Genetic lineage tracing analysis of c-kit+ stem/progenitor cells revealed a contribution to vascular injury-induced neointimal lesions

Epicardial SMARCA4 deletion exacerbates cardiac injury in myocardial infarction and is related to the inhibition of epicardial epithelial-mesenchymal transition

The reactivated adult epicardium produces epicardium-derived cells (EPDCs) via epithelial-mesenchymal transition (EMT) to benefit the recovery of the heart after myocardial infarction (MI). SMARCA4 is the core catalytic subunit of the chromatin re-modeling complex, which has the potential to target some reactivated epicardial genes in MI. However, the effects of epicardial SMARCA4 on MI remain uncertain. This study found that SMARCA4 was activated over time in epicardial cells following MI, and some of activated cells belonged to downstream differentiation types of EPDCs. This study used tamoxifen to induce lineage tracing and SMARCA4 deletion from epicardial cells in Wt1-CreER;Smarca4fl/fl;Rosa26-RFP adult mice. Epicardial SMARCA4 deletion reduces the number of epicardial cells in adult mice, which was related to changes in the activation, proliferation, and apoptosis of epicardial cells. Epicardial SMARCA4 deletion reduced collagen deposition and angiogenesis in the infarcted area, exacerbated cardiac injury in MI. The exacerbation of cardiac injury was related to the inhibition of generation and differentiation of EPDCs. The alterations in EPDCs were associated with inhibited transition between E-CAD and N-CAD during the epicardial EMT, coupled with the down-regulation of WT1, SNAIL1, and PDGF signaling. In conclusion, this study suggests that Epicardial SMARCA4 plays a critical role in cardiac injury caused by MI, and its regulatory mechanism is related to epicardial EMT. Epicardial SMARCA4 holds potential as a novel molecular target for treating MI.

Progress of the study of pericytes and their potential research value in adenomyosis

Pericytes (PCs) are versatile cells integral to the microcirculation wall, exhibiting specific stem cell traits. They are essential in modulating blood flow, ensuring vascular permeability, maintaining homeostasis, and aiding tissue repair process. Given their involvement in numerous disease-related pathological and physiological processes, the regulation of PCs has emerged as a focal point of research. Adenomyosis is characterized by the presence of active endometrial glands and stroma encased by an enlarged and proliferative myometrial layer, further accompanied by fibrosis and new blood vessel formation. This distinct pathological condition might be intricately linked with PCs. This article comprehensively reviews the markers associated with PCs, their contributions to angiogenesis, blood flow modulation, and fibrotic processes. Moreover, it provides a comprehensive overview of the current research on adenomyosis pathophysiology, emphasizing the potential correlation and future implications regarding PCs and the development of adenomyosis.

Elevated c-kit expression in failed autologous arteriovenous fistulas in end-stage renal disease patients

BACKGROUND

Serum stem cell factor is elevated in end-stage renal disease (ESRD) patients. This study aimed to investigate the expression of the c-kit receptor, which is the specific membrane receptor of stem cell factor, in failed autologous arteriovenous fistulas (AVFs) in end-stage renal disease patients.

METHODS

A total of 14 ESRD patients with initial AVFs creation and 16 ESRD patients with reconstruction were enrolled in this study. Hematoxylin and eosin (H&E) and elastic Verhoeff-Van Gieson (EVG) staining were used for histomorphometric analyses. Immunohistochemistry was used to examine the expression of c-kit in the intima, and a correlation analysis was performed with the intimal area and the percentage of area stenosis. A double-label immunofluorescence method was used to explore the colocalization of c-kit with α-smooth muscle actin (α-SMA) and CD31. The expression of c-kit and the related PI3K/Akt signaling axis, including PI3K, P-PI3K, Akt, P-Akt473, P-Akt308, and mTOR, was measured by western blotting.

RESULTS

Internal elastic lamina (IEL) area, intimal area, percentage of area stenosis, and average optical density (AOD) of c-kit in the intima were significantly higher in the failed group than in the preoperative group (p ⩽ 0.001). The AOD of c-kit in the intima was positively correlated with the intimal area and the percentage of stenosis (intimal area: R = 0.744, p < 0.001; the percentage of stenosis: R = 0.923, p < 0.001). C-kit colocalized with α-SMA but not with CD31 in studies of c-kit target cells. Moreover, the levels of c-kit and P-PI3K, P-Akt473 and mTOR in the PI3K/Akt axis were also higher in the failed group than in the initial group (p < 0.05).

