Slug regulates the Dll4-Notch-VEGFR2 axis to control endothelial cell activation and angiogenesis

Kaempferol promotes angiogenesis through HIF-1α/VEGF-A/Notch1 pathway in ischemic stroke rats

Stroke is a severe disease characterized by the obstruction of blood vessels in the central nervous system. An essential therapeutic strategy for ischemic stroke is strengthening angiogenesis, which effectively promotes the long-term recovery of neurological function. Therefore, it is critical to explore and develop new drugs that promote angiogenesis after ischemic stroke. Kaempferol has been employed to treat ischemic diseases; However, its proangiogenic effects in ischemic stroke remain unclear. In the study, we explored the long-term therapeutic effects and mechanisms of kaempferol on ischemic stroke in vivo and in vitro. A rat model of autologous thrombus stroke and oxygen-glucose deprivation (OGD)-induced human brain microvascular endothelial cells (HBMECs) model was established to assess the effects of kaempferol in vivo (50 mg/kg/d, ig, 14 d) and in vitro (0.1, 0.3, 1 μmol L-1). The results showed that long-term administration of kaempferol ameliorated neurological deficits and infarct volume in ischemic stroke rats. In addition, kaempferol relieved vascular embolization; enhanced microvascular endothelial cell survival, proliferation, migration, and lumen formation; increased the density of microvessels in the peri-infarct cortex; and promoted neovascular structure remodeling by increasing the coverage of astrocyte end-feet and expression of tight-junction proteins (TJPs). Further analysis revealed that the HIF-1α/VEGF-A/Notch1 signaling pathway was activated by kaempferol, and that inhibition of Notch1 blocked kaempferol-induced angiogenesis. Taken together, our results indicate that kaempferol exerts neuroprotective effects by stimulating endogenous angiogenesis and neovascular structural remodeling via the HIF-1α/VEGF-A/Notch1 signaling pathway, suggesting the therapeutic potential of kaempferol in ischemic stroke.

Glycated ECM Derived Carbon Dots Inhibit Tumor Vasculogenic Mimicry by Disrupting RAGE Nuclear Translocation and Its Interaction With HMGB1

This study investigates the role of advanced glycation end-products (AGEs) in tumor vasculogenic mimicry (VM). Using high-sugar diet animal models and glycated extracellular matrix (ECM) ex vivo models, AGEs derived is demonstrated from glycated ECM significantly enhanced tumor growth and VM formation. However, carbon dots (egCDs) derived from glycated ECM effectively inhibit tumor growth and VM formation in this glycated microenvironment. Mechanistic studies show that AGEs from glycated ECM bind to the Receptor of Advanced Glycation Endproducts (RAGE) receptors on tumor cells, promoting RAGE nuclear translocation and binding with high mobility group box 1 (HMGB1), which increases the transcription of Snail family transcriptional repressor 2 (SNAI2), thereby driving VM formation. However, egCDs competitively bind to RAGE, promoting its lysosomal degradation and blocking VM formation induced by the RAGE-HMGB1-SNAI2 axis. In conclusion, this study demonstrates that egCDs can target RAGE and promote its lysosomal degradation to block VM formation induced by glycated ECM. This finding not only reveals the transformation of glycated ECM from a pro-VM factor to an anti-VM therapeutic agent after carbonization, but also provides a theoretical basis for the innovative strategy of "reconstructing pathogenic substances into carbon dots to reverse disease-driving factors into therapeutic targeting carriers".

SB218078 inhibits angiogenesis and epithelial-mesenchymal transition in breast cancer

Purpose

Small-molecule inhibitors of vascular endothelial growth factor receptor 2 (VEGFR2) face clinical limitations due to adverse effects. This study aimed to evaluate the novel compound SB218078 as a dual-targeting agent against both tumor angiogenesis and epithelial-mesenchymal transition (EMT) in breast cancer, while exploring its mechanisms of action.

Methods

The anti-angiogenic effects of SB218078 were investigated using in vitro models of endothelial cell migration, invasion, and tube formation, alongside in vivo zebrafish developmental angiogenesis assays. Breast cancer progression was assessed through cellular proliferation, migration, invasion tests, and mouse xenograft models. Mechanistic studies focused on the Chk1/ZEB1 signaling axis, validated through genetic interventions.

Results

SB218078 effectively suppressed angiogenesis by inhibiting endothelial cell functions and disrupting developmental vascular networks in zebrafish. It also impeded breast cancer cell aggressiveness and tumor growth in vivo. Mechanistically, SB218078 selectively targeted ZEB1-an EMT transcription factor-via Chk1 inhibition, with ZEB1 knockdown mimicking its anti-angiogenic effects, while ZEB1 overexpression reversed this activity.

Conclusion

SB218078 emerges as a promising dual-action therapeutic candidate for breast cancer, simultaneously blocking angiogenesis and EMT through the Chk1-ZEB1 axis. Its specificity for ZEB1, distinct from other EMT regulators, offers a novel strategy to overcome the limitations of traditional VEGFR2 inhibitors, warranting further preclinical development.

Secretomes From Non-Small Cell Lung Cancer Cells Induce Endothelial Plasticity Through a Partial Endothelial-to-Mesenchymal Transition

AIM

The tumor microenvironment (TME) of non-small cell lung cancer (NSCLC) is highly heterogeneous and is involved in tumorigenesis and resistance to therapy. Among the cells of the TME, endothelial cells are associated with the latter processes through endothelial-to-mesenchymal transition (EndMT). During EndMT, endothelial cells (ECs) progressively lose their endothelial phenotype in favor of a mesenchymal phenotype, which favors the production of cancer-associated fibroblasts (CAFs). Our study aimed to investigate the consequences of exposure to different lung tumor secretomes on EC phenotype and plasticity.

MATERIALS AND METHODS

Conditioned media (CM) were prepared from the tumor cell lines A549, H1755, H23, H1437, and H1975. Proliferation and migration of ECs treated with these CMs were assessed by Cyquant and Incucyte technologies, respectively. The angiogenic capacity of ECs was assessed by following tubulogenesis on Matrigel. Phenotypic changes in treated ECs were detected by flow cytometry. Morphological analysis of actin fibers was performed by immunohistochemistry, while proteomic analysis by mass spectrometry was used to identify the protein content of secretomes.

RESULTS

A change of the endothelial phenotype was found when human umbilical vein endothelial cells (HUVECs) were treated with different CMs. This phenotypic change was associated with a morphological change, an increase in both stress fiber expression and spontaneous migration. Furthermore, an increase in mesenchymal markers (α-SMA and CD44) confirmed the phenotypic changes. However, the secretomes did not modify the rate of double-labeled cells (vWF+/α-SMA+ or CD31+/CD44+). Proteomic analysis identified potential targets involved in the EndMT with therapeutic relevance.

CONCLUSION

Taken together, these data suggest that CMs can induce partial EndMT.

Microenvironmental determinants of endothelial cell heterogeneity

During development, endothelial cells (ECs) undergo an extraordinary specialization by which generic capillary microcirculatory networks spanning from arteries to veins transform into patterned organotypic zonated blood vessels. These capillary ECs become specialized to support the cellular and metabolic demands of each specific organ, including supplying tissue-specific angiocrine factors that orchestrate organ development, maintenance of organ-specific functions and regeneration of injured adult organs. Here, we illustrate the mechanisms by which microenvironmental signals emanating from non-vascular niche cells induce generic ECs to acquire specific inter-organ and intra-organ functional attributes. We describe how perivascular, parenchymal and immune cells dictate vascular heterogeneity and capillary zonation, and how this system is maintained through tissue-specific signalling activated by vasculogenic and angiogenic factors and deposition of matrix components. We also discuss how perturbation of organotypic vascular niche cues lead to erasure of EC signatures, contributing to the pathogenesis of disease processes. We also describe approaches that use reconstitution of tissue-specific signatures of ECs to promote regeneration of damaged organs.

