To study the gene expressions of suppressors of cytokine signaling (SOCS1, 2, 3) and cytokine-inducible SH2-domain 1(CIS-1) in chondrocytes of osteoarthritis (OA) patients and healthy controls, and also analyze the effects of IL-1β and TNF-α on the levels of mRNA encoding these SOCS family members.
Chondrocytes were isolated from patients of OA and joint replacement due to traffic accident by sequential treatment with trypsin, hyaluronidase and collagenase B. Total RNA was extracted from the same chondrocytes, and the levels of SOCS1, 2, 3 and CIS-1 mRNA were determined by real-time qRT-PCR. In addition, healthy chondrocytes were cultured with and without a mixture of IL-1β and oncostatin M (OSM, both 2.5 ng/mL) or TNF-α (10 ng/mL). The short-term cultures with single cytokine treatment were harvested 24 and 72 h after treatment, and the long-term cultures were maintained for 4-5 weeks until confluent with periodical cytokine stimulation. Total RNA was extracted and mRNA levels of SOCS1, 2, 3 and CIS-1 mRNA were detected by qRT-PCR.
The SOCS2 and CIS-1 mRNA levels were reduced by approximately 8-fold in OA samples compared to controls (P<0.01), whereas SOCS1 and SOCS3 showed similar expression patterns in OA and control chondrocytes (P>0.05). The SOCS2 and CIS-1 mRNA levels declined by 5-fold and 3-fold with long-term treatment with IL-1β and OSM or IL-1β and TNF-α, respectively (P<0.05).
In OA patients, the expressions of SOCS2 and CIS-1 decreased, while SOCS1 and SOCS3 were unaffected. Long-term treatment with inflammatory cytokines mimicking OA effect attenuated the expressions of SOCS2 and CIS-1 in chondrocytes.