ABSTRACT
OBJECTIVES: Although high abundant cystatin c (CysC) in cerebrospinal fluid (CSF) is well known, its ambiguous role associated with pain still remains unclear. This study evaluated the effects of intrathecal CysC content from chronic pain caused by osteoarthritis (OA) and the novel relationship with matrix metalloproteinases 2 and 9 (MMP2 and MMP9) in CSF. METHODS: Samples of CSF were obtained from 8 elderly patients (65 y and above) with OA with lower limb pain for at least 6 months (OA group) and 8 sex-matched and age-matched relatively healthy elderly individuals without any pain problems (control group). The intrathecal CysC, MMP2, and MMP9 were examined by Western blotting. The analysis of CysC cleavage under different conditions was performed through silver staining and using mass-spectroscopy (SELDI-TOF) on 2 groups. RESULTS: Expression of full-length CysC and pro-MMP2 proteins showed statistically significant upregulation (P=0.0004 vs. 0.03), and expression of MMP9 protein showed downregulation (P=0.007) in the OA group. Both MMP9 and MMP2 initiated the mechanism for full-length CysC cleavage only in the presence of CSF. However, MMP9 showed greater ability than MMP2 for CysC cleavage in control and OA groups in sliver staining. Incubation of CSF with the MMP9 inhibitor led to the suppression of CysC cleavage in SELDI-TOF. DISCUSSION: These findings provide the first in vivo evidence on a relationship between CysC and gelatinases (MMP2 and MMP9), and could facilitate further investigation of novel interactions among these proteins within the proteomics field, especially protein-protein interactions involved in pain.