CONCLUSIONS

C-kit and related proteins associated with the PI3K/Akt pathway were elevated in failed AVFs among ESRD patients and that the expression level of c-kit in the intima correlates with the degree of AVF stenosis.

Correlation between stem cell molecular phenotype and atherosclerotic plaque neointima formation and analysis of stem cell signal pathways

Vascular stem cells exist in the three-layer structure of blood vessel walls and play an indispensable role in angiogenesis under physiological conditions and vascular remodeling under pathological conditions. Vascular stem cells are mostly quiescent, but can be activated in response to injury and participate in endothelial repair and neointima formation. Extensive studies have demonstrated the differentiation potential of stem/progenitor cells to repair endothelium and participate in neointima formation during vascular remodeling. The stem cell population has markers on the surface of the cells that can be used to identify this cell population. The main positive markers include Stem cell antigen-1 (Sca1), Sry-box transcription factor 10 (SOX10). Stromal cell antigen 1 (Stro-1) and Stem cell growth factor receptor kit (c-kit) are still controversial. Different parts of the vessel have different stem cell populations and multiple markers. In this review, we trace the role of vascular stem/progenitor cells in the progression of atherosclerosis and neointima formation, focusing on the expression of stem cell molecular markers that occur during neointima formation and vascular repair, as well as the molecular phenotypic changes that occur during differentiation of different stem cell types. To explore the correlation between stem cell molecular markers and atherosclerotic diseases and neointima formation, summarize the differential changes of molecular phenotype during the differentiation of stem cells into smooth muscle cells and endothelial cells, and further analyze the signaling pathways and molecular mechanisms of stem cells expressing different positive markers participating in intima formation and vascular repair. Summarizing the limitations of stem cells in the prevention and treatment of atherosclerotic diseases and the pressing issues that need to be addressed, we provide a feasible scheme for studying the signaling pathways of vascular stem cells involved in vascular diseases.

Restenosis after Coronary Stent Implantation: Cellular Mechanisms and Potential of Endothelial Progenitor Cells (A Short Guide for the Interventional Cardiologist)

Coronary stents are among the most common therapies worldwide. Despite significant improvements in the biocompatibility of these devices throughout the last decades, they are prone, in as many as 10–20% of cases, to short- or long-term failure. In-stent restenosis is a multifactorial process with a complex and incompletely understood pathophysiology in which inflammatory reactions are of central importance. This review provides a short overview for the clinician on the cellular types responsible for restenosis with a focus on the role of endothelial progenitor cells. The mechanisms of restenosis are described, along with the cell-based attempts made to prevent it. While the focus of this review is principally clinical, experimental evidence provides some insight into the potential implications for prevention and therapy of coronary stent restenosis.

Vascular Stem/Progenitor Cells in Vessel Injury and Repair

Vascular repair upon vessel injury is essential for the maintenance of arterial homeostasis and function. Stem/progenitor cells were demonstrated to play a crucial role in regeneration and replenishment of damaged vascular cells during vascular repair. Previous studies revealed that myeloid stem/progenitor cells were the main sources of tissue regeneration after vascular injury. However, accumulating evidences from developing lineage tracing studies indicate that various populations of vessel-resident stem/progenitor cells play specific roles in different process of vessel injury and repair. In response to shear stress, inflammation, or other risk factors-induced vascular injury, these vascular stem/progenitor cells can be activated and consequently differentiate into different types of vascular wall cells to participate in vascular repair. In this review, mechanisms that contribute to stem/progenitor cell differentiation and vascular repair are described. Targeting these mechanisms has potential to improve outcome of diseases that are characterized by vascular injury, such as atherosclerosis, hypertension, restenosis, and aortic aneurysm/dissection. Future studies on potential stem cell-based therapy are also highlighted.

Nonbone Marrow CD34+ Cells Are Crucial for Endothelial Repair of Injured Artery

[Figure: see text].

