Mechanical injury and IL-1β regulated LOXs and MMP-1, 2, 3 expression in ACL fibroblasts co-cultured with synoviocytes.

Interleukin (IL)-1β in the joint cavity increases to promote healing after anterior cruciate ligament (ACL) injury. Synovial tissue is a major joint microenvironmental regulator after ACL injury. The purpose of this study was to investigate the effects of synovial cells (SCs) on lysyl oxidase (LOX) and matrix metalloproteinase (MMP) production by ACL fibroblasts (ACLfs) in the presence of IL-1β. This study sheds light on the regulation of LOX and MMP-1, -2, -3 expression by ACLfs co-cultured with SCs and treated with IL-1β. LOX and MMP-1, 2, 3 gene/protein expression in IL-1β/stretch-stimulated ACLfs co-cultured with SCs were measured by real-time quantitative PCR and Western blot. Meanwhile, MMP-2 activity was analyzed by zymogram. The results showed that co-culture with SCs increased LOX and MMP-1, -2, -3 gene and protein expression in the presence of IL-1β. Next, ACLfs were subjected to 12% mechanical stretch to simulate pathological injury. Under these conditions, SCs inhibited IL-1β-mediated upregulation of LOXs. However, IL-1β enhanced the expression of MMP-1, -2, -3 in injured ACLfs. SCs can either inhibit or increase LOX production in the presence of IL-1β, while promoting the accumulation of MMP in injured ACLfs. These results may provide crucial insights into the mechanisms underlying ACL poor healing capacity after injury.