Characterization of synovial fluid cytokine profiles in chronic meniscal tear of the knee

Abstract

Concentrations of pro- and anti-inflammatory cytokines in synovial fluid samples collected from patients with chronic meniscal tears were investigated. An acute inflammatory response is generally reported 24-48 h after knee injury, but the largest body of data available in literature concerns anterior cruciate ligament injury and very little information is available about the balance of soluble factors in the synovial fluid of knees with chronic meniscal tears. Sixty-nine patients (46 males and 23 females) with meniscal tear that occurred more than 3 months earlier were enrolled. According to cartilage integrity assessment by arthroscopic examination, patients were assigned to one of the following groups: (i) no chondral damage (n = 18); (ii) chondral damage graded from I to II (n = 15); and (iii) chondral damage graded from III to IV (n = 37). In all groups, levels of IL-10 and inflammatory cytokines IL-6, TNF-α, and IL-8 where greater compared with those reported in the intact population; by contrast, levels of IL-1ra and IL-1β were significantly lower. Interestingly, IL-6 levels were higher in female than male patients. Cytokine levels did not correlate with degree of chondral damage. IL-6 and IL-1ra levels positively correlated with IL-1β, and negatively correlated with TNF-α. Interestingly, levels of IL-1β and TNF-α were inversely correlated. Our data demonstrate increased levels of pro-inflammatory cytokines (IL-6, IL-8, and TNF-α) in the chronic phase of meniscal trauma. This pro-inflammatory state is maintained in the joint from the time of initial injury to several months later and could be a key factor in hampering cartilage regeneration. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:340-346, 2017.

Metabolic responses of meniscal explants to injury and inflammation ex vivo

“…Further, the combination of impact injury and cytokine stimulation resulted in the most consistent significant increases in IL‐6, IL‐8, and KC production. These findings are in agreement with previous clinical studies that found significantly higher synovial fluid concentrations of IL‐6 and IL‐8 in patients with meniscal injury compared to uninjured controls, and IL‐6 production is increased in injured meniscal tissue obtained from clinical patients . Taken together, the clinical and basic science data suggest that, after injury to the meniscus, there is an initial surge in production of IL‐6, IL‐8, and KC, which is exacerbated by injury‐associated inflammation and/or pre‐existing OA.…”

Inflammatory and degenerative phases resulting from anterior cruciate rupture in a non‐invasive murine model of post‐traumatic osteoarthritis

“…After ACL rupture, IL‐6 was upregulated within the joint within 3‐days post‐injury and preceded significant increases in Cd11b + macrophages, and increased inflammatory and degradative scores. This is consistent with elevated IL‐6 concentrations detected in synovial fluids in humans after joint injury . IL‐17A expression increased at days‐14 to ‐21 mirroring the abundance of F4/80 + cells, correlating with OA scores, particularly OA and subchondral bone components.…”

Amniotic Suspension Allograft Modulates Inflammation in a Rat Pain Model of Osteoarthritis

“…Some mechanical factors leading to degradation include malalignment of the lower extremity, ligament and meniscal tears, or a combination . Ligament and meniscal tears often have a biologic effect with degradation mediated through the release of pro‐inflammatory cytokines, including interleukin‐1β (IL‐1β) and tumor necrosis factor‐α (TNF‐α), and matrix metalloproteinases (MMPs) . Mechanical factors are exacerbated by excessive weight; it has been reported that every 5 kg gain in weight increases knee OA risk by 36%, with higher body mass index (BMI) leading to more severe knee degeneration .…”