Endothelial-Ercc1 DNA repair deficiency provokes blood-brain barrier dysfunction

Aging of the brain vasculature plays a key role in the development of neurovascular and neurodegenerative diseases, thereby contributing to cognitive impairment. Among other factors, DNA damage strongly promotes cellular aging, however, the role of genomic instability in brain endothelial cells (EC) and its potential effect on brain homeostasis is still largely unclear. We here investigated how endothelial aging impacts blood-brain barrier (BBB) function by using excision repair cross complementation group 1 (ERCC1)-deficient human brain ECs and an EC-specific Ercc1 knock out (EC-KO) mouse model. In vitro, ERCC1-deficient brain ECs displayed increased senescence-associated secretory phenotype expression, reduced BBB integrity, and higher sprouting capacities due to an underlying dysregulation of the Dll4-Notch pathway. In line, EC-KO mice showed more P21+ cells, augmented expression of angiogenic markers, and a concomitant increase in the number of brain ECs and pericytes. Moreover, EC-KO mice displayed BBB leakage and enhanced cell adhesion molecule expression accompanied by peripheral immune cell infiltration into the brain. These findings were confined to the white matter, suggesting a regional susceptibility. Collectively, our results underline the role of endothelial aging as a driver of impaired BBB function, endothelial sprouting, and increased immune cell migration into the brain, thereby contributing to impaired brain homeostasis as observed during the aging process.

CD90's role in vascularization and healing of rib fractures: insights from Dll4/notch regulation

BACKGROUND

Vascularization after rib fracture is a crucial physiological process that is essential for the repair and healing of the rib. Studies have shown that CD90 plays a critical role in regulating rib fracture healing, but the underlying mechanism of its role has not been fully elucidated.

METHODS

CD90 adenovirus knockout mice were used to construct a rib injury model. The bone healing was observed by micro-CT. CD31/EMCN immunofluorescence staining was performed on bone tissue to observe the density of H-shaped and L-shaped blood vessels at the site of bone injury. CD31 and EMCN dual-stained single cells from the rib fracture sites were detected by flow cytometry. The periosteal stem cells transfected with CD90 or Notch1 overexpression and silencing vector were co-cultured with osteoblast MC3T3-E1 in osteogenic induction medium. Moreover, bone microvascular endothelial cells were extracted from the rib injury and co-cultured with the periosteal stem cells transfected with CD90. CCK-8 was used to detect cell viability, RT-qPCR and Western blot were used to detect Notch1, Notch2, Notch3, Notch4, CD31, HIF-1α, CD90, RUNX2, OCN and OPN expression. Alkaline phosphatase (ALP) staining and alizarin red staining were used to observe mineralized nodules. Immunofluorescence staining was used to detect the expression of Dll4, Notch, and CD90 in each group of cells. The angiogenesis experiment was conducted to observe cellular vascular formation.

RESULTS

Compared with the Adsh-NC group, the bone healing in the Adsh-CD90 group was significantly impaired, with a marked reduction in the number and volume of blood vessels at the rib fracture site, as evidenced by CD31/EMCN immunofluorescence staining, which showed a reduction in the number of H type vessels at the site of bone injury. It was found that CD90 depletion can inhibit the signaling of Dll4/Notch in the rib fracture site. Furthermore, we found that overexpression of Notch1 reverses the impairment of tubule formation in bone microvascular endothelial cells caused by CD90 suppression.r.Dll4 protein reverses the inhibitory effect of CD90 deletion on periosteal stem cells and MC3T3-E1 cell viability and osteogenesis. In the end, we found that overexpression of Notch1 and CD90 can promote angiogenesis of bone microvascular endothelial cells and Notch pathway activation.

CONCLUSION

CD90 can affect vascular formation in mouse rib fractures, and CD90 may be regulated by Dll4/Notch.

Ginsenoside Re inhibits non-small cell lung cancer progression by suppressing macrophage M2 polarization induced by AMPKα1/STING positive feedback loop

Tumor-associated macrophages (TAMs) in non-small cell lung cancer (NSCLC) promote tumor cell metastasis by interacting with cancer cells. Ginsenoside Re is capable of modulating the host immune system and exerts anticancer effects through multiple pathways. Both AMPK and STING are involved in the regulation of MΦ polarization, thereby affecting tumor progression. However, whether there is a regulatory relationship between them and its effect on MΦ polarization and tumor progression is unclear. The aim of this study was to provide mechanistic evidence that ginsenoside Re modulates MΦ phenotype through inhibition of the AMPKα1/STING positive feedback loop and thus exerts an antimetastatic effect in NSCLC immunotherapy. Cell culture models and conditioned media (CM) systems were constructed, and the treated MΦ were analyzed by database analysis, RT-PCR, Western blotting, flow cytometry, and immunofluorescence to determine the regulatory relationship between AMPK and STING and the effects of ginsenoside Re on MΦ polarization and tumor cells migration. The effects of ginsenoside Re (10, 20 mg/kg/day) on TAMs phenotype as well as tumor progression in mice were assessed by HE staining, immunohistochemical staining, and Western blotting. In this study, AMPKα1/STING positive feedback loop in NSCLC TAMs induced M2 type polarization, which in turn promoted NSCLC cell migration. In addition, ginsenoside Re was discovered to inhibit M2-like MΦ polarization, thereby inhibiting NSCLC cell migration. Mechanistically, Re was able to inhibit the formation of the AMPKα1/STING positive feedback loop, thereby inhibiting its induction of M2-like MΦ and consequently inhibiting the epithelial-mesenchymal transition (EMT) process of NSCLC cells. Furthermore, in mouse models, Re was found to suppress LLC tumor growth and colonization by inhibiting M2-type polarization of TAMs. Our finding indicates that ginsenoside Re can effectively modulate MΦ polarization and thus play an important role in antimetastatic immunotherapy of NSCLC.

The role of MDM2 in angiogenesis: implications for endothelial tip cell formation

In the present study, we examined the role of MDM2 in the angiogenesis process and its potential association with the sprouting of endothelial tip cells. To address this, we performed hypoxia-treated gastric cancer cells (HGC-27) to quantitative RT-PCR and Western blot analysis to measure the levels of MDM2 and VEGF-A mRNA and protein expression. Subsequently, we employed siRNA to disrupt MDM2 expression, followed by hypoxia treatment. The expression levels of MDM2 and VEGF-A mRNA and protein were subsequently reassessed. Additionally, ELISA was utilized to quantify the secretion levels of VEGF-A in each experimental group. A conditioned medium derived from HGC-27 cells treated with different agents was employed to assess its influence on the formation of EA.hy926 endothelial tip cells, using various techniques including Transwell plates migration assays, wound healing experiments, vascular formation assays, scanning electron microscopy, and immunofluorescence staining. These findings demonstrated that the in vitro knockdown of MDM2 in the conditioned medium exhibited significant inhibitory effects on endothelial cell migration, wound healing, and vascular formation. Additionally, the intervention led to a reduction in the presence of CD34+ tip cells and the formation of filopodia in endothelial cells, while partially restoring the integrity of tight junctions. Subsequent examination utilizing RNA-seq revealed that the suppression of MDM2 in HGC-27 cells resulted in the downregulation of the PI3K/AKT signaling pathway. Consequently, this downregulation led to an elevation in angiogenic effects induced by hypoxia.

