The therapeutic potential of targeting the endothelial-to-mesenchymal transition

Integrated transcriptomics of human blood vessels defines a spatially controlled niche for early mesenchymal progenitor cells

Human blood vessel walls show concentric layers, with the outermost tunica adventitia harboring mesenchymal progenitor cells. These progenitor cells maintain vessel homeostasis and provide a robust cell source for cell-based therapies. However, human adventitial stem cell niche has not been studied in detail. Here, using spatial and single-cell transcriptomics, we characterized the phenotype, potential, and microanatomic distribution of human perivascular progenitors. Initially, spatial transcriptomics identified heterogeneity between perivascular layers of arteries and veins and delineated the tunica adventitia into inner and outer layers. From this spatial atlas, we inferred a hierarchy of mesenchymal progenitors dictated by a more primitive cell with a high surface expression of CD201 (PROCR). When isolated from humans and mice, CD201Low expression typified a mesodermal committed subset with higher osteogenesis and less proliferation than CD201High cells, with a downstream effect on canonical Wnt signaling through DACT2. CD201Low cells also displayed high translational potential for bone tissue generation.

Cross-Species Insights into Trophoblast Invasion During Placentation Governed by Immune-Featured Trophoblast Cells

Proper development of the placenta, the transient support organ forms after embryo implantation, is essential for a successful pregnancy. However, the regulation of trophoblast invasion, which is most important during placentation, remains largely unknown. Here, rats, mice, and pigs are used as biomedical models, used scRNA-seq to comparatively elucidate the regulatory mechanism of placental trophoblast invasion, and verified it using a human preeclampsia disease model combined with scStereo-seq. A dual-featured type of immune-featured trophoblast (iTrophoblast) is unexpectedly discovered. Interestingly, iTrophoblast only exists in invasive placentas and regulates trophoblast invasion during placentation. In a normally developing placenta, iTrophoblast gradually transforms from an immature state into a functional mature state as it develops. Whereas in the developmentally abnormal preeclamptic placenta, disordered iTrophoblast transformation leads to the accumulation of immature iTrophoblasts, thereby disrupting trophoblast invasion and ultimately leading to the progression of preeclampsia.

Transcriptome Analysis of Choroidal Endothelium Links Androgen Receptor Role to Central Serous Chorioretinopathy

BACKGROUND

Central Serous Chorioretinopathy (CSCR) manifests as fluid accumulation between the neurosensory retina and the retinal pigment epithelium (RPE). Elevated levels of steroid hormones have been implicated in CSCR pathogenesis. This investigation aims to delineate the gene expression patterns of CSCR-associated risk and steroid receptors across human choroidal cell types and RPE cells to discern potential underlying mechanisms.

METHODS

This study utilized a comprehensive query of transcriptomic data derived from non-pathological human choroid and RPE cells.

FINDINGS

CSCR-associated genes such as PTPRB, CFH, and others are predominantly expressed in the choroidal endothelium as opposed to the RPE. The androgen receptor, encoded by the AR gene, demonstrates heightened expression in the macular endothelium compared to peripheral regions, unlike other steroid receptor genes. AR-expressing endothelial cells display an augmented responsiveness to Transforming growth factor beta (TGF-β), indicating a propensity towards endothelial to mesenchymal transition (endMT) transcriptional profiling.

INTERPRETATION

These results highlight the proclivity of CSCR to manifest primarily within the choroidal vasculature rather than the RPE, suggesting its categorization as a vascular eye disorder. This study accentuates the pivotal role of androgenic steroids, in addition to glucocorticoids. The observed linkage to TGF-β-mediated endMT provides a potential mechanistic insight into the disease's etiology.

N-Cadherin Targeted Melanin Nanoparticles Reverse the Endothelial-Mesenchymal Transition in Vascular Endothelial Cells to Potentially Slow the Progression of Atherosclerosis and Cancer

Endothelial-mesenchymal transition (EndoMT) of vascular endothelial cells has recently been considered as a key player in the early progression of a variety of vascular and nonvascular diseases, including atherosclerosis, cancer, and organ fibrosis. However, current strategies attempting to identify pharmacological inhibitors to block the regulatory pathways of EndoMT suffer from poor selectivity, unwanted side effects, and a heterogeneous response from endothelial cells with different origins. Furthermore, EndoMT inhibitors focus on preventing EndoMT, leaving the endothelial cells that have already undergone EndoMT unresolved. Here, we report the design of a simple but powerful nanoparticle system (i.e., N-cadherin targeted melanin nanoparticles) to convert cytokine-activated, mesenchymal-like endothelial cells back to their original endothelial phenotype. We term this process "Reversed EndoMT" (R-EndoMT). R-EndoMT allows the impaired endothelial barriers to recover their quiescence and intactness, with significantly reduced leukocyte and cancer cell adhesion and transmigration, which could potentially stop atheromatous plaque formation and cancer metastasis in the early stages. R-EndoMT is achieved on different endothelial cell types originating from arteries, veins, and capillaries, independent of activating cytokines. We reveal that N-cadherin targeted melanin nanoparticles reverse EndoMT by downregulating an N-cadherin dependent RhoA activation pathway. Overall, this approach offers a different prospect to treat multiple EndoMT-associated diseases by designing nanoparticles to reverse the phenotypical transition of endothelial cells.

Endothelial to mesenchymal transition: at the axis of cardiovascular health and disease

Endothelial cells (ECs) line the luminal surface of blood vessels and play a major role in vascular (patho)-physiology by acting as a barrier, sensing circulating factors and intrinsic/extrinsic signals. ECs have the capacity to undergo endothelial-to-mesenchymal transition (EndMT), a complex differentiation process with key roles both during embryonic development and in adulthood. EndMT can contribute to EC activation and dysfunctional alterations associated with maladaptive tissue responses in human disease. During EndMT, ECs progressively undergo changes leading to expression of mesenchymal markers while repressing EC lineage-specific traits. This phenotypic and functional switch is considered to largely exist in a continuum, being characterized by a gradation of transitioning stages. In this report, we discuss process plasticity and potential reversibility and the hypothesis that different EndMT-derived cell populations may play a different role in disease progression or resolution. In addition, we review advancements in the EndMT field, current technical challenges, as well as therapeutic options and opportunities in the context of cardiovascular biology.

Exploring the mechanism of atherosclerosis and the intervention of traditional Chinese medicine combined with mesenchymal stem cells based on inflammatory targets

Atherosclerosis (AS) is a chronic inflammatory vascular disease, which is the common pathological basis of cardiovascular and cerebrovascular diseases. The immune inflammatory response throughout the course of AS has been evidenced by studies, in which a large number of immune cells and inflammatory factors play a crucial role in the pathogenesis of AS. The inflammation related to AS is mainly mediated by inflammatory cytokines (IL-1β, IL-6, IL-18, TNF-α, hs-CRP, SAA), inflammatory enzymes (Lp-PLA2, sPLA2-IIA, MMPs), and inflammatory signaling pathways (P38 MAPK signaling pathway, NF-κB signaling pathway, TLR2/4 signaling pathway). It is involved in the pathophysiological process of AS, and the degree of inflammation measured by it can be used to evaluate the risk of progression of AS plaque instability. In recent years, traditional Chinese medicine (TCM) has shown the advantage of minimal side effects in immune regulation and has made some progress in the prevention and treatment of AS. Mesenchymal stem cells (MSCs), as self-renewal, highly differentiated, and pluripotent stem cells with anti-inflammatory properties and immune regulation, have been widely used for AS treatment. They also play an important inflammation-immune regulatory function in AS. Notably, in terms of regulating immune cells and inflammatory factors, compared with TCM and its compound, the combination therapy has obvious anti-inflammatory advantages over the use of MSCs alone. It is an important means to further improve the efficacy of AS and provides a new way for the prevention and treatment of AS.

