(A) Experimental workflow of eliminating intimal CX3CR1⁺ macrophages to observe TAA development in Cx3cr1-CreER^T2iDTR^F/+Fbn1^C1041G/+ mice. (B) Flow cytometry analysis of CX3CR1⁺ macrophages in aortic root and ascending aortas from 21-week-old Cx3cr1-CreER^T2iDTR^F/+Fbn1^C1041G/+ mice with or without DT-mediated depletion. The average quantity of CX3CR1⁺ macrophages in the vehicle group was set as 100%, while that in the DT group was relative to that in the vehicle group. n = 9 for vehicle and n = 8 for DT. *P < 0.05 by unpaired Student’s t test. (C) En face immunofluorescence staining of intimal CX3CR1⁺ macrophages (red) and VE-cadherin (green) in ascending aortas from 21-week-old Cx3cr1-CreER^T2iDTR^F/+Fbn1^C1041G/+ mice with or without DT-mediated depletion. The nuclei were stained blue with DAPI. Scale bars: 20 μm. Data were quantified as the relative fluorescence intensities of CX3CR1 staining in intima averaged from 4 randomly selected areas for each mouse. The average of intensities of CX3CR1 staining in vehicle group were set as 1, while the intensities in DT group were presented as the relative values. n = 4 mice. *P < 0.05 by unpaired Student’s t test. (D) Representative transthoracic echocardiographic images of the aortic root and ascending aortas in Cx3cr1-CreER^T2iDTR^F/+Fbn1^C1041G/+ mice at different ages with or without DT-mediated depletion. Scale bars: 2 mm. White arrows depict the sinus of Valsalva measurements. Yellow arrows depict ascending aorta measurement. (E) Quantification of aortic root and ascending aorta diameters measured by transthoracic echocardiography. n = 10 for vehicle and n = 8 for DT. *P < 0.05 by repeated-measures ANOVA with the Greenhouse-Geisser adjustment followed by Bonferroni’s post hoc comparisons. (F) EVG staining of the aortic roots in 21-week-old Cx3cr1-CreER^T2iDTR^F/+Fbn1^C1041G/+ mice with or without DT-mediated depletion. n = 8 for each group. *P < 0.05 by Mann-Whitney U test for elastin degradation grade and unpaired Student’s t test for aortic thickness.