Objective Chronic rhinosinusitis was often exacerbated by viral infection.A disruption of the mechanisms that regulate the activity of matrix metallopmteinases(MMPs)during viral infection was one possible mechanism responsible for the cxacerbation.The purpose of study was to achieve a better understanding of MMP expression in hasal epithelial cells after viral infection.Methotis Human nasal epithelial cells were isolated from nasal polyp specimens obtained during endoscopic endonasal surgery in chronic rhinosinusitis patients.The expression of MMP-2,MMP-9,and tissue inhibitor of mctallopmteinase (TIMP).1 mRNA in primary human nasal polyp epithelial cells after double stranded RNA(ds RNA) stimulation were investigated.Results Among the genes whose expression was evaluated,only expression of MMP-9 mRNA increased significantly after dsRNA stimulation(22.61±5.47 fold increase,Z=-2.52,P=0.012).Conclusions The significant up-regulation of MMP-9 mRNA,which Was not modulated by TIMP-1,was an additional siyrec of increased pmteolytic activity in virus-infected upper airways that might contribute to the exacerbation of chronic rhinosinusitis with nasal polyps.