Mmp1a and Mmp1b are not functional orthologs to human MMP1 in cigarette smoke induced lung disease

Matrix Metalloproteinase 1 (MMP1, collagenase-1) expression is implicated in a number of diseased states including emphysema and malignant tumors. The cigarette-smoke induced expression of this interstitial collegenase has been studied extensively and its inhibition proposed as a novel therapeutic treatment for tobacco related diseases such as chronic obstructive pulmonary disease (COPD) and lung cancer. However, a limitation in MMP1 research is the inability to take advantage of natural in vivo studies as most research has been performed in vitro or via animal models expressing human forms of the gene due to the lack of a rodent ortholog of MMP1. The present study examines the function of two possible mouse orthologs of human MMP1 known as Mmp1a and Mmp1b. Using genomic sequence analysis and expression analysis of these enzymes, the data demonstrate that neither MMP1a nor MMP1b behave in the same manner as human MMP1 in the presence of cigarette smoke. These findings establish that the two commonly proposed orthologs of MMP1, Mmp1a and Mmp1b, provide substantial limitations for use in examining MMP1 induced lung disease in mouse models of cigarette smoke emphysema.