Abdominal aortic aneurysm (AAA) is one of a number of diseases associated with a prominent inflammatory cell infiltrate and local destruction of structural matrix macromolecules. This inflammatory infiltrate is predominately composed of T lymphocytes and macrophages. Delineating specific contribution of these inflammatory cells and their cytokines in AAA formation is the key to understanding AAA and other chronic inflammatory disease processes. Our previous studies have demonstrated that macrophages are the major source of matrix metalloproteinase-9, which is required for aneurysmal degeneration in the murine AAA model. However, the role of CD4+ T cells, the most abundant infiltrates in aneurysmal aortic tissue, is uncertain. In the present study, we found that in the absence of CD4+ T cells, mice are resistant to aneurysm induction. Previous studies have shown that IFN-γ levels are increased in AAA. IFN-γ is a main product of T cells. Intraperitoneal IFN-γ was able to partially reconstitute aneurysms in CD4−/− mice. Furthermore, mice with a targeted deletion of IFN-γ have attenuation of MMP expression and inhibition of aneurysm development. Aneurysms in IFN-γ−/− mice can be reconstituted by reinfusion of competent splenocytes from the corresponding wild-type mice. This study demonstrates the pivotal role that T cells and the T cell cytokine, IFN-γ, play in orchestrating matrix remodeling in AAA. This study has important implications for other degenerative diseases associated with matrix destruction.

The circulating doxycycline levels of the patients are comparable with those achieved in mice. Doxycycline accounts for an inhibition of 33% to 66% of the aortic growth. The findings suggest that standard doxycycline doses could inhibit AAA growth in humans.

BackgroundThe fibroblast-populated 3D collagen matrix is a model of tissue and healing which has been used since the 1980's. It was hypothesized that anchorage disruption of the collagen matrix would produce p53-dependent apoptosis in the embedded fibroblasts, but results of hypothesis testing were variant.FindingsThe response of p53 to anchorage disruption in 3D culture or to UV irradiation in 2D culture was influenced both by fibroblast strain and culture conditions. It also was determined that data scatter in a collagen matrix contraction assay was related to fibroblast strain and possibly to technical factors, such as cell culture technician and/or number of matrices utilized. Subsequent analysis suggested that phenotypic drift and/or inter-strain genetic variability may have been responsible for the data scatter. In addition, several technical factors were identified that may have contributed to the scatter.ConclusionExperimentation with human foreskin fibroblasts in both 2D and 3D culture can produce variant data. The underlying cause of the data scatter appears to be partially due to the biologic variability of the fibroblast.

The technique of RNA interference (RNAi) was trialed in primary human foreskin fibroblasts, both in monolayer culture and in the fibroblast-populated collagen matrix. Knockdown of lamin A/C, p53, and FAK was possible with low-confluency (<50%) monolayer fibroblasts, a transfection vehicle concentration of 1%, and an siRNA concentration of 25-50 nM. Knockdown also was possible in the collagen matrix using similar reagent concentrations and a cellular density of one million fibroblasts per ml of matrix. Optimization of transfection conditions appeared to be important to increase knockdown efficiency. Consistent with prediction, knockdown of FAK induced apoptosis in the fibroblast-populated collagen matrix.