Morphological Characterization of the Levator Veli Palatini Muscle in Children Born With Cleft Palates

Tissue engineering strategies combining molecular targets against inflammation and fibrosis, and umbilical cord blood stem cells to improve hampered muscle and skin regeneration following cleft repair

Cleft lip with or without cleft palate is a congenital deformity that occurs in about 1 of 700 newborns, affecting the dentition, bone, skin, muscles and mucosa in the orofacial region. A cleft can give rise to problems with maxillofacial growth, dental development, speech, and eating, and can also cause hearing impairment. Surgical repair of the lip may lead to impaired regeneration of muscle and skin, fibrosis, and scar formation. This may result in hampered facial growth and dental development affecting oral function and lip and nose esthetics. Therefore, secondary surgery to correct the scar is often indicated. We will discuss the molecular and cellular pathways involved in facial and lip myogenesis, muscle anatomy in the normal and cleft lip, and complications following surgery. The aim of this review is to outline a novel molecular and cellular strategy to improve musculature and skin regeneration and to reduce scar formation following cleft repair. Orofacial clefting can be diagnosed in the fetus through prenatal ultrasound screening and allows planning for the harvesting of umbilical cord blood stem cells upon birth. Tissue engineering techniques using these cord blood stem cells and molecular targeting of inflammation and fibrosis during surgery may promote tissue regeneration. We expect that this novel strategy improves both muscle and skin regeneration, resulting in better function and esthetics after cleft repair.

Structural Changes Following Velopharyngeal Resistance Training (Continuous Positive Airway Pressure Therapy): A Preliminary Report

OBJECTIVE

To evaluate the feasibility/effectiveness of using magnetic resonance imaging (MRI) to document velopharyngeal (VP) structural changes induced by continuous positive airway pressure (CPAP) therapy.

OUTCOME MEASURES

Changes in velar length and thickness, levator veli palatini (LVP) length and thickness, velar volume, and intravelar muscular proportion along the course of CPAP therapy participation (Pre-CPAP, Post-CPAP, and withdrawal).

RESULTS

Velar and LVP lengths remained nearly the same, with the median changes (Δ) less than 0.6%, across repeated conditions. Although varying in magnitudes of change, median velar volume (Δ4%), velar thickness (Δ20%), LVP thickness (Δ17%), and intravelar muscular proportion (Δ10%) illustrated a consistent pattern of increases following the 8-week CPAP therapy. These VP structural measurements slightly decreased but remained above the pretraining condition after 8-week detraining.

CONCLUSIONS

This report successfully demonstrated that MRI is a viable tool to document CPAP therapy-induced VP structural changes while providing preliminary empirical data.

Morphological and molecular comparisons between tibialis anterior muscle and levator veli palatini muscle: A preliminary study on their augmentation potential

Tibialis anterior (TA) muscle and other somite-derived limb muscles remain the prototype in skeletal muscle study. The majority of head muscles, however, develop from branchial arches and maintain a number of heterogeneities in comparison with their limb counterparts. Levator veli palatini (LVP) muscle is a deep-located head muscle responsible for breathing, swallowing and speech, and is central to cleft palate surgery, yet lacks morphological and molecular investigation. In the present study, multiscale in vivo analyses were performed to compare TA and LVP muscle in terms of their myofiber composition, in-situ stem cell population and augmentation potential. TA muscle was identified to be primarily composed of type 2B myofibers while LVP muscle primarily consisted of type 2A and 2X myofibers. In addition, LVP muscle maintained a higher percentage of centrally-nucleated myofibers and a greater population of satellite cells. Notably, TA and LVP muscle responded to exogenous Wnt7a stimulus in different ways. Three weeks after Wnt7a administration, TA muscle exhibited an increase in myofiber number and a decrease in myofiber size, while LVP muscle demonstrated no significant changes in myofiber number or myofiber size. These results suggested that LVP muscle exhibits obvious differences in comparison with TA muscle. Therefore, knowledge acquired from TA muscle studies requires further testing before being applied to LVP muscle.

Mechanical cues in orofacial tissue engineering and regenerative medicine

Cleft lip and palate patients suffer from functional, aesthetical, and psychosocial problems due to suboptimal regeneration of skin, mucosa, and skeletal muscle after restorative cleft surgery. The field of tissue engineering and regenerative medicine (TE/RM) aims to restore the normal physiology of tissues and organs in conditions such as birth defects or after injury. A crucial factor in cell differentiation, tissue formation, and tissue function is mechanical strain. Regardless of this, mechanical cues are not yet widely used in TE/RM. The effects of mechanical stimulation on cells are not straight-forward in vitro as cellular responses may differ with cell type and loading regime, complicating the translation to a therapeutic protocol. We here give an overview of the different types of mechanical strain that act on cells and tissues and discuss the effects on muscle, and skin and mucosa. We conclude that presently, sufficient knowledge is lacking to reproducibly implement external mechanical loading in TE/RM approaches. Mechanical cues can be applied in TE/RM by fine-tuning the stiffness and architecture of the constructs to guide the differentiation of the seeded cells or the invading surrounding cells. This may already improve the treatment of orofacial clefts and other disorders affecting soft tissues.

Feasibility study to assess clinical applications of 3-T cine MRI coupled with synchronous audio recording during speech in evaluation of velopharyngeal insufficiency in children

BACKGROUND

In the past decade, there has been increased utilization of magnetic resonance imaging (MRI) in evaluating and understanding velopharyngeal insufficiency (VPI). To our knowledge, none of the prior studies with MRI has simultaneously linked the audio recordings of speech during cine MRI acquisition with the corresponding images and created a video for evaluating VPI.

