cephalometric radiographs, maximal posterior bite force and labial force were measured to determine changes in their functional capacities and dentofacial morphology. Furthermore, the thickness and echogenicity of the masseter muscle were measured during clenching.

Statistical evaluation

Unpaired t-tests were performed to evaluate the differences between the DMD patients and their healthy matched controls; paired t-tests were used to assess the changes that occurred within each group between T1 and T2.

Results

Between T1 and T2 the following changes were observed: widening of the lower dental arch for the DMD patients of 2.6mm (±0.9mm) compared to a slight reduction of -0.1mm (±0.8mm) for the control group (P = 0.001). We found a statistically significant reduction of the sagittal skeletal intermaxillary relationship (ANB-angle) of 2.0° (±2.0°) in the DMD group (P = 0.012). In T1 and T2, the maximal posterior bite force and the labial force were lower for the DMD patients compared to the control group (P = 0.001), who showed an increase during this period.

Conclusion

The results indicate that DMD influences the facial morphology, dental arch dimensions and oral functional capacities. The longitudinal perspective of this study revealed that the worsening of most of the measured parameters is associated with the progression of the disease. Besides the expected deterioration of the functional measurements, we found in all patients, a marked transverse increase of the posterior part of the dental arches, more in the lower than in the upper, resulting in posterior crossbites, as well as a tendency towards a skeletal Class III relationship.

Dystrophic changes in masticatory muscles related chewing problems and malocclusions in Duchenne muscular dystrophy

Dysphagia in Duchenne muscular dystrophy (DMD) worsens with age, with increasingly effortful mastication. The aims of this study were to describe mastication problems in consecutive stages in a group of patients with DMD and to determine related pathophysiological aspects of masticatory muscle structure, tongue thickness, bite force and dental characteristics. Data from 72 patients with DMD (4.3 to 28.0 years), divided into four clinical stages, were collected in a cross sectional study. Problems with mastication and the need for food adaptations, in combination with increased echogenicity of the masseter muscle, were already found in the early stages of the disease. A high percentage of open bites and cross bites were found, especially in the later stages. Tongue hypertrophy also increased over time. Increased dysfunction, reflected by increasingly abnormal echogenicity, of the masseter muscle and reduced occlusal contacts (anterior and posterior open bites) were mainly responsible for the hampered chewing. In all, this study shows the increasing involvement of various elements of the masticatory system in progressive Duchenne muscular dystrophy. To prevent choking and also nutritional deficiency, early detection of chewing problems by asking about feeding and mastication problems, as well as asking about food adaptations made, is essential and can lead to timely intervention.

A Rare Case Report of Neurodegenerative Disease: Duchenne Muscular Dystrophy in Two Male Siblings

Duchenne muscular dystrophy (DMD) is an recessive X-linked mediated, musculoskeletal disorder that affects only males. It is the most common and severe form of muscular dystrophy where there is failure to manufacture dystrophin. Clinically, it is characterized by progressive muscle wasting eventually leading to premature death. This case report describes the genetic, oral and systemic findings in two cases of DMD in male siblings.

How to cite this article: Suneja B, Suneja ES, Adlakha VK, Chandna P. A Rare Case Report of Neurodegenerative Disease: Duchenne Muscular Dystrophy in Two Male Siblings. Int J Clin Pediatr Dent 2015;8(2):163-165.

Reduced mandibular range of motion in Duchenne Muscular Dystrophy: predictive factors

Patients with Duchenne muscular dystrophy (DMD) experience negative effects upon feeding and oral health. We aimed to determine whether the mandibular range of motion in DMD is impaired and to explore predictive factors for the active maximum mouth opening (aMMO). 23 patients with DMD (mean age 16.7 ± 7.7 years) and 23 controls were assessed using a questionnaire about mandibular function and impairments. All participants underwent a clinical examination of the masticatory system, including measurement of mandibular range of motion and variables related to mandibular movements. In all patients, quantitative ultrasound of the digastric muscle and the geniohyoid muscle and the motor function measure (MFM) scale were performed. The patients were divided into early and late ambulatory stage (AS), early non-ambulatory stage (ENAS) and late non-ambulatory stage (LNAS). All mandibular movements were reduced in the patient group (P < 0.001) compared to the controls. Reduction in the aMMO (<40 mm) was found in 26% of the total patient group. LNAS patients had significantly smaller mandibular movements compared to AS and ENAS (P < 0.05). Multiple linear regression analysis for aMMO revealed a positive correlation with the body height and disease progression, with MFM total score as the strongest independent risk factor (R(2) = 0.71). Mandibular movements in DMD are significantly reduced and become more hampered with loss of motor function, including the sitting position, arm function, and neck and head control. We suggest that measurement of the aMMO becomes a part of routine care of patients with DMD.

