To investigate the molecular mechanism of extracellular matrix overdeposition in hypertrophic scar tissues and to explore MMPs gene therapy for hypertrophic scar. Methods: Hypertrophic scarderived and normal skin-derived fibroblasts were cultured and a recombinant retrovirus vector containing MMP-3 gene was constructed and then transfected into hypertrophic scar fibroblasts. Expressive level of MMP-3 mRNA was detected by dot blotting, and the activity of MMPs was determined by DNP-peptide.Results: Lower expression of MMP-3 mRNA and fewer DNP-peptide hydrolyzed fragments were observed in hypertrophic scar-derived fibroblasts compared with normal skin-derived fibroblasts. Transfection of MMP-3gene into hypertrophic scar-derived fibroblasts could enhance the expression of MMP-3 mRNA (3. 4 fold)and the de novo capacity to hydrolyze DNP-peptide (2. 1 fold). Conclusion: Overdeposition of extracellular matrix in hypertrophic scar tissue was related to low expression of MMP-3 due to its down-degradation of extracellular matrix. MMP-3 gene transfection could be a better way to treat hypertrophic scars by degrading extracellular matrix.