Characterization of Laryngeal Muscle Stem Cell Survival and Proliferation

Satellite cell capacity for functional adaptation of masseter muscle in Class II and Class III patients after orthognathic surgery-a pilot study

AIM

The aim of the prospective pilot study was to analyze the biomarkers CD34, Pax7, Myf5, and MyoD for stimulation of satellite cells (SCs), which are responsible for functional adaptation.

SUBJECTS AND METHODS

Forty-five Caucasian patients were consecutively recruited from the Maxillo-Facial-Surgery at TU Dresden. Eleven orthognathic Class III patients, 24 Class II patients, and 10 controls with Class I were involved in the study. Tissue samples from masseter muscle were taken from the patients pre-surgically (T1) and 7 months later (T2). Samples from controls were taken during the extraction of third molars in the mandible. Polymerase chain reaction (PCR) for relative quantification of gene expression was calculated with the delta delta cycle threshold (ΔΔCT) method.

RESULTS

The results show significant differences for the marker of SC stimulation between the controls, the patient groups, males, and females. The gene expression of CD34 was post-surgically upregulated for Class III (0.35-0.77, standard deviation [SD] = 0.39, P < 0.05) in comparison with controls. For Pax7, there was a significant difference shown between the retrognathic and the prognathic group because of downregulation in Class II patients (1.64-0.76, SD = 0.55, P < 0.05). In Class III patients, there was a significant upregulation for Myf5 (0.56-1.05, SD = 0.52, P < 0.05) after surgery too.

CONCLUSIONS

The significant decline of Pax7 in Class II patients indicates a deficiency of stimulated SC post-surgically. The expression of CD34 and Myf5 in Class II stayed unchanged. In contrast, there was an upregulation for all Class III patients, mainly in females, shown post-surgically. This may be one reason for weak functional adaptation and relapse in Class II patients.

Notch expression profile and satellite cell stimulation in masseter muscle before and after orthognathic surgery

The aim of this prospective study was to compare the expression of the Notch receptor family with the biomarker for stimulation of satellite cells (SC), which are responsible for functional adaptation. Tissue samples from the masseter muscle were taken presurgically and 7 months later. Samples from controls came from the extraction of third molars. The expression of Notch 1 to 4 and the satellite cell markers CD34, Pax7, and MyoD1 were investigated. PCR was used for relative quantification of gene expression, which was calculated with the ΔΔC_T method. The study involved 38 white patients - 10 prognathic, 18 retrognathic, and 10 orthognathic controls. The median value for Notch 1 was significantly reduced presurgically for prognathic (0.46, SD 0.45) and retrognathic (0.57, SD 0.35) patients compared with the controls. Postsurgically, Notch 2 was significantly upregulated in the prognathic group (0.55, SD 0.28/1.37, SD 0.85). Similarly, there was upregulation of Notch 3 in the prognathic group (0.33, SD 0.42/0.59, SD 1.37) and downregulation in retrognathic patients (0.59, SD 0.79/0.52, SD 0.97). Upregulations for the satellite cell markers CD34 and Pax7 were also found in prognathic patients. The significant upregulation of Notch 1-3 and CD34 in prognathics, but unchanged MyoD expression, signals high stimulation for SC and maintenance of the regeneration cell pool. A lower expression of Notch and SC in retrognathic patients could be responsible for weak functional adaptation.

Skeletal muscle cell transplantation: models and methods

Xenografts of skeletal muscle are used to study muscle repair and regeneration, mechanisms of muscular dystrophies, and potential cell therapies for musculoskeletal disorders. Typically, xenografting involves using an immunodeficient host that is pre-injured to create a niche for human cell engraftment. Cell type and method of delivery to muscle depend on the specific application, but can include myoblasts, satellite cells, induced pluripotent stem cells, mesangioblasts, immortalized muscle precursor cells, and other multipotent cell lines delivered locally or systemically. Some studies follow cell engraftment with interventions to enhance cell proliferation, migration, and differentiation into mature muscle fibers. Recently, several advances in xenografting human-derived muscle cells have been applied to study and treat Duchenne muscular dystrophy and Facioscapulohumeral muscular dystrophy. Here, we review the vast array of techniques available to aid researchers in designing future experiments aimed at creating robust muscle xenografts in rodent hosts.

Novel murine xenograft model for the evaluation of stem cell therapy for profound dysphagia

OBJECTIVES/HYPOTHESIS

Dysphagia is common and costly. Treatments are limited and innovative therapies are required. The tongue is essential for safe, effective swallowing and is a natural target for regenerative therapy. Muscle-derived stem cells (MDSCs) hold potential to restore dynamic function, and their application in the damaged tongue is appealing. We examined the safety and efficacy of human MDSC implantation into a novel mouse tongue model.

STUDY DESIGN

Animal study.

METHODS

Adult immune-deficient mice were randomized to surgical (hemiglossectomy) and nonsurgical groups. Animals underwent lingual injection of human MDSCs or saline (control). Groups were followed for 12 weeks. The primary outcome was MDSC survival measured by an in vivo imaging system (IVIS). Secondary outcomes included animal survival and weight. Comparisons were made using a Mann-Whitney U test with an α of .05.

