Comparative gene array analyses of severe elastic fiber defects in late embryonic and newborn mouse aorta

Abstract

Elastic fibers provide reversible elasticity to the large arteries and are assembled during development when hemodynamic forces are increasing. Mutations in elastic fiber genes are associated with cardiovascular disease. Mice lacking expression of the elastic fiber genes elastin ( Eln−/−), fibulin-4 ( Efemp2−/−), or lysyl oxidase ( Lox−/−) die at birth with severe cardiovascular malformations. All three genetic knockout models have elastic fiber defects, aortic wall thickening, and arterial tortuosity. However, Eln−/− mice develop arterial stenoses, while Efemp2−/− and Lox−/− mice develop ascending aortic aneurysms. We performed comparative gene array analyses of these three genetic models for two vascular locations and developmental stages to determine differentially expressed genes and pathways that may explain the common and divergent phenotypes. We first examined arterial morphology and wall structure in newborn mice to confirm that the lack of elastin, fibulin-4, or lysyl oxidase expression provided the expected phenotypes. We then compared gene expression levels for each genetic model by three-way ANOVA for genotype, vascular location, and developmental stage. We found three genes upregulated by genotype in all three models, Col8a1, Igfbp2, and Thbs1, indicative of a common response to severe elastic fiber defects in developing mouse aorta. Genes that are differentially regulated by vascular location or developmental stage in all three models suggest mechanisms for location or stage-specific disease pathology. Comparison of signaling pathways enriched in all three models shows upregulation of integrins and matrix proteins involved in early wound healing, but not of mature matrix molecules such as elastic fiber proteins or fibrillar collagens.

Protein malnutrition during lactation affects thoracic aortic tunica media thickness in Wistar rat pups

“…According to Hill et al 20 , a low-iron diet in chicks up to 3 weeks of age had no effect on elastin or collagen content in relation to total proteins, despite the fact that the experimental group weighed less than controls. However, they found that fibrillin-3 was disorganized and less abundant, which could have caused the fragmentation of elastic fibers and elastic lamellae in diffuse networks.…”

Deletion of type VIII collagen reduces blood pressure, increases carotid artery functional distensibility and promotes elastin deposition

“…[43] reported that VSMCs deficient in elastin (Eln −/− ) have reduced VSMC marker expression, but enhanced proliferative and migratory capacity, resulting in vessel stenosis in Eln −/− mice, similar to our Col8 +/+ VSMCs. Eln −/− mice also have Col8a1 as their most upregulated transcript [15] , suggesting that Col-8 contributes to the synthetic and hyper-proliferative phenotype of those VSMCs.…”

“…The expression timeline of these proteins are consistent with this hypothesis [34] . Elastin-mediated regulation of Col-8 expression would also explain why Col8a1 is the most upregulated transcript in Eln −/− mice [15] . Moreover, since the pattern of expression of Col-8 can be described as fetal gene reprogramming during disease, the loss of intact elastic fibers and tropoelastin signaling may be a mechanistic cue to turn on Col-8 expression.…”

“…Elastic fiber synthesis involves nearly 30 different proteins including tropoelastin, microfibrillar proteins, lysyl oxidase (LOX) and fibulins [14] . Importantly, systemic deletions of elastin (Eln −/− ), LOX (Lox −/− ) or fibulin-4 (Efemp2 −/− ) all result in mice that die at birth due to severe cardiovascular malformations [15] . Mice of all three genotypes present with detrimental elastic fiber defects, vessel tortuosity and wall thickening.…”

“…Eln −/− mice suffer from arterial stenosis, whereas Lox −/− and Efemp2 −/− mice develop ascending aortic aneurysms. A hallmark feature of each of the three knockout (KO) mouse models was that the transcript for Col-8 ( Col8a1 ) was the most upregulated mRNA in arteries relative to arteries from control mice [15] . This dramatic upregulation of Col8a1 in mice deficient in elastic fiber proteins suggests that the non-fibrillar collagen may be important to maintain vessel structure, and may be necessary for matrix deposition and organization.…”