Netrin‑4 promotes VE‑cadherin expression in endothelial cells through the NF‑κB signaling pathway

Netrin-4 (NTN4), a secreted protein from the Netrin family, has been recognized for its role in vascular development, endothelial homeostasis and angiogenesis. Vascular endothelial (VE)-cadherin is a specialized adhesion protein located at the intercellular junctions of endothelial cells (ECs), and regulates migration, proliferation and permeability. To date, the relationship between NTN4 and VE-cadherin in ECs remains unclear. In the present study, human umbilical vein ECs (HUVECs) were transfected with NTN4 overexpression plasmid, resulting in NTN4 overexpression. Reverse transcription-quantitative PCR and western blotting were used to determine gene and protein expression. CCK8, wound healing, and Transwell assays were performed to evaluate cell proliferation, migration and permeability. NTN4 overexpression decreased HUVEC viability and migration. In addition, NTN4 overexpression increased the expression of VE-cadherin and decreased the permeability of HUVECs. Subsequent studies showed that NTN4 overexpression increased the NF-κB protein level and decreased IκB-α protein expression in HUVECs. In HUVECs treated with NF-κB inhibitor pyrrolidine dithiocarbamate, the expression of VE-cadherin failed to increase with NTN4 overexpression. Taken together, the results indicated that NTN4 overexpression increased VE-cadherin expression through the activation of the NF-κB signaling pathway in HUVECs. The present findings revealed a novel regulatory mechanism for VE-cadherin expression and suggested a novel avenue for future research on the role of NTN4 in endothelial barrier-related diseases.

Normalization of Snai1-mediated vessel dysfunction increases drug response in cancer

Blood vessels in tumors are often dysfunctional. This impairs the delivery of therapeutic agents to and distribution among the cancer cells. Subsequently, treatment efficacy is reduced, and dose escalation can increase adverse effects on non-malignant tissues. The dysfunctional vessel phenotypes are attributed to aberrant pro-angiogenic signaling, and anti-angiogenic agents can ameliorate traits of vessel dysfunctionality. However, they simultaneously reduce vessel density and thereby impede drug delivery and distribution. Exploring possibilities to improve vessel functionality without compromising vessel density in the tumor microenvironment, we evaluated transcription factors (TFs) involved in epithelial-mesenchymal transition (EMT) as potential targets. Based on similarities between EMT and angiogenic activation of endothelial cells, we hypothesized that these TFs, Snai1 in particular, might serve as key regulators of vessel dysfunctionality. In vitro, experiments demonstrated that Snai1 (similarly Slug and Twist1) regulates endothelial permeability, permissiveness for tumor cell transmigration, and tip/stalk cell formation. Endothelial-specific, heterozygous knock-down of Snai1 in mice improved vascular quality in implanted tumors. This resulted in better oxygenation and reduced metastasis. Notably, the tumors in Snai1KD mice responded significantly better to chemotherapeutics as drugs were transported into the tumors at strongly increased rates and more homogeneously distributed. Thus, we demonstrate that restoring vessel homeostasis without affecting vessel density is feasible in malignant tumors. Combining such vessel re-engineering with anti-cancer drugs allows for strategic treatment approaches that reduce treatment toxicity on non-malignant tissues.

Notch signaling pathway in cancer: from mechanistic insights to targeted therapies

Notch signaling, renowned for its role in regulating cell fate, organ development, and tissue homeostasis across metazoans, is highly conserved throughout evolution. The Notch receptor and its ligands are transmembrane proteins containing epidermal growth factor-like repeat sequences, typically necessitating receptor-ligand interaction to initiate classical Notch signaling transduction. Accumulating evidence indicates that the Notch signaling pathway serves as both an oncogenic factor and a tumor suppressor in various cancer types. Dysregulation of this pathway promotes epithelial-mesenchymal transition and angiogenesis in malignancies, closely linked to cancer proliferation, invasion, and metastasis. Furthermore, the Notch signaling pathway contributes to maintaining stem-like properties in cancer cells, thereby enhancing cancer invasiveness. The regulatory role of the Notch signaling pathway in cancer metabolic reprogramming and the tumor microenvironment suggests its pivotal involvement in balancing oncogenic and tumor suppressive effects. Moreover, the Notch signaling pathway is implicated in conferring chemoresistance to tumor cells. Therefore, a comprehensive understanding of these biological processes is crucial for developing innovative therapeutic strategies targeting Notch signaling. This review focuses on the research progress of the Notch signaling pathway in cancers, providing in-depth insights into the potential mechanisms of Notch signaling regulation in the occurrence and progression of cancer. Additionally, the review summarizes pharmaceutical clinical trials targeting Notch signaling for cancer therapy, aiming to offer new insights into therapeutic strategies for human malignancies.

Multiple cis-regulatory elements control prox1a expression in distinct lymphatic vascular beds

During embryonic development, lymphatic endothelial cell (LEC) precursors are distinguished from blood endothelial cells by the expression of Prospero-related homeobox 1 (Prox1), which is essential for lymphatic vasculature formation in mouse and zebrafish. Prox1 expression initiation precedes LEC sprouting and migration, serving as the marker of specified LECs. Despite its crucial role in lymphatic development, Prox1 upstream regulation in LECs remains to be uncovered. SOX18 and COUP-TFII are thought to regulate Prox1 in mice by binding its promoter region. However, the specific regulation of Prox1 expression in LECs remains to be studied in detail. Here, we used evolutionary conservation and chromatin accessibility to identify enhancers located in the proximity of zebrafish prox1a active in developing LECs. We confirmed the functional role of the identified sequences through CRISPR/Cas9 mutagenesis of a lymphatic valve enhancer. The deletion of this region results in impaired valve morphology and function. Overall, our results reveal an intricate control of prox1a expression through a collection of enhancers. Ray-finned fish-specific distal enhancers drive pan-lymphatic expression, whereas vertebrate-conserved proximal enhancers refine expression in functionally distinct subsets of lymphatic endothelium.

ID1high/activin Ahigh glioblastoma cells contribute to resistance to anti-angiogenesis therapy through malformed vasculature

Although bevacizumab (BVZ), a representative drug for anti-angiogenesis therapy (AAT), is used as a first-line treatment for patients with glioblastoma (GBM), its efficacy is notably limited. Whereas several mechanisms have been proposed to explain the acquisition of AAT resistance, the specific underlying mechanisms have yet to be sufficiently ascertained. Here, we established that inhibitor of differentiation 1 (ID1)high/activin Ahigh glioblastoma cell confers resistance to BVZ. The bipotent effect of activin A during its active phase was demonstrated to reduce vasculature dependence in tumorigenesis. In response to a temporary exposure to activin A, this cytokine was found to induce endothelial-to-mesenchymal transition via the Smad3/Slug axis, whereas prolonged exposure led to endothelial apoptosis. ID1 tumors showing resistance to BVZ were established to be characterized by a hypovascular structure, hyperpermeability, and scattered hypoxic regions. Using a GBM mouse model, we demonstrated that AAT resistance can be overcome by administering therapy based on a combination of BVZ and SB431542, a Smad2/3 inhibitor, which contributed to enhancing survival. These findings offer valuable insights that could contribute to the development of new strategies for treating AAT-resistant GBM.

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.