PRELP secreted from mural cells protects the function of blood brain barrier through regulation of endothelial cell-cell integrity

Introduction: Proline/arginine-rich end leucine-rich repeat protein (PRELP), is a small secreted proteoglycan expressed by pericytes and vascular smooth muscle cells surrounding the brain vasculature of adult mouse. Methods: We utilised a Prelp knockout (Prelp -/-) mouse model to interrogate vasculature integrity in the brain alongside performing in vitro assays to characterise PRELP application to endothelial cells lines. Our findings were supplemented with RNA expression profiling to elucidate the mechanism of how PRELP maintains neurovasculature function. Results: Prelp -/- mice presented with neuroinflammation and reducedneurovasculature integrity, resulting in IgG and dextran leakage in the cerebellum and cortex. Histological analysis of Prelp -/- mice revealed reducedcell-cell integrity of the blood brain barrier, capillary attachment of pericytes andastrocyte end-feet. RNA-sequencing analysis found that cell-cell adhesion andinflammation are affected in Prelp -/- mice and gene ontology analysis as well as gene set enrichment analysis demonstrated that inflammation related processes and adhesion related processes such as epithelial-mesenchymal transition and apical junctions were significantly affected, suggesting PRELP is a regulator of cell-cell adhesion. Immunofluorescence analysis showed that adhesion junction protein expression levels of cadherin, claudin-5, and ZO-1, was suppressed in Prelp -/- mice neurovasculature. Additionally, in vitro studies revealed that PRELP application to endothelial cells enhances cell-cell integrity, induces mesenchymal-endothelial transition and inhibits TGF-β mediated damage to cell-cell adhesion. Discussion: Our study indicates that PRELP is a novel endogenous secreted regulator of neurovasculature integrity and that PRELP application may be a potential treatment for diseases associated with neurovascular damage.

GDF15 affects venous thrombosis by promoting EndMT through smad2/p-smad2 pathway

BACKGROUND

Endothelial-to-mesenchymal transition (EndMT) is a pathophysiological change in the vascular endothelium commonly seen in the cardiovascular system. Elevated serum Growth differiention factor 15 (GDF15) has been reported in VTE patients, but the relationship and mechanism between GDF15, EndMT and VTE are still unclear.

METHODS

We performed a retrospective clinical study, and human serum GDF15 expression levels were detected. The mouse DVT model was established through subtotal ligation of the mouse inferior vena cava, and then we detected intimal changes and thrombi in the stenotic inferior vena cava by haematoxylin-eosin (HE) staining, Masson staining, and Sirius Red staining. The expression levels of GDF15 and SM22 were detected by immunohistochemistry and RT‒qPCR. Serum samples of mice were collected, and the expression level of GDF15 in serum was detected. Human umbilical vein endothelial cells (HUVECs) were stimulated with a cytokine mixture (TGF-β1 + TNF-α + IL-1β). The role and mechanism of GDF15 in EndMT and VTE were detected in HUVECs and in a DVT mice model.

RESULTS

We found that serum GDF15 levels in both VTE patients and mouse DVT models were higher than those in the control group. EndMT was increased in the stenotic vascular tissue of mice. Further experiments showed that GDF15 could promote the EndMT of HUVECs and reduce their anticoagulation and antifibrinolytic ability through the smad2/p-smad2/snail pathway. Inhibition of mature GDF15 release can significantly reduce venous thrombotic fibre deposition in mice.

CONCLUSIONS

GDF15 positively promotes EndMT through activation of the Smad2/psmad2/snail pathway, and inhibition of GDF15 expression can alleviate the EndMT process, further improving the coagulation and fibrinolytic function of endothelial cells and thus reducing the local fibre deposition of venous thrombi.

The Exosome-Transmitted lncRNA LOC100132249 Induces Endothelial Dysfunction in Diabetic Retinopathy

Diabetic retinopathy (DR), one of the most common microangiopathic complications in diabetes, causes severe visual damage among working-age populations. Retinal vascular endothelial cells, the key cell type in DR pathogenesis, are responsible for abnormal retinal angiogenesis in advanced stages of DR. The roles of exosomes in DR have been largely unknown. In this study, we report the first evidence that exosomes derived from the vitreous humor of patients with proliferative DR (PDR-exo) promote proliferation, migration, and tube formation of human retinal vascular endothelial cells (HRVECs). We identified long noncoding RNA (lncRNA) LOC100132249 enrichment in PDR-exo via high-throughput sequencing. This lncRNA, also mainly derived from HRVECs, promoted angiogenesis both in vitro and in vivo. Mechanistically, LOC100132249 acted as a competing endogenous sponge of miRNA-199a-5p (miR-199a-5p), thus regulating the endothelial-mesenchymal transition promoter SNAI1 via activation of the Wnt/β-catenin pathway and ultimately resulting in endothelial dysfunction. In conclusion, our findings underscored the pathogenic role of endothelial-derived exosomes via the LOC100132249/miR-199a-5p/SNAI1 axis in DR angiogenesis and may shed light on new therapeutic strategies for future treatment of DR.

ARTICLE HIGHLIGHTS

This study provides the first evidence that exosomes derived from vitreous humor from patients with proliferative diabetic retinopathy participate in angiogenesis. The findings demonstrate an unreported long noncoding RNA (lncRNA), LOC100132249, by exosomal sequencing of vitreous humor. The newly found lncRNA LOC100132249, mainly derived from endothelial cells, promotes angiogenesis via an miRNA-199a-5p/SNAI1/Wnt/β-catenin axis in a pro-endothelial-mesenchymal transition manner.

Epithelial-Mesenchymal Plasticity and Endothelial-Mesenchymal Transition in Cutaneous Wound Healing

Epithelial and endothelial cells possess the inherent plasticity to undergo morphological, cellular, and molecular changes leading to their resemblance of mesenchymal cells. A prevailing notion has been that cutaneous wound reepithelialization involves partial epithelial-to-mesenchymal transition (EMT) of wound-edge epidermal cells to enable their transition from a stationary state to a migratory state. In this review, we reflect on past findings that led to this notion and discuss recent studies that suggest a refined view, focusing predominantly on in vivo results using mammalian excisional wound models. We highlight the concept of epithelial-mesenchymal plasticity (EMP), which emphasizes a reversible conversion of epithelial cells across multiple intermediate states within the epithelial-mesenchymal spectrum, and discuss the critical importance of restricting EMT for effective wound reepithelialization. We also outline the current state of knowledge on EMP in pathological wound healing, and on endothelial-to-mesenchymal transition (EndMT), a process similar to EMT, as a possible mechanism contributing to wound fibrosis and scar formation. Harnessing epithelial/endothelial-mesenchymal plasticity may unravel opportunities for developing new therapeutics to treat human wound healing pathologies.

Endothelial mechanobiology in atherosclerosis

Cardiovascular disease (CVD) is a serious health challenge, causing more deaths worldwide than cancer. The vascular endothelium, which forms the inner lining of blood vessels, plays a central role in maintaining vascular integrity and homeostasis and is in direct contact with the blood flow. Research over the past century has shown that mechanical perturbations of the vascular wall contribute to the formation and progression of atherosclerosis. While the straight part of the artery is exposed to sustained laminar flow and physiological high shear stress, flow near branch points or in curved vessels can exhibit 'disturbed' flow. Clinical studies as well as carefully controlled in vitro analyses have confirmed that these regions of disturbed flow, which can include low shear stress, recirculation, oscillation, or lateral flow, are preferential sites of atherosclerotic lesion formation. Because of their critical role in blood flow homeostasis, vascular endothelial cells (ECs) have mechanosensory mechanisms that allow them to react rapidly to changes in mechanical forces, and to execute context-specific adaptive responses to modulate EC functions. This review summarizes the current understanding of endothelial mechanobiology, which can guide the identification of new therapeutic targets to slow or reverse the progression of atherosclerosis.

Endothelial-to-mesenchymal transition: New insights into vascular calcification

With the continuous progress of atherosclerosis research, the significant pathological change of it--vascular calcification (VC), gains increasing attention. In recent years, numerous studies have demonstrated that it is an independent predictor of death risk of cardiovascular disease, and it has a strong correlation with poor clinical prognosis. As the world's population continues to age, the occurrence of VC is expected to reach its highest point in the near future. Therefore, it is essential to investigate ways to prevent or even reverse this process for clinical purposes. Endothelial-to-mesenchymal transition (EndMT) describes the progressive differentiation of endothelial cells into mesenchymal stem cells (MSCs) under various stimuli and acquisition of pluripotent cell characteristics. More and more studies show that EndMT plays a vital role in various cardiovascular diseases, including atherosclerosis, vascular calcification and heart valvular disease. EndMT is also involved in the formation and progression of VC. This review vividly describes the history, characteristics of EndMT and how it affects the endothelial cell process, then focuses on the relationship between vascular endothelium, EndMT, amino acid metabolism, and vascular calcification. Finally, it overviews the signal pathway of EndMT and drugs targeting EndMT, hoping to provide new ideas and a theoretical basis for studying potential therapeutic targets of VC.

