Attenuated synovial fluid ghrelin levels are linked with cartilage damage, meniscus injury, and clinical symptoms in patients with knee anterior cruciate ligament deficiency.

BACKGROUND

The meniscus injury and post-traumatic knee osteoarthritis (PTOA) following anterior cruciate ligament (ACL) lesions often cause great burdens to patients. Ghrelin, a recently identified 28-amino-acid peptide, has been shown to inhibit inflammation and perform as a growth factor for chondrocyte.

OBJECTIVE

This study was aimed at investigating ghrelin concentration in synovial fluid and its association with the degree of meniscus injury, articular degeneration, and clinical severity in patients suffering from anterior cruciate ligament (ACL) deficiency.

METHODS

61 ACL deficiency patients admitted to our hospital were drafted in the current study. The Noyes scale and Mankin scores were used to assess articular cartilage damage arthroscopically and histopathologically, respectively. The Lysholm scores and International Knee Documentation Committee (IKDC) subjective scores were utilized to evaluate the clinical severity. The radiological severity of meniscus injury was assessed by MR imaging. Serum and synovial fluid ghrelin levels were determined using enzyme linked immunosorbent assay (ELISA). The cartilage degradation markers collagen type II C-telopeptide (CTX-II) and cartilage oligomeric matrix protein (COMP) in addition to inflammatory markers interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) were also examined. Receiver operating characteristic (ROC) curve was performed and the area under curve (AUC) was calculated to assess the diagnostic value of ghrelin levels for the prediction of the MRI grading for meniscus injury by comparing with other biomarkers.

RESULTS

SF ghrelin levels were positively related to Lysholm and IKDC scores. PTOA patients with grade 3 showed significantly decreased levels of ghrelin in SF compared with those with grade 2. The ghrelin levels in SF were negatively related to MRI signal grades for meniscus injury. SF ghrelin levels were also inversely associated with Noyes scale and Mankin scores, and levels of inflammation markers IL-6, TNF-α, and degradation biomarkers COMP and CTX-II. ROC analysis showed that ghrelin was more valuable for severe meniscus injury diagnosis by MRI imaging.

CONCLUSIONS

Synovial fluid ghrelin levels demonstrated an independent and negative association with meniscus injury, cartilage damage, and clinical severity in patients with ACL deficiency. Ghrelin in SF might serve as a potential cartilage protective factor for PTOA. Local application of ghrelin as a potential adjuvant therapy for delaying cartilage degeneration following ACL injury deserves further study.