Desmin and nerve terminal expression during embryonic development of the lateral pterygoid muscle in mice

Downregulation of SOX9 expression in developing entheses adjacent to intramembranous bone

Entheses are classified into three types: fibrocartilaginous, fibrous, and periosteal insertions. However, the mechanism behind the development of fibrous entheses and periosteal insertions remains unclear. Since both entheses are part of the temporomandibular joint (TMJ), this study analyzes the TMJ entheses. Here, we show that SOX9 expression is negatively regulated during TMJ enthesis development, unlike fibrocartilage entheses which are modularly formed by SCX and SOX9 positive progenitors. The TMJ entheses was adjacent to the intramembranous bone rather than cartilage. SOX9 expression was diminished during TMJ enthesis development. To clarify the functional role of Sox9 in the development of TMJ entheses, we examined these structures in TMJ using Wnt1Cre;Sox9flox/+ reporter mice. Wnt1Cre;Sox9flox/+ mice showed enthesial deformation at the TMJ. Next, we also observed a diminished SOX9 expression area at the enthesis in contact with the clavicle's membranous bone portion, similar to the TMJ entheses. Together, these findings reveal that the timing of SOX9 expression varies with the ossification development mode.

Effects of Myostatin on Nuclear Morphology at the Myotendinous Junction

Myostatin (Myo) is known to suppress skeletal muscle growth, and was recently reported to control tendon homeostasis. The purpose of the present study was to investigate the regulatory involvement of Myo in the myotendinous junction (MTJ) in vivo and in vitro. After Achilles tendon injury in mice, we identified unexpected cell accumulation on the tendon side of the MTJ. At postoperative day 7 (POD7), the nuclei had an egg-like profile, whereas at POD28 they were spindle-shaped. The aspect ratio of nuclei on the tendon side of the MTJ differed significantly between POD7 and POD28 (p = 4.67 × 10−34). We then investigated Myo expression in the injured Achilles tendon. At the MTJ, Myo expression was significantly increased at POD28 relative to POD7 (p = 0.0309). To investigate the action of Myo in vitro, we then prepared laminated sheets of myoblasts (C2C12) and fibroblasts (NIH3T3) (a pseudo MTJ model). Myo did not affect the expression of Pax7 and desmin (markers of muscle development), scleraxis and temonodulin (markers of tendon development), or Sox9 (a common marker of muscle and tendon development) in the cell sheets. However, Myo changed the nuclear morphology of scleraxis-positive cells arrayed at the boundary between the myoblast sheet and the fibroblast sheet (aspect ratio of the cell nuclei, myostatin(+) vs. myostatin(-): p = 0.000134). Myo may strengthen the connection at the MTJ in the initial stages of growth and wound healing.

Factors Involved in Morphogenesis in the Muscle-Tendon-Bone Complex

A decline in the body's motor functions has been linked to decreased muscle mass and function in the oral cavity and throat; however, aging of the junctions of the muscles and bones has also been identified as an associated factor. Basic and clinical studies on the muscles, tendons and bones, each considered independently, have been published. In recent years, however, research has focused on muscle attachment as the muscle-tendon-bone complex from various perspectives, and there is a growing body of knowledge on SRY-box9 (Sox9) and Mohawk(Mkx), which has been identified as a common controlling factor and a key element. Myostatin, a factor that inhibits muscle growth, has been identified as a potential key element in the mechanisms of lifetime structural maintenance of the muscle-tendon-bone complex. Findings in recent studies have also uncovered aspects of the mechanisms of motor organ complex morphostasis in the superaged society of today and will lay the groundwork for treatments to prevent motor function decline in older adults.

Switching of Sox9 expression during musculoskeletal system development

The musculoskeletal system, which comprises muscles, tendons, and bones, is an efficient tissue complex that coordinates body movement and maintains structural stability. The process of its construction into a single functional and complex organization is unclear. SRY-box containing gene 9 (Sox9) is expressed initially in pluripotent cells and subsequently in ectodermal, endodermal, and mesodermal derivatives. This study investigated how Sox9 controls the development of each component of the musculoskeletal system. Sox9 was expressed in MTJ, tendon, and bone progenitor cells at E13 and in bone at E16. We detected Sox9 expression in muscle progenitor cells using double-transgenic mice and myoblastic cell lines. However, we found no Sox9 expression in developed muscle. A decrease in Sox9 expression in muscle-associated connective tissues, tendons, and bones led to hypoplasia of the cartilage and its attachment to tendons and muscle. These results showed that switching on Sox9 expression in each component (muscle, tendon, and bone) is essential for the development of the musculoskeletal system. Sox9 is expressed in not only tendon and bone progenitor cells but also muscle progenitor cells, and it controls musculoskeletal system development.