RESULTS

Human MDSCs survived to the endpoint demonstrating 132% ± 465% and 15% ± 11% bioluminescence by IVIS at 12 weeks in hemiglossectomy and nonsurgical groups, respectively. All but one animal (hemiglossectomy with saline injection) survived to the study endpoint. Mean weight increased from baseline in all groups, with the greatest change observed in hemiglossectomy mice with MDSC injection (baseline 24.5 g ± 3.9 g; delta 5.9 g ± 4.6 g), exceeding the weight gain seen in surgical control mice (baseline 24.9 g ± 4.2 g, delta 2.7 g ± 1.4 g) (P = .04).

CONCLUSIONS

MDSCs exhibited over 100% survival at 3 months when injected into an immune-deficient hemiglossectomy mouse model. Tongue-injured animals injected with MDSCs exhibited superior weight gain after hemiglossectomy than control animals (P < .05). These data support further investigation into the use of autologous MDSCs as a potential treatment for dysphagia secondary to tongue weakness and fibrosis LEVEL OF EVIDENCE: NA Laryngoscope, 127:E359-E363, 2017.

Neonatal Satellite Cells Form Small Myotubes In Vitro

Although palatal muscle reconstruction in patients with cleft palate takes place during early childhood, normal speech development is often not achieved. We hypothesized that the intrinsic properties of head satellite cells (SCs) and the young age of these patients contribute to the poor muscle regeneration after surgery. First, we studied the fiber type distribution and the expression of SC markers in ex vivo muscle tissue from head (branchiomeric) and limb (somite-derived) muscles from neonatal (2-wk-old) and young (9-wk-old) rats. Next, we cultured SCs isolated from these muscles for 5, 7, and 9 d, and investigated the in vitro expression of SC markers, as well as changes in proliferation, early differentiation, and fusion index (myotube formation) in these cells. In our ex vivo samples, we found that virtually all myofibers in both the masseter (Mass) and the levator veli palatini (LVP) muscles contained fast myosin heavy chain (MyHC), and a small percentage of digastric (Dig) and extensor digitorum longus myofibers also contained slow MyHC. This was independent of age. More SCs were found in muscles from neonatal rats as compared with young rats [17.6 (3.8%) v. 2.3 (1.6%); P < 0.0001]. In vitro, young branchiomeric head muscle (BrHM) SCs proliferated longer and differentiated later than limb muscle SCs. No differences were found between SC cultures from the different BrHMs. SC cultures from neonatal muscles showed a much higher proliferation index than those from young animals at 5 d (0.8 v. 0.2; P < 0.001). In contrast, the fusion index in neonate SCs was about twice as low as that in SCs from young muscles at 9 d [27.6 (1.4) v. 62.8 (10.2), P < 0.0001]. In conclusion, SCs from BrHM differ from limb muscles especially in their delayed differentiation. SCs from neonatal muscles form myotubes less efficiently than those from young muscles. These age-dependent differences in stem cell properties urge careful consideration for future clinical applications in patients with cleft palate.

A muscle stem cell for every muscle: variability of satellite cell biology among different muscle groups

The human body contains approximately 640 individual skeletal muscles. Despite the fact that all of these muscles are composed of striated muscle tissue, the biology of these muscles and their associated muscle stem cell populations are quite diverse. Skeletal muscles are affected differentially by various muscular dystrophies (MDs), such that certain genetic mutations specifically alter muscle function in only a subset of muscles. Additionally, defective muscle stem cells have been implicated in the pathology of some MDs. The biology of muscle stem cells varies depending on the muscles with which they are associated. Here we review the biology of skeletal muscle stem cell populations of eight different muscle groups. Understanding the biological variation of skeletal muscles and their resident stem cells could provide valuable insight into mechanisms underlying the susceptibility of certain muscles to myopathic disease.

Effects of aging on thyroarytenoid muscle regeneration

OBJECTIVES/HYPOTHESIS

Regenerative properties of age-associated changes in the intrinsic laryngeal muscles following injury are unclear. The purpose of this study was to investigate the regenerative properties of the thyroarytenoid (TA) muscle in an aging rat model. The hypothesis was that following myotoxic injury, old animals would exhibit a decrease in mitotic activities of muscle satellite cells when compared with younger rats, suggesting reduced regenerative potential in the aging rat TA muscle.

STUDY DESIGN

Animal group comparison.

METHODS

Regeneration responses following injury to the TA muscle were examined in 18 young adult, middle-aged, and old Fischer 344/Brown Norway rats. TA muscle fiber cross-sectional area (CSA), satellite cell mitosis (number/fiber), and regeneration index (CSA injured side/CSA noninjured side) were measured and compared across age groups.

RESULTS

Young adult animals had a significantly higher regeneration index than the middle-aged and old groups. Within the lateral region of the TA muscle (LTA), the regeneration index was significantly higher in the young adult animals than in the middle-aged and old animals. The regeneration index of the medial TA was significantly higher than the LTA across all age groups.

CONCLUSIONS

The regenerative capacity of the TA muscle is impaired with increasing age.