Extracellular matrix alterations in hypertension : effects of emilin1deficiency in mouse aorta

Objective Emilin1, an extracellular matrix glycoprotein, regulates blood pressure by inhibiting transforming growth factor (TGF)-β1 processing. Emilin1 knockout mice are hypertensive. A proteomic approach was performed to characterize transgenic mouse models in order to understand molecular mechanisms involved in hypertension pathogenesis. Design and method We examined the proteomic profiles of aorta in two animal models, constitutive Emilin1 knockout mouse and tamoxifen-inducible vascular smooth muscle cells specific knockout mice (Emilin1flox/flox;Smmhc-Cre-ERT2). Wild-type mice and Smmhc-Cre-ERT2 mice treated by tamoxifen respectively were used as controls. Qualitative and quantitative differences in the proteome were obtained by the combination of two proteomics techniques, 2D-DIGE and ICPL, and the differentially expressed proteins were identified by MALDI-ToF/ToF or LC-ESI-MS/MS mass spectrometry. A comparative analysis of the two different experimental datasets was performed by DeCyder and Warp-LC (Proteinscape) softwares in order to cluster samples according to protein expression levels. Results Both techniques showed similar functional groups of proteins involved in hypertension pathogenesis, but complementary proteins were identified. Variations were observed in metabolism, stress response, cell adhesion and in contractile/structural proteins. These classes resulted over-expressed in Emilin1 knockout model and down-expressed in Emilin1flox/flox;Smmhc-Cre-ERT2 mouse. Conclusions This study shows the most important alterations due to Emilin1 deficiency in mouse aorta. In Emilin1 knockout mouse there is a general down-regulation of aorta proteins. In this model Emilin1 gene is expressed neither in smooth muscle nor in endothelial cells and blood vessels are constitutively smaller than controls. These results indicate that the KO model reflects the adaptation to a congenital hypertension condition. Emilin1flox/flox;Smmhc-Cre-ERT2 mice show an up-regulation in the majority of cellular proteins involved in hypertension pathogenesis. In this model, the conditional silencing of Emilin1 gene is restricted to smooth muscle cells of blood vessels which are normal in size. The observed molecular alterations can be considered as putative biomarkers to monitor the onset of the disease.