Heterozygous loss-of-function SMAD3 (Mothers against decapentaplegic homolog 3) mutations lead to aneurysm-osteoarthritis syndrome (AOS). In the present study, we found that mice lacking Smad3 had a vascular phenotype similar to AOS, marked by the progressive development of aneurysms. These aneurysms were associated with various pathological changes in transmural inflammatory cell infiltration. Bone marrow transplants from Smad3–/– mice induced aortitis and aortic root dilation in irradiated WT recipient mice. Transplantation of CD4+ T cells from Smad3–/– mice also induced aortitis in Smad3+/+ recipient mice, while depletion of CD4+ T cells in Smad3–/– mice reduced the infiltration of inflammatory cells in the aortic root. Furthermore, IFN-γ deficiency increased, while IL-17 deficiency decreased, disease severity in Smad3+/– mice. Cytokine secretion was measured using a cytokine quantibody array, and Smad3–/– CD4+ T cells secreted more GM-CSF than Smad3+/+ CD4+ T cells. GM-CSF induced CD11b+Gr-1+Ly-6Chi inflammatory monocyte accumulation in the aortic root, but administration of anti–GM-CSF mAb to Smad3–/– mice resulted in significantly less inflammation and dilation in the aortic root. We also identified a missense mutation (c.985A>G) in a family of thoracic aortic aneurysms. Intense inflammatory infiltration and GM-CSF expression was observed in aortas specimens of these patients, suggesting that GM-CSF is potentially involved in the development of AOS.
Authors
Ping Ye, Wenhao Chen, Jie Wu, Xiaofan Huang, Jun Li, Sihua Wang, Zheng Liu, Guohua Wang, Xiao Yang, Peng Zhang, Qiulun Lv, Jiahong Xia
(A) Immunostaining for LAP–TGF-β, p-Smad2, p-ERK1/2 and p-JNK1 on slides of aortic root and ascending aorta from Smad3+/+ and Smad3–/– mice aged 1 or 4 months. IHC analysis reveals that the positive staining of LAP–TGF-β, p-Smad2, p-Erk1/2, and p-JNK1 are predominantly located in the infiltrating inflammatory cells in the aortic root of 1-month-old Smad3–/– mice, while there are increased expression and nuclear translocation of p-Smad2, p-ERK1/2, and p-JNK1 in the aortic media of 4-month-old Smad3–/– mice. Original magnification, ×400. (B) Representative Western blot showing Smad1/5, Smad2, ERK1/2, JNK1, p-Smad1/5, p-Smad2, p-ERK1/2, and p-JNK1 levels in proximal ascending aortas from Smad3+/+ and Smad3–/– mice (1 and 4 months of age). The ratio between Smad1/5, Smad2, ERK1/2, JNK1, p-Smad1/5, p-Smad2, p-ERK1/2, and p-JNK1 to GAPDH levels is shown. *P < 0.01; **P < 0.001.