KRAS mutation-induced EndMT of brain arteriovenous malformation is mediated through the TGF-β/BMP-SMAD4 pathway

OBJECTIVE

Somatic KRAS mutations have been identified in the majority of brain arteriovenous malformations (bAVMs), and subsequent in vivo experiments have confirmed that KRAS mutation in endothelial cells (ECs) causes AVMs in mouse and zebrafish models. Our previous study demonstrated that the KRASG12D mutant independently induced the endothelial-mesenchymal transition (EndMT), which was reversed by treatment with the lipid-lowering drug lovastatin. However, the underlying mechanisms of action were unclear.

METHODS

We used human umbilical vein ECs (HUVECs) overexpressing the KRASG12D mutant for Western blotting, quantitative real-time PCR, and immunofluorescence and wound healing assays to evaluate the EndMT and determine the activation of downstream pathways. Knockdown of SMAD4 by RNA interference was performed to explore the role of SMAD4 in regulating the EndMT. BAVM ECs expressing the KRASG12D mutant were obtained to verify the SMAD4 function. Finally, we performed a coimmunoprecipitation assay to probe the mechanism by which lovastatin affects SMAD4.

RESULTS

HUVECs infected with KRASG12D adenovirus underwent the EndMT. Transforming growth factor beta (TGF-β) and bone morphogenetic protein (BMP) signalling pathways were activated in the KRASG12D-mutant HUVECs and ECs in bAVM tissue. Knocking down SMAD4 expression in both KRASG12D-mutant HUVECs and ECs in bAVM tissues inhibited the EndMT. Lovastatin attenuated the EndMT by downregulating p-SMAD2/3, p-SMAD1/5 and acetylated SMAD4 expression in KRASG12D-mutant HUVECs.

CONCLUSIONS

Our findings suggest that the KRASG12D mutant induces the EndMT by activating the ERK-TGF-β/BMP-SMAD4 signalling pathway and that lovastatin inhibits the EndMT by suppressing TGF-β/BMP pathway activation and SMAD4 acetylation.

Targeting Epsins to Inhibit Fibroblast Growth Factor Signaling While Potentiating Transforming Growth Factor-β Signaling Constrains Endothelial-to-Mesenchymal Transition in Atherosclerosis

BACKGROUND

Epsin endocytic adaptor proteins are implicated in the progression of atherosclerosis; however, the underlying molecular mechanisms have not yet been fully defined. In this study, we determined how epsins enhance endothelial-to-mesenchymal transition (EndoMT) in atherosclerosis and assessed the efficacy of a therapeutic peptide in a preclinical model of this disease.

METHODS

Using single-cell RNA sequencing combined with molecular, cellular, and biochemical analyses, we investigated the role of epsins in stimulating EndoMT using knockout in Apoe-/- and lineage tracing/proprotein convertase subtilisin/kexin type 9 serine protease mutant viral-induced atherosclerotic mouse models. The therapeutic efficacy of a synthetic peptide targeting atherosclerotic plaques was then assessed in Apoe-/- mice.

RESULTS

Single-cell RNA sequencing and lineage tracing revealed that epsins 1 and 2 promote EndoMT and that the loss of endothelial epsins inhibits EndoMT marker expression and transforming growth factor-β signaling in vitro and in atherosclerotic mice, which is associated with smaller lesions in the Apoe-/- mouse model. Mechanistically, the loss of endothelial cell epsins results in increased fibroblast growth factor receptor-1 expression, which inhibits transforming growth factor-β signaling and EndoMT. Epsins directly bind ubiquitinated fibroblast growth factor receptor-1 through their ubiquitin-interacting motif, which results in endocytosis and degradation of this receptor complex. Consequently, administration of a synthetic ubiquitin-interacting motif-containing peptide atheroma ubiquitin-interacting motif peptide inhibitor significantly attenuates EndoMT and progression of atherosclerosis.

CONCLUSIONS

We conclude that epsins potentiate EndoMT during atherogenesis by increasing transforming growth factor-β signaling through fibroblast growth factor receptor-1 internalization and degradation. Inhibition of EndoMT by reducing epsin-fibroblast growth factor receptor-1 interaction with a therapeutic peptide may represent a novel treatment strategy for atherosclerosis.

The G-Protein-Coupled Formyl Peptide Receptor 2 Promotes Endothelial-Mesenchymal Transition in Diabetic Retinopathy

INTRODUCTION

In proliferative diabetic retinopathy (PDR), retinal neovascularization is the essential pathogenic process that is linked to endothelial-to-mesenchymal transition (EndoMT) induced by high glucose (HG). This pathophysiological process may be regulated by a G-protein-coupled chemoattractant receptor FPR2 (mouse Fpr2), involved in inflammatory cell migration and proliferation. In the current study, we investigated the role of Fpr2 in regulating EndoMT and the underlying mechanisms during diabetic retinopathy progression.

METHODS

FPR2 agonist or inhibitor was added to human microvascular endothelial cells (HMECs) exposed to normal glucose or HG. Morphologic, phenotypic, and functional changes of HMECs as well as the formation of microvasculature related to EndoMT were assessed. EndoMT biomarkers were detected in the retinal tissues of diabetic mice and fibrovascular epiretinal membranes (FVMs) from patients with PDR.

RESULTS

HG upregulated FPR2 in HMECs, which triggered morphological changes, and the cells acquired mesenchymal phenotype, with enhanced cell migration, viability, and angiogenic process shown by tube formation and aortic ring sprouting. Inhibition of FPR2 attenuated HG-induced EndoMT and endothelial cell migration to form vessel-like tube structures. RNA sequence and protein analysis further revealed that inhibition of FPR2 decreased the expression of genes associated with EndoMT. ERK1/2 and P38 signaling pathway was activated in HMECs, promoting neovascularization in HG-induced EndoMT of HMECs. In vivo, increased expression of mesenchymal markers was detected in the retina of diabetic mice and FVMs from patients with PDR. FPR2 deficiency was associated with diminished EndoMT-related phenotypic changes in the retina of diabetic mice.

CONCLUSIONS

FPR2 is actively involved in the progression of EndoMT that may contribute to the pathogenesis of PDR. Thus, FPR2 may be a potential therapeutic target for PDR.

Celastrol: The new dawn in the treatment of vascular remodeling diseases

Evidence is mounting that abnormal vascular remodeling leads to many cardiovascular diseases (CVDs). This suggests that vascular remodeling can be a crucial target for the prevention and treatment of CVDs. Recently, celastrol, an active ingredient of the broadly used Chinese herb Tripterygium wilfordii Hook F, has attracted extensive interest for its proven potential to improve vascular remodeling. Substantial evidence has shown that celastrol improves vascular remodeling by ameliorating inflammation, hyperproliferation, and migration of vascular smooth muscle cells, vascular calcification, endothelial dysfunction, extracellular matrix remodeling, and angiogenesis. Moreover, numerous reports have proven the positive effects of celastrol and its therapeutic promise in treating vascular remodeling diseases such as hypertension, atherosclerosis, and pulmonary artery hypertension. The present review summarizes and discusses the molecular mechanism of celastrol regulating vascular remodeling and provides preclinical proof for future clinical applications of celastrol.

Exosomal miR-3131 derived from endothelial cells with KRAS mutation promotes EndMT by targeting PICK1 in brain arteriovenous malformations

AIMS

To explore the underlying mechanism by which low-frequency KRAS mutations result in extensive EndMT occurrence.

METHODS

Exosomes derived from primarily cultured brain arteriovenous malformation (bAVMs) and human umbilical vein endothelial cells (HUVECs) transfected with KRAS^G12D , KRAS^WT , or KRAS^NC lentiviruses were isolated, and their effects on HUVECs were identified by western blotting and immunofluorescence staining. The expression levels of exosomal microRNAs (miRNAs) were evaluated by miRNA microarray, followed by functional experiments on miR-3131 and detection of its downstream target, and miR-3131 inhibitor in reversing the EndMT process induced by KRAS^G12D -transfected HUVECs and bAVM endothelial cells (ECs) were explored.

RESULTS

Exosomes derived from KRAS^G12D bAVM ECs and KRAS^G12D -transfected HUVECs promoted EndMT in HUVECs. MiR-3131 levels were highest in the exosomes of KRAS^G12D -transfected HUVECs, and HUVECs transfected with the miR-3131 mimic acquired mesenchymal phenotypes. RNA-seq and dual-luciferase reporter assays revealed that PICK1 is the direct downstream target of miR-3131. Exosomal miR-3131 was highly expressed in KRAS^G12D bAVM^exos compared with non-KRAS-mutant bAVM^exos or HUVEC^exos . Finally, a miR-3131 inhibitor reversed EndMT in HUVECs treated with exosomes or the supernatant of KRAS^G12D -transfected HUVECs and KRAS^G12D bAVM ECs.

