Thoracic aortic aneurysms (TAAs) result from dysregulated remodeling of the vascular extracellular matrix (ECM) which may occur as a result of altered resident cellular function. The present study tested the hypothesis that aortic fibroblasts undergo a stable change in cellular phenotype during TAA formation.
Primary murine aortic fibroblasts were isolated from normal and TAA-induced aortas (4-wks post-induction with 0.5M CaCl2 15 min) by outgrowth method. Normal and TAA cultures were examined using a focused PCR array to determine fibroblast-specific changes in gene expression in the absence and presence of biological stimulation (endothelin-1, phorbol-12-myristate-13-acetate, angiotensin II). The relative expression of 38 genes, normalized to 4 housekeeping genes, was determined and genes displaying a minimum 2-fold increase/decrease or genes with significantly different normalized Ct values were considered to have altered expression.
At steady state TAA fibroblasts revealed elevated expression of several MMPs (Mmp2, Mmp11, Mmp14), collagen genes/elastin (Col1a1, Col1a2, Col3a1, Eln), and other matrix proteins, as well as decreased expression of Mmp3, Timp3, and Ltbp1. Moreover, gene expression profiles in TAA fibroblasts were different than normal fibroblasts after equivalent biological stimuli.
This study demonstrated for the first time that isolated primary aortic fibroblasts from TAA-induced mice possess a unique and stable gene expression profile, and when challenged with biological stimuli, induce a transcriptional response that is different from normal aortic fibroblasts. Together, these data suggest that aortic fibroblasts undergo a stable phenotypic change during TAA development which may drive the enhancement of ECM proteolysis in TAA progression.