Different Roles of Stem/Progenitor Cells in Vascular Remodeling

Significance: Since the discovery of vascular stem cells, there has been considerable advancement in comprehending the nature and functions of these cells. Due to their differentiation potential to repair endothelial cells and to participate in lesion formation during vascular remodeling, it is crucial to elucidate vascular stem cell behaviors and the mechanisms underlying this process, which could provide new chances for the design of clinical therapeutic application of stem cells. Recent Advances: Over the past decades, major progress has been made on progenitor/vascular stem cells in the field of cardiovascular research. Vascular stem cells are mostly latent in their niches and can be bioactivated in response to damage and get involved in endothelial repair and smooth muscle cell aggregation to generate neointima. Accumulating evidence has been shown recently, using genetic lineage tracing mouse models, to particularly provide solutions to the nature of vascular stem cells and to monitor both cell migration and the process of differentiation during physiological angiogenesis and in vascular diseases. Critical Issues: This article reviews and summarizes the current research progress of vascular stem cells in this field and highlights future prospects for stem cell research in regenerative medicine. Future Directions: Despite recent advances and achievements of stem cells in cardiovascular research, the nature and cell fate of vascular stem cells remain elusive. Further comprehensive studies using new techniques including genetic cell lineage tracing and single-cell RNA sequencing are essential to fully illuminate the role of stem cells in vascular development and diseases. Antioxid. Redox Signal. 35, 192-203.

Endothelial cell plasticity at the single-cell level

The vascular endothelium is characterized by a remarkable level of plasticity, which is the driving force not only of physiological repair/remodeling of adult tissues but also of pathological angiogenesis. The resulting heterogeneity of endothelial cells (ECs) makes targeting the endothelium challenging, no less because many EC phenotypes are yet to be identified and functionally inventorized. Efforts to map the vasculature at the single-cell level have been instrumental to capture the diversity of EC types and states at a remarkable depth in both normal and pathological states. Here, we discuss new EC subtypes and functions emerging from recent single-cell studies in health and disease. Interestingly, such studies revealed distinct metabolic gene signatures in different EC phenotypes, which deserve further consideration for therapy. We highlight how this metabolic targeting strategy could potentially be used to promote (for tissue repair) or block (in tumor) angiogenesis in a tissue or even vascular bed-specific manner.

Application of genetic cell-lineage tracing technology to study cardiovascular diseases

Cardiovascular diseases are leading causes that threaten people's life. To investigate cells that are involved in disease development and tissue repair, various technologies have been introduced. Among these technologies, lineage tracing is a powerful tool to track the fate of cells in vivo, providing deep insights into cellular behavior and plasticity. In cardiac diseases, newly formed cardiomyocytes and endothelial cells are found from proliferation of local cells, while fibroblasts and macrophages are originated from diverse cell sources. Similarly, in response to vascular injury, various sources of cells including media smooth muscle cells, endothelium, resident progenitors and bone marrow cells are involved in lesion formation and/or vessel regeneration. In summary, current review summarizes the development of lineage tracing techniques and their utilizations in investigating roles of different cell types in cardiovascular diseases.

Perivascular tissue stem cells are crucial players in vascular disease

Perivascular tissue including adipose layer and adventitia have been considered to play pivotal roles in vascular development and disease progression. Recent studies showed that abundant stem/progenitorcells (SPCs) are present in perivascular tissues. These SPCs exhibit capability to proliferate and differentiate into specific terminal cells. Adult perivascular SPCs are quiescent in normal condition, once activated by specific molecules (e.g., cytokines), they migrate toward the lumen side where they differentiate into both smooth muscle cells (SMCs) and endothelial cells (ECs), thus promoting intima hyperplasia or endothelial regeneration. In addition, perivascular SPCs can also regulate vascular diseases via other ways including but not limited to paracrine effects, matrix protein modulation and microvessel formation. Perivascular SPCs have also been shown to possess therapeutic potentials due to the capability to differentiate into vascular cells and regenerate vascular structures. This review summarizes current knowledge on resident SPCs features and discusses the potential benefits of SPCs therapy in vascular diseases.

