Enhanced Arterial Medial Calcification in Mice with Smooth Muscle‐Specific Deletion of Lysosomal Acid Ceramidase.

Abstract

Arterial medial calcification (AMC) is associated with transition of arterial smooth muscle cells (SMCs) to osteogenic phenotype. These arterial SMCs secrete matrix vesicles or exosomes to form the first nidus for mineralization. However, the mechanisms mediating exosome excretion in SMCs remain poorly understood. Whether SMC‐specific lysosomal Asah1 gene (acid ceramidase (AC) gene code in mice) expression and associated lysosomal ceramide signaling are required for osteogenic phenotype change and exosome excretion are unknown. In the present study, we used Asah1fl/fl/SMcre mice with SMC‐specific deletion of lysosomal AC and Smpd1trg/SMcre with SMC‐specific overexpression of acid sphingomyelinase (ASM) gene (mouse gene code: Smpd1) to demonstrate the role of lysosomal ceramide signaling pathway in AMC. Using high dose of vitamin D (500,000 IU/kg/day) to induce AMC, Asah1fl/fl/SMcre mice were found to have increased expression of RUNX2 and osteopontin, but downregulation of SM22‐α (SMC marker) with decreased ratio of α‐SMA vs. vimentin in coronary and aortic media compared to their littermates (Asah1fl/fl/WT and WT/WT mice). Asah1fl/fl/SMcre mice also had augmented AnX2 and ALP expression (exosome markers) and reduced co‐localization of lysosome marker (LAMP‐1) with multivesicular body marker (VPS16) in both coronary and aortic media. Morphological examinations confirmed that severe AMC occurred in both aorta and coronary arteries in Asah1fl/fl/SMcre, but not in their littermates. In Smpd1trg/SMcre mice, similar biochemical and morphological changes were found to Asah1fl/fl/SMcre mice. These data indicate that lysosomal AC in SMC plays a critical role in osteogenic phenotype change, exosome release and mineral deposition in the mouse model of AMC and that lysosomal ceramide signaling pathway may control exosome excretion and osteogenic phenotype transition in SMCs that determine the development of AMC.Support or Funding Information(Supported by NIH grants HL057244, HL075316 and HL122937).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.