A New Editor of Smooth Muscle Phenotype

Role of EZH2-mediated epigenetic modification on vascular smooth muscle in cardiovascular diseases: A mini-review

Vascular smooth muscle cells (VSMCs) are integral to the pathophysiology of cardiovascular diseases (CVDs). Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, plays a crucial role in epigenetic regulation of VSMCs gene expression. Emerging researches suggest that EZH2 has a dual role in VSMCs, contingent on the pathological context of specific CVDs. This mini-review synthesizes the current knowledge on the mechanisms by which EZH2 regulates VSMC proliferation, migration and survival in the context of CVDs. The goal is to underscore the potential of EZH2 as a therapeutic target for CVDs treatment. Modulating EZH2 and its associated epigenetic pathways in VSMCs could potentially ameliorate vascular remodeling, a key factor in the progression of many CVDs. Despite the promising outlook, further investigation is warranted to elucidate the epigenetic mechanisms mediated by EZH2 in VSMCs, which may pave the way for novel epigenetic therapies for conditions such as atherosclerosis and hypertension.

Mesenchymal Regulation of the Microvascular Niche in Chronic Lung Diseases

The adult lung is comprised of diverse vascular, epithelial, and mesenchymal progenitor cell populations that reside in distinct niches. Mesenchymal progenitor cells (MPCs) are intimately associated with both the epithelium and the vasculature, and new evidence is emerging to describe their functional roles in these niches. Also emerging, following lineage analysis and single cell sequencing, is a new understanding of the diversity of mesenchymal cell subpopulations in the lung. However, several gaps in knowledge remain, including how newly defined MPC lineages interact with cells in the vascular niche and the role of adult lung MPCs during lung repair and regeneration following injury, especially in chronic lung diseases. Here we summarize how the current evidence on MPC regulation of the microvasculature during tissue homeostasis and injury may inform studies on understanding their role in chronic lung disease pathogenesis or repair. © 2019 American Physiological Society. Compr Physiol 9:1431-1441, 2019.

Inhibition of polycomb repressor complex 2 ameliorates neointimal hyperplasia by suppressing trimethylation of H3K27 in vascular smooth muscle cells

BACKGROUND AND PURPOSE

The increased proliferation and migration of vascular smooth muscle cells (VSMCs) after arterial injury contributes greatly to the pathogenesis of neointimal hyperplasia. As a major component of epigenetics, histone methylation plays an important role in several cardiovascular diseases. However, its role in restenosis is still unclear.

EXPERIMENTAL APPROACH

Human aortic VSMCs were challenged with PDGF-BB, and total histones were extracted and analysed by HPLC/MS. For the in vivo study, rats were subjected to wire-guided common carotid injury.

KEY RESULTS

PDGF-BB markedly increased the H3K27me3 level, as demonstrated by use of HPLC/MS and confirmed by western blot analysis. Enhancer of zeste homologue 2 (EZH2), the histone H3K27 methyltransferase component of polycomb repressive complex 2, was also up-regulated by PDGF-BB in VSMCs, and in the neointimal hyperplasia induced by wire injury of the rat carotid artery. Furthermore, inhibiting H3K27me3 by treatment with 3-μM UNC1999, an EZH2/1 inhibitor, significantly suppressed PDGF-BB-induced VSMC proliferation compared with the PDGF-BB-treated group. Consistently, neointimal formation was significantly attenuated by oral or perivascular administration of UNC1999 compared with the sham group. Mechanistically, the increase in H3K27me3 inhibited the transcription of the cyclin-dependent kinase inhibitor p16^INK4A and thus promoted VSMC proliferation.

CONCLUSIONS AND IMPLICATIONS

Vascular injury elevated the expression of EZH2 and the downstream target H3K27me3, which suppressed p16^INK4A expression in VSMCs and promoted VSMC proliferation and neointimal hyperplasia. EZH2 inhibition might be a potential therapeutic target for restenosis.

Disruption of lineage specification in adult pulmonary mesenchymal progenitor cells promotes microvascular dysfunction

Pulmonary vascular disease is characterized by remodeling and loss of microvessels and is typically attributed to pathological responses in vascular endothelium or abnormal smooth muscle cell phenotypes. We have challenged this understanding by defining an adult pulmonary mesenchymal progenitor cell (MPC) that regulates both microvascular function and angiogenesis. The current understanding of adult MPCs and their roles in homeostasis versus disease has been limited by a lack of genetic markers with which to lineage label multipotent mesenchyme and trace the differentiation of these MPCs into vascular lineages. Here, we have shown that lineage-labeled lung MPCs expressing the ATP-binding cassette protein ABCG2 (ABCG2+) are pericyte progenitors that participate in microvascular homeostasis as well as adaptive angiogenesis. Activation of Wnt/β-catenin signaling, either autonomously or downstream of decreased BMP receptor signaling, enhanced ABCG2+ MPC proliferation but suppressed MPC differentiation into a functional pericyte lineage. Thus, enhanced Wnt/β-catenin signaling in ABCG2+ MPCs drives a phenotype of persistent microvascular dysfunction, abnormal angiogenesis, and subsequent exacerbation of bleomycin-induced fibrosis. ABCG2+ MPCs may, therefore, account in part for the aberrant microvessel function and remodeling that are associated with chronic lung diseases.