Structure and functional evaluation of tendon-skeletal muscle constructs engineered in vitro

Area of Science:

• Biomedical Engineering
• Tissue Engineering
• Skeletal Muscle Physiology

Background:

• The myotendinous junction (MTJ) is crucial for force transmission during muscle contraction.
• Maintaining MTJ integrity is vital for skeletal muscle function.
• Understanding MTJ biomechanics is key for treating muscle injuries and diseases.

Purpose of the Study:

• To evaluate contractile and structural characteristics of 3-D skeletal muscle constructs co-cultured with various tendon tissues.
• To determine if engineered muscle-tendon interfaces remain intact under force generation.
• To compare engineered MTJ properties with in vivo neonatal MTJs.

Main Methods:

• Co-culture of 3-D skeletal muscle with engineered or native rat-tail tendon segments.
• Measurement of construct diameter, maximum isometric force, and specific force.
• Tensile loading to failure, optical strain recording, and tangent modulus determination.
• Histological analysis (Trichrome Masson staining) and immunofluorescence for paxillin expression at the MTJ.

Main Results:

• No significant differences in diameter, maximum force, or specific force were observed between groups.
• Engineered MTJs were robust, withstanding loads beyond physiological strain.
• Constructs predominantly failed within the muscle region, not at the MTJ.
• Increased expression and localization of paxillin were observed at the MTJ.

Conclusions:

• Successfully engineered 3-D muscle-tendon constructs with functionally viable MTJs.
• The engineered MTJs exhibited structural and protein expression patterns similar to neonatal MTJs in vivo.
• These constructs provide a viable model for studying MTJ biomechanics and developing regenerative therapies.