Abstract 760: Alterations in Fibroblast Phenotype during Murine Thoracic Aortic Aneurysm Development
Thoracic aortic aneurysms (TAAs) result from maladaptive remodeling of the vascular extracellular matrix (ECM). In addition to structural protein changes, resident cellular profiles are altered leaving the fibroblast as the predominant cell type within the vascular wall. The present study tests the hypothesis that fibroblast phenotype is also altered during TAA development. Primary murine aortic fibroblasts were isolated from normal (n=4) and TAA aortas (n=3; 4-wks post-induction; topical 0.5M CaCl2 15 min) by the outgrowth method. Cultures were established and passages 3–5 were used for gene expression profiling in the absence of stimulation. Relative expression of 30 genes (MMPs, ECM proteins, transcription factors) normalized to 4 house keeping genes was measured by quantitative real-time PCR. Genes displaying a minimum 2-fold increase/decrease or genes with significantly different normalized Ct values (t-test, TAA vs. control; p<0.05) were considered to have altered expression Steady state gene expression of 4-wk TAA versus normal fibroblasts revealed elevated expression of Mmp2, Mmp11, Mmp15, Col1a1, Col1a2, Col3a1, Eln, Lamb2, Fn1, Fbn2, Spp1, Sparc, Fos, and Fosb, and decreased expression of Mmp3, Timp3, Ltbp1, Sp1, and Junb (Figure⇓). This study demonstrates for the first time that isolated aortic fibroblasts from 4-wk TAAs possess a unique gene expression profile as compared to normal fibroblasts. This suggests they have undergone a stable phenotypic change, which may be the result of a clonal expansion of a subset of cells, and may play a significant role in TAA development through the enhancement of ECM proteolysis.