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

Background: the 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. methods: adolescent 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. results: increases 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. conclusion: taken 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. © 2014 haslauer et al.; licensee biomed central ltd.