Characterization of Synovial Cytokine Patterns in Bucket-Handle and Posterior Horn Meniscal Tears

Correlation of meniscus tear type with synovial inflammation and the therapeutic potential of docosapentaenoic acid

BACKGROUND

Synovitis, characterized by inflammation of the synovial membrane, is commonly induced by meniscus tears. However, significant differences in inflammatory responses and the key inflammatory mediators of synovium induced by different types of meniscal tears remain unclear.

METHODS

Magnetic resonance imaging (MRI) was employed to identify the type of meniscus tear, and the quantification of synovial inflammation was assessed through H&E staining assay. Transcription and expression levels of IL-1β and IL-6 were evaluated using bioinformatics, ELISA, RT-qPCR, and IHC of CD68 staining assays. The therapeutic potential of Docosapentaenoic Acid (DPA) was determined through network pharmacology, ELISA, and RT-qPCR assays. The safety of DPA was assessed using colony formation and EdU staining assays.

RESULTS

The results indicate that both IL-1β and IL-6 play pivotal roles in synovitis pathogenesis, with distinct expression levels across various subtypes. Among tested meniscus tears, oblique tear and bucket handle tear induced the most severe inflammation, followed by radial tear and longitudinal tear, while horizontal tear resulted in the least inflammation. Furthermore, in synovial inflammation induced by specific meniscus tears, the anterior medial tissues exhibited significantly higher local inflammation than the anterior lateral and suprapatellar regions, highlighting the clinical relevance and practical guidance of anterior medial tissues' inflammatory levels. Additionally, we identified the essential omega-3 fatty acid DPA as a potential therapeutic agent for synovitis, demonstrating efficacy in blocking the transcription and expression of IL-1β and IL-6 with minimal side effects.

CONCLUSION

These findings provide valuable insights into the nuanced nature of synovial inflammation induced by various meniscal tear classifications and contribute to the development of new adjunctive therapeutic agents in the management of synovitis.

Prokineticin 2 and Cytokine Content in the Synovial Fluid of Knee Osteoarthritis and Traumatic Meniscal Tear Patients: Preliminary Results

Knee osteoarthritis (OA) is a chronic degenerative inflammatory-based condition caused by a cascade of different intra-articular molecules including several cytokines. Among the cytokines, prokineticins (PKs) have recently been identified as important mediators of inflammation and pain. This observational study examined the potential involvement of PK2 in degenerative or traumatic knee disease. Fifteen patients presenting knee osteoarthritis (OA group) and 15 patients presenting a traumatic meniscal tear (TM group) were studied. Synovial fluid samples from affected knees were assessed for PK2, IL-10, and TNF-α using the ELISA method. At a long-term follow-up (minimum 5 years, mean = 6.1 years), patients in the TM group underwent clinical re-evaluation with PROMs (Tegner Activity Scale, IKDC, Lysholm, SKV); in addition, X-ray visualization was used to assess the presence of secondary OA. PK2 was detected in synovial fluids of both TM and OA patients and the levels were comparable between the two groups, while IL-10 levels were significantly greater in the OA group than those in TM patients. PK2 levels correlated with those of IL-10. PK2 levels were greater in blood effusions compared to clear samples, did not differ significantly between sexes, nor were they related to differences in weight, height, or injury (meniscal laterality, time since dosing). No correlation was found between PROMs and radiological classifications in patients in the TM group at final follow-up. These data are the first observations of PK2 in synovial fluid following traumatic meniscus injury. These findings suggest possible further prognostic indices and therapeutic targets to limit the development of secondary OA.

The Interplay of Biomechanical and Biological Changes Following Meniscus Injury

PURPOSE OF REVIEW

Meniscus injury often leads to joint degeneration and post-traumatic osteoarthritis (PTOA) development. Therefore, the purpose of this review is to outline the current understanding of biomechanical and biological repercussions following meniscus injury and how these changes impact meniscus repair and PTOA development. Moreover, we identify key gaps in knowledge that must be further investigated to improve meniscus healing and prevent PTOA.

