Notch Signaling in Vascular Endothelial and Mural Cell Communications

Blood vessel organoids generated by base editing and harboring single nucleotide variation in Notch3 effectively recapitulate CADASIL-related pathogenesis

Human blood vessel organoids (hBVOs) offer a promising platform for investigating vascular diseases and identifying therapeutic targets. In this study, we focused on in vitro modeling and therapeutic target finding of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), the most common form of hereditary stroke disorder caused by mutations in the NOTCH3 gene. Despite the identification of these mutations, the underlying pathological mechanism is elusive, and effective therapeutic approaches are lacking. CADASIL primarily affects the blood vessels in the brain, leading to ischemic strokes, migraines, and dementia. By employing CRISPR/Cas9 base-editing technology, we generated human induced pluripotent stem cells (hiPSCs) carrying Notch3 mutations. These mutant hiPSCs were differentiated into hBVOs. The NOTCH3 mutated hBVOs exhibited CADASIL-like pathology, characterized by a reduced vessel diameter and degeneration of mural cells. Furthermore, we observed an accumulation of Notch3 extracellular domain (Notch3ECD), increased apoptosis, and cytoskeletal alterations in the NOTCH3 mutant hBVOs. Notably, treatment with ROCK inhibitors partially restored the disconnection between endothelial cells and mural cells in the mutant hBVOs. These findings shed light on the pathogenesis of CADASIL and highlight the potential of hBVOs for studying and developing therapeutic interventions for this debilitating human vascular disorder.

Progress to Clarify How NOTCH3 Mutations Lead to CADASIL, a Hereditary Cerebral Small Vessel Disease

Notch signaling is conserved in C. elegans, Drosophila, and mammals. Among the four NOTCH genes in humans, NOTCH1, NOTCH2, and NOTCH3 are known to cause monogenic hereditary disorders. Most NOTCH-related disorders are congenital and caused by a gain or loss of Notch signaling activity. In contrast, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) caused by NOTCH3 is adult-onset and considered to be caused by accumulation of the mutant NOTCH3 extracellular domain (N3ECD) and, possibly, by an impairment in Notch signaling. Pathophysiological processes following mutant N3ECD accumulation have been intensively investigated; however, the process leading to N3ECD accumulation and its association with canonical NOTCH3 signaling remain unknown. We reviewed the progress in clarifying the pathophysiological process involving mutant NOTCH3.

Biology of vascular mural cells

The vasculature consists of vessels of different sizes that are arranged in a hierarchical pattern. Two cell populations work in concert to establish this pattern during embryonic development and adopt it to changes in blood flow demand later in life: endothelial cells that line the inner surface of blood vessels, and adjacent vascular mural cells, including smooth muscle cells and pericytes. Despite recent progress in elucidating the signalling pathways controlling their crosstalk, much debate remains with regard to how mural cells influence endothelial cell biology and thereby contribute to the regulation of blood vessel formation and diameters. In this Review, I discuss mural cell functions and their interactions with endothelial cells, focusing on how these interactions ensure optimal blood flow patterns. Subsequently, I introduce the signalling pathways controlling mural cell development followed by an overview of mural cell ontogeny with an emphasis on the distinguishing features of mural cells located on different types of blood vessels. Ultimately, I explore therapeutic strategies involving mural cells to alleviate tissue ischemia and improve vascular efficiency in a variety of diseases.

miR-342-5p promotes vascular smooth muscle cell phenotypic transition through a negative-feedback regulation of Notch signaling via targeting FOXO3

AIM

Under various pathological conditions such as cancer, vascular smooth muscle cells (vSMCs) transit their contractile phenotype into phenotype(s) characterized by proliferation and secretion, a process called vSMC phenotypic transition (vSMC-PT). Notch signaling regulates vSMC development and vSMC-PT. This study aims to elucidate how the Notch signal is regulated.

MAIN METHODS

Gene-modified mice with a SM22α-CreER^T2 transgene were generated to activate/block Notch signaling in vSMCs. Primary vSMCs and MOVAS cells were cultured in vitro. RNA-seq, qRT-PCR and Western blotting were used to evaluated gene expression level. EdU incorporation, Transwell and collagen gel contraction assays were conducted to determine the proliferation, migration and contraction, respectively.

KEY FINDINGS

Notch activation upregulated, while Notch blockade downregulated, miR-342-5p and its host gene Evl in vSMCs. However, miR-342-5p overexpression promoted vSMC-PT as shown by altered gene expression profile, increased migration and proliferation, and decreased contraction, while miR-342-5p blockade exhibited the opposite effects. Moreover, miR-342-5p overexpression significantly suppressed Notch signaling, and Notch activation partially abolished miR-342-5p-induced vSMC-PT. Mechanically, miR-342-5p directly targeted FOXO3, and FOXO3 overexpression rescued miR-342-5p-induced Notch repression and vSMC-PT. In a simulated tumor microenvironment, miR-342-5p was upregulated by tumor cell-derived conditional medium (TCM), and miR-342-5p blockade abrogated TCM-induced vSMC-PT. Meanwhile, conditional medium from miR-342-5p-overexpressing vSMCs significantly enhanced tumor cell proliferation, while miR-342-5p blockade had the opposite effects. Consistently, in a co-inoculation tumor model, miR-342-5p blockade in vSMCs significantly delayed tumor growth.

SIGNIFICANCE

miR-342-5p promotes vSMC-PT through a negative-feedback regulation of Notch signaling via downregulating FOXO3, which could be a potential target for cancer therapy.