CONCLUSION

Exosomal miR-3131 promotes EndMT in KRAS-mutant bAVMs, and miR-3131 might be a potential biomarker and therapeutic target in KRAS^G12D -mutant bAVMs.

EndMT-derived mesenchymal stem cells: a new therapeutic target to atherosclerosis treatment

Cardiovascular diseases, such as coronary artery disease and stroke, are the main threats to human health worldwide. Atherosclerosis, a chronic inflammatory disorder, plays a role as an initiator of all of the above-mentioned diseases. Cell therapy for diseases has attracted widespread attention. Mesenchymal stem cells (MSCs) are a type of stem cell that still exist in adults and have the characteristics of self-renewal ability, pluripotent differentiation potential, immunomodulation, tissue regeneration, anti-inflammation and low immunogenicity. In light of the properties of MSCs, some researchers have begun to target MSCs to create a possible way to alleviate atherosclerosis. Most of these studies are focused on MSC transplantation, injecting MSCs to modulate macrophages, the key inflammatory cell in atherosclerosis plaque. According to recent studies, researchers found that endothelial-to-mesenchymal transition (EndMT) has something to do with atherosclerosis development. A new cell type MSC might also appear during the EndMT process. In this article, we summarize the characteristics of MSCs, the latest progress of MSC research and its application prospects, and in view of the process of EndMT occurring in atherosclerosis, we propose some new ideas for the treatment of atherosclerosis by targeting MSCs.

Fibrotic Scar in CNS Injuries: From the Cellular Origins of Fibroblasts to the Molecular Processes of Fibrotic Scar Formation

Central nervous system (CNS) trauma activates a persistent repair response that leads to fibrotic scar formation within the lesion. This scarring is similar to other organ fibrosis in many ways; however, the unique features of the CNS differentiate it from other organs. In this review, we discuss fibrotic scar formation in CNS trauma, including the cellular origins of fibroblasts, the mechanism of fibrotic scar formation following an injury, as well as the implication of the fibrotic scar in CNS tissue remodeling and regeneration. While discussing the shared features of CNS fibrotic scar and fibrosis outside the CNS, we highlight their differences and discuss therapeutic targets that may enhance regeneration in the CNS.

Endothelial cell heterogeneity and microglia regulons revealed by a pig cell landscape at single-cell level

Pigs are valuable large animal models for biomedical and genetic research, but insights into the tissue- and cell-type-specific transcriptome and heterogeneity remain limited. By leveraging single-cell RNA sequencing, we generate a multiple-organ single-cell transcriptomic map containing over 200,000 pig cells from 20 tissues/organs. We comprehensively characterize the heterogeneity of cells in tissues and identify 234 cell clusters, representing 58 major cell types. In-depth integrative analysis of endothelial cells reveals a high degree of heterogeneity. We identify several functionally distinct endothelial cell phenotypes, including an endothelial to mesenchymal transition subtype in adipose tissues. Intercellular communication analysis predicts tissue- and cell type-specific crosstalk between endothelial cells and other cell types through the VEGF, PDGF, TGF-β, and BMP pathways. Regulon analysis of single-cell transcriptome of microglia in pig and 12 other species further identifies MEF2C as an evolutionally conserved regulon in the microglia. Our work describes the landscape of single-cell transcriptomes within diverse pig organs and identifies the heterogeneity of endothelial cells and evolutionally conserved regulon in microglia.

Palmitic acid promotes endothelial-to-mesenchymal transition via activation of the cytosolic DNA-sensing cGAS-STING pathway

Elevated levels of plasma free fatty acids (FFAs) lead to endothelial dysfunction, a process that is involved in the pathogenesis of atherosclerosis. Endothelial-to-mesenchymal transformation (EndMT) has been reported to accelerate endothelial dysfunction during the process of atherosclerosis. However, the underlying mechanisms of EndMT remain poorly understood. The present study aimed to investigate the role of the cytosolic DNA-sensing cyclic GMP-AMP synthase-stimulator interferon gene (cGAS-STING) pathway in palmitic acid (PA)-induced EndMT. Human aortic endothelial cells (HAECs) were exposed to different concentrations of PA, and subsequently its effects on EndMT and the cGAS-STING pathway were assessed. To investigate the role of cGAS-STING pathway on PA-induced EndMT, RNA interference was used to knockdown the expression of cGAS in HAECs prior to their exposure to PA. First, it was observed that PA reduced cell viability and intracellular nitric oxide production, and increased migratory capacity of the HAECs as well as the cellular oxidative stress response, leading to EndMT. Moreover, it was observed that the cGAS-STING pathway was activated in PA-exposed primary HAECs. Activating cGAS-STING pathway via mtDNA directing lead to EndMT in HAECs. Interestingly, cGAS knockdown by RNA interference attenuated PA-induced inflammation, oxidative stress and EndMT in HAECs. Taken together, the results of the present study suggested that the cytosolic DNA-sensing cGAS-STING pathway may have important roles in PA-induced EndMT in endothelial cells.

Hemin-Induced Endothelial Dysfunction and Endothelial to Mesenchymal Transition in the Pathogenesis of Pulmonary Hypertension Due to Chronic Hemolysis

Pulmonary hypertension in sickle cell disease is an independent predictor of mortality, yet the pathogenesis of pulmonary vascular disease in chronic hemolytic disorders remains incompletely understood and treatment options are limited primarily to supportive care. The release of extracellular hemoglobin has been implicated in the development of pulmonary hypertension, and in this study we explored the direct effects of hemin, the oxidized moiety of heme, on the pulmonary artery endothelium. We found that low dose hemin exposure leads to significantly increased endothelial cell proliferation, migration, and cytokine release as markers of endothelial dysfunction. Protein expression changes in our pulmonary artery endothelial cells showed upregulation of mesenchymal markers after hemin treatment in conjunction with a decrease in endothelial markers. Endothelial to mesenchymal transition (EndoMT) resulting from hemin exposure was further confirmed by showing upregulation of the transcription factors SNAI1 and SLUG, known to regulate EndoMT. Lastly, given the endothelial dysfunction and phenotypic transition observed, the endothelial cytoskeleton was considered a potential novel target. Inhibiting myosin light chain kinase, to prevent phosphorylation of myosin light chain and cytoskeletal contraction, attenuated hemin-induced endothelial hyper-proliferation, migration, and cytokine release. The findings in this study implicate hemin as a key inducer of endothelial dysfunction through EndoMT, which may play an important role in pulmonary vascular remodeling during the development of pulmonary hypertension in chronic hemolytic states.

Endothelial Dysfunction and Diabetic Cardiomyopathy

The cardiovascular complications contribute to a majority of diabetes associated morbidity and mortality, accounting for 44% of death in those patients with type 1 diabetes mellitus (DM) and 52% of deaths in type 2 DM. Diabetes elicits cardiovascular dysfunction through 2 major mechanisms: ischemic and non-ischemic. Non-ischemic injury is usually under-recognized although common in DM patients, and also a pathogenic factor of heart failure in those diabetic individuals complicated with ischemic heart disease. Diabetic cardiomyopathy (DCM) is defined as a heart disease in which the myocardium is structurally and functionally abnormal in the absence of coronary artery disease, hypertensive, valvular, or congenital heart disorders in diabetic patients, theoretically caused by non-ischemic injury solely. Current therapeutic strategies targeting DCM mainly address the increased blood glucose levels, however, the effects on heart function are disappointed. Accumulating data indicate endothelial dysfunction plays a critical role in the initiation and development of DCM. Hyperglycemia, hyperinsulinemia, and insulin resistance cause the damages of endothelial function, including barrier dysfunction, impaired nitric oxide (NO) activity, excessive reactive oxygen species (ROS) production, oxidative stress, and inflammatory dysregulation. In turn, endothelial dysfunction promotes impaired myocardial metabolism, intracellular Ca²⁺ mishandling, endoplasmic reticulum (ER) stress, mitochondrial defect, accumulation of advanced glycation end products, and extracellular matrix (ECM) deposit, leads to cardiac stiffness, fibrosis, and remodeling, eventually results in cardiac diastolic dysfunction, systolic dysfunction, and heart failure. While endothelial dysfunction is closely related to cardiac dysfunction and heart failure seen in DCM, clinical strategies for restoring endothelial function are still missing. This review summarizes the timely findings related to the effects of endothelial dysfunction on the disorder of myocardium as well as cardiac function, provides mechanical insights in pathogenesis and pathophysiology of DCM developing, and highlights potential therapeutic targets.