RECENT FINDINGS

Following meniscus injury, both biomechanical and biological alterations frequently occur in multiple tissues in the joint. Biomechanically, meniscus tears compromise the ability of the meniscus to transfer load in the joint, making the cartilage more vulnerable to increased strain. Biologically, the post-injury environment is often characterized by an increase in pro-inflammatory cytokines, catabolic enzymes, and immune cells. These multi-faceted changes have a significant interplay and result in an environment that opposes tissue repair and contributes to PTOA development. Additionally, degenerative changes associated with OA may cause a feedback cycle, negatively impacting the healing capacity of the meniscus. Strides have been made towards understanding post-injury biological and biomechanical changes in the joint, their interplay, and how they affect healing and PTOA development. However, in order to improve clinical treatments to promote meniscus healing and prevent PTOA development, there is an urgent need to understand the physiologic changes in the joint following injury. In particular, work is needed on the in vivo characterization of the temporal biomechanical and biological changes that occur in patients following meniscus injury and how these changes contribute to PTOA development.

Characterization of microRNA Levels in Synovial Fluid from Knee Osteoarthritis and Anterior Cruciate Ligament Tears

This study investigated modifications of microRNA expression profiles in knee synovial fluid of patients with osteoarthritis (OA) and rupture of the anterior cruciate ligament (ACL). Twelve microRNAs (26a-5p, 27a-3p, let7a-5p, 140-5p, 146-5p, 155-5p, 16-5p,186-5p, 199a-3p, 210-3p, 205-5p, and 30b-5p) were measured by real-time quantitative polymerase chain reaction (RT-qPCR) in synovial fluids obtained from 30 patients with ACL tear and 18 patients with knee OA. These 12 miRNAs were chosen on the basis of their involvement in pathological processes of bone and cartilage. Our results show that miR-26a-5p, miR-186-5p, and miR-30b-5p were expressed in the majority of OA and ACL tear samples, whereas miR-199a-3p, miR-210-3p, and miR-205-5p were detectable only in a few samples. Interestingly, miR-140-5p was expressed in only one sample of thirty in the ACL tear group. miR-140-5p has been proposed to modulate two genes (BGN and COL5A1100) that are involved in ligamentous homeostasis; their altered expression could be linked with ACL rupture susceptibility. The expression of miR-30b-5p was higher in OA and chronic ACL groups compared to acute ACL samples. We provide evidence that specific miRNAs could be detected not only in synovial fluid of patients with OA, but also in post-traumatic ACL tears.

Combination of Lidocaine and IL-1Ra Is Effective at Reducing Degradation of Porcine Cartilage Explants

BACKGROUND

Posttraumatic inflammation after joint injury, ranging from sprains to articular fracture, contributes to the development of arthritis, and the administration of interleukin 1 (IL-1) receptor antagonist (IL-1Ra) is a potential intervention to mitigate this response. Although IL-1Ra mitigates cartilage degenerative changes induced by IL-1, lidocaine is used for local pain management in acute joint injury. Intra-articular delivery of both drugs in combination would be a novel and possibly disease-modifying treatment. However, it is not known whether the interaction with lidocaine at clinical concentrations (1%) would alter the efficacy of IL-1Ra to protect cartilage from the catabolic effects of IL-1.

HYPOTHESIS

Treatment of articular cartilage with IL-1Ra in combination with a clinically relevant concentration of lidocaine (1%) will inhibit the catabolic effects of IL-1α in a manner similar to treatment with IL-1Ra alone.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fresh porcine cartilage explants were harvested, challenged with IL-1α, and incubated for 72 hours with IL-1Ra or a combination of IL-1Ra and lidocaine. The primary outcome was total sulfated glycosaminoglycan (sGAG) release. Additional experiments assessed the effect of storage temperature and premixing of IL-1Ra and lidocaine on sGAG release. All explants were histologically assessed for cartilage degradation using a modified Mankin grading scale.

