Changes in myosin expression in denervated laryngeal muscle

Area of Science:

• Neuroscience
• Muscle Physiology
• Biochemistry

Background:

• Laryngeal muscles are crucial for vocalization and airway protection.
• Chronic denervation impacts muscle fiber composition and protein expression.
• Myosin heavy chain (MyHC) isoforms determine muscle contraction speed and function.

Purpose of the Study:

• To investigate the effects of chronic denervation on MyHC content and muscle fiber type in rat laryngeal muscles.
• To determine the time course of these changes after recurrent laryngeal nerve sectioning.
• To compare the response of different laryngeal muscles (PCA and TA) to denervation.

Main Methods:

• Recurrent laryngeal nerve sectioning in rats, followed by muscle removal at 3 weeks, 3 months, and 6 months.
• Myofibrillar adenosine triphosphatase staining for fiber type determination.
• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and densitometry for MyHC isoform quantification.

Main Results:

• Denervation caused a progressive reduction and near-complete loss of type I MyHC in the posterior cricoarytenoid (PCA) muscle.
• A concomitant increase in fast-contracting type II MyHCs was observed in the PCA muscle.
• The laryngeal-specific type IIL MyHC isoform and MyHC expression in the thyroarytenoid (TA) muscle remained relatively constant post-denervation.

Conclusions:

• Type I MyHC expression in laryngeal muscles is dependent on neural input, similar to limb skeletal muscles.
• The laryngeal-specific type IIL MyHC isoform may be regulated by distinct factors.
• These findings provide insights into the molecular mechanisms underlying laryngeal muscle plasticity and adaptation to denervation.