Temporalis muscle hypertrophy and reduced skull eccentricity in Duchenne muscular dystrophy

Muscle hypertrophy and muscle weakness are well known in Duchenne muscular dystrophy. Decreased muscle force can have secondary effects on skeletal growth and development such as facial and dental morphology changes. In this study, we quantified temporal muscle thickness, circumference, and eccentricity of the skull and the head on T1-weighted magnetic resonance imaging (MRI) scans of the head of 15 Duchenne muscular dystrophy patients and 15 controls. Average temporal muscle thickness was significantly increased in patients (12.9 ± 5.2 mm) compared to controls (6.8 ± 1.4 mm) (P < .0001), whereas the shape of the skull was significantly rounder compared to controls. Temporal muscle thickness and skull eccentricity were significantly negatively correlated in patients, and positively in controls. Hypertrophy of the temporal muscles and changes in skull eccentricity appear to occur early in the course of Duchenne muscular dystrophy. Further studies in younger patients are needed to confirm a causal relationship.

WITHDRAWN: Age-dependent muscle dystrophy related changes of craniofacial morphology in mdx mice

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Talin, vinculin and nestin expression in orofacial muscles of dystrophin deficient mdx mice

The activity of cytoskeletal proteins like talin, vinculin and nestin increases in muscle that regenerates. Little is known about their role or at least their expression in the process of regeneration in masticatory muscles of mdx mice, a model of Duchenne muscular dystrophy. To determine a potential role of cytoskeletal proteins in the regeneration process of mdx masticatory muscles, we examined the expression of talin 1, talin 2, vinculin and nestin in 100-day-old control and mdx mice using quantitative RT-PCR, Western blot analyses and histochemistry. The protein expression of talin 1, talin 2, nestin and vinculin in mdx muscles remained unchanged as compared with normal mice. However, in mdx masseter it was found a relative increase of nestin compared to controls. The protein expression of talin 1 and vinculin tended to be increased in mdx tongue and talin 2 to diminish in mdx masseter and temporal muscle. In mdx mice, we found significantly lower percentage of transcripts coding for nestin, talin 1, talin 2 and vinculin in masseter (p < 0.05) and temporal muscle (p < 0.001). In contrast, the mRNA expression of nestin was found to be increased in mdx tongue. Activated satellite cells, myoblasts and immature regenerated muscle fibres in mdx masseter and temporal revealed positive staining for nestin. The findings of the presented work suggest dystrophin-lack-associated changes in the expression of cytoskeletal proteins in mdx masticatory muscles could be compensatory for dystrophin absence. The expression of nestin may serve as an indicator for the regeneration in the orofacial muscles.

Profiling type I collagen gene expression in growing mandibular structures

We conducted a temporal gene expression analysis with type I collagen in the coronoid process, alveolar process and mandibular angle of the rat. We observed gene expression cross-sectionally across different important physiological time points in the rat postnatal life in order to observe in which developmental stage mandibular development mainly occur. This study indicates prominent type I collagen expression at day 10 postpartum in the mandibular ramus and at day 21 in the alveolar process. These findings correspond well with previously obtained data from proliferation studies in facial bone suggesting that craniofacial growth in the rat occurs mainly between days 10 and 21.

Oral health considerations in muscular dystrophies

Muscular dystrophies (MD) are a heterogeneous group of inherited neuromuscular disorders characterized by muscle necrosis and progressive muscle weakness. It is important for oral healthcare providers to be familiar with MD as special considerations are necessary to provide appropriate and safe dental care for these medically complex patients. This article briefly reviews the more common types of MD, namely, Duchenne MD, Becker MD, Emery-Dreifuss MD, facioscapulo-humeral MD, limb-girdle MD, oculopharyngeal MD, and myotonic dystrophy. Aspects of their epidemiology, pathophysiology, clinical presentation, diagnosis, and medical management as well as oral health considerations are discussed.

