Smooth muscle cell-specific deletion of Lkb1 in mice led to progressive aortic dilation and premature death.
Lkb1-deficient vascular smooth muscle cells (VSMCs) transformed into fibroblast-like and chondrocyte-like cells, contributing to blood vessel rupture.
Decreased Lkb1 expression in human aortic aneurysm tissue was observed compared to control tissue.
Lkb1 regulates the expression of a protein that influences the splicing of pyruvate kinase isoforms, affecting metabolism.
An increased ratio of one pyruvate kinase isoform was associated with a shift towards aerobic glycolysis in Lkb1-deficient VSMCs.
Activation of PKM2 with a specific compound improved VSMC function and reduced aortic dilation in affected mice.
Simplified
AIMS: Vascular smooth muscle cell () plasticity is a state in which VSMCs undergo phenotypic switching from a quiescent contractile phenotype into other functionally distinct phenotypes. Although emerging evidence suggests that VSMC plasticity plays critical roles in the development of vascular diseases, little is known about the key determinant for controlling VSMC plasticity and fate.
METHODS AND RESULTS: We found that smooth muscle cell-specific deletion of Lkb1 in tamoxifen-inducible Lkb1flox/flox;Myh11-Cre/ERT2 mice spontaneously and progressively induced aortic/arterial dilation, aneurysm, rupture, and premature death. Single-cell RNA sequencing and imaging-based lineage tracing showed that Lkb1-deficient VSMCs transdifferentiated gradually from early modulated VSMCs to fibroblast-like and chondrocyte-like cells, leading to ossification and blood vessel rupture. Mechanistically, Lkb1 regulates polypyrimidine tract binding protein 1 (Ptbp1) expression and controls alternative splicing of (PKM) isoforms 1 and 2. Lkb1 loss in VSMC results in an increased PKM2/PKM1 ratio and alters the metabolic profile by promoting aerobic glycolysis. Treatment with PKM2 activator TEPP-46 rescues VSMC transformation and aortic dilation in Lkb1flox/flox;Myh11-Cre/ERT2 mice. Furthermore, we found that Lkb1 expression decreased in human aortic aneurysm tissue compared to control tissue, along with changes in markers of VSMC fate.
CONCLUSION: Lkb1, via its regulation of Ptbp1-dependent alterative splicing of PKM, maintains VSMC in contractile states by suppressing VSMC plasticity.
Key numbers
40 of 42
Aortic Rupture Incidence
Percentage of mice with aortic rupture after Lkb1 deletion.
21.8%
Transformation Rates
Percentage of VSMCs transformed into fibroblast-like cells at 4.5 months post-TAM induction.
18.2%
Transformation Rates
Percentage of VSMCs transformed into chondrocyte-like cells at 4.5 months post-TAM induction.
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