Tendon collagen synthesis declines with immobilization in elderly humans: no effect of anti-inflammatory medication

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAID) are used as pain killers during periods of unloading caused by traumatic occurrences or diseases. However, it is unknown how the tendon protein turnover and mechanical properties responds to unloading and subsequent loading in elderly humans, and especially whether NSAIDs affect tendon adaptation during such periods. Thus, we studied the influence of NSAID upon the human patellar tendon protein synthesis and mechanical properties during immobilization and subsequent rehabilitating resistance training.

METHODS: 19 men (60-80 yrs, range) were randomly assigned to NSAID (Ibuprofen 1200 mg/d, Ibu) or placebo (Plc). One lower limb was immobilized in a cast for two weeks and retrained for six weeks. Tendon collagen protein synthesis, expression of gene related to collagen turnover and remodeling, size, signal intensity (from magnetic resonance imaging), and mechanical properties were investigated.

RESULTS: Tendon collagen synthesis decreased (p<0.001), whereas tendon size and mechanical properties were generally unchanged with immobilization, and NSAID treatment did not influence this. Matrix metalloproteinase-2 mRNA tended to increase (p<0.1) after immobilization in both groups, whereas scleraxis mRNA decreased with inactivity in the Plc group only (p<0.05).

CONCLUSION: In elderly human tendons, collagen protein synthesis decreased after two weeks of immobilization, whereas tendon stiffness and modulus were only marginally reduced, and NSAID had no influence upon this. This indicates an importance of mechanical loading for maintenance of tendon collagen turnover. However, reduced collagen production induced by short-term unloading may only marginally affect tendon mechanical properties in elderly individuals.