Abstract
Extracellular signal-regulated kinase (ERK)-2 is presumed to play an important role in the development of post-traumatic joint contractures. Using a rat injury model, we investigated whether treatment with ERK2 small interfering RNA (siRNA) could reduce the extent of joint capsule fibrosis after an induced injury. Rats were separated into three groups (n = 32 each): non-operated control group, operated contracture group and contracture-treatment group. Stable post-traumatic joint contracture was created through surgical intra-articular joint injury followed by eight weeks of immobilization. In the contracture-treatment group, the rats were treated with lentivirus (LV)-mediated ERK2 siRNA at days 3 and 7 post-surgery. The posterior joint capsule was assessed by western blotting, immunohistochemistry and biochemical analysis for changes in ERK2, phosphorylated (p)-ERK2, myofibroblast, total collagen and relative collagen Type III expression level. Biomechanical testing was used to assess the development of flexion contractures. Statistical analysis was performed using an analysis of variance. In the operated contracture group, rats that developed flexion contractures also showed elevated phosphorylated p-ERK2 expression. In the contracture-treatment group, ERK2 siRNA significantly reduced p-ERK2 expression levels, as well as the severity of flexion contracture development (p < 0.01). Myofibroblast numbers and measurements of total collagen content were also significantly reduced following ERK2 siRNA (p < 0.01). Relative collagen type III expression as a proportion of total of Types I and III collagen, however, was significantly increased in response to ERK2 siRNA (p < 0.01). Our findings demonstrate a role for ERK2 in the induction of joint capsule fibrosis after injury. Furthermore, we show that development of flexion contractures and the resultant increase of joint capsule fibrosis can be reduced by LV-mediated ERK2 siRNA treatment.
Highlights
Joint contracture of the elbow is a common secondary complication caused by prolonged immobility of the joint following treatment or injury
We show that development of flexion contractures and the resultant increase of joint capsule fibrosis can be reduced by LV-mediated ERK2 small interfering RNA (siRNA) treatment
We previously demonstrated that ERK2 plays crucial roles in suppressing collagen expression and cell proliferation in TGF-β1-activated fibroblasts harvested from joint adhesion tissue in rats [22]
Summary
Joint contracture of the elbow is a common secondary complication caused by prolonged immobility of the joint following treatment or injury It results in an approximate 10%–15% reduction in joint motion and usually requires revision surgery [1,2]. We showed that the local delivery of extracellular signal-regulated kinase (ERK) siRNA using a lentivirus (LV) could effectively and safely ameliorate the formation of joint adhesion in a rat model [15]. This result reflected the predominant role of ERK2 in joint adhesion formation. LV-mediated ERK2 siRNA was used to inhibit ERK2 expression and phosphorylation in a model of joint capsule fibrosis
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