Cellular and Molecular Crosstalk of Graft Endothelial Cells During AMR: Effector Functions and Mechanisms

Graft endothelial cell (EC) injury is central to the pathogenesis of antibody-mediated rejection (AMR). The ability of donor-specific antibodies (DSA) to bind C1q and activate the classical complement pathway is an efficient predictor of graft rejection highlighting complement-dependent cytotoxicity as a key process operating during AMR. In the past 5 y, clinical studies further established the cellular and molecular signatures of AMR revealing the key contribution of other, IgG-dependent and -independent, effector mechanisms mediated by infiltrating NK cells and macrophages. Beyond binding to alloantigens, DSA IgG can activate NK cells and mediate antibody-dependent cell cytotoxicity through interacting with Fcγ receptors (FcγRs) such as FcγRIIIa (CD16a). FcRn, a nonconventional FcγR that allows IgG recycling, is highly expressed on ECs and may contribute to the long-term persistence of DSA in blood. Activation of NK cells and macrophages results in the production of proinflammatory cytokines such as TNF and IFNγ that induce transient and reversible changes in the EC phenotype and functions promoting coagulation, inflammation, vascular permeability, leukocyte trafficking. MHC class I mismatch between transplant donor and recipient can create a situation of "missing self" allowing NK cells to kill graft ECs. Depending on the microenvironment, cellular proximity with ECs may participate in macrophage polarization toward an M1 proinflammatory or an M2 phenotype favoring inflammation or vascular repair. Monocytes/macrophages participate in the loss of endothelial specificity in the process of endothelial-to-mesenchymal transition involved in renal and cardiac fibrosis and AMR and may differentiate into ECs enabling vessel and graft (re)-endothelialization.

Cytoskeleton Reorganization in EndMT-The Role in Cancer and Fibrotic Diseases

Chronic inflammation promotes endothelial plasticity, leading to the development of several diseases, including fibrosis and cancer in numerous organs. The basis of those processes is a phenomenon called the endothelial–mesenchymal transition (EndMT), which results in the delamination of tightly connected endothelial cells that acquire a mesenchymal phenotype. EndMT-derived cells, known as the myofibroblasts or cancer-associated fibroblasts (CAFs), are characterized by the loss of cell–cell junctions, loss of endothelial markers, and gain in mesenchymal ones. As a result, the endothelium ceases its primary ability to maintain patent and functional capillaries and induce new blood vessels. At the same time, it acquires the migration and invasion potential typical of mesenchymal cells. The observed modulation of cell shape, increasedcell movement, and invasion abilities are connected with cytoskeleton reorganization. This paper focuses on the review of current knowledge about the molecular pathways involved in the modulation of each cytoskeleton element (microfilaments, microtubule, and intermediate filaments) during EndMT and their role as the potential targets for cancer and fibrosis treatment.

Effects of miRNAs, lncRNAs and circRNAs on osteoporosis as regulatory factors of bone homeostasis (Review)

Osteoporosis is a common metabolic bone disorder typically characterized by decreased bone mass and an increased risk of fracture. At present, the detailed molecular mechanism underlying the development of osteoporosis remains to be elucidated. Accumulating evidence shows that non-coding (nc)RNAs, such as microRNAs (miRNAs), long ncRNAs (lncRNAs) and circular RNAs (circRNAs), play significant roles in osteoporosis through the post-transcriptional regulation of gene expression as regulatory factors. Previous studies have demonstrated that ncRNAs participate in maintaining bone homeostasis by regulating physiological and developmental processes in osteoblasts, osteoclasts and bone marrow stromal cells. In the present review, the latest research investigating the involvement of miRNAs, lncRNAs and circRNAs in regulating the differentiation, proliferation, apoptosis and autophagy of cells that maintain the bone microenvironment in osteoporosis is summarized. Deeper insight into the aspects of osteoporosis pathogenesis involving the deregulation of ncRNAs could facilitate the development of therapeutic approaches for osteoporosis.

Endothelial-Mesenchymal Transition in Cardiovascular Disease

Endothelial-to-mesenchymal transition is a dynamic process in which endothelial cells suppress constituent endothelial properties and take on mesenchymal cell behaviors. To begin the process, endothelial cells loosen their cell-cell junctions, degrade the basement membrane, and migrate out into the perivascular surroundings. These initial endothelial behaviors reflect a transient modulation of cellular phenotype, that is, a phenotypic modulation, that is sometimes referred to as partial endothelial-to-mesenchymal transition. Loosening of endothelial junctions and migration are also seen in inflammatory and angiogenic settings such that endothelial cells initiating endothelial-to-mesenchymal transition have overlapping behaviors and gene expression with endothelial cells responding to inflammatory signals or sprouting to form new blood vessels. Reduced endothelial junctions increase permeability, which facilitates leukocyte trafficking, whereas endothelial migration precedes angiogenic sprouting and neovascularization; both endothelial barriers and quiescence are restored as inflammatory and angiogenic stimuli subside. Complete endothelial-to-mesenchymal transition proceeds beyond phenotypic modulation such that mesenchymal characteristics become prominent and endothelial functions diminish. In proadaptive, regenerative settings the new mesenchymal cells produce extracellular matrix and contribute to tissue integrity whereas in maladaptive, pathologic settings the new mesenchymal cells become fibrotic, overproducing matrix to cause tissue stiffness, which eventually impacts function. Here we will review what is known about how TGF (transforming growth factor) β influences this continuum from junctional loosening to cellular migration and its relevance to cardiovascular diseases.

Heteronemin Suppresses Lymphangiogenesis through ARF-1 and MMP-9/VE-Cadherin/Vimentin

Lymphatic metastasis is a biological procedure associated with the pathogenesis of several diseases, especially in tumor metastasis. Therefore, regulation of lymphangiogenesis has become a promising strategy for cancer therapy. In this study, we aimed to investigate the anti-lymphangiogenic effect of heteronemin (SP-1) isolated from the sponge Hyrtios sp. in vitro and in vivo. Human lymphatic endothelial cells (LECs) were utilized to evaluate the anti-lymphangiogenic effect of SP-1 in vitro. Molecular docking, western blotting, flow-cytometry, MTT and ELISA were performed to investigate the mechanism of action. For in vivo approaches, the transgenic (fli1:EGFP; gata1:DsRed) zebrafish and mouse ear sponges were used. Molecular docking studies showed that SP-1 is a potent vascular endothelial growth factor receptor 3 (VEGFR-3)-binding compound. Treatment of LEC with SP-1 reduced the phosphorylation of VEGFR-3. SP-1 suppressed the development of the thoracic duct in zebrafish and mouse lymphangiogenesis ear sponges in vivo. Mechanistically, SP-1 induced the cell cycle arrest of LECs in the G0/G1 phase and reduced the downstream of VEGFR-3, such as phosphorylated MEK/ERK and NF-κB. In addition, SP-1 inhibited LECs' tubulogenesis and migration through the ARF-1 and MMP-9/VE-cadherin/vimentin. Overall, anti-lymphangiogenic properties of SP-1 occur by downregulating the VEGFR-3 cascade, ARF-1 and MMP-9/VE-cadherin/vimentin. Collectively, these results proposed that SP-1 might be a potential candidate for the treatment of lymphangiogenesis-associated diseases.

New Insights into Profibrotic Myofibroblast Formation in Systemic Sclerosis: When the Vascular Wall Becomes the Enemy

In systemic sclerosis (SSc), abnormalities in microvessel morphology occur early and evolve into a distinctive vasculopathy that relentlessly advances in parallel with the development of tissue fibrosis orchestrated by myofibroblasts in nearly all affected organs. Our knowledge of the cellular and molecular mechanisms underlying such a unique relationship between SSc-related vasculopathy and fibrosis has profoundly changed over the last few years. Indeed, increasing evidence has suggested that endothelial-to-mesenchymal transition (EndoMT), a process in which profibrotic myofibroblasts originate from endothelial cells, may take center stage in SSc pathogenesis. While in arterioles and small arteries EndoMT may lead to the accumulation of myofibroblasts within the vessel wall and development of fibroproliferative vascular lesions, in capillary vessels it may instead result in vascular destruction and formation of myofibroblasts that migrate into the perivascular space with consequent tissue fibrosis and microvessel rarefaction, which are hallmarks of SSc. Besides endothelial cells, other vascular wall-resident cells, such as pericytes and vascular smooth muscle cells, may acquire a myofibroblast-like synthetic phenotype contributing to both SSc-related vascular dysfunction and fibrosis. A deeper understanding of the mechanisms underlying the differentiation of myofibroblasts inside the vessel wall provides the rationale for novel targeted therapeutic strategies for the treatment of SSc.

