A synoviocytes and synovial fluid interaction model for osteoarthritis study: modulation of anabolic and catabolic markers

Abstract

Purpose: Synovial fluid is an interstitial fluid secreted by fibroblastic cells in the synovial membrane. The physiological functions of synovial fluid may include reduction of friction, shock absorption, nutrient, and waste transportation in the joint. In addition, previous studies showed various types of cells reside in synovial fluid. Those are inflammatory cells such as macrophages and T cells, and mesenchymal stem cells (MSCs), those are considered to contribute the tissue homeostasis and regeneration. We have reported that pathological conditions such as joint injury or joint inflammation increased both cellular components and inflammatory cytokine levels in synovial fluid. We predict that both of them may play important roles during the recovery process after joint injury or surgery. In this study, we aimed to analyze the dynamic changes of cellular components in synovial fluid after anterior cruciate ligament reconstruction surgery (ACL-R) and compared them with the biochemical parameters such as inflammatory cytokine levels in synovial fluid from each patient. Here we report that the population of CD66b-positive Granulocytes surged in the early stage after ACL-R and positively correlated with IL1 beta and IL8 levels in synovial fluid. Methods: This study was approved by the Ethics Committee of this institute. All patients included in this study gave their full, written, informed consent for participation prior to the operative procedure. Synovial fluid was obtained from patients who underwent ACL-R from February 2013 till March 2014 in our University's Hospital (just before surgery, day 3e4, day 19e21, and day 35 post surgery: n¼58). Cellular components in synovial fluid were analyzed by flow cytometry (BD FACS Verse). In this study, we quantitated the population of T-cells (CD3, CD4, CD8), Granulocytes (CD66b), Macrophages (CD11b, CD14), and MSCs (CD73, CD90, CD105, CD44) in each time point. Inflammatory cytokine levels in synovial fluid (IL1 beta, IL2, IL6, IL8, IL10, TNF alpha, and IFN gamma) were quantitated by ELISA. Kruskal-Wallis test and Peasons correlation analysis were employed for statistical analysis and probability values less than 0.05 were considered as significant. Results: Flow cytometric analyses detected T cells, Granulocytes, Macrophages, and MSCs in synovial fluid. Dynamic analysis indicated that T cell and Macrophage populations in synovial fluid surged at day 19e21 post surgery (1.3-fold and 7.8-fold respectively if compared with that before surgery). Population of MSC gradually increased with time post surgery (1.2-fold at day 35; compared to the population before surgery). Granulocyte population significantly increased at day 3e4 post surgery. We observed the highest individual variation in Granulocyte population between the patients (minimum 0.1% and maximum 96.5% at day 3e4). To examine if the individual variation of Granulocyte population correlates clinical conditions of each patient, we compared it with cytokine levels in synovial fluid at day 3e4 post ACL-R. Among the cytok...