RESULTS

The combination of IL-1Ra and lidocaine, premixed at various time points and stored at room temperature or 4°C, was as effective as IL-1Ra alone at inhibiting IL-1α-mediated sGAG release. Mankin histopathology scores supported these findings.

CONCLUSION

Our hypothesis was supported, and results indicated that the combination of IL-1Ra and lidocaine was as efficacious as IL-1Ra treatment alone in acutely mitigating biological cartilage injury due to IL-1α in an explant model.

CLINICAL SIGNIFICANCE

The combination of IL-1Ra and lidocaine is stable when reagents are stored in advance of administration at varying temperatures, providing clinically relevant information about storage of medications. The ability to premix and store this drug combination for intra-articular delivery may provide a novel treatment after joint injury to provide pain relief and block inflammation-induced catabolism of joint tissues.

Resolvin E1 and Cytokines Environment in Skeletally Immature and Adult ACL Tears

The intra-articular synovial fluid environment in skeletally immature patients following an ACL tear is complex and remains undefined. Levels of inflammatory and anti-inflammatory cytokines change significantly in response to trauma and collectively define the inflammatory environment. Of these factors the resolvins, with their inherent anti-inflammatory, reparative, and analgesic properties, have become prominent. This study examined the levels of resolvins and other cytokines after ACL tears in skeletally immature and adult patients in order to determine if skeletal maturity affects the inflammatory pattern. Skeletally immature and adult patients with an anterior cruciate ligament injury and meniscal tears were prospectively enrolled over a 5-month period. Synovial fluid samples were obtained before surgery quantifying Resolvin E1, IL-1β, TNF-α, and IL-10 by ELISA. Comparisons between skeletally immature patients and adults, the influence of meniscal tear, growth plate maturity and time from trauma were analyzed. Skeletally immature patients had significantly greater levels of Resolvin E1 and IL-10 compared with adults with an isolated anterior cruciate ligament lesion. Among the injured skeletally immature patients Resolvin E1 levels were greater in the open growth plate group compared with those with closing growth plates. Moreover, levels of Resolvin E1 and IL-10 appeared to decrease with time. Our results suggest that skeletally immature patients have a stronger activation of the Resolvin pattern compared to adult patients and that synovial fluid Resolvins could play an antinflammatory role in the knee after anterior cruciate ligament lesion and that its activity may be synergistic with that of IL-10.

Discoid meniscus in human fetuses: A systematic review

BACKGROUND

Discoid meniscus (DM) is a rare variant of regular knee anatomy. Compared to standard meniscus it is thicker and abnormal in shape; these characteristics make it more prone to tear. It is a congenital defect whose correct etiology is still debated and far from being clarified. The purpose of this systematic review is to evaluate evidences of DM in human fetuses in order to assess whether embryological development may have a role.

METHODS

A systematic review was performed on PubMed, Scopus, and Embase with different combinations of the keywords "discoid meniscus", "embryology", "fetus", "neonatal". Search yielded 1013 studies, on which we performed a primary evaluation.

RESULTS

Seven studies were considered including a total of 1378 fetal menisci specimens, from 396 different fetuses. Discoid shape was not found represented as a normal stage of prenatal development. From 782 lateral menisci analyzed, only 86 (10.86%) were discoid (13 complete, 73 incomplete type). None of medial menisci was found to be discoid. Lateral meniscus was observed to cover a larger surface of tibial plateau than medial one until 28th gestational week.

CONCLUSION

Lateral meniscus seems to be more prone to discoid shape for its natural tendency of covering a larger surface of the tibial plateau during fetal stages. However the fact that a discoid shape was not found in the majority of fetuses suggests that it is not a normal stage of fetal development. To support a single etiological factor it will be appropriate to have further morphological and morphometric studies.