GTF2H4 regulates partial EndMT via NF-κB activation through NCOA3 phosphorylation in ischemic diseases

Partial endothelial-to-mesenchymal transition (EndMT) is an intermediate phenotype observed in endothelial cells (ECs) undergoing a transition toward a mesenchymal state to support neovascularization during (patho)physiological angiogenesis. Here, we investigated the occurrence of partial EndMT in ECs under hypoxic/ischemic conditions and identified general transcription factor IIH subunit 4 (GTF2H4) as a positive regulator of this process. In addition, we discovered that GTF2H4 collaborates with its target protein excision repair cross-complementation group 3 (ERCC3) to co-regulate partial EndMT. Furthermore, by using phosphorylation proteomics and site-directed mutagenesis, we demonstrated that GTF2H4 was involved in the phosphorylation of receptor coactivator 3 (NCOA3) at serine 1330, which promoted the interaction between NCOA3 and p65, resulting in the transcriptional activation of NF-κB and the NF-κB/Snail signaling axis during partial EndMT. In vivo experiments confirmed that GTF2H4 significantly promoted partial EndMT and angiogenesis after ischemic injury. Collectively, our findings reveal that targeting GTF2H4 is promising for tissue repair and offers potential opportunities for treating hypoxic/ischemic diseases.

Tensile Stress-Activated and Exosome-Transferred YAP/TAZ-Notch Circuit Specifies Type H Endothelial Cell for Segmental Bone Regeneration

The Ilizarov technique has been continuously innovated to utilize tensile stress (TS) for inducing a bone development-like regenerative process, aiming to achieve skeletal elongation and reconstruction. However, it remains uncertain whether this distraction osteogenesis (DO) process induced by TS involves the pivotal coupling of angiogenesis and osteogenesis mediated by type H endothelial cells (THECs). In this study, it is demonstrated that the Ilizarov technique induces the formation of a metaphysis-like architecture composed of THECs, leading to segmental bone regeneration during the DO process. Mechanistically, cell-matrix interactions-mediated activation of yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) transcriptionally upregulates the expression of Notch1 and Delta-like ligand 4, which act as direct positive regulators of THECs phenotype, in bone marrow endothelial cells (BMECs) upon TS stimulation. Simultaneously, the Notch intracellular domain enhances YAP/TAZ activity by transcriptionally upregulating YAP expression and stabilizing TAZ protein, thus establishing the YAP/TAZ-Notch circuit. Additionally, TS-stimulated BMECs secrete exosomes enriched with vital molecules in this positive feedback pathway, which can be utilized to promote segmental bone defect healing, mimicking the therapeutic effects of Ilizarov technique. The findings advance the understanding of TS-induced segmental bone regeneration and establish the foundation for innovative biological therapeutic strategies aimed at activating THECs.

Blood endothelium transition and phenotypic plasticity: A key regulator of integrity/permeability in response to ischemia

In the human body, the 1013 blood endothelial cells (ECs) which cover a surface of 500-700 m2 (Mai et al., 2013) are key players of tissue homeostasis, remodeling and regeneration. Blood vessel ECs play a major role in the regulation of metabolic and gaz exchanges, cell trafficking, blood coagulation, vascular tone, blood flow and fluid extravasation (also referred to as blood vascular permeability). ECs are heterogeneous in various capillary beds and have the exquisite capacity to cope with environmental changes by regulating their gene expression. Ischemia has major detrimental effects on the endothelium and ischemia-induced regulation of vascular integrity is of paramount importance for human health, as small amounts of fluid accumulation in the interstitium may be responsible for major effects on organ functions and patients outcome. In this review, we will here focus on the stimuli and the molecular mechanisms that control blood endothelium maintenance and phenotypic plasticity/transition involved in controlling blood capillary leakage that might open new avenues for therapeutic applications.

CD40 is expressed in the subsets of endothelial cells undergoing partial endothelial-mesenchymal transition in tumor microenvironment

Tumor progression and metastasis are regulated by endothelial cells undergoing endothelial-mesenchymal transition (EndoMT), a cellular differentiation process in which endothelial cells lose their properties and differentiate into mesenchymal cells. The cells undergoing EndoMT differentiate through a spectrum of intermediate phases, suggesting that some cells remain in a partial EndoMT state and exhibit an endothelial/mesenchymal phenotype. However, detailed analysis of partial EndoMT has been hampered by the lack of specific markers. Transforming growth factor-β (TGF-β) plays a central role in the induction of EndoMT. Here, we showed that inhibition of TGF-β signaling suppressed EndoMT in a human oral cancer cell xenograft mouse model. By using genetic labeling of endothelial cell lineage, we also established a novel EndoMT reporter cell system, the EndoMT reporter endothelial cells (EMRECs), which allow visualization of sequential changes during TGF-β-induced EndoMT. Using EMRECs, we characterized the gene profiles of multiple EndoMT stages and identified CD40 as a novel partial EndoMT-specific marker. CD40 expression was upregulated in the cells undergoing partial EndoMT, but decreased in the full EndoMT cells. Furthermore, single-cell RNA sequencing analysis of human tumors revealed that CD40 expression was enriched in the population of cells expressing both endothelial and mesenchymal cell markers. Moreover, decreased expression of CD40 in EMRECs enhanced TGF-β-induced EndoMT, suggesting that CD40 expressed during partial EndoMT inhibits transition to full EndoMT. The present findings provide a better understanding of the mechanisms underlying TGF-β-induced EndoMT and will facilitate the development of novel therapeutic strategies targeting EndoMT-driven cancer progression and metastasis.

Role of cell rearrangement and related signaling pathways in the dynamic process of tip cell selection

Angiogenesis is a complex, highly-coordinated and multi-step process of new blood vessel formation from pre-existing blood vessels. When initiated, the sprouting process is spearheaded by the specialized endothelial cells (ECs) known as tip cells, which guide the organization of accompanying stalk cells and determine the function and morphology of the finally-formed blood vessels. Recent studies indicate that the orchestration and coordination of angiogenesis involve dynamic tip cell selection, which is the competitive selection of cells to lead the angiogenic sprouts. Therefore, this review attempt to summarize the underlying mechanisms involved in tip cell specification in a dynamic manner to enable readers to gain a systemic and overall understanding of tip cell formation, involving cooperative interaction of cell rearrangement with Notch and YAP/TAZ signaling. Various mechanical and chemical signaling cues are integrated to ensure the right number of cells at the right place during angiogenesis, thereby precisely orchestrating morphogenic functions that ensure correct patterning of blood vessels. Video Abstract.

Expression of Tumor Suppressor FHIT Is Regulated by the LINC00173-SNAIL Axis in Human Lung Adenocarcinoma

Long non-coding RNAs (lncRNAs) play a critical role in a variety of human diseases such as cancer. Here, to elucidate a novel function of a lncRNA called LINC00173, we investigated its binding partner, target gene, and its regulatory mechanism in lung adenocarcinoma, including the A549 cell line and patients. In the A549 cell line, RNA immunoprecipitation (RIP) assays revealed that LINC00173 efficiently binds to SNAIL. RNA-seq and RT-qPCR analyses revealed that the expression of FHIT was decreased upon LINC00173 depletion, indicating that FHIT is a target gene of LINC00173. Overexpression of SNAIL suppressed and depletion of SNAIL increased the expression of FHIT, indicating that SNAIL negatively regulates FHIT. The downregulation of FHIT expression upon LINC00173 depletion was restored by additional SNAIL depletion, revealing a LINC00173-SNAIL-FHIT axis for FHIT regulation. Data from 501 patients with lung adenocarcinoma also support the existence of a LINC00173-SNAIL-FHIT axis, as FHIT expression correlated positively with LINC00173 (p = 1.75 × 10-6) and negatively with SNAIL (p = 7.00 × 10-5). Taken together, we propose that LINC00173 positively regulates FHIT gene expression by binding to SNAIL and inhibiting its function in human lung adenocarcinoma. Thus, this study sheds light on the LINC00173-SNAIL-FHIT axis, which may be a key mechanism for carcinogenesis and progression in human lung adenocarcinoma.

