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Sternohyoid and diaphragm muscle form and function during postnatal development in the rat
R A O'Connell1, J Carberry, K D O'Halloran
1School of Medicine and Medical Science, University College Dublin, Dublin, Ireland. ruth.oconnell@ucd.ie
Experimental Physiology
|May 28, 2013
Summary
Postnatal development increases the force and fatigue resistance of breathing muscles, including the sternohyoid and diaphragm. This maturation is linked to myosin heavy chain (MHC) shifts, occurring faster in the sternohyoid, impacting airway calibre control.
Area of Science:
- Physiology
- Developmental Biology
- Respiratory Medicine
Background:
- Co-ordinated action of thoracic pump and pharyngeal dilator muscles is essential for airway patency and respiratory stability.
- While diaphragm development is well-studied, the developmental trajectory of airway dilator muscles remains largely unknown.
- Understanding airway dilator muscle maturation is crucial for maintaining airway calibre and effective ventilation.
Purpose of the Study:
- To investigate the postnatal development of sternohyoid and diaphragm muscles in Wistar rat pups.
- To determine changes in isometric contractile properties, fatigue resistance, and myosin heavy chain (MHC) phenotype during postnatal maturation.
- To assess the impact of these developmental changes on muscle oxidative and glycolytic capacities.
Main Methods:
- Isometric contractile and endurance properties of sternohyoid and diaphragm muscles were measured in Wistar rat pups at postnatal days 10, 20, and 30.
- Myosin heavy chain (MHC) isoform composition was analyzed using immunofluorescence.
- Muscle oxidative (succinate dehydrogenase) and glycolytic (glycerol-3-phosphate dehydrogenase) capacities were assessed via histochemistry.
Main Results:
- Peak isometric force and fatigue resistance increased significantly in both sternohyoid and diaphragm muscles with postnatal maturation.
- A shift in MHC phenotype occurred, with developmental MHC disappearing by postnatal day 20 and MHC2B increasing significantly from postnatal day 10 to 30.
- The sternohyoid muscle exhibited accelerated MHC maturation compared to the diaphragm, with earlier and greater increases in MHC2B and MHC2X expression.
Conclusions:
- Postnatal increases in force-generating capacity and fatigue resistance in breathing muscles are driven by a shift in MHC phenotype.
- The accelerated maturation of the sternohyoid muscle relative to the diaphragm suggests potential implications for in vivo airway calibre regulation.
- Further research into airway dilator muscle development is warranted to fully understand its role in respiratory homeostasis.
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