Abstract 109: Exosomes from Mesenchymal Stem Cells Suppress Aortic Elastin Induced Inflammation in Macrophages

Abstract

Introduction: Mesenchymal Stem Cells (MSCs) from bone marrow have been shown to attenuate aortic aneurysm formation in a variety of rodent models. These effects appear to rely on modulation of systemic inflammation, including the attenuation of macrophage mediated inflammation. Elastin appears to play a significant role in inducing this inflammation and stimulating macrophages to express an M1 phenotype. Here we evaluate the effects human elastin and elastin break down products on macrophage phenotype. We also evaluate the role of human exosomes derived from MSCs on modulating the effect of elastin on macrophage phenotype. Methods: Human peripheral blood monocytes were collected and cultured for six days to isolate human macrophages. The cells were then treated with digested elastin from human aortic tissue or the human peptide VGVAPG in combination with human MSCs or exosomes derived from human MSCs. The phenotype of the macrophages was then analyzed using enzyme linked immune sandwich assays for tumor necrosis factor alpha (TNF-a) secretion, quantitative real time PCR and flow-cytometry for cellular proteins. Results: Macrophages cultured with digested elastin from aortic tissue showed a significant dose response increase in TNF-a production and cell surface markers consistent with an M1 phenotype. In addition, transcripts for pro-inflammatory cytokines significantly increased after exposure to digested elastin. Similar results were obtained using the elastin peptide sequence VGVAPG. Co-culture with MSCs significantly attenuated elastin induced macrophage TNF-a production, production of pro-inflammatory transcripts and M1 related proteins. When MSC derived exosomes were cultured with macrophages, pro-inflammatory markers and TNF-a production was reduced below baseline levels, even after stimulation with elastin peptide. Conclusions: Macrophages develop an M1 phenotype in response to digested aortic elastin and elastin derived peptides. This response is significantly attenuated by exosomes derived from human MSCs