Rpl13a snoRNAs Downregulate Smooth Muscle Cell COX4I2 and Promote Neointimal Hyperplasia

Area of Science:

• Cardiovascular Biology
• Molecular Biology
• RNA Biology

Background:

• Reactive oxygen species (ROS) exacerbate vascular smooth muscle cell (SMC) activation and neointimal hyperplasia in arterial injury and atherosclerosis.
• Small nucleolar RNAs (snoRNAs) encoded by the Rpl13a locus are identified as key regulators of cellular ROS levels.

Purpose of the Study:

• To investigate the role of Rpl13a snoRNAs in regulating SMC activation and neointimal hyperplasia in vivo and in vitro.
• To elucidate the molecular mechanisms by which Rpl13a snoRNAs influence ROS production and SMC function.

Main Methods:

• Utilized Rpl13a snoRNA knockout (snoKO) mice and wild-type (WT) littermates.
• Induced neointimal hyperplasia via carotid artery endothelial denudation in mice.
• Performed in vitro functional assays and proteomic analyses on primary SMCs from WT and snoKO mice.
• Investigated snoRNA-guided mRNA 2'-O-methylation in HEK293T cells with specific snoRNA deletions.

Main Results:

• snoKO mice exhibited reduced arterial ROS, inflammation, and neointimal hyperplasia compared to WT mice.
• In vitro, snoKO SMCs showed decreased ROS, migration, proliferation, and inflammatory signaling.
• Reduced ROS in snoKO SMCs and aortas correlated with increased mitochondrial COX4I2 protein, a regulator of mitochondrial ROS.
• Deletion of U32A snoRNA in HEK293T cells reduced COX4I2 mRNA 2'-O-methylation, upregulating COX4I2 protein.

Conclusions:

• Rpl13a snoRNAs are critical drivers of SMC activation and neointimal hyperplasia.
• Rpl13a snoRNAs elevate SMC ROS levels, partly through post-transcriptional downregulation of COX4I2 expression.
• Targeting Rpl13a snoRNAs may offer a therapeutic strategy for preventing or treating vascular diseases associated with neointimal hyperplasia.