Compromised Exercise Capacity and Mitochondrial Dysfunction in the Osteogenesis Imperfecta Murine (oim) Mouse Model

Area of Science:

• Biochemistry
• Genetics
• Physiology

Background:

• Osteogenesis Imperfecta (OI) is a heritable connective tissue disorder characterized by skeletal fragility, often due to collagen gene defects.
• Muscle weakness is a less understood symptom of OI, despite its impact on patients' quality of life.
• Understanding the link between bone and muscle in OI is crucial due to their interconnected signaling pathways.

Purpose of the Study:

• To investigate the mechanisms underlying muscle weakness in a mouse model of severe OI (oim/oim mice).
• To assess the effects of exercise on muscle and bone strength in OI mice.
• To identify potential cellular pathologies contributing to compromised muscle function in OI.

Main Methods:

• WT and oim/oim mice were subjected to weight-bearing (wheel-running) and non-weight-bearing (swimming) exercise.
• Muscle strength and physical activity levels were compared between WT and oim/oim mice.
• Mitochondrial function, including respiration, biogenesis, mitophagy, and enzyme activity, was analyzed in gastrocnemius muscle.

Main Results:

• Oim/oim mice exhibited significantly reduced running distance compared to WT mice, with minimal improvement from exercise.
• Severe mitochondrial dysfunction was observed in oim/oim gastrocnemius muscle, including decreased respiration rates (52-65%).
• Alterations in mitochondrial biogenesis, mitophagy markers, electron transport chain components, and citrate synthase activity were noted in oim/oim mice.

Conclusions:

• Mitochondrial dysfunction is a significant factor contributing to muscle weakness in the oim/oim mouse model.
• Compromised muscle function in OI may be linked to inherent mitochondrial pathology.
• These findings highlight the importance of addressing mitochondrial health in OI management.