Expression changes of inflammatory cytokines and MMPs in knee joint of rabbits after posterior cruciate ligament rupture

ObjectiveTo observe the contents of inflammatory cytokines (IL-1β, IL-6, IL-8 and TNF-α) and levels of MMPs mRNA expression in knee joints of rabbits after posterior cruciate ligament (PCL) injury, and explore the mechanism of difficult repair by itself after PCL injury.

MethodsEighty adult New Zealand white rabbits were divided into the sham operation group (40 rats) and PCL injury group (40 rats) according to the random number table method.The PCL was revealed after the posterior paratellar medial incision of the right posterior limb, and the incision was sutured in sham operation group.The 1/2 PCL was cut after the posterior paratellar medial incision of the right posterior limb, and the incision was sutured in PCL injury group.Ten rabbits in each group were randomly sacrificed on the 3rd, 7th, 14th and 21st day after modeling, respectively, and the knee joint fluid of right hind limb, synovial membrane and PCL tissue were harvested.The contents of inflammatory cytokines (IL-1β, IL-6, IL-8 and TNF-α) in joint fluid were detected using the enzyme-linked immunosorbent assay (ELISA), and the levels of MMP-1, MMP-2 and MMP-3 mRNA in synovial membrane and PCL tissue were detected using RT-PCR.

ResultsAfter modeling, the levels of IL-1β, IL-6, IL-8 and TNF-α in joint fluid of PCL injury group increased compared with the sham operation group.On the 3rd day after modeling, the contents of inflammatory cytokines in joint fluid of PCL injury group reached the peak.On the 7th, 14th and 21st day, the contents of inflammatory cytokines in PCL injury group decreased, but which was still higher than those in sham operation group (P < 0.01).After modeling, the levels of MMP-1, MMP-2 and MMP-3 mRNA expression in synovial and PCL tissue of PCL injury group increased compared with the sham operation group.On the 3rd day after modeling, the levels of MMPs mRNA expression of PCL injury group reached the peak.On the 7th, 14th and 21st day, the levels of MMPs mRNA expression in PCL injury group decreased, but which was still higher than those in sham operation group (P < 0.01).

ConclusionsAfter the PCL injury of rabbits, the contents of inflammatory cytokines in joint fluid, and the enhanced activity of MMPs induces the excessive degradation of extracellular matrix in synovial tissue and PCL tissue, which may be an important cause of difficult repair by itself after PCL injury.