Liver X receptor alpha ensures blood-brain barrier function by suppressing SNAI2

In Alzheimer's disease (AD) more than 50% of the patients are affected by capillary cerebral amyloid-angiopathy (capCAA), which is characterized by localized hypoxia, neuro-inflammation and loss of blood-brain barrier (BBB) function. Moreover, AD patients with or without capCAA display increased vessel number, indicating a reactivation of the angiogenic program. The molecular mechanism(s) responsible for BBB dysfunction and angiogenesis in capCAA is still unclear, preventing a full understanding of disease pathophysiology. The Liver X receptor (LXR) family, consisting of LXRα and LXRβ, was reported to inhibit angiogenesis and particularly LXRα was shown to secure BBB stability, suggesting a major role in vascular function. In this study, we unravel the regulatory mechanism exerted by LXRα to preserve BBB integrity in human brain endothelial cells (BECs) and investigate its role during pathological conditions. We report that LXRα ensures BECs identity via constitutive inhibition of the transcription factor SNAI2. Accordingly, deletion of brain endothelial LXRα is associated with impaired DLL4-NOTCH signalling, a critical signalling pathway involved in vessel sprouting. A similar response was observed when BECs were exposed to hypoxia, with concomitant LXRα decrease and SNAI2 increase. In support of our cell-based observations, we report a general increase in vascular SNAI2 in the occipital cortex of AD patients with and without capCAA. Importantly, SNAI2 strongly associated with vascular amyloid-beta deposition and angiopoietin-like 4, a marker for hypoxia. In hypoxic capCAA vessels, the expression of LXRα may decrease leading to an increased expression of SNAI2, and consequently BECs de-differentiation and sprouting. Our findings indicate that LXRα is essential for BECs identity, thereby securing BBB stability and preventing aberrant angiogenesis. These results uncover a novel molecular pathway essential for BBB identity and vascular homeostasis providing new insights on the vascular pathology affecting AD patients.

Lactate receptor GPR81 drives breast cancer growth and invasiveness through regulation of ECM properties and Notch ligand DLL4

BACKGROUND

The lactate receptor GPR81 contributes to cancer development through unclear mechanisms. Here, we investigate the roles of GPR81 in three-dimensional (3D) and in vivo growth of breast cancer cells and study the molecular mechanisms involved.

METHODS

GPR81 was stably knocked down (KD) in MCF-7 human breast cancer cells which were subjected to RNA-seq analysis, 3D growth, in situ- and immunofluorescence analyses, and cell viability- and motility assays, combined with KD of key GPR81-regulated genes. Key findings were additionally studied in other breast cancer cell lines and in mammary epithelial cells.

RESULTS

GPR81 was upregulated in multiple human cancer types and further upregulated by extracellular lactate and 3D growth in breast cancer spheroids. GPR81 KD increased spheroid necrosis, reduced invasion and in vivo tumor growth, and altered expression of genes related to GO/KEGG terms extracellular matrix, cell adhesion, and Notch signaling. Single cell in situ analysis of MCF-7 cells revealed that several GPR81-regulated genes were upregulated in the same cell clusters. Notch signaling, particularly the Notch ligand Delta-like-4 (DLL4), was strikingly downregulated upon GPR81 KD, and DLL4 KD elicited spheroid necrosis and inhibited invasion in a manner similar to GPR81 KD.

CONCLUSIONS

GPR81 supports breast cancer aggressiveness, and in MCF-7 cells, this occurs at least in part via DLL4. Our findings reveal a new GPR81-driven mechanism in breast cancer and substantiate GPR81 as a promising treatment target.

Two NOTCH1 O-fucose sites have opposing functions in mouse retinal angiogenesis

Previous in vitro studies demonstrated that Fringe glycosylation of the NOTCH1 extracellular domain at O-fucose residues in Epidermal Growth Factor-like Repeats (EGFs) 6 and 8 is a significant contributor to suppression of NOTCH1 activation by JAG1 or enhancement of NOTCH1 activation by DLL1, respectively. In this study, we sought to evaluate the significance of these glycosylation sites in a mammalian model by generating 2 C57BL/6J mouse lines carrying NOTCH1 point mutations, which eliminate O-fucosylation and Fringe activity at EGFs 6 (T232V) or 8 (T311V). We assessed changes to morphology during retinal angiogenesis, a process in which expression of Notch1, Jag1, Dll4, Lfng, Mfng, and Rfng genes coordinate cell-fate decisions to grow vessel networks. In the EGF6 O-fucose mutant (6f/6f) retinas, we observed reduced vessel density and branching, suggesting that this mutant is a Notch1 hypermorph. This finding agrees with prior cell-based studies showing that the 6f mutation increased JAG1 activation of NOTCH1 during co-expression with inhibitory Fringes. Although we predicted that the EGF8 O-fucose mutant (8f/8f) would not complete embryonic development due to the direct involvement of the O-fucose in engaging ligand, the 8f/8f mice were viable and fertile. In the 8f/8f retina, we measured increased vessel density consistent with established Notch1 hypomorphs. Overall, our data support the importance of NOTCH1 O-fucose residues for pathway function and confirms that single O-glycan sites are rich in signaling instructions for mammalian development.

Delta- like ligand 4- expressing macrophages and human diseases: Insights into pathophysiology and therapeutic opportunities

Macrophages are key players in the immune response and have been implicated in various human diseases, including atherosclerosis, cancer, and chronic inflammatory disorders. While numerous studies have delved into the nuances of macrophage behavior in these conditions, there remains a gap in understanding the specific role of Delta-like ligand 4 (Dll4)-expressing macrophages and their overarching implications across these diseases. Among the plethora of factors expressed by macrophages, Dll4 has emerged as a molecule of particular interest. Recent studies have highlighted its unique role in modulating macrophage functions and its potential implications in various diseases. This review seeks to consolidate existing knowledge, address this gap, and present a comprehensive overview of Dll4-expressing macrophages in the context of these disorders and highlight their potential as therapeutic targets. We examined the involvement of Dll4-expressing macrophages in multiple human diseases such as atherosclerosis, cancer and chronic inflammatory diseases, emphasizing their influence on disease progression. We also discussed the challenges, limitations, and emerging research areas in targeting Dll4-expressing macrophages and provide an outlook on potential therapeutic strategies for the treatment of these diseases. By addressing the previously existing research gap, we've provided a roadmap that brings together fragmented insights, paving the way for more holistic research and potentially more effective therapeutic strategies centered on Dll4-expressing macrophages.

Endothelial cell plasticity in kidney fibrosis and disease

Renal endothelial cells demonstrate an impressive remodeling potential during angiogenic sprouting, vessel repair or while transitioning into mesenchymal cells. These different processes may play important roles in both renal disease progression or regeneration while underlying signaling pathways of different endothelial cell plasticity routes partly overlap. Angiogenesis contributes to wound healing after kidney injury and pharmaceutical modulation of angiogenesis may home a great therapeutic potential. Yet, it is not clear whether any differentiated endothelial cell can proliferate or whether regenerative processes are largely controlled by resident or circulating endothelial progenitor cells. In the glomerular compartment for example, a distinct endothelial progenitor cell population may remodel the glomerular endothelium after injury. Endothelial-to-mesenchymal transition (EndoMT) in the kidney is vastly documented and often associated with endothelial dysfunction, fibrosis, and kidney disease progression. Especially the role of EndoMT in renal fibrosis is controversial. Studies on EndoMT in vivo determined possible conclusions on the pathophysiological role of EndoMT in the kidney, but whether endothelial cells really contribute to kidney fibrosis and if not what other cellular and functional outcomes derive from EndoMT in kidney disease is unclear. Sequencing data, however, suggest no participation of endothelial cells in extracellular matrix deposition. Thus, more in-depth classification of cellular markers and the fate of EndoMT cells in the kidney is needed. In this review, we describe different signaling pathways of endothelial plasticity, outline methodological approaches and evidence for functional and structural implications of angiogenesis and EndoMT in the kidney, and eventually discuss controversial aspects in the literature.

