Rat Model of Achilles Tendon Disorder

Abstract

Three-month-old male rats were subjected 3 times weekly for 1 h to eccentric exercise of one triceps surae muscle (30 stimulations/min) under general anesthesia in order to induce Achilles tendon disorder corresponding to paratenonitis and tendinosis in man. Net muscle work during the sessions ranged between 0.67 and 4.37 mJ (mean 1.72, SD 0.77). After 9 and 13 sessions, respectively, 2 rats started to show gait alterations during the functional test which was performed 2–3 times weekly. These rats were killed after additional sessions which showed a worsening of the limp. The other trained rats and controls did not limp and were killed after 7–11 weeks. Histologic evaluation of the Achilles tendons from the exercised limb showed in the majority of the cases hypervascularization, increased number of nerve filaments and increased immunoreactivity for substance P and calcitonin gene-related peptide. The tendons from the nonstimulated limb looked normal. The distribution of collagen types I and II appeared normal in the tendon and its insertion to the calcaneus. Inflammation of the epi- and paratenon could be provoked in the rat, but tendon changes corresponding to chronic tendinosis did not develop within 11 weeks with the used training regime. The clinical relevance of this model for chronic tendon disease needs to be evaluated further.

Tendinosis-like Histologic and Molecular Changes of the Achilles Tendon to Repetitive Stress: A Pilot Study in Rats

“…Numerous investigators have used animal models for tendon injuries [1, 3, 7-9, 22, 24, 25, 28, 29]. These models are of two types: those analyzing injuries attributable to chemicals or sectioning [9,28] and those analyzing injuries attributable to repetitive overuse simulating overloading [1,3,7,8,22,24,25,29]. Chemical and sectioning injuries do not reflect realistic tendon injuries.…”

“…Chemical and sectioning injuries do not reflect realistic tendon injuries. The animal models of repetitive overuse activity can be further divided into two subcategories: simple overuse activity [24,25] and overuse activity associated with eccentric muscle contraction [1,3,7,8,22,29]. The studies reporting findings suggestive of chronic tendinopathy [3,7,22,29] tended to be based on protocols inducing overuse activity by simulating repetitive eccentric contractions, whereas those based on simple overuse [24,25] are associated with findings suggesting a reparative response to injury.…”

“…The animal models of repetitive overuse activity can be further divided into two subcategories: simple overuse activity [24,25] and overuse activity associated with eccentric muscle contraction [1,3,7,8,22,29]. The studies reporting findings suggestive of chronic tendinopathy [3,7,22,29] tended to be based on protocols inducing overuse activity by simulating repetitive eccentric contractions, whereas those based on simple overuse [24,25] are associated with findings suggesting a reparative response to injury. Further, repetitive eccentric contraction techniques in these models [1,3,7,8,22,29] differ from the eccentric contraction exercise methods used to treat general Achilles tendon injuries [19] in that they involve more repetitive overloading.…”

The use of motion analysis to measure pain-related behaviour in a rat model of degenerative tendon injuries

“…Significant changes in the gait parameters of the contralateral limbs in collagenase-treated rats suggested adaptive motions to reduce mechanical allodynia in the injured limbs. Our results indicate that motion analysis was useful for the detection of knee pain associated with patellar tendon injuries at longer time points post injury as compared to previous studies which worked on relatively short-term inflammatory pain (Coulthard, 2003), Achilles tendon injuries (Messner, 1999) or arthritic knee (Simjee 2004). …”

“…Gait recording was performed at the time points aforementioned with a similar set-up described by Messner (1999). At each time point, each rat was encouraged to walk in a 1.5-meter straight enclosed walkway with darkened ends.…”