Endothelial heterogeneity and plasticity

Vascular endothelial cells are highly plastic and show great phenotypic heterogeneity. In recent years, emerging technologies have identified a range of novel endothelial phenotypes and functions. In this Special Issue of Angiogenesis, we present a series of papers from leading experts in the field, highlighting the heterogeneity and plasticity of endothelial cells in health and disease.

EndMT Regulation by Small RNAs in Diabetes-Associated Fibrotic Conditions: Potential Link With Oxidative Stress

Diabetes-associated complications, such as retinopathy, nephropathy, cardiomyopathy, and atherosclerosis, the main consequences of long-term hyperglycemia, often lead to organ dysfunction, disability, and increased mortality. A common denominator of these complications is the myofibroblast-driven excessive deposition of extracellular matrix proteins. Although fibroblast appears to be the primary source of myofibroblasts, other cells, including endothelial cells, can generate myofibroblasts through a process known as endothelial to mesenchymal transition (EndMT). During EndMT, endothelial cells lose their typical phenotype to acquire mesenchymal features, characterized by the development of invasive and migratory abilities as well as the expression of typical mesenchymal products such as α-smooth muscle actin and type I collagen. EndMT is involved in many chronic and fibrotic diseases and appears to be regulated by complex molecular mechanisms and different signaling pathways. Recent evidence suggests that small RNAs, in particular microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are crucial mediators of EndMT. Furthermore, EndMT and miRNAs are both affected by oxidative stress, another key player in the pathophysiology of diabetic fibrotic complications. In this review, we provide an overview of the primary redox signals underpinning the diabetic-associated fibrotic process. Then, we discuss the current knowledge on the role of small RNAs in the regulation of EndMT in diabetic retinopathy, nephropathy, cardiomyopathy, and atherosclerosis and highlight potential links between oxidative stress and the dyad small RNAs-EndMT in driving these pathological states.

Contributions of the Endothelium to Vascular Calcification

Vascular calcification (VC) increases morbidity and mortality and constitutes a significant obstacle during percutaneous interventions and surgeries. On a cellular and molecular level, VC is a highly regulated process that involves abnormal cell transitions and osteogenic differentiation, re-purposing of signaling pathways normally used in bone, and even formation of osteoclast-like cells. Endothelial cells have been shown to contribute to VC through a variety of means. This includes direct contributions of osteoprogenitor cells generated through endothelial-mesenchymal transitions in activated endothelium, with subsequent migration into the vessel wall. The endothelium also secretes pro-osteogenic growth factors, such as bone morphogenetic proteins, inflammatory mediators and cytokines in conditions like hyperlipidemia, diabetes, and renal failure. High phosphate levels caused by renal disease have deleterious effects on the endothelium, and induction of tissue non-specific alkaline phosphatase adds to the calcific process. Furthermore, endothelial activation promotes proteolytic destruction of the internal elastic lamina that serves, among other things, as a stabilizer of the endothelium. Appropriate bone mineralization is highly dependent on active angiogenesis, but it is unclear whether the same relationship exists in VC. Through its location facing the vascular lumen, the endothelium is the first to encounter circulating factor and bone marrow-derived cells that might contribute to osteoclast-like versus osteoblast-like cells in the vascular wall. In the same way, the endothelium may be the easiest target to reach with treatments aimed at limiting calcification. This review provides a brief summary of the contributions of the endothelium to VC as we currently know them.

Endothelial-to-mesenchymal transition in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by significant vascular alterations and multi-organ fibrosis. Microvascular alterations are the first event of SSc and injured endothelial cells (ECs) may transdifferentiate towards myofibroblasts, the cells responsible for fibrosis and collagen deposition. This process is identified as endothelial-to-mesenchymal transition (EndMT), and understanding of its development is pivotal to identify early pathogenetic events and new therapeutic targets for SSc. In this review, we have highlighted the molecular mechanisms of EndMT and summarize the evidence of the role played by EndMT during the development of progressive fibrosis in SSc, also exploring the possible therapeutic role of its inhibition.

Transplantation of Apoptosis-Resistant Endothelial Progenitor Cells Improves Renal Function in Diabetic Kidney Disease

Background

Diabetic kidney disease is associated with glomerulosclerosis and poor renal perfusion. Increased capillary formation and improved perfusion may help to halt or reverse the injury. Transplanting apoptosis‐resistant p53‐silenced endothelial progenitor cells (p53sh‐EPCs) may help improve vascularization and renal perfusion and could be more beneficial than another stem cell such as the mouse mesenchymal stromal cell (mMSC).

Methods and Results

Hyperglycemia and proteinuria were confirmed at 8 to 10 weeks in streptozotocin‐induced type1 diabetic C57Bl/6 mice, followed by transplantation of 0.3 million p53sh‐EPCs, Null‐EPCs (control), or mMSC under each kidney capsule. Urine was collected weekly for creatinine and protein levels. Blood pressure was measured by direct arterial cannulation and renal perfusion was measured by renal ultrasound. The kidneys were harvested for histology and mRNA expression. Reduction of protein/creatinine (AUC) was observed in p53sh‐EPC‐transplanted mice more than null‐EPC (1.8‐fold, P=0.03) or null‐mMSC (1.6‐fold, P=0.04, n=4) transplanted mice. Markers for angiogenesis, such as endothelial nitric oxide synthase (1.7‐fold, P=0.06), were upregulated post p53sh‐EPC transplantation compared with null EPC. However, vascular endothelial growth factor‐A expression was reduced (7‐fold, P=0.0004) in mMSC‐transplanted mice, compared with p53sh‐EPC‐transplanted mice. Isolectin‐B4 staining of kidney section showed improvement of glomerular sclerosis when p53sh‐EPC was transplanted, compared with null‐EPC or mMSC. In addition, mean and peak renal blood velocity (1.3‐fold, P=0.01, 1.4‐fold, P=0.001, respectively) were increased in p53sh‐EPC‐transplanted mice, relative to null‐EPC transplanted mice.

Conclusions

Apoptosis‐resistant p53sh EPC transplantation could be beneficial in the treatment of diabetic kidney disease by decreasing proteinuria, and improving renal perfusion and glomerular architecture.

A novel role of kallikrein-related peptidase 8 in the pathogenesis of diabetic cardiac fibrosis

Rationale: Among all the diabetic complications, diabetic cardiomyopathy, which is characterized by myocyte loss and myocardial fibrosis, is the leading cause of mortality and morbidity in diabetic patients. Tissue kallikrein-related peptidases (KLKs) are secreted serine proteases, that have distinct and overlapping roles in the pathogenesis of cardiovascular diseases. However, whether KLKs are involved in the development of diabetic cardiomyopathy remains unknown.The present study aimed to determine the role of a specific KLK in the initiation of endothelial-to-mesenchymal transition (EndMT) during the pathogenesis of diabetic cardiomyopathy.