Dan-Deng-Tong-Nao softgel capsule promotes angiogenesis of cerebral microvasculature to protect cerebral ischemia reperfusion injury via activating HIF-1α-VEGFA-Notch1 signaling pathway

BACKGROUND

A proprietary Chinese herbal product called Dan-Deng-Tong-Nao softgel capsule (DDTNC) is used to treat ischemic stroke. However, the preventive mechanisms of DDTNC against cerebral ischemia reperfusion injury (CIRI) haven not been characterized.

OBJECTIVE

To explore the mechanisms of protective effects of DDTNC against CIRI from both internal and external levels.

METHODS

Chemical characterization was performed using UPLC. The potential protective mechanisms of DDTNC against CIRI were predicted using network pharmacology. Model of middle cerebral artery occlusion/reperfusion (MCAO/R) was established in rats. An model of brain microvascular endothelial cells (BMECs) induced by oxygen-glucose deprivation/reoxygenation (OGD/R) was also established. We evaluated neurological deficits, cerebral infarct volume, cortical neuron damage, and mitochondrial swelling in vivo. We evaluated the expression of VEGFR2, VEGFA, HIF-1α, CD31, and CD34 in ischemic cortex, and VEGF, bFGF, BDNF, angiostatin, and endostatin in serum of rats and in BMEC supernatants. We also evaluated cell viability, cytotoxicity, intracellular ROS, apoptosis, and migration ability in vitro.

RESULTS

Seven components were detected in DDTNC. KEGG enrichment analysis showed that DDTNC may modulate angiogenesis via the HIF-1 signaling pathway. DDTNC treatment reduced neurological score and infarct volume, and improved cell morphology of damaged neurons. Transmission electron microscopy showed that DDTNC reduced mitochondria swelling in cortical neurons. Furthermore, DDTNC reduced intracellular ROS and inhibited apoptosis. DDTNC boosted the expression of CD31, CD34, VEGFR2, VEGFA and HIF-1α, highlighting its involvement in angiogenesis, according to immunofluorescence studies. Furthermore, DDTNC enhanced tube formation and migration of BMECs in vitro. ELISA and western blotting indicated that DDTNCCSF induced the expression of VEGF, BDNF and bFGF, reduced the level of angiostatin and endostatin, increased the protein expression of VEGFA, Notch1 and HIF-1α in vitro and in vivo.

CONCLUSIONS

DDTNC promoted angiogenesis to protect brain tissue against MCAO/R, and exerted protective effects against OGD/R in BMECs via activating HIF-1α-VEGFA-NOTCH1 signal transduction pathway.

The role of nanotherapy in head and neck squamous cell carcinoma by targeting tumor microenvironment

Head and neck squamous cell carcinomas (HNSCCs) refers to a group of highly malignant and pathogenically complex tumors. Traditional treatment methods include surgery, radiotherapy, and chemotherapy. However, with advancements in genetics, molecular medicine, and nanotherapy, more effective and safer treatments have been developed. Nanotherapy, in particular, has the potential to be an alternative therapeutic option for HNSCC patients, given its advantageous targeting capabilities, low toxicity and modifiability. Recent research has highlighted the important role of the tumor microenvironment (TME) in the development of HNSCC. The TME is composed of various cellular components, such as fibroblasts, vascular endothelial cells, and immune cells, as well as non-cellular agents such as cytokines, chemokines, growth factors, extracellular matrix (ECM), and extracellular vesicles (EVs). These components greatly influence the prognosis and therapeutic efficacy of HNSCC, making the TME a potential target for treatment using nanotherapy. By regulating angiogenesis, immune response, tumor metastasis and other factors, nanotherapy can potentially alleviate HNSCC symptoms. This review aims to summarize and discuss the application of nanotherapy that targets HNSCC's TME. We highlight the therapeutic value of nanotherapy for HNSCC patients.

Prerequisite endocardial-mesenchymal transition for murine cardiac trabecular angiogenesis

Coronary heart disease damages the trabecular myocardium, and the regeneration of trabecular vessels may alleviate ischemic injury. However, the origins and developmental mechanisms of trabecular vessels remain unknown. Here, we show that murine ventricular endocardial cells generate trabecular vessels through an "angioEMT" mechanism. Time course fate mapping defined a specific wave of trabecular vascularization by ventricular endocardial cells. Single-cell transcriptomics and immunofluorescence identified a subpopulation of ventricular endocardial cells that underwent endocardial-mesenchymal transition (EMT) before these cells generated trabecular vessels. Ex vivo pharmacological activation and in vivo genetic inactivation experiments identified an EMT signal in ventricular endocardial cells involving SNAI2-TGFB2/TGFBR3, which was a prerequisite for later trabecular-vessel formation. Additional loss- and gain-of-function genetic studies showed that VEGFA-NOTCH1 signaling regulated post-EMT trabecular angiogenesis by ventricular endocardial cells. Our finding that trabecular vessels originate from ventricular endocardial cells through a two-step angioEMT mechanism could inform better regeneration medicine for coronary heart disease.

DLL4 promotes partial endothelial-to-mesenchymal transition at atherosclerosis-prone regions of arteries

Flowing blood regulates vascular development, homeostasis and disease by generating wall shear stress which has major effects on endothelial cell (EC) physiology. Low oscillatory shear stress (LOSS) induces a form of cell plasticity called endothelial-to-mesenchymal transition (EndMT). This process has divergent effects; in embryos LOSS-induced EndMT drives the development of atrioventricular valves, whereas in adult arteries it is associated with inflammation and atherosclerosis. The Notch ligand DLL4 is essential for LOSS-dependent valve development; here we investigated whether DLL4 is required for responses to LOSS in adult arteries. Analysis of cultured human coronary artery EC revealed that DLL4 regulates the transcriptome to induce markers of EndMT and inflammation under LOSS conditions. Consistently, genetic deletion of Dll4 from murine EC reduced SNAIL (EndMT marker) and VCAM-1 (inflammation marker) at a LOSS region of the murine aorta. We hypothesized that endothelial Dll4 is pro-atherogenic but this analysis was confounded because endothelial Dll4 negatively regulated plasma cholesterol levels in hyperlipidemic mice. We conclude that endothelial DLL4 is required for LOSS-induction of EndMT and inflammation regulators at atheroprone regions of arteries, and is also a regulator of plasma cholesterol.

The tissue-specific transcriptional landscape underlines the involvement of endothelial cells in health and disease

Endothelial cells (ECs) that line vascular and lymphatic vessels are being increasingly recognized as important to organ function in health and disease. ECs participate not only in the trafficking of gases, metabolites, and cells between the bloodstream and tissues but also in the angiocrine-based induction of heterogeneous parenchymal cells, which are unique to their specific tissue functions. The molecular mechanisms regulating EC heterogeneity between and within different tissues are modeled during embryogenesis and become fully established in adults. Any changes in adult tissue homeostasis induced by aging, stress conditions, and various noxae may reshape EC heterogeneity and induce specific transcriptional features that condition a functional phenotype. Heterogeneity is sustained via specific genetic programs organized through the combinatory effects of a discrete number of transcription factors (TFs) that, at the single tissue-level, constitute dynamic networks that are post-transcriptionally and epigenetically regulated. This review is focused on outlining the TF-based networks involved in EC specialization and physiological and pathological stressors thought to modify their architecture.

