View Abstract

A5779 - Unraveling the Role of MT1-mmp in Alveolar Epithelial Cells During Pulmonary Fibrosis
Author Block: L. Placido1, M. Maldonado1, F. Toscano1, Y. Romero1, J. Cisneros2, M. Selman2, A. Pardo1; 1Biochemical, UNAM, Mexico, Mexico, 2Inst Nac De Enfermedades Respiratorias, Mexico, Mexico.
Rationale Idiopathic pulmonary fibrosis (IPF) is a progressive epithelial-driven disease where an aberrantly activated lung epithelium produces multiple mediators that induce the expansion of the fibroblast population and exaggerated accumulation of extracellular matrix. Among these, matrix metalloproteases (MMPs) play a central role in not only the abnormal tissue remodeling but also influencing the epithelial and mesenchymal cell behavior. Previous studies in our laboratory indicated that MMP-14 (also known as MT1-MMP) is increased in the alveolar epithelium of IPF and in experimental fibrosis. MMP-14 is a membrane-bounded protease responsible for pericellular collagenolysis and activation of other proteases such as MMP-2. However, since Mmp14 knockout mouse is lethal, the specific role of this enzyme in lung fibrosis has been challenging to evaluate. The aim of the study was to examine the role of Mmp14 in an experimental model of lung fibrosis induced on conditional mice specific for AEC type 2. Methods A triple transgenic conditional mouse was created from Cre/rtTA/SP-c and loxPMmp14 (kindly donated by Ana Mora and López-Otín). Mmp14 homozygous loxP (loxPMmp14) mice were used to generated Cre/SP-c/rtTA/loxP/Mmp14; five generations were needed to obtain homozygous conditional mice (cKO-Mmp14) for these studies. The loss of Mmp14 expression was induced by doxycycline. These mice did not present any difference in phenotype, lifespan or reproductive defects compared to wild-type. Cre/SPc/rtTa/loxP/Mmp14 with and without doxycicline stimulus were treated with an intratracheal injection of bleomycin or PBS and sacrificed at, 21 and 120 days. Results remarkably, at three weeks after instillation, doxycycline/bleomycin cKO-Mmp14 mice displayed severe morphological lesions and significantly higher accumulation of collagen. In the resolution stage (twelve weeks after instillation), doxycycline/bleomycin cKO-Mmp14 mice revealed an incomplete resolution of the fibrotic lesions. To analyze the molecular mechanisms gain- and loss-of-function experiments were performed with human alveolar epithelial cells (A549). Overexpression of MMP14 was sufficient to have a significant increase in proliferation and migration. In addition, cells that overexpressed Mmp14 increases the expression levels of fibronectin after TGF-β1 treatment suggesting that this enzyme may contribute to epithelial-mesenchymal transition Conclusions These findings demonstrated that deficiency of Mmp14 in AEC2 promotes fibrosis and reduces fibrosis resolution and suggest that this enzyme is critical for a normal wound healing response and for resolution of scarring.