Expression of osteopontin in synovial tissue of rheumatoid arthritis: its relation to disease activity and severity

ABSTRACT

To demonstrate the expression of osteopontin in synovial tissue of patients with rheumatoid arthritis and to correlate it with disease activity and severity in order to find out its possible role in the pathogenesis of the disease. This study was conducted on 30 RA patients and 10 control subjects with post traumatic knee injury. All patients were subjected to full medical history taking, thorough clinical examination with special attention to articular manifestations [Modified disease activity score] [DAS], and spread severity index [SSI]. Laboratory investigations included CBC, ESR, CRP and RF. Radiological investigations included plain x-ray of the affected knee joint using Larsen's score for assessment of joint damage and expression of osteopontin [OPN] in synovial tissues of both patients and controls was determined by immunohistochemical staining of formalin fixed, paraffin embedded synovial tissues. We demonstrated by immunohistochemistry that OPN was detected as brown cytoplasmic staining expressed predominantly in the lining layer of rheumatoid synovium rather than the sublining layer and it was absent in the lymphoid aggregates. In contrast, synovial tissue of the control group showed weak scattered staining for OPN. We found a highly statistical significant difference between RA patients and controls regarding the synovial expression of OPN which was highly associated with the activity. Also, percentage of OPN positive cells was highly associated with the severity of RA assessed clinically by SSI and radiological [p<0.01]. Osteopontin is critically involved in the pathogenesis of both inflammatory and joint-destructive processes in rheumatoid arthritis. OPN may reflect disease activity and can be used as a marker of disease severity