DLL4-Notch signalling in acute-on-chronic liver failure: State of the art and perspectives

Acute-on-chronic liver failure (ACLF) is a syndrome characterized by acute decompensation of chronic liver disease associated with multiple-organ failures and high short-term mortality. Acute insults to patients with chronic liver disease can lead to ACLF, among which, hepatitis B virus-related ACLF is the most common type of liver failure in the Asia-Pacific region. Currently, immune-metabolism disorders and systemic inflammation are proposed to be the main mechanisms of ACLF. The resulting cholestasis and intrahepatic microcirculatory dysfunction accelerate the development of ACLF. Treatments targeting immune regulation, metabolic balance, microcirculation maintenance and bile duct repair can alleviate inflammation and restore the tissue structure. An increasing number of studies have demonstrated that delta-like ligand 4 (DLL4), one of the Notch signalling ligands, plays a vital role in immune regulation, metabolism, angiogenesis, and biliary regeneration, which participate in liver pathological and physiological processes. The detailed mechanism of the DLL4-Notch signalling pathway in ACLF has rarely been investigated. Here, we review the evidence showing that DLL4-Notch signalling is involved in ACLF and analyse the potential role of DLL4 in the treatment of ACLF.

Endothelial to Mesenchymal Transition in Health and Disease

The endothelium is one of the largest organ systems in the body, and data continue to emerge regarding the importance of endothelial cell (EC) dysfunction in vascular aging and a range of cardiovascular diseases (CVDs). Over the last two decades and as a process intimately related to EC dysfunction, an increasing number of studies have also implicated endothelial to mesenchymal transition (EndMT) as a potentially disease-causal pathobiologic process that is involved in a multitude of differing CVDs. However, EndMT is also involved in physiologic processes (e.g., cardiac development), and transient EndMT may contribute to vascular regeneration in certain contexts. Given that EndMT involves a major alteration in the EC-specific molecular program, and that it potentially contributes to CVD pathobiology, the clinical translation opportunities are significant, but further molecular and translational research is needed to see these opportunities realized.

Angiotensin-converting enzyme inhibitor promotes angiogenesis through Sp1/Sp3-mediated inhibition of notch signaling in male mice

Angiogenesis is a critical pathophysiological process involved in organ growth and various diseases. Transcription factors Sp1/Sp3 are necessary for fetal development and tumor growth. Sp1/Sp3 proteins were downregulated in the capillaries of the gastrocnemius in patients with critical limb ischemia samples. Endothelial-specific Sp1/Sp3 knockout reduces angiogenesis in retinal, pathological, and tumor models and induced activation of the Notch1 pathway. Further, the inactivation of VEGFR2 signaling by Notch1 contributes to the delayed angiogenesis phenotype. Mechanistically, endothelial Sp1 binds to the promoter of Notch1 and inhibits its transcription, which is enhanced by Sp3. The proangiogenic effect of ACEI is abolished in Sp1/Sp3-deletion male mice. We identify USP7 as an ACEI-activated deubiquitinating enzyme that translocated into the nucleus binding to Sp1/Sp3, which are deacetylated by HDAC1. Our findings demonstrate a central role for endothelial USP7-Sp1/Sp3-Notch1 signaling in pathophysiological angiogenesis in response to ACEI treatment.

A Self-Sustaining Antioxidant Strategy for Effective Treatment of Myocardial Infarction

Myocardial infarction (MI) is the leading cause of death worldwide and can lead to the loss of cardiac function and heart failure. Reactive oxygen species (ROS) play a key role in the pathological progression of MI. The levels and effects of ROS are significantly different in three unique pathological stages of MI, and most antioxidants cannot make corresponding adjustments to eliminate ROS, which leads to a great compromise to treat MI with antioxidants. Herein, an innovative self-sustaining antioxidant strategy is developed to treat MI with self-sustaining selenium-embedded nanoparticles (SSSe NPs). SSSe NPs possess unique self-sustaining antioxidant effects at different pathological stages of MI. This strategy of on-demand ROS elimination during different pathological stages demonstrated excellent MI treatment efficacy and effectively reversed heart failure to normal heart function. The therapeutic mechanism of SSSe NPs is intensively investigated through a series of experiments and mainly involved five critical aspects of myocardial repair: protecting mitochondria, reducing cardiomyocyte apoptosis and ferroptosis, reducing inflammation and fibrosis, and promoting angiogenesis. This strategy not only provides a promising treatment option for MI but also offers inspiration for other ischemic diseases.

Hypoxia-induced carbonic anhydrase mediated dorsal horn neuron activation and induction of neuropathic pain

ABSTRACT

Neuropathic pain, such as that seen in diabetes mellitus, results in part from central sensitisation in the dorsal horn. However, the mechanisms responsible for such sensitisation remain unclear. There is evidence that disturbances in the integrity of the spinal vascular network can be causative factors in the development of neuropathic pain. Here we show that reduced blood flow and vascularity of the dorsal horn leads to the onset of neuropathic pain. Using rodent models (type 1 diabetes and an inducible endothelial-specific vascular endothelial growth factor receptor 2 knockout mouse) that result in degeneration of the endothelium in the dorsal horn, we show that spinal cord vasculopathy results in nociceptive behavioural hypersensitivity. This also results in increased hypoxia in dorsal horn neurons, depicted by increased expression of hypoxia markers such as hypoxia inducible factor 1α, glucose transporter 3, and carbonic anhydrase 7. Furthermore, inducing hypoxia through intrathecal delivery of dimethyloxalylglycine leads to the activation of dorsal horn neurons as well as mechanical and thermal hypersensitivity. This shows that hypoxic signalling induced by reduced vascularity results in increased hypersensitivity and pain. Inhibition of carbonic anhydrase activity, through intraperitoneal injection of acetazolamide, inhibited hypoxia-induced pain behaviours. This investigation demonstrates that induction of a hypoxic microenvironment in the dorsal horn, as occurs in diabetes, is an integral process by which neurons are activated to initiate neuropathic pain states. This leads to the conjecture that reversing hypoxia by improving spinal cord microvascular blood flow could reverse or prevent neuropathic pain.

Role of Snai2 and Notch signaling in salivary gland myoepithelial cell fate

Myoepithelial (ME) cells in exocrine glands exhibit both epithelial and mesenchymal features, contributing to fluid secretion through contraction. However, the regulation mechanism of behind this unique phenotype in salivary glands remains unclear. We established a flow cytometry-based purification method using cell surface molecules, epithelial cell adhesion molecule (EpCAM) and alpha 6 integrin (CD49f), to characterize ME cells. EpCAM⁺CD49f^high cells showed relatively high expression of ME cell-marker genes, such as alpha-smooth muscle actin (α-SMA). For lineage tracing and strict isolation, tdTomato⁺EpCAM⁺CD49f^high-ME cells were obtained from myosin heavy chain 11 (Myh11) -CreER^T2/tdTomato mice. Transcriptome analysis revealed that expression of genes involved in the epithelial-mesenchymal transition, including Snai2, were upregulated in the ME cell-enriched subset. Snai2 suppression in stable ME cells decreased α-SMA and increased Krt14 expression, suggesting that ME cell features may be controlled by the epithelial-mesenchymal balance regulated by Snai2. In contrast, ME cells showed reduced ME properties and expressed the ductal markers Krt18/19 under sphere culture conditions. Notch signaling was activated under sphere culture conditions; excessive activation of Notch signaling accelerated Krt18/19 expression, but reduced α-SMA and Snai2 expression, suggesting that the behavior of Snai2-expressing ME cells may be controlled by Notch signaling.