OBJECTIVE

To develop an MRI protocol with static and cine sequences during phonation to evaluate for VPI in children and compare the findings to nasopharyngoscopy and videofluoroscopy.

MATERIALS AND METHODS

Five children, ages 8-16 years, with known VPI, who had previously undergone nasopharyngoscopy and videofluoroscopy, were included. MRI examination was performed on a 3-T Siemens scanner. Anatomical data was obtained using an isotropic T2-weighted 3-D SPACE sequence with multiplanar reformation capability. Dynamic data was obtained using 2-D FLASH cine sequences of the airway in three imaging planes during phonation. Audio recordings were captured by a MRI compatible optical microphone.

RESULTS

All five cases had MRI and nasopharyngoscopy and four had videofluoroscopy performed. VPI was identified by MRI in all five patients. The location and severity of the velopharyngeal gap, closure pattern, velar size and shape and levator veli palatini (LVP) muscle were identified in all patients. MRI was superior in visualizing the integrity of the LVP muscle. MRI was unable to identify hemipalatal weakness in one case. In a case of stress-induced VPI, occurring only during clarinet playing, cine MRI demonstrated discordant findings of a velopharyngeal gap during phonatory tasks but not with instrument playing. Overall, there was satisfactory correlation among MRI, nasopharyngoscopy and videofluoroscopy findings.

CONCLUSION

Cine MRI of the airway during speech is a noninvasive, well-tolerated diagnostic imaging tool that has the potential to serve as a guide prior to and after surgical correction of VPI. MRI provided superior anatomical detail of the levator musculature. The creation of a video with recorded phonation allowed correlation between palatal movements and specific phonatory tasks.

Magnetic Resonance Imaging of Velar Muscle Tissue Distribution in Healthy Adults

OBJECTIVES

To examine muscle tissue distribution along the length of the velum in living individuals using magnetic resonance imaging (MRI).

DESIGN

Using the three-dimensional MRI data acquired from 10 normal white adults, two area measures including the muscular area and the total velar area were obtained from 10 oblique slices running perpendicular to velar length. A polynomial regression analysis was performed where the proportion of the muscular to the total velar area was regressed on the slice numbers running along the length of the velum.

RESULTS

The proportion of the muscular to total velar area increased from the anterior section of the velum, reaching a maximum (33.24%) in the midsection, and decreasing in the posterior section of the velum. A third-order (cubic) polynomial function that best illustrated the proportional data (R(2) = .47) was derived.

CONCLUSIONS

The present study demonstrated that MRI is a viable tool to examine the muscle tissue distribution of the velum in living individuals. Although the overall pattern in the muscle tissue distribution of the healthy velum was similar to that reported in previous literature based on cadaver specimens, the participants in the present study appeared to have greater muscular proportion of the velum. The muscular proportion measure derived from the healthy living individuals can be used as an additional parameter accounting for sufficient intravelar muscle mass for future studies.

Strategies to improve regeneration of the soft palate muscles after cleft palate repair

Children with a cleft in the soft palate have difficulties with speech, swallowing, and sucking. These patients are unable to separate the nasal from the oral cavity leading to air loss during speech. Although surgical repair ameliorates soft palate function by joining the clefted muscles of the soft palate, optimal function is often not achieved. The regeneration of muscles in the soft palate after surgery is hampered because of (1) their low intrinsic regenerative capacity, (2) the muscle properties related to clefting, and (3) the development of fibrosis. Adjuvant strategies based on tissue engineering may improve the outcome after surgery by approaching these specific issues. Therefore, this review will discuss myogenesis in the noncleft and cleft palate, the characteristics of soft palate muscles, and the process of muscle regeneration. Finally, novel therapeutic strategies based on tissue engineering to improve soft palate function after surgical repair are presented.

Thickness and Histologic and Histochemical Properties of the Superior Pharyngeal Constrictor Muscle in Velocardiofacial Syndrome

BACKGROUND

Velocardiofacial syndrome (VCFS) is one of the most common multiple anomaly syndromes in humans. Pharyngeal hypotonia, one of the most common findings in VCFS, contributes to hypernasal speech, which occurs in approximately 75% of individuals with VCFS.

OBJECTIVE

To evaluate the thickness and histologic and histochemical properties of the superior pharyngeal constrictor (SPC) muscle in patients with VCFS to determine whether a muscle abnormality exists that might contribute to the hypotonia seen in these patients. Subjects The SPC muscle thickness in 26 VCFS patients (18 male and 8 female; age range, 3-29 years) was compared with SPC muscle thickness in age- and sex-matched controls using magnetic resonance images. The histologic and histochemical properties of the SPC muscle in 9 VCFS patients (6 male and 3 female; age range, 4-12 years) were compared with SPC muscle in 3 adult cadavers without VCFS (all male; age range, 80-86 years) using specimens obtained during pharyngeal flap surgery.

RESULTS

The thickness of the SPC muscle was significantly less in patients with VCFS (2.03 mm) than in patients without VCFS (2.85 mm). The SPC muscle contained a significantly greater proportion of type 1 fibers in patients with VCFS (27.7%) than in adults without VCFS (17.9%), and the diameter of the type 1 fibers was significantly smaller in patients with VCFS (21.6 micro m) than in adults without VCFS (26.6 micro m).

CONCLUSIONS

Differences in the thickness and histologic and histochemical properties of the SPC muscle found in patients with VCFS compared with individuals without VCFS may offer insight into the cause of pharyngeal hypotonia and hypernasal speech seen in these patients.