Swallowing difficulties in Duchenne muscular dystrophy: indications for feeding assessment and outcome of videofluroscopic swallow studies

Feeding difficulties are known to occur with advancing age in Duchenne muscular dystrophy (DMD). We evaluated the role of videofluoroscopy swallow study (VFSS) in a group of 30 DMD patients with feeding difficulties. Indications for feeding assessment were: respiratory infections potentially attributable to aspiration (n=10) and/or episodes of choking (n=24) subdivided into isolated choking events (n=8) and regular choking during swallowing (n=16). Indications for assessment were analysed in relation to the VFSS results. Median age at assessment was 17.13 years (range 6-31.4). Twenty-four VFSS were performed. Prolonged chewing and effortful bolus transport for solids increased with age. Swallow trigger was normal in the majority of cases. All patients had some post-swallow pharyngeal residue around the laryngeal inlet increasing in volume with age. Although this residue did not result in aspiration, it was worse in patients that were frequently choking. Three patients intermittently had penetration of the supraglottic space that did not reach the vocal folds during the swallow. Our results suggest that reported swallowing problems when assessed are not always associated with difficulties on VFSS. It is the oral phase of swallowing that is most significantly affected in DMD. The pharyngeal phase is well triggered but is weak with incomplete pharyngeal clearance leaving pharyngeal residue. Insufficient or effortful chewing coupled with weak clearance may predispose them to choking episodes either as a one off event or with increasing frequency with age. This study suggests that VFSS may not be of additional benefit to careful feeding history and observation in DMD with feeding difficulties.

Dentofacial characteristics of growing patients with Duchenne muscular dystrophy: a morphological study

Occlusal traits and craniofacial morphology were studied in growing patients with Duchenne muscular dystrophy (DMD). Sixteen patients from 6 to 20 years of age were examined and compared with 16 healthy male individuals matched according to age. The dental arches and occlusal traits of both groups were analysed on dental casts and compared with the norms of healthy individuals from the literature. Lateral cephalograms of the patients were compared with normal individuals by using scored values based on standard deviations in order to compensate for heterogeneity in the age of the subjects. Statistical analysis was undertaken for continuous variables with a paired Student's t-test and non-continuous variables with a chi-square test. Linear regressions were used to evaluate the influence of age. A high prevalence of malocclusions was found, including posterior crossbites, anterior and lateral open bites, a tendency towards mesio-occlusion due to a skeletal Class III malocclusion, and dental compensations of the Class III relationship by retrusion of the lower incisors. Both upper and lower arches were widened posteriorly. The lower arches were even wider than the upper arches, resulting in frequent posterior crossbites. No significant skeletal vertical deviations were observed in this group of DMD patients, except for the maxillary plane angle (NL/NSL) that was larger than normal, while the anterior upper face height (NSp) was smaller. However, no difference was found in lower face height. The posterior enlargement of the dental arches and the dentoalveolar development towards an Angle Class III relationship were significantly related to age and found more frequently among the older subjects.

The effects of muscular dystrophy on the craniofacial shape of Mus musculus

Skeletal anomalies are common in patients with muscular dystrophy, despite an absence of mutations to genes that specifically direct skeletogenesis. In order to understand these anomalies further, we examined two strains of muscular dystrophy (laminin- and merosin-deficient) relative to controls, to determine how the weakened muscle forces affected skull shape in a mouse model. Shape was characterized with geometric morphometric techniques, improving upon the limited analytical power of the standard linear measurements. Through these techniques, we document the specific types of cranial skeletal deformation produced by the two strains, each with individual shape abnormalities. The mice with merosin deficiency (with an earlier age of onset) developed skulls with more deformation, probably related to the earlier ontogenetic timing of disease onset. Future examinations of these mouse models may provide insight regarding the impact of muscular forces and the production and maintenance of craniofacial integration and modularity.