Objective: To investigate the potential role of matrix metalloproteinase-9 (MMP-9) in Henoch-Schönlein purpura (HSP), an acute type of systemic vasculitis in children.
Methods: In this study, 24 children with HSP and ten healthy children (HC) were enrolled from February 2003 to July 2004. Blood samples were obtained from all the children. The total levels of MMP-9 in the plasma were detected by enzyme-linked immunosorbent assay (ELISA). The second blood samples were obtained from eight of the 24 HSP patients in the convalescent phase. MMP-9 of circulating white blood cells was detected by immunocytochemistry.
Results: Plasma MMP-9 levels in the acute phase of HSP (249.75 ng/mL) were significantly higher than in HC (191.00 ng/mL) (p = 0.034). Immunocytochemistry showed that MMP-9 was positive in the circulating white blood cells. The MMP-9 levels in the convalescent phases were lower than in the acute phase in six cases, but increased in the other two cases, and one of these two cases had recurrence of purpuric rashes in the lower extremities for 3 months.
Conclusion: MMP-9 plays an important role in the vascular destruction of HSP, and circulating white blood cells may be a source of the MMP-9 secreted into the circulation.