Methods and Results-By screening gene expression profiles of KLKs, it was found that KLK8 was highly induced in the myocardium of mice with streptozotocin-induced diabetes. KLK8 deficiency attenuated diabetic cardiac fibrosis, and rescued the impaired cardiac function in diabetic mice. Small interfering RNA (siRNA)-mediated KLK8 knockdown significantly attenuated high glucose-induced endothelial damage and EndMT in human coronary artery endothelial cells (HCAECs). Diabetes-induced endothelial injury and cardiac EndMT were significantly alleviated in KLK8-deficient mice. In addition, transgenic overexpression of KLK8 led to interstitial and perivascular cardiac fibrosis, endothelial injury and EndMT in the heart. Adenovirus-mediated overexpression of KLK8 (Ad-KLK8) resulted in increases in endothelial cell damage, permeability and transforming growth factor (TGF)-β1 release in HCAECs. KLK8 overexpression also induced EndMT in HCAECs, which was alleviated by a TGF-β1-neutralizing antibody. A specificity protein-1 (Sp-1) consensus site was identified in the human KLK8 promoter and was found to mediate the high glucose-induced KLK8 expression. Mechanistically, it was identified that the vascular endothelial (VE)-cadherin/plakoglobin complex may associate with KLK8 in HCAECs. KLK8 cleaved the VE-cadherin extracellular domain, thus promoting plakoglobin nuclear translocation. Plakoglobin was required for KLK8-induced EndMT by cooperating with p53. KLK8 overexpression led to plakoglobin-dependent association of p53 with hypoxia inducible factor (HIF)-1α, which further enhanced the transactivation effect of HIF-1α on the TGF-β1 promoter. KLK8 also induced the binding of p53 with Smad3, subsequently promoting pro-EndMT reprogramming via the TGF-β1/Smad signaling pathway in HCAECs. The in vitro and in vivo findings further demonstrated that high glucose may promote plakoglobin-dependent cooperation of p53 with HIF-1α and Smad3, subsequently increasing the expression of TGF-β1 and the pro-EndMT target genes of the TGF-β1/Smad signaling pathway in a KLK8-dependent manner.

Conclusions: The present findings uncovered a novel pro-EndMT mechanism during the pathogenesis of diabetic cardiac fibrosis via the upregulation of KLK8, and may contribute to the development of future KLK8-based therapeutic strategies for diabetic cardiomyopathy.

Resveratrol-Elicited PKC Inhibition Counteracts NOX-Mediated Endothelial to Mesenchymal Transition in Human Retinal Endothelial Cells Exposed to High Glucose

Diabetes-associated long-term hyperglycaemia leads to oxidative stress-mediated fibrosis in different tissues and organs. Endothelial-to-mesenchymal-transition (EndMT) appears to play a role in diabetes-associated fibrotic conditions. Here, we investigate whether EndMT is implicated in the diabetic retinopathy fibrotic process and evaluate the possibility that resveratrol could counteract EndMT by inhibiting high glucose (HG)-induced increases in ROS. Primary Human Retinal Endothelial Cells (HRECs) were either pre-treated for 24 h with 1 µM resveratrol or left untreated, then glucose (30 mM) was applied at 3-day intervals for 10 days. qRT-PCR and ELISA were used to detect mRNA or protein expression of endothelial markers (CD31, CDH5, vWF) or mesenchymal markers (VIM, αSMA and collagen I), respectively. Intracellular ROS levels were measured with carboxy-DCFDA, while NOX-associated ROS levels were evaluated using the NADPH-specific redox biosensor p47-roGFP. Treatment of HRECs with HG increased intracellular ROS levels and promoted phenotype shifting towards EndMT, evidenced by decreased expression of endothelial markers concomitant with increased expression of mesenchymal ones. HG-induced EndMT appears to be mediated by NADPH-associated ROS generation as pre-treatment of HRECs with resveratrol or the NADPH inhibitor, diphenyleneiodonium chloride (DPI), attenuated ROS production and EndMT transition, suggesting that the effect of resveratrol on HG-induced ROS occurs via down-regulation of NADPH oxidase. It is worth noting that resveratrol or Chelerythrine, a Protein kinase C (PKC) inhibitor, reduce ROS and EndMT in HG-exposed cells, suggesting that NADPH activation occurs via a PKC-dependent mechanism. Taken together, our results provide the basis for a resveratrol-based potential protective therapy to prevent diabetic-associated complications.

Oxidized LDL Causes Endothelial Apoptosis by Inhibiting Mitochondrial Fusion and Mitochondria Autophagy

Oxidized low-density lipoprotein (ox-LDL)-induced endothelial dysfunction is an initial step toward atherosclerosis development. Mitochondria damage correlates with ox-LDL-induced endothelial injury through an undefined mechanism. We explored the role of optic atrophy 1 (Opa1)-related mitochondrial fusion and mitophagy in ox-LDL-treated endothelial cells, focusing on mitochondrial damage and cell apoptosis. Oxidized low-density lipoprotein treatment reduced endothelial cell viability by increasing apoptosis. Endothelial cell proliferation and migration were also impaired by ox-LDL. At the molecular level, mitochondrial dysfunction was induced by ox-LDL, as demonstrated by decreased mitochondrial membrane potential, increased mitochondrial reactive oxygen species production, augmented mitochondrial permeability transition pore openings, and elevated caspase-3/9 activity. Mitophagy and mitochondrial fusion were also impaired by ox-LDL. Opa1 overexpression reversed this effect by increasing endothelial cell viability and decreasing apoptosis. Interestingly, inhibition of mitophagy or mitochondrial fusion through transfection of siRNAs against Atg5 or Mfn2, respectively, abolished the protective effects of Opa1. Our results illustrate the role of Opa1-related mitochondrial fusion and mitophagy in sustaining endothelial cell viability and mitochondrial homeostasis under ox-LDL stress.

Matrine attenuates cardiomyocyte ischemia-reperfusion injury through activating AMPK/Sirt3 signaling pathway

Matrine has been found to affect cell viability and function. In the present study, we explored the cardioprotective role of matrine in cardiomyocyte damage under hypoxia/reoxygenation. In vitro, cardiomyocyte hypoxia/reoxygenation was used to mimic ischemia/reperfusion injury in the presence of matrine. After exposure to hypoxia/reoxygenation, cardiomyocyte viability was reduced and cell apoptosis was increased; this alteration was inhibited by matrine. At the molecular levels, Sirt3 and AMPK were significantly downregulated by hypoxia/reoxygenation injury whereas matrine administration was able to upregulate Sirt3 and AMPK expression and activity in the presence of hypoxia/reoxygenation. Interestingly, inhibition of Sirt3/AMPK pathway abolished the cardioprotective action of matrine on cardiomyocyte in the presence of hypoxia/reoxygenation injury, resulting into cardiomyocyte viability reduction and cell death augmentation. Altogether, our results demonstrated a novel role played by matrine in regulating cardiomyocyte viability and death in the presence of hypoxia/reoxygenation, with a potential application in the clinical practice for the treatment of patients with myocardial infarction.

SERCA overexpression reduces reperfusion-mediated cardiac microvascular damage through inhibition of the calcium/MCU/mPTP/necroptosis signaling pathways

Endothelial cells lining the microvasculature are particularly vulnerable to the deleterious effects of cardiac ischemia/reperfusion (I/R) injury, a susceptibility that is partially mediated by dysregulated intracellular calcium signals. Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) functions to recycle calcium from the cytosol back to the endoplasmic reticulum. The purpose of this study is to explore the roles and mechanisms of SERCA in protecting microcirculation against cardiac I/R injury. Our data showed that overexpression of SERCA significantly reduced I/R-induced luminal stenosis and vascular wall edema, possibly through normalization of the ratio between eNOS and ET-1. I/R-induced erythrocyte morphological changes in micro-vessels could be reversed by SERCA overexpression through transcriptional inhibition of the expression of adhesive factors. In addition, SERCA-sustained endothelial barrier integrity reduced the likelihood of inflammatory cells infiltrating the myocardium. Furthermore, we found that SERCA overexpression attenuated intracellular calcium overload, suppressed mitochondrial calcium uniporter (MCU) expression, and prevented the abnormal opening of mitochondrial permeability transition pores (mPTP) in I/R-treated cardiac microvascular endothelial cells (CMECs). Interestingly, the administration of calcium activator or MCU agonist induced endothelial necroptosis in vitro and thus abolished the microvascular protection afforded by SERCA in reperfused heart tissue in vivo. In conclusion, by using gene delivery strategies to specifically target SERCA in vitro and in vivo, we identify a potential novel pathway by which SERCA overexpression protects microcirculation against cardiac I/R injury in a manner dependent on the calcium/MCU/necroptosis pathway. These findings should be taken into consideration in the development of pharmacological strategies for therapeutic interventions against cardiac microvascular I/R injury.

TGF-β Signaling: A Therapeutic Target to Reinstate Regenerative Plasticity in Vascular Dementia?

