Deficiency in Aim2 affects viability and calcification of vascular smooth muscle cells from murine aortas and angiotensin-II induced aortic aneurysms

• Published in: Molecular medicine (Cambridge, Mass.) Vol. 26; no. 1; p. 87
• Main Authors: Wortmann, Markus, Arshad, Muhammad, Hakimi, Maani, Böckler, Dittmar, Dihlmann, Susanne
• Format: Journal Article
• Language: English
• Published: England BioMed Central 15.09.2020; BMC
• Subjects: Age; Aneurysms; Aortic aneurysm; Aortic aneurysms; Calcification; Cell culture; Cell growth; Coronary vessels; Experiments; Extracellular matrix; Genotype & phenotype; Inflammasome; Phenotype transition; Proliferation; Senescence; Smooth muscle; Ultrasonic imaging; VSMC; United States > US; Germany; Senescence; Inflammasome; Proliferation; VSMC; Aortic aneurysm; Phenotype transition
• ISSN: 1076-1551; 1528-3658
• DOI: 10.1186/s10020-020-00212-z

Phenotypic transformation of vascular smooth muscle cells is a key element in vascular remodeling and aortic aneurysm growth. Previously, deletion of several inflammasome components decreased formation of aortic aneurysm (AA) in the Angiotensin II (AngII) -induced mouse model. We hypothesized that the inflammasome sensor Absent in melanoma 2 (Aim2) might affect the phenotype of vascular smooth muscle cells (VSMC), thereby reducing AA formation. Aim2-/- mice and wild-type (WT) C57Bl/6 J mice were used as an animal model. VSMC were isolated from 6 months old mice and grown in vitro. Young (passage 3-5) and senescent (passage 7-12) cells were analyzed in vitro for calcification in mineralization medium by Alizarin Red S staining. Expression of calcification and inflammatory markers were studied by real-time RT-PCR and Western blotting, release of cytokines was determined by ELISA. To induce AA, osmotic mini-pumps loaded with AngII (1500 ng/kg bodyweight/min) were implanted for 28 days in male mice at 6 months of age. Compared with VSMC from WT mice, VSMC isolated from Aim2-/- mice were larger, less viable, and underwent stronger calcification in mineralization medium, along with induction of Bmp4 and repression of Tnfsf11/Rankl gene expression. In addition, Aim2 deficiency was associated with reduced inflammasome gene expression and release of Interleukin-6. Using the mouse model of AngII induced AA, Aim2 deficiency reduced AA incidence to 48.4% (15/31) in Aim2-/- mice versus 76.5% (13/17) in WT mice. In contrast to Aim2-/- mice, AA from WT mice expressed significantly increased levels of alpha-smooth muscle actin/Acta2, indicating tissue remodeling. Reduced cell proliferation in Aim2-/- mice was indicated by significantly increased p16ink4a/Cdkn2a expression in untreated and AngII-infused aortas, and by significantly lower amounts of proliferating (Ki67 positive) VSMC in AngII-infused Aim2-/- mice. Our results suggest a role for Aim2 in regulating VSMC proliferation and transition to an osteoblast-like or osteoclast-like phenotype, thereby modulating the response of VSMC in aortic remodeling and AA formation.