Abstract
OBJECTIVE: To investigate the serum and synovial fluid levels of CSF-1 in patients with knee osteoarthritis (KOA) and evaluate its clinical significance. METHODS: We selected 143 patients with KOA who received treatment at our hospital from June 2021 to August 2024. Enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of CSF-1, IL-6, IL-1β, CRP, and HIF-1α in the serum of all study subjects, as well as the levels of these markers in the synovial fluid of all KOA patients. The Kellgren and Lawrence (KL) grading system was used to assess the radiographic severity of all KOA patients. Additionally, we also collected the Visual Analog Scale (VAS) scores and the Western Ontario McMaster University Osteoarthritis Index (WOMAC). Western blot (WB) was used to detect the expression levels of inflammatory factors in macrophages after CSF-1 stimulation. RESULTS: Compared to healthy volunteers, KOA patients exhibited significantly elevated levels of serum CSF-1, IL-6, IL-1β, CRP, and HIF-1α (p < 0.05). The advanced group of KOA patients had significantly higher levels of serum and synovial fluid CSF-1 compared to the early group. Synovial fluid CSF-1 levels were associated with inflammation and disease severity in KOA patients. CSF-1 stimulation significantly increased the expression of CSF-1R, IL-6, TNF-α, IL-1β, HIF-1α, and MMP-3 in macrophages. Moreover, synovial fluid and serum CSF-1, synovial fluid HIF-1α, and synovial fluid IL-6 were identified as risk factors for advanced KOA. CONCLUSION: Our findings indicated that the serum and synovial fluid levels of CSF-1 were significantly increased in KOA patients, even higher in patients with KL grade 3-4. Moreover, CSF-1 was identified as a risk factor associated with advanced stage KOA.