Correlation between senescence-associated beta-galactosidase expression in articular cartilage and disease severity of patients with knee osteoarthritis.

Aim The purposes of this study were to investigate senescence-associated beta-galactosidase (SA-beta-Gal) levels in articular cartilage of knee osteoarthritis (OA) and the relationship with severity of the disease. Methods All the 50 cartilage tissues, including normal (controls) and OA cartilage were ascribed to four groups of normal, mild lesions, moderate lesions and severe lesions on the basis of the modified Mankin score. Immunohistochemistry was used to assess the SA-beta-Gal expression in articular cartilage. Results No SA-beta-Gal staining was observed in the normal articular cartilage samples. SA-beta-Gal staining was found in a subset of the chondrocytes close to the lesion site of mild, moderate and severe damaged knee OA cartilage. The percentage of SA-beta-Gal-positive chondrocytes in articular cartilage was 0% in controls, 13.00 ± 5.77% in mild lesions, 31.65 ± 6.91% in moderate lesions and 51.95 ± 6.21% in severe lesions. SA-beta-Gal expression in mild lesions, moderate lesions and severe lesions was higher compared with that of controls (P < 0.0001). SA-beta-Gal expression in moderate lesions and severe lesions were higher with respect to mild lesion samples (P < 0.0001). SA-beta-Gal expression in severe lesions was elevated compared with those of moderate lesions (P < 0.0001). Subsequent analysis showed that articular cartilage SA-beta-Gal levels correlated with severity of disease (Spearman's ρ = 0.94, P < 0.0001). Conclusion SA-beta-Gal expression in articular cartilage is associated with progressive knee OA joint damage and is a potential indictor of disease severity.