Hindlimb Skeletal Muscle Function and Skeletal Quality and Strength in +/G610C Mice With and Without Weight-Bearing...

Area of Science:

• Orthopedics
• Genetics
• Biomedical Engineering

Background:

• Osteogenesis imperfecta (OI) is a heritable connective tissue disorder causing fragile bones.
• Bone strength is linked to muscle mass and physical activity.
• Children with OI type I often have reduced exercise capacity and muscle strength.

Purpose of the Study:

• To investigate muscle function, physical activity, and exercise response in a mouse model of Osteogenesis imperfecta (OI).
• To determine if muscle weakness in OI is due to inactivity or intrinsic muscle pathology.
• To assess the impact of a treadmill exercise regimen on bone quality in OI mice.

Main Methods:

• Used heterozygous G610C OI model mice (+/G610C) and wild-type littermates.
• Evaluated hindlimb muscle function and spontaneous physical activity levels.
• Assessed response to an 8-week treadmill exercise regimen.
• Analyzed femoral biomechanical properties (torsional loading) and bone material characteristics (Raman spectroscopy).

Main Results:

• +/G610C mice exhibited normal hindlimb muscle function and activity levels compared to wild-type mice.
• OI mice successfully completed the 8-week treadmill exercise regimen.
• Exercise increased femoral stiffness and shear modulus in OI mice, associated with altered collagen content.
• Tibial cortical bone showed similar crystallinity and mineral/matrix ratios across genotypes and exercise groups.

Conclusions:

• The G610C OI mouse model displays normal muscle function and activity, challenging the notion of intrinsic muscle pathology in this OI type.
• Weight-bearing exercise can enhance certain biomechanical properties of bone in OI mice.
• More intensive exercise protocols may be necessary to achieve significant improvements in overall bone quality in Osteogenesis imperfecta.