Calcaneal Tendon Collagen Fiber Morphometry and Aging.

Area of Science:

• Biomaterials Science
• Developmental Biology
• Biophysics

Background:

• Tendons are crucial musculoskeletal tissues composed primarily of fibrillar collagen.
• Understanding collagen development and its structural organization is vital for comprehending tendon biomechanics and aging.

Purpose of the Study:

• To investigate the natural development of fibrillar collagen in rabbit Achilles tendons across different age groups.
• To analyze the impact of microtome sectioning on collagen fiber patterns and assess age-related changes in tendon structure.

Main Methods:

• Label-free second harmonic generation (SHG) microscopy was employed to image intact and microtome-sectioned Achilles tendons from rabbits aged ~7 days to ~38 months.
• Quantitative analysis of collagen crimp pattern parameters, including amplitude (A) and wavelength (Λ), was performed.

Main Results:

• Microtome sectioning introduced age-dependent artifacts in collagen fiber patterns; younger rabbits showed irregular patterns, while older rabbits exhibited patterns parallel to the load axis.
• Intact tendons consistently displayed collagen fiber patterns aligned with the load axis across all ages.
• Tendon crimp amplitude and wavelength showed significant age-dependent variations, increasing with sexual maturity and then decreasing in amplitude while wavelength continued to increase in fully mature animals.

Conclusions:

• Microtome sectioning artifacts are age-dependent and can alter the observed collagen structure.
• The collagen crimp pattern in tendons serves as a sensitive indicator of physical growth and developmental stages.
• SHG microscopy provides valuable insights into age-related structural changes in fibrillar collagen within tendons.