Anti-inflammatory cytokine profile in early human tendon repair

The aim of this study was to assess inflammation and the presence and relative levels of cytokines, which may be involved in regulating early human Achilles tendon healing. Nine patients with acute Achilles tendon rupture were included, operated on and post-operatively immobilized. Two weeks post-operatively, microdialysis of the peritendinous interstitial compartment was performed in the healing and intact contralateral Achilles tendons. Quantification of tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-1 beta, IL-6, IL-8, IL-10, IL-12p70 and IL-17A was accomplished using a cytometric bead array. Prostaglandin (PG) E-2 levels were measured by enzyme immunoassay. None of the patients displayed detectable PGE(2) levels. Pro-inflammatory cytokines were below detection levels (IFN gamma, IL-12, and IL-17) or did not differ between injured and control tendons (IL-1 beta and TNF). Notably, IL-6, IL-8 and IL-10 concentrations in the healing Achilles tendon were significantly elevated: 13-fold (p = 0.009), 28-fold (p = 0.02), and 3.7-fold (p = 0.03), respectively. At 2 weeks post-human Achilles tendon rupture, healing is characterized by a resolving inflammatory phase and up-regulation of IL-6, IL-8 and IL-10. The absence of inflammation suggests that at this time point, these cytokines may be associated with anti-inflammatory and regenerative effects on the tendon healing process.