The Effect of Vidian Neurectomy on Pulmonary Function in Patients with Allergic Rhinitis and Chronic Rhinosinusitis with Nasal Polyps

BACKGROUND

At present, the effect of operation intervention on pulmonary function is not clear in patients with allergic rhinitis and chronic rhinosinusitis with nasal polyps (AR&CRSwNP). This study was conducted to investigate the effect of vidian neurectomy on pulmonary function and airway hyperresponsiveness (AHR) in patients with AR&CRSwNP.

METHODS

The incidences of AHR, bronchial asthma (BA) and pulmonary function impairment in 112 patients with AR&CRSwNP were investigated. Subsequently, we evaluated the outcome of vidian neurectomy and its effect on pulmonary function and AHR. Furthermore, we explored the correlation between postoperative level of eosinophilic cationic protein (ECP) and the changes of pulmonary function indices or dose of methacholine.

RESULTS

In this study, the incidences of pulmonary function impairment, bronchial asthma, and AHR in patients with AR&CRSwNP were 61.61%, 69.64%, and 66.96%, respectively. Particularly, vidian neurectomy effectively alleviated nasal symptoms, improved pulmonary function, and reduced AHR in AR&CRSwNP patients. Furthermore, the postoperative level of ECP, IgE, Interleukin-4 and Interleukin-IL-5 was dramatically decreased, and there was an obvious inverse correlation between ECP level and pulmonary function index or dose of methacholine.

CONCLUSIONS

Vidian neurectomy is effective in alleviating nasal symptoms, improving pulmonary function, and reducing the risk of AHR of patients with AR&CRSwNP by decreasing the level of ECP.

Morphological association between the muscles and bones in the craniofacial region

The strains of inbred laboratory mice are isogenic and homogeneous for over 98.6% of their genomes. However, geometric morphometric studies have demonstrated clear differences among the skull shapes of various mice strains. The question now arises: why are skull shapes different among the mice strains? Epigenetic processes, such as morphological interaction between the muscles and bones, may cause differences in the skull shapes among various mice strains. To test these predictions, the objective of this study is to examine the morphological association between a specific part of the skull and its adjacent muscle. We examined C57BL6J, BALB/cA, and ICR mice on embryonic days (E) 12.5 and 16.5 as well as on postnatal days (P) 0, 10, and 90. As a result, we found morphological differences between C57BL6J and BALB/cA mice with respect to the inferior spine of the hypophyseal cartilage or basisphenoid (SP) and the tensor veli palatini muscle (TVP) during the prenatal and postnatal periods. There was a morphological correlation between the SP and the TVP in the C57BL6J, BALB/cA, and ICR mice during E15 and P0. However, there were not correlation between the TVP and the SP during P10. After discectomy, bone deformation was associated with a change in the shape of the adjacent muscle. Therefore, epigenetic modifications linked to the interaction between the muscles and bones might occur easily during the prenatal period, and inflammation seems to allow epigenetic modifications between the two to occur.

Developmental mechanism of muscle-tendon-bone complex in the fetal soft palate

OBJECTIVE

This study was performed to investigate how the palatine aponeurosis, medial pterygoid process (MPP) of the sphenoid bone, and tensor veli palatini (TVP) muscle form the pulley: muscle-tendon-bone complex.

DESIGN

Mice at embryonic day (ED) 14-17 were used as sample in this study. Azan staining was performed to observe the morphology, and immunohistochemical staining of desmin was performed to closely observe the development of the myotendinous junction. To confirm the bone formation process, immunohistochemical staining of type II collagen (col II), tartrate-resistant acid phosphatase (TRAP), and alkaline phosphatase (ALP) staining were performed. Furthermore, to objectively evaluate bone formation, the major axis and width of the MPP were measured, and osteoclasts that appeared in the MPP were counted.

RESULTS

At ED 14 and 14.5, ALP showed a reaction throughout the MPP. The col II-positive area expanded until ED 16.5, but it was markedly reduced at ED 17. The TVP initially contacted with the palatine aponeurosis at ED 16.5. The major axis and width of the MPP and the number of TRAP-positive osteoclasts were significantly increased as the TVP and palatine aponeurosis joined.

CONCLUSIONS

Therefore, in addition to the tissue units: muscle, tendon, and bone, the interaction in organogenesis promotes rapid growth of the pulley: muscle-tendon-bone complex.