The calcium binding protein S100β marks hedgehog-responsive resident vascular stem cells within vascular lesions

A hallmark of subclinical atherosclerosis is the accumulation of vascular smooth muscle cell (SMC)-like cells leading to intimal thickening. While medial SMCs contribute, the participation of hedgehog-responsive resident vascular stem cells (vSCs) to lesion formation remains unclear. Using transgenic eGFP mice and genetic lineage tracing of S100β vSCs in vivo, we identified S100β/Sca1 cells derived from a S100β non-SMC parent population within lesions that co-localise with smooth muscle α-actin (SMA) cells following iatrogenic flow restriction, an effect attenuated following hedgehog inhibition with the smoothened inhibitor, cyclopamine. In vitro, S100β/Sca1 cells isolated from atheroprone regions of the mouse aorta expressed hedgehog signalling components, acquired the di-methylation of histone 3 lysine 4 (H3K4me2) stable SMC epigenetic mark at the Myh11 locus and underwent myogenic differentiation in response to recombinant sonic hedgehog (SHh). Both S100β and PTCH1 cells were present in human vessels while S100β cells were enriched in arteriosclerotic lesions. Recombinant SHh promoted myogenic differentiation of human induced pluripotent stem cell-derived S100β neuroectoderm progenitors in vitro. We conclude that hedgehog-responsive S100β vSCs contribute to lesion formation and support targeting hedgehog signalling to treat subclinical arteriosclerosis.

C-Kit, a Double-Edged Sword in Liver Regeneration and Diseases

Previous studies have reported an important role of c-kit in embryogenesis and adulthood. Activation of the SCF/KIT signal transduction pathway is customarily linked to cell proliferation, migration and survival thus influence hematopoiesis, pigmentation, and spermatogenesis. The role of c-kit in the liver is controversial, it is however argued that it is a double-edged sword in liver regeneration and diseases. First, liver c-kit⁺ cells, including oval cells, bile epithelial cells, and part of hepatocytes, participate in liver tissue repair by regenerating target cells according to the type of liver injury. At the same time, c-kit⁺ mast cells, act as immature progenitors in circulation, playing a critical role in liver fibrosis. Furthermore, c-kit is also a proto-oncogene. Notably, c-kit overexpression regulates gastrointestinal stromal tumors. Various studies have explored on c-kit and hepatocellular carcinoma, nevertheless, the intricate roles of c-kit in the liver are largely understudied. Herein, we extensively summarize previous studies geared toward providing hints for future clinical and basic research.

Single-cell gene profiling and lineage tracing analyses revealed novel mechanisms of endothelial repair by progenitors

Stem/progenitor cells (SPCs) have been implicated to participate in vascular repair. However, the exact role of SPCs in endothelial repair of large vessels still remains controversial. This study aimed to delineate the cellular heterogeneity and possible functional role of endogenous vascular SPCs in large vessels. Using single-cell RNA-sequencing (scRNA-seq) and genetic lineage tracing mouse models, we uncovered the cellular heterogeneity of SPCs, i.e., c-Kit+ cells in the mouse aorta, and found that endogenous c-Kit+ cells acquire endothelial cell fate in the aorta under both physiological and pathological conditions. While c-Kit+ cells contribute to aortic endothelial turnover in the atheroprone regions during homeostasis, recipient c-Kit+ cells of nonbone marrow source replace both luminal and microvessel endothelial cells in transplant arteriosclerosis. Single-cell pseudotime analysis of scRNA-seq data and in vitro cell experiments suggest that vascular SPCs display endothelial differentiation potential and undergo metabolic reprogramming during cell differentiation, in which AKT/mTOR-dependent glycolysis is critical for endothelial gene expression. These findings demonstrate a critical role for c-Kit lineage cells in aortic endothelial turnover and replacement, and may provide insights into therapeutic strategies for vascular diseases.

miRNA-200c-3p promotes endothelial to mesenchymal transition and neointimal hyperplasia in artery bypass grafts

