Age and gender related differences in load-strain response in C57Bl/6 mice

Area of Science:

• Biomechanical engineering
• Gerontology
• Musculoskeletal research

Background:

• Age-related changes in bone mechanical properties are crucial for understanding skeletal health and fracture risk.
• Previous studies often lack direct comparison of bone responses within the same animal across different ages.
• Accurate strain measurement techniques are vital for characterizing bone mechanical behavior.

Purpose of the Study:

• To investigate age-related alterations in the mechanical strain response of male and female mouse tibia and ulna.
• To compare the efficacy of digital image correlation (DIC) versus traditional strain gaging for detecting these changes.
• To analyze age-associated variations in bone mechanical properties within individual animals.

Main Methods:

• Axial compression tests were performed on tibia and ulna bones from male and female C57Bl/6 mice at 6, 12, and 22 months of age.
• Strain measurements were acquired using both non-contact digital image correlation (DIC) and standard strain gages.
• Three distinct load levels were applied, with 6-7 animals per age group and sex.

Main Results:

• Digital image correlation (DIC) identified significantly more differences in strain response compared to strain gaging.
• Male ulna exhibited higher DIC strains than strain gage measurements at multiple time points and load levels.
• Ulna stiffness increased with age in both sexes, showing reduced strain (0.4-0.8 times) in 22-month-old mice versus 6-month-old mice.
• Male tibia demonstrated a three-fold increase in strain at 22 months compared to 6 months under an 11.5 N load.

Conclusions:

• Digital image correlation (DIC) is a superior method for detecting subtle age-related changes in bone mechanical properties.
• Bone mechanical properties, specifically ulna stiffness and male tibia strain, change significantly with aging in mice.
• These findings highlight the importance of age and sex in bone biomechanics and the utility of advanced measurement techniques.