Vascular dementia (VaD) is the second leading form of memory loss after Alzheimer's disease (AD). Currently, there is no cure available. The etiology, pathophysiology and clinical manifestations of VaD are extremely heterogeneous, but the impaired cerebral blood flow (CBF) represents a common denominator of VaD. The latter might be the result of atherosclerosis, amyloid angiopathy, microbleeding and micro-strokes, together causing blood-brain barrier (BBB) dysfunction and vessel leakage, collectively originating from the consequence of hypertension, one of the main risk factors for VaD. At the histopathological level, VaD displays abnormal vascular remodeling, endothelial cell death, string vessel formation, pericyte responses, fibrosis, astrogliosis, sclerosis, microglia activation, neuroinflammation, demyelination, white matter lesions, deprivation of synapses and neuronal loss. The transforming growth factor (TGF) β has been identified as one of the key molecular factors involved in the aforementioned various pathological aspects. Thus, targeting TGF-β signaling in the brain might be a promising therapeutic strategy to mitigate vascular pathology and improve cognitive functions in patients with VaD. This review revisits the recent understanding of the role of TGF-β in VaD and associated pathological hallmarks. It further explores the potential to modulate certain aspects of VaD pathology by targeting TGF-β signaling.

Analysis of endothelial-to-haematopoietic transition at the single cell level identifies cell cycle regulation as a driver of differentiation

BACKGROUND

Haematopoietic stem cells (HSCs) first arise during development in the aorta-gonad-mesonephros (AGM) region of the embryo from a population of haemogenic endothelial cells which undergo endothelial-to-haematopoietic transition (EHT). Despite the progress achieved in recent years, the molecular mechanisms driving EHT are still poorly understood, especially in human where the AGM region is not easily accessible.

RESULTS

In this study, we take advantage of a human pluripotent stem cell (hPSC) differentiation system and single-cell transcriptomics to recapitulate EHT in vitro and uncover mechanisms by which the haemogenic endothelium generates early haematopoietic cells. We show that most of the endothelial cells reside in a quiescent state and progress to the haematopoietic fate within a defined time window, within which they need to re-enter into the cell cycle. If cell cycle is blocked, haemogenic endothelial cells lose their EHT potential and adopt a non-haemogenic identity. Furthermore, we demonstrate that CDK4/6 and CDK1 play a key role not only in the transition but also in allowing haematopoietic progenitors to establish their full differentiation potential.

CONCLUSION

We propose a direct link between the molecular machineries that control cell cycle progression and EHT.

Aneuploid Circulating Tumor-Derived Endothelial Cell (CTEC): A Novel Versatile Player in Tumor Neovascularization and Cancer Metastasis

Hematogenous and lymphogenous cancer metastases are significantly impacted by tumor neovascularization, which predominantly consists of blood vessel-relevant angiogenesis, vasculogenesis, vasculogenic mimicry, and lymphatic vessel-related lymphangiogenesis. Among the endothelial cells that make up the lining of tumor vasculature, a majority of them are tumor-derived endothelial cells (TECs), exhibiting cytogenetic abnormalities of aneuploid chromosomes. Aneuploid TECs are generated from “cancerization of stromal endothelial cells” and “endothelialization of carcinoma cells” in the hypoxic tumor microenvironment. Both processes crucially engage the hypoxia-triggered epithelial-to-mesenchymal transition (EMT) and endothelial-to-mesenchymal transition (EndoMT). Compared to the cancerization process, endothelialization of cancer cells, which comprises the fusion of tumor cells with endothelial cells and transdifferentiation of cancer cells into TECs, is the dominant pathway. Tumor-derived endothelial cells, possessing the dual properties of cancerous malignancy and endothelial vascularization ability, are thus the endothelialized cancer cells. Circulating tumor-derived endothelial cells (CTECs) are TECs shed into the peripheral circulation. Aneuploid CD31⁺ CTECs, together with their counterpart CD31^- circulating tumor cells (CTCs), constitute a unique pair of cellular circulating tumor biomarkers. This review discusses a proposed cascaded framework that focuses on the origins of TECs and CTECs in the hypoxic tumor microenvironment and their clinical implications for tumorigenesis, neovascularization, disease progression, and cancer metastasis. Aneuploid CTECs, harboring hybridized properties of malignancy, vascularization and motility, may serve as a unique target for developing a novel metastasis blockade cancer therapy.

Characterization of Tumor Blood Vasculature Expression of Human Invasive Bladder Cancer by Laser Capture Microdissection and Transcriptional Profiling

Tumor-associated blood vessels differ from normal vessels and play key roles in tumor progression. We aimed to identify biomolecules that are expressed differentially in human bladder cancer-associated blood vessels to find novel biomarkers and mechanisms involved in tumor-associated angiogenesis. The transcriptome of tumor blood vasculature from human invasive bladder carcinoma (I-BLCA) and normal bladder tissue vasculature was compared using differential expression and unsupervised hierarchical clustering analyses. Pathway analysis identified up-regulation of genes involved in the proliferation, cell cycle, angiogenesis, inflammation, and transforming growth factor-β signaling in tumor blood vasculature. A common consensus gene expression signature was identified between bladder cancer tumor blood vasculature with tumor blood vasculature of other solid cancers, which correlated with the overall survival of patients with several of the solid cancers investigated in The Cancer Genome Atlas data set. In bladder tumor blood vasculature, the secreted factor angiopoietin-like protein 2 (ANGPTL2), was confirmed to be up-regulated by quantitative RT-PCR and immunohistochemical staining. The up-regulation of ANGPTL2 in plasma was also observed in non-invasive bladder carcinoma and I-BLCA. We semiquantitatively analyzed expression of ANGPTL2 in tissue microarrays from I-BLCA and surprisingly found an opposite correlation between staining intensity and progression-free survival. Our results indicate that ANGPTL2 might serve as a potential biomarker to predict progression-free survival in I-BLCA.

Obstruction of Small Arterioles in Patients with Critical Limb Ischemia due to Partial Endothelial-to-Mesenchymal Transition

Critical limb ischemia (CLI) is a hazardous manifestation of atherosclerosis and treatment failure is common. Abnormalities in the arterioles might underlie this failure but the cellular pathobiology of microvessels in CLI is poorly understood. We analyzed 349 intramuscular arterioles in lower limb specimens from individuals with and without CLI. Arteriolar densities were 1.8-fold higher in CLI muscles. However, 33% of small (<20 μm) arterioles were stenotic and 9% were completely occluded. The lumens were closed by bulky, re-oriented endothelial cells expressing abundant N-cadherin that uniquely localized between adjacent and opposing endothelial cells. S100A4 and SNAIL1 were also expressed, supporting an endothelial-to-mesenchymal transition. SMAD2/3 was activated in occlusive endothelial cells and TGFβ1 was increased in the adjacent mural cells. These findings identify a microvascular closure process based on mesenchymal transitions in a hyper-TGFß environment that may, in part, explain the limited success of peripheral artery revascularization procedures.

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Small arterioles in patients with critical limb ischemia can be narrowed or closed

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Arteriolar occlusion is due to bulky endothelial cells

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Bulky endothelial cells have partially transitioned to mesenchymal cells

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Occlusive cells interlock laterally and apically via N-cadherin neo-adhesions

Cancer Biology and Prevention in Diabetes

The available evidence suggests a complex relationship between diabetes and cancer. Epidemiological data suggest a positive correlation, however, in certain types of cancer, a more complex picture emerges, such as in some site-specific cancers being specific to type I diabetes but not to type II diabetes. Reports share common and differential mechanisms which affect the relationship between diabetes and cancer. We discuss the use of antidiabetic drugs in a wide range of cancer therapy and cancer therapeutics in the development of hyperglycemia, especially antineoplastic drugs which often induce hyperglycemia by targeting insulin/IGF-1 signaling. Similarly, dipeptidyl peptidase 4 (DPP-4), a well-known target in type II diabetes mellitus, has differential effects on cancer types. Past studies suggest a protective role of DPP-4 inhibitors, but recent studies show that DPP-4 inhibition induces cancer metastasis. Moreover, molecular pathological mechanisms of cancer in diabetes are currently largely unclear. The cancer-causing mechanisms in diabetes have been shown to be complex, including excessive ROS-formation, destruction of essential biomolecules, chronic inflammation, and impaired healing phenomena, collectively leading to carcinogenesis in diabetic conditions. Diabetes-associated epithelial-to-mesenchymal transition (EMT) and endothelial-to-mesenchymal transition (EndMT) contribute to cancer-associated fibroblast (CAF) formation in tumors, allowing the epithelium and endothelium to enable tumor cell extravasation. In this review, we discuss the risk of cancer associated with anti-diabetic therapies, including DPP-4 inhibitors and SGLT2 inhibitors, and the role of catechol-o-methyltransferase (COMT), AMPK, and cell-specific glucocorticoid receptors in cancer biology. We explore possible mechanistic links between diabetes and cancer biology and discuss new therapeutic approaches.