Increasing evidence has suggested a critical role for endothelial‐to‐mesenchymal transition (EndoMT) in a variety of pathological conditions. MicroRNA‐200c‐3p (miR‐200c‐3p) has been implicated in epithelial‐to‐mesenchymal transition. However, the functional role of miR‐200c‐3p in EndoMT and neointimal hyperplasia in artery bypass grafts remains largely unknown. Here we demonstrated a critical role for miR‐200c‐3p in EndoMT. Proteomics and luciferase activity assays revealed that fermitin family member 2 (FERM2) is the functional target of miR‐200c‐3p during EndoMT. FERMT2 gene inactivation recapitulates the effect of miR‐200c‐3p overexpression on EndoMT, and the inhibitory effect of miR‐200c‐3p inhibition on EndoMT was reversed by FERMT2 knockdown. Further mechanistic studies revealed that FERM2 suppresses smooth muscle gene expression by preventing serum response factor nuclear translocation and preventing endothelial mRNA decay by interacting with Y‐box binding protein 1. In a model of aortic grafting using endothelial lineage tracing, we observed that miR‐200c‐3p expression was dramatically up‐regulated, and that EndoMT contributed to neointimal hyperplasia in grafted arteries. MiR‐200c‐3p inhibition in grafted arteries significantly up‐regulated FERM2 gene expression, thereby preventing EndoMT and reducing neointimal formation. Importantly, we found a high level of EndoMT in human femoral arteries with atherosclerotic lesions, and that miR‐200c‐3p expression was significantly increased, while FERMT2 expression levels were dramatically decreased in diseased human arteries. Collectively, we have documented an unexpected role for miR‐200c‐3p in EndoMT and neointimal hyperplasia in grafted arteries. Our findings offer a novel therapeutic opportunity for treating vascular diseases by specifically targeting the miR‐200c‐3p/FERM2 regulatory axis. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Hematopoietic Stem Cell Transcription Factors in Cardiovascular Pathology

Transcription factors as multifaceted modulators of gene expression that play a central role in cell proliferation, differentiation, lineage commitment, and disease progression. They interact among themselves and create complex spatiotemporal gene regulatory networks that modulate hematopoiesis, cardiogenesis, and conditional differentiation of hematopoietic stem cells into cells of cardiovascular lineage. Additionally, bone marrow-derived stem cells potentially contribute to the cardiovascular cell population and have shown potential as a therapeutic approach to treat cardiovascular diseases. However, the underlying regulatory mechanisms are currently debatable. This review focuses on some key transcription factors and associated epigenetic modifications that modulate the maintenance and differentiation of hematopoietic stem cells and cardiac progenitor cells. In addition to this, we aim to summarize different potential clinical therapeutic approaches in cardiac regeneration therapy and recent discoveries in stem cell-based transplantation.

Roles of klotho and stem cells in mediating vascular calcification (Review)

Vascular calcification, characterized by the active deposition of calcium phosphate in the vascular walls, is commonly observed in aging, diabetes mellitus and chronic kidney disease. This process is mediated by different cell types, including vascular stem/progenitor cells. The anti-aging protein klotho may act as an inhibitor of vascular calcification through direct effects on vascular stem/progenitor cells with osteogenic differentiation potential. A better understanding of the possible effects of klotho on vascular stem/progenitor cells may provide novel insight into the cellular and molecular mechanisms of klotho deficiency-related vascular calcification and disease. The klotho protein may be considered as a promising therapeutic agent for treating vascular calcification and disease and calcification-related vascular diseases.

Impact of Local Alloimmunity and Recipient Cells in Transplant Arteriosclerosis

RATIONALE

Transplant arteriosclerosis is the major limitation to long-term survival of solid organ transplantation. Although both immune and nonimmune cells have been suggested to contribute to this process, the complex cellular heterogeneity within the grafts, and the underlying mechanisms regulating the disease progression remain largely uncharacterized.

OBJECTIVE

We aimed to delineate the cellular heterogeneity within the allografts, and to explore possible mechanisms underlying this process.

METHODS AND RESULTS

Here, we reported the transcriptional profiling of 11 868 cells in a mouse model of transplant arteriosclerosis by single-cell RNA sequencing. Unbiased clustering analyses identified 21 cell clusters at different stages of diseases, and focused analysis revealed several previously unknown subpopulations enriched in the allografts. Interestingly, we found evidence of the local formation of tertiary lymphoid tissues and suggested a possible local modulation of alloimmune responses within the grafts. Intercellular communication analyses uncovered a potential role of several ligands and receptors, including Ccl21a and Cxcr3, in regulating lymphatic endothelial cell-induced early chemotaxis and infiltration of immune cells. In vivo mouse experiments confirmed the therapeutic potential of CCL21 and CXCR3 neutralizing antibodies in transplant arteriosclerosis. Combinational use of genetic lineage tracing and single-cell techniques further indicate the infiltration of host-derived c-Kit⁺ stem cells as heterogeneous populations in the allografts. Finally, we compared the immune response between mouse allograft and atherosclerosis models in single-cell RNA-seq analysis. By analyzing susceptibility genes of disease traits, we also identified several cell clusters expressing genes associated with disease risk.

