Gene expression of catabolic inflammatory cytokines peak before anabolic inflammatory cytokines after ACL injury in a preclinical model

Abstract

BackgroundThe response of the joint to anterior cruciate ligament (ACL) injury has not been fully characterized. In particular, the characterization of both catabolic factors, including interleukin-6 (IL-6), interleukin-8 (IL-8), and markers of ongoing tissue damage (CRP), and anabolic factors, including vascular endothelial growth factor (VEGF), transforming growth factor β-induced (TGFβI), and the presence of CD163+ macrophages, have not been well defined. In this study, we hypothesized ACL injury would catalyze both catabolic and anabolic processes and that these would have different temporal profiles of expression.MethodsAdolescent Yucatan minipigs were subjected to ACL transection. Within the joint, gene expression levels of IL-6, IL-8, VEGF, and TGFβI were quantified in the synovium, ligament, and provisional scaffold located between the torn ligament ends at days 1, 5, 9, and 14 post-injury. Macrophage infiltration was also assessed in the joint tissues over the two week period. Serum C-reactive protein (CRP) levels were measured at multiple time points between 1 hour to 14 days after injury.ResultsIncreases in IL-6 and IL-8 gene expression peaked at day 1 after injury in the synovium and ligament. CRP levels were significantly increased at day 3 before returning to pre-injury levels. VEGF and TGFβI gene expression did not significantly increase until day 9 in the synovium and were unchanged in the other tissues. CD163+ macrophages increased in the ligament and synovium until day 9.ConclusionTaken together, these results suggest that the response within the joint is primarily catabolic in the first three days after injury, switching to a more anabolic phase by nine days after injury. The effect of medications which alter these processes may thus depend on the timing of administration after injury.

Immediate Administration of Intraarticular Triamcinolone Acetonide After Joint Injury Modulates Molecular Outcomes Associated With Early Synovitis

“…Synovial membrane total cellularity and C1,2C fragments. The area occupied by nuclei throughout the synovial membrane biopsy specimen (intima and stroma) was 13% (95% confidence interval [95% CI] 9-16) in the intact group and increased after ACLT to 21% (95% CI [16][17][18][19][20][21][22][23][24][25][26][27] in the ACLT group (P 5 0.02). The mean total cellularity in the steroid group was between the mean values in the other groups (17% [95% CI [15][16][17][18]).…”

“…Targeted analyses demonstrated a pronounced increase in synovial gene expression of pro-inflammatory cytokines at the first day post-injury followed by increasing levels of protease gene expression, synovial fluid markers of collagen fragments and CD163 expressing synovial macrophages that remained markedly elevated at 14 days post-injury. [21,22] Using this model, we tested the hypothesis that the immediate intraarticular application of triamcinolone acetonide would result in the mitigation of the injury-induced synovitis and subsequent collagen degradation at 14 days after ACL transection. Further, we have utilized the tissue samples generated in this preclinical efficacy trial in combination with a functional genomics approach to characterize the synovial response to injury on a cellular and molecular level with the aim to identify those changes that are strongly associated with the extent of collagen degradation.…”

“…In the intact group, total cellularity was 13% (95% confidence interval [95% CI] 9-16) and the C1,2C concentration was 0.24 mg/ml (95% CI 0.08-0.39). In the ACLT group, significant increases were observed in total cellularity (to 21% [95% CI [16][17][18][19][20][21][22][23][24][25][26][27]) and C1,2C concentration (to 0.49 mg/ml [95% CI 0.39-0.59]). Compared to values in the ACLT group, total cellularity in the steroid group was nonsignificantly decreased to 17% (95% CI 15-18) (P 5 0.26) and C1,2C concentration in the steroid group was significantly decreased to 0.29 mg/ml (95% CI 0.23-0.35) (P 5 0.04).…”

Bone marrow mesenchymal stem cell-derived exosomes promote rotator cuff tendon-bone healing by promoting angiogenesis and regulating M1 macrophages in rats

“…as TNF-α, IL-1β, IL-6, and IL-8, promote the progress of acute in ammation, restrain the directional differentiation of MSCs, block the secretion of extracellular matrix proteoglycans, and slow the tendonbone healing [28][29][30][31][32]. Therefore, we speculated that BMSC-Exos could inhibit the production of proin ammatory factors and promote tendon-bone healing.…”

“…Since an in ammatory response is adverse to tendon-bone healing, the effect of proin ammatory factors such as tumor necrosis factor-α (TNF-α), IL-1β, IL-6, and IL-8 should be suppressed as much as possible in the early postoperative period [28][29][30][31][32]. We injected BMSC-Exos at 0, 1, 2, and 3 weeks after reconstruction, and ELISA was used to detect the levels of proin ammatory factors in the serum of rats at 1, 2, 3, and 4 weeks after reconstruction.…”