Targeting Metabolic Alterations To Boost Smooth Muscle Cell Differentiation And Prevent Moyamoya- like Cerebrovascular Disease

Moyamoya disease (MMD), characterized by occlusive lesions in the distal carotid arteries, is a malignant cause of pediatric stroke. Surgical revascularization is the mainstay treatment, but peri- and postoperative ischemic complications are common. The disease is highly genetically heterogeneous, with multiple identified genes accounting for only a small percentage of cases. Identifying a common pathway of disease pathogenesis would enhance care for MMD patients. Heterozygous ACTA2 p.R179 pathogenic variants cause MMD-like cerebrovascular disease. Smooth muscle cells (SMCs) from a conditional knock-in mouse model ( Acta2 SMC-R179C/+ ) and from patient-derived induced pluripotent stem cells (iPSCs) are incompletely differentiated, leading to SMC migration and proliferation that may drive the occlusive lesions. Further, Acta2 SMC-R179C/+ SMCs have increased glycolysis and reduced oxidative respiration on Seahorse analyses. Molecular characterization showed that Acta2 SMC-R179C/+ SMCs have reduced mitochondrial mass and decreased complex I activity. Nicotinamide riboside (NR) treatment increases oxidative respiration and complex I activity in Acta2 SMC-R179C/+ SMCs, and surprisingly also increases differentiation and decreases migration. To assess if this pathway is generalizable beyond ACTA2 patients, we used SMCs with other pediatric MMD-associated variants: loss-of-function variants in Pcnt (explanted from a mouse model) and a pathogenic variant in RNF213 (generated via Crispr/Cas9 in human iPSCs). Pcnt KO SMCs are less differentiated, more proliferative and migratory, and have increased glycolysis evident on Seahorse analyses compared with control SMCs. RNF213 variant SMCs also have increased glycolysis and a blunted response to differentiation-inducing growth factors. These data provide preliminary evidence for a common and therapeutically targetable pathway in pediatric MMD patients.