CONCLUSIONS

Our study provides a transcriptional and cellular landscape of transplant arteriosclerosis, which could be fundamental to understanding the initiation and progression of this disease. CCL21/CXCR3 was also identified as important regulators of immune response and may serve as potential therapeutic targets in disease treatment.

Perivascular Adipose Tissue Regulates Vascular Function by Targeting Vascular Smooth Muscle Cells

Adipose tissues are present at multiple locations in the body. Most blood vessels are surrounded with adipose tissue which is referred to as perivascular adipose tissue (PVAT). Similarly to adipose tissues at other locations, PVAT harbors many types of cells which produce and secrete adipokines and other undetermined factors which locally modulate PVAT metabolism and vascular function. Uncoupling protein-1, which is considered as a brown fat marker, is also expressed in PVAT of rodents and humans. Thus, compared with other adipose tissues in the visceral area, PVAT displays brown-like characteristics. PVAT shows a distinct function in the cardiovascular system compared with adipose tissues in other depots which are not adjacent to the vascular tree. Growing and extensive studies have demonstrated that presence of normal PVAT is required to maintain the vasculature in a functional status. However, excessive accumulation of dysfunctional PVAT leads to vascular disorders, partially through alteration of its secretome which, in turn, affects vascular smooth muscle cells and endothelial cells. In this review, we highlight the cross talk between PVAT and vascular smooth muscle cells and its roles in vascular remodeling and blood pressure regulation.

Message in a Bottle: Upgrading Cardiac Repair into Rejuvenation

Ischaemic cardiac disease is associated with a loss of cardiomyocytes and an intrinsic lack of myocardial renewal. Recent work has shown that the heart retains limited cardiomyocyte proliferation, which remains inefficient when facing pathological conditions. While broadly active in the neonatal mammalian heart, this mechanism becomes quiescent soon after birth, suggesting loss of regenerative potential with maturation into adulthood. A key question is whether this temporary regenerative window can be enhanced via appropriate stimulation and further extended. Recently the search for novel therapeutic approaches for heart disease has centred on stem cell biology. The “paracrine effect” has been proposed as a promising strategy to boost endogenous reparative and regenerative mechanisms from within the cardiac tissue by exploiting the modulatory potential of soluble stem cell-secreted factors. As such, growing interest has been specifically addressed towards stem/progenitor cell-secreted extracellular vesicles (EVs), which can be easily isolated in vitro from cell-conditioned medium. This review will provide a comprehensive overview of the current paradigm on cardiac repair and regeneration, with a specific focus on the role and mechanism(s) of paracrine action of EVs from cardiac stromal progenitors as compared to exogenous stem cells in order to discuss the optimal choice for future therapy. In addition, the challenges to overcoming translational EV biology from bench to bedside for future cardiac regenerative medicine will be discussed.

Adenosine, Via A2B Receptors, Inhibits Human (P-SMC) Progenitor Smooth Muscle Cell Growth

c-Kit+ progenitor smooth muscle cells (P-SMCs) can develop into SMCs that contribute to injury-induced neointimal thickening. Here, we investigated whether adenosine reduces P-SMC migration and proliferation and whether this contributes to adenosine's inhibitory actions on neointima formation. In human P-SMCs, 2-chloroadenosine (stable adenosine analogue) and BAY60-6583 (A_2B agonist) inhibited P-SMC proliferation and migration. Likewise, increasing endogenous adenosine by blocking adenosine metabolism with erythro-9-(2-hydroxy-3-nonyl) adenine (inhibits adenosine deaminase) and 5-iodotubercidin (inhibits adenosine kinase) attenuated P-SMC proliferation and migration. Neither N⁶-cyclopentyladenosine (A₁ agonist), CGS21680 (A_2A agonist), nor N⁶-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (A₃ agonist) affected P-SMC proliferation or migration. 2-Chloroadenosine increased cyclic AMP, reduced Akt phosphorylation (activates cyclin D expression), and reduced levels of cyclin D1 (promotes cell-cycle progression). Moreover, 2-chloroadenosine inhibited expression of Skp2 (promotes proteolysis of p27^Kip1) and upregulated levels of p27^Kip1 (negative cell-cycle regulator). A_2B receptor knockdown prevented the effects of 2-chloroadenosine on cyclic AMP production and P-SMC proliferation and migration. Likewise, inhibition of adenylyl cyclase and protein kinase A rescued P-SMCs from the inhibitory effects of 2-chloroadenosine. The inhibitory effects of adenosine were similar in male and female P-SMCs. In vivo, peri-arterial (rat carotid artery) 2-chloroadenosine (20 μmol/L for 7 days) reduced neointimal hyperplasia by 64.5% (P<0.05; intima/media ratio: control, 1.4±0.02; treated, 0.53±0.012) and reduced neointimal c-Kit+ cells. Adenosine inhibits P-SMC migration and proliferation via the A_2B receptor/cyclic AMP/protein kinase A axis, which reduces cyclin D1 expression and activity via inhibiting Akt phosphorylation and Skp2 expression and upregulating p27^kip1 levels. Adenosine attenuates neointima formation in part by inhibiting infiltration and proliferation of c-Kit+ P-SMCs.

