OBJECTIVE : To explore the MMP-1/TIMP-1 expressions in rectal submucosa of females with obstructed defecation syndrome (ODS) associated with internal rectal prolapse (IRP). METHODS : Fifty-six female patients with ODS associated with IRP were enrolled as Case group, and 43 female hemorrhoids of stages III-IV without constipation and IRP were enrolled as Control group. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry were performed to test the expressions of MMP-1/TIMP-1 in the rectal submucosa. Western blotting was used to examine protein expressions of MMP-1/TIMP-1 and pro-inflammatory cytokines (IL-6 and TNF-α) in the rectal submucosa. EVG staining was conducted to detect collagen and elastic fibers in rectal submucosa. RESULTS : The increased expression of MMP-1 was negatively linked to the decreased TIMP-1 level in the rectal submucosa of patients with ODS associated with IRP. Besides, the expressions of IL-6 and TNF-α were increased in the Case group as compared with the Control group. Additionally, ODS severity and the pro-inflammatory cytokines was positively linked to MMP-1, but negatively related to TIMP-1 in Case group. EVG staining showed that the area ratios of collagen and elastic fibers were lower in Case group than Control group. Through Pearson's correlation analysis, the area ratios of collagen and elastic fibers were positively associated with MMP-1 expression, but negatively correlated with TIMP-1 expression in rectal submucosa of patients with ODS associated with IRP. CONCLUSIONS : Elevated MMP-1 and reduced TIMP-1 were found in ODS associated with IRP, which was related to the ODS severity, inflammation and contents of collagen and elastic fibers.