AIM: To examine the expression of metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the colonic mucosa of patients with ulcer- ative colitis (UC). METHODS: Reverse transcription-polymerase chain re- action (RT-PCR) and immunohistochemistry were used to study the expression of MMP-1 and TIMP-1 at both mRNA and protein levels in patients with UC and con- trols. The relationship between MMP-1 mRNA, TIMP-1 mRNA, MMP-1 mRNA/TIMP-1 mRNA ratio and the sever- ity of clinical symptoms of the patients with UC were also analyzed. RESULTS: The expression of MMP-1 mRNA and TIMP-1 mRNA in the ulcerated and inflamed colonic mucosa was signifi cantly higher than that in the non-inflamed colonic mucosa (P < 0.001), but there was no statistically signif i- cant difference in the non-inflamed colonic mucosa of UC patients and normal controls (P > 0.05). The mRNA ex- pression of MMP-1 and TIMP-1 in ulcerated colonic mu- cosa of UC patients was increased by 80-fold and 2.2-fold, respectively when compared with the normal controls. In the inflamed colonic mucosa, the increase was 30-fold and 1.6-fold, respectively. Immunohistochemical analy- sis showed that among the ulcerated, inflamed, and non-inflamed colonic mucosae of UC patients and the normal controls, the positive rate of MMP-1 expression was 87%, 87%, 40% and 35% respectively, and the positive rate of TIMP-1 expression was 89%, 89%, 80% and 75%, respectively. Furthermore, the expression of MMP-1 mRNA, TIMP-1 mRNA and the MMP-1 mRNA/ TIMP-1 mRNA ratio were correlated with the severity of clinical symptoms (P <0.05).CONCLUSION: Excessive expression of MMP-1 in the diseased colonic mucosa causes excessive hydrolysis of the extracellular matrix (ECM) and ulceration in UC pa-tients. MMP-1 mRNA, TIMP-1 mRNA and MMP-1 mRNA/ TIMP-1 mRNA ratio can be used as biomarkers to judge the severity of clinical symptoms in patients with UC. Exogenous TIMP-1 or MMP-1 inhibitor therapy is a novel treatment for patients with UC. AIM: To examine the expression of metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the colonic mucosa of patients with ulcer-ative colitis (UC). METHODS: Reverse transcription-polymerase chain re - action (RT-PCR) and immunohistochemistry were used to study the expression of MMP-1 and TIMP-1 at both mRNA and protein levels in patients with UC and con- trols. The relationship between MMP-1 mRNA, TIMP-1 mRNA RESULTS: The expression of MMP-1 mRNA and TIMP-1 mRNA in the ulcerated and inflamed colonic mucosa was signifi cantly higher than that in the non-inflamed colonic mucosa (P <0.001), but there was no significant signif i-cant difference in the non-inflamed colonic mucosa of UC patients and normal controls (P> 0.05) - pression of MMP-1 and TIMP-1 in ulcerated colonic mucosa of UC patients was increased by 80-fold and 2.2 -fold, respectively when compared with the normal controls. In the inflamed colonic mucosa, the increase was 30-fold and 1.6-fold, respectively. Immunohistochemical analy- sis showed that among the ulcerated, inflamed, and non-inflamed colonic mucosae of UC patients and the normal controls, the positive rate of MMP-1 expression was 87%, 87%, 40% and 35% respectively, and the positive rate of TIMP-1 expression was 89%, 89%, 80% and 75% (P <0.05). CONCLUSION: Excessive expression of MMP-1 mRNA, TIMP-1 mRNA and the MMP-1 mRNA ratio were correlated with the severity of clinical symptoms in the diseased colonic mucosa causes excessive hydrolysis of the extracellular matrix (ECM) and ulceration in UC pa-tients. MMP-1 mRNA, TIMP-1 mRNA and MMP-1 mRNA / TIMP-1 mRNA ratio can be used as biomarkers to judge the severity of clinical symptoms in patients with UC. Exogenous TIMP-1 or MMP-1 inhibitor therapy is a novel treatment for patients with UC.