Plasticity of vascular resident mesenchymal stromal cells during vascular remodeling

Vascular remodeling is a complex and dynamic pathological process engaging many different cell types that reside within the vasculature. Mesenchymal stromal/stem cells (MSCs) refer to a heterogeneous cell population with the plasticity to differentiate toward multiple mesodermal lineages. Various types of MSC have been identified within the vascular wall that actively contribute to the vascular remodeling process such as atherosclerosis. With the advances of genetic mouse models, recent findings demonstrated the crucial roles of MSCs in the progression of vascular diseases. This review aims to provide an overview on the current knowledge of the characteristics and behavior of vascular resident MSCs under quiescence and remodeling conditions, which may lead to the development of novel therapeutic approaches for cardiovascular diseases.

Recipient c-Kit Lineage Cells Repopulate Smooth Muscle Cells of Transplant Arteriosclerosis in Mouse Models

Supplemental Digital Content is available in the text.

Rationale:

Transplantation-accelerated arteriosclerosis is one of the major challenges for long-term survival of patients with solid organ transplantation. Although stem/progenitor cells have been implicated to participate in this process, the cells of origin and underlying mechanisms have not been fully defined.

Objective:

The objective of our study was to investigate the role of c-Kit lineage cells in allograft-induced neointima formation and to explore the mechanisms underlying this process.

Methods and Results:

Using an inducible lineage tracing Kit-CreER;Rosa26-tdTomato mouse model, we observed that c-Kit is expressed in multiple cell types in the blood vessels, rather than a specific stem/progenitor cell marker. We performed allograft transplantation between different donor and recipient mice, as well as bone marrow transplantation experiments, demonstrating that recipient c-Kit⁺ cells repopulate neointimal smooth muscle cells (SMCs) and leukocytes, and contribute to neointima formation in an allograft transplantation model. c-Kit–derived SMCs originate from nonbone marrow tissues, whereas bone marrow-derived c-Kit⁺ cells mainly generate CD45⁺ leukocytes. However, the exact identity of c-Kit lineage cells contributing to neointimal SMCs remains unclear. ACK2 (anti-c-Kit antibody), which specifically binds and blocks c-Kit function, ameliorates allograft-induced arteriosclerosis. Stem cell factor and TGF (transforming growth factor)-β1 levels were significantly increased in blood and neointimal lesions after allograft transplantation, by which stem cell factor facilitated c-Kit⁺ cell migration through the stem cell factor/c-Kit axis and downstream activation of small GTPases, MEK (mitogen-activated protein kinase kinase)/ERK (extracellular signal–regulated kinase)/MLC (myosin light chain), and JNK (c-Jun N-terminal kinase)/c-Jun signaling pathways, whereas TGF-β1 induces c-Kit⁺ cell differentiation into SMCs via HK (hexokinase)-1–dependent metabolic reprogramming and a possible downstream O-GlcNAcylation of myocardin and serum response factor.

Conclusions:

Our findings provide evidence that recipient c-Kit lineage cells contribute to vascular remodeling in an allograft transplantation model, in which the stem cell factor/c-Kit axis is responsible for cell migration and HK-1–dependent metabolic reprogramming for SMC differentiation.