Objective
Ultrasound has been therapeutically applied for pain control in rheumatoid arthritis although little physiologic effects of sonication on rheumatoid tissue were known. This investigation was conducted to determine the effects of sonication on the cell proliferation and matrix metalloproteinase (MMP) production of cultured fibroblast like synoviocytes (FLS) derived from synovial tissues of rheumatoid arthritis.

Method
Pulsed ultrasound (1.0 MH_Z, 20 msec on, 80 msec off) with varying intensities (0, 0.1, 0.25, 0.5, 0.75, 1.0 W/cm²) was applied to experimental cell groups growing as monolayers in culture plates for varying durations (0, 30, 90, 180 seconds) in the presence and absence of interleukin-1β (IL-1β).

Results
There were no significant differences in thymidine incorporation between 0, 30, 90 and 180 second sonication groups with 0.5 W/cm² after 1 day and 2 days. There were no significant differences in thymidine incorporation between 0, 0.1, 0.25, 0.5, 0.75, 1.0 W/cm² sonication groups 1 day and 2 days after 90 second sonication. There were significant increase in MMP-1 (p=0.025) and MMP-3 production (p=0.000) of FLS after sonication in the absence of IL-1β but there were no significant differences in MMP-1 and MMP-3 production in the presence of IL-1β. And MMP-1 and MMP-3 production were increased significantly in the presence of IL-1β but not than in the absence of IL-1β.

Conclusion
While comparisons made between a limited number of FLS cell lines must be open to question, the overall consistency of the findings suggest sonication with nonthermal effect is not the contraindication in rheumatoid arthritis treatment but further study is needed in vivo in animal and in clinical studies.