Increased expression of IL-6 family members in tendon pathology

Kirsten Legerlotz, Eleanor R Jones, Hazel R C Screen, Graham P Riley, Kirsten Legerlotz, Eleanor R Jones, Hazel R C Screen, Graham P Riley

Abstract

Objectives: Histological examination of pathological tendon generally does not reveal signs of inflammation. However, the inflammatory cytokine IL-6 has been shown to be expressed in ruptured rotator cuff tendon. The aim of this study was to investigate the expression of IL-6 family members in painful posterior tibialis tendon (PTT) and in painful and ruptured Achilles tendon (AT) compared with normal tendon.

Methods: AT samples were obtained from cadavers (normal) or from patients undergoing surgical procedures to treat chronic painful tendinopathy or ruptured tendon. PTT samples were obtained from patients undergoing surgery for other reasons (normal) and from patients with PTT dysfunction (painful). Total RNA was extracted and mRNA expression was analysed by quantitative real-time PCR.

Results: Collagen type I α-chain I (COL1A1) expression was increased in both painful PTT and AT compared with normal. Ciliary neurotrophic factor levels were increased in painful PTT only. In the painful AT, cyclooxygenase-2 (COX2) and IL-6 expression increased compared with normal. In the ruptured AT, levels of VEGF A, COX2, oncostatin-M, leukaemia inhibitory factor and IL-6 expression were higher compared with both normal and painful AT. IL-6R expression decreased in both painful and ruptured AT compared with normal.

Conclusion: Painful AT and PTT show different expression patterns, indicating a substantial difference between those two tendinopathies. Inflammatory markers are up-regulated in painful and particularly in ruptured AT, pointing towards a role of inflammation not only in rupture healing, but also in Achilles tendinopathy.

Figures

F ig . 1
Fig. 1
Expression of mRNA in (A) normal, painful and ruptured AT and (B) normal and painful PTT. Values are normalized to the mean of EIF4A2 and topo-1. Data are presented as box-and-whisker plots. The median is represented by the line within the box, while the box extends from the 25th to the 75th percentile. The whiskers show the highest and lowest values. *Significantly different from control specimens; **significant difference between painful and ruptured specimens (P ≤ 0.05; Mann–Whitney U-test).

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