Inflammatory cells do not decrease the ultimate tensile strength of intact tendons in vivo and in vitro: protective...

Area of Science:

• Biochemistry
• Histology
• Biomechanics
• Cell Biology

Background:

• Inflammatory cells contribute to various pathological processes.
• The role of inflammation in tendon dysfunction remains under-investigated.
• Investigating inflammation's impact on tendons requires understanding its interaction with mechanical stress.

Purpose of the Study:

• To determine if acute inflammation, without mechanical trauma, damages intact collagen fibers.
• To analyze the biochemical, histological, and biomechanical effects of leukocyte invasion on tendons.
• To assess if mechanical loading protects collagen from inflammatory cell-induced damage.

Main Methods:

• Carrageenan injection induced leukocyte accumulation in rat Achilles tendons.
• Assessed matrix metalloproteinase (MMP) and tissue inhibitor of matrix metalloproteinase (TIMP) levels.
• Analyzed hydroxyproline content, load to failure, and in vitro mechanical stress effects on collagen bundles.

Main Results:

• Leukocyte accumulation increased MMP activity and decreased TIMP content.
• No significant changes were observed in hydroxyproline content or load to failure.
• In vitro mechanical stress protected collagen bundles from inflammatory cell degradation.

Conclusions:

• Acute inflammation does not damage intact, mechanically stressed collagen fibers.
• Mechanically loaded collagen exhibits intrinsic resistance to proteolytic degradation.
• This protective effect is independent of increased TIMP levels.