Aging-related changes in respiratory system mechanics and morphometry in mice

Area of Science:

• Pulmonary physiology
• Aging research
• Respiratory mechanics

Background:

• Previous studies suggested linear aging of mouse respiratory mechanics.
• These studies used limited age groups (young vs. old).
• Lifespan changes in lung function and structure require more detailed investigation.

Purpose of the Study:

• To investigate age-related changes in respiratory system mechanics and lung morphometry across a wider age spectrum in C57BL/6 mice.
• To determine if aging-related lung changes evolve linearly or nonlinearly.
• To assess lung morphometry, including mean linear intercept (Lm) and airway collagen deposition, in aging mice.

Main Methods:

• Respiratory system mechanics were assessed in mice aged 2, 6, 18, 24, and 30 months.
• Respiratory system impedance was measured across a frequency range at various positive end-expiratory pressures (PEEP).
• Lung morphometry, including mean linear intercept (Lm) and airway collagen, was analyzed after fixation.

Main Results:

• A nonlinear decrease in respiratory system resistance and increase in dynamic compliance and hysteresis were observed between 2 and 24 months.
• In 30-month-old mice, resistance increased, and compliance/hysteresis decreased compared to 24-month-old mice.
• An aging-related increase in Lm, indicative of emphysematous changes, was found, with no increase in airway collagen.

Conclusions:

• Mouse lung aging is characterized by nonlinear changes in mechanical properties and morphometry.
• Respiratory system resistance, dynamic compliance, and hysteresis do not change linearly with age.
• Emphysematous-like changes (increased Lm) occur with aging, but airway collagen deposition does not increase.