Detection of insulin-like growth factor I and II in synovial tissue specimens of patients with rheumatoid arthritis and osteoarthritis by in situ hybridization.

Objective: To study the expression of insulin-like growth factor I and II (IGF I and II) in synovial tissue specimen of patients with rheumatoid arthritis (RA) and osteoarthritis (OA).

Methods: Synovial tissue sections were examined for the expression of IGF I and II by in situ hybridization using digoxigenin labeled antisense and sense RNA probes.

Results: The antisense probe of IGF I reacted with all specimens. IGF II mRNA was expressed in 7/7 RA and 4/5 OA tissues. Cells of the synovial lining and subsynovial layer bound both antisense probes, whereas inflammatory infiltrates of RA tissues were labeled rarely.

Conclusion: The significant number of cells in the synovium that express IGF I and II mRNA suggests a role of IGF in repair mechanisms of articular cartilage in response to injury and effects on fibroblast growth within the synovium.