title: COX-2 inhibition impairs mechanical stimulation of early tendon healing in rats by reducing the response to microdamage.
abstract: Early tendon healing can be stimulated by mechanical loading and inhibited by cyclooxygenase (COX) inhibitors (nonsteroidal anti-inflammatory drugs). Therefore, we investigated if impairment of tendon healing by a COX-2 inhibitor (parecoxib) is related to loading. Because loading might infer microdamage, which also stimulates healing, we also investigated if this effect is inhibited by parecoxib. The Achilles tendon was transected in 114 rats. Three degrees of loading were used: full loading, partial unloading, and unloading (no unloading, Botox injections in the plantar flexor muscles, or Botox in combination with tail suspension). For each loading condition, the rats received either parecoxib or saline. In a second experiment, rats were unloaded with Botox, and the tendon was subjected to microdamage by needling combined with either saline or parecoxib. Mechanical testing day 7 showed that there was a significant interaction between loading and parecoxib for peak force at failure (P < 0.01). However, logarithmic values showed no significant interaction, meaning that we could not exclude that the inhibitory effect of parecoxib was proportionate to the degree of loading. Microbleeding was common in the healing tissue, suggesting that loading caused microdamage. Needling increased peak force at failure (P < 0.01), and this effect of microdamage was almost abolished by parecoxib (P < 0.01). Taken together, this suggests that COX-2 inhibition impairs the positive effects of mechanical loading during tendon healing, mainly by reducing the response to microdamage.
authors.affiliation: Orthopaedics, Department of Clinical and Experimental Medicine, Faculty of Health Science, Linköping University, Linköping, Sweden malin.hammerman@liu.se.
authors.forename: Malin
authors.initials: M
authors.lastname: Hammerman
authors.affiliation: Orthopaedics, Department of Clinical and Experimental Medicine, Faculty of Health Science, Linköping University, Linköping, Sweden.
authors.forename: Parmis
authors.initials: P
authors.lastname: Blomgran
authors.affiliation: Orthopaedics, Department of Clinical and Experimental Medicine, Faculty of Health Science, Linköping University, Linköping, Sweden.
authors.forename: Sandra
authors.initials: S
authors.lastname: Ramstedt
authors.affiliation: Orthopaedics, Department of Clinical and Experimental Medicine, Faculty of Health Science, Linköping University, Linköping, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Aspenberg
mesh_terms: D000125:Achilles Tendon / Q000187:drug effects*; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001696:Biomechanical Phenomena / Q000187:drug effects / Q000502:physiology; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology*; D005260:Female; D019417:Hindlimb Suspension / Q000379:methods; D007555:Isoxazoles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013708:Tendon Injuries / Q000188:drug therapy*; D014945:Wound Healing / Q000187:drug effects*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D052246:Cyclooxygenase 2 Inhibitors; D007555:Isoxazoles; C409945:parecoxib
keywords: COX-2; NSAIDs; mechanical stimulation; microdamage; tendon healing