New Insight on 2D In Vitro Angiogenesis Models: All That Stretches Is Not a Tube

Highlights

Abstract

A Matrigel-based tube formation assay is a simple and widely accepted 2D angiogenesis model in vitro. Extracellular matrix (EM) proteins and growth factors (GFs) from Matrigel^TM exclusively trigger endothelial cell (EC) tubular network (ETN) formation. Co-culture of ECs with mesenchymal stromal cells (MSCs) is another and more reliable in vitro angiogenesis assay. MSCs modulate ETN formation through intercellular interactions and as a supplier of EM and GFs. The aim of the present study was to compare the expression profile of ECs in both models. We revealed upregulation of the uPA, uPAR, Jagged1, and Notch2 genes in dividing/migrating ECs and for ECs in both experimental models at 19 h. The expression of endothelial–mesenchymal transition genes largely increased in co-cultured ECs whereas Notch and Hippo signaling pathway genes were upregulated in ECs on Matrigel^TM. We showed that in the co-culture model, basement membrane (BM) deposition is limited only to cell-to-cell contacts in contrast to Matrigel^TM, which represents by itself fully pre-assembled BM matrix. We suggest that ETN in a co-culture model is still in a dynamic process due to immature BM whereas ECs in the Matrigel^TM assay seem to be at the final stage of ETN formation.

Neuroinflammatory disease disrupts the blood-CNS barrier via crosstalk between proinflammatory and endothelial-to-mesenchymal-transition signaling

Breakdown of the blood-central nervous system barrier (BCNSB) is a hallmark of many neuroinflammatory disorders, such as multiple sclerosis (MS). Using a mouse model of MS, experimental autoimmune encephalomyelitis (EAE), we show that endothelial-to-mesenchymal transition (EndoMT) occurs in the CNS before the onset of clinical symptoms and plays a major role in the breakdown of BCNSB function. EndoMT can be induced by an IL-1β-stimulated signaling pathway in which activation of the small GTPase ADP ribosylation factor 6 (ARF6) leads to crosstalk with the activin receptor-like kinase (ALK)-SMAD1/5 pathway. Inhibiting the activation of ARF6 both prevents and reverses EndoMT, stabilizes BCNSB function, reduces demyelination, and attenuates symptoms even after the establishment of severe EAE, without immunocompromising the host. Pan-inhibition of ALKs also reduces disease severity in the EAE model. Therefore, multiple components of the IL-1β-ARF6-ALK-SMAD1/5 pathway could be targeted for the treatment of a variety of neuroinflammatory disorders.

Clinical disease course and survival outcomes following disease recurrence in adenoid cystic carcinoma with and without NOTCH signaling pathway activation

BACKGROUND

Adenoid cystic carcinoma (ACC) is a rare salivary cancer. The highest rates of disease recurrence are in patients with NOTCH pathway activation, reported in up to 20%. Novel drugs targeting NOTCH signaling are under investigation in the recurrent/metastatic (R/M) setting. To understand their clinical utility, there is an urgent need to better characterize the disease course and outcomes following current standard of care treatment.

METHODS

120 patients with R/M ACC underwent clinical review at a single UK Cancer Centre. Patients were retrospectively assessed for tumor NOTCH pathway activation using next generation sequencing (NGS) targeting NOTCH1/2/3 genes and/or NOTCH1 intra-cellular domain (NICD1) immunohistochemistry. Demographic and treatment data were extracted from the clinical notes. Kaplan-Meier survival analysis was performed using log rank test.

RESULTS

NOTCH pathway activation was identified in 13/120 patients (11 %). In 12/101 patients analyzed by NGS, NOTCH1/3 activating somatic mutations were identified, and a further patient was identified with NICD1 diffuse nuclear staining in whom NGS testing was not possible. Patients with NOTCH pathway activation had shorter median RFS (1.1 vs 3.4 years, p = 0.2032) and significantly reduced median OS from diagnosis (4.0 vs 16.3 years, p < 0.0001). There was significantly reduced median OS from time of disease recurrence/metastasis (1.9 vs 9.6 years, p < 0.0001).

CONCLUSION

This study clearly demonstrates a reduction in OS from time of first confirmed disease recurrence/metastasis for patients with NOTCH pathway activated ACC. This provides support for developing new drugs for this sub-group of patients, for whom clinical outcomes are significantly worse and effective treatments are lacking.

Integrated analysis of Helicobacter pylori-related prognostic gene modification patterns in the tumour microenvironment of gastric cancer

Background

Helicobacter pylori (HP) infection is one of the leading causes of gastric cancer (GC). However, the interaction between HP and the TME, and its carcinogenic mechanism remains unknown.

Methods

The HP-related prognostic genes were identified based on HP infection-related gene markers and HP infection sample datasets by risk method and NMF algorithm. Principal component analysis (PCA) algorithm was used to constructed the HPscore system. The “limma” R package was employed to determine differentially expressed genes. In addition, the R packages, such as “xCell” and “GSVA”, was used to analyze the relationship between the HPscore and tumor microenvironment. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to verify the expression levels of 28 HP-related prognostic genes in tissues.

Results

We successfully identified 28 HP-related prognostic genes that accurately classified the GC population. There are significant differences in survival between different subgroups (high-, low-risk and cluster_1,2). Thereafter, the HPscore system was constructed to evaluate the signatures of the 28 HP-related prognostic genes. The overall survival rate in the high-HPscore group was poor and immunological surveillance was reduced, whereas the low-HPscore group had a survival advantage and was related to the inflammatory response. HPscore was also strongly correlated with the tumour stage, TME cell infiltration and stemness. The qRT-PCR results showed that DOCK4 expression level of 28 HP-related prognostic genes was higher in gastric cancer tissues than in adjacent tissues.

Conclusions

HP signatures play a crucial role in the TME and tumourigenesis. HPscore evaluation of a single tumour sample can help identify the TME characteristics and the carcinogenic mechanism of GC patients infected with HP, based on which personalized treatment can be administered.

The Notch Signaling Pathway Contributes to Angiogenesis and Tumor Immunity in Breast Cancer

Breast cancer in women is the first leading tumor in terms of incidence worldwide. Some subtypes of BC lack distinct molecular targets and exhibit therapeutic resistance; these patients have a poor prognosis. Thus, the search for new molecular targets is an ongoing challenge for BC therapy. The Notch signaling pathway is found in both vertebrates and invertebrates, and it is a highly conserved in the evolution of the species, controlling cellular fates such as death, proliferation, and differentiation. Numerous studies have shown that improper activation of Notch signaling may lead to excessive cell proliferation and cancer, with tumor-promoting and tumor-suppressive effects in various carcinomas. Thus, inhibitors of Notch signaling are actively being investigated for the treatment of various tumors. The role of Notch signaling in BC has been widely studied in recent years. There is a growing body of evidence suggesting that Notch signaling has a pro-oncogenic role in BC, and the tumor-promoting effect is largely a result of the diverse nature of tumor immunity. Immunological abnormality is also a factor involved in the pathogenesis of BC, suggesting that Notch signaling could be a target for BC immunotherapies. Furthermore, angiogenesis is essential for BC growth and metastasis, and the Notch signaling pathway has been implicated in angiogenesis, so studying the role of Notch signaling in BC angiogenesis will provide new prospects for the treatment of BC. We summarize the potential roles of the current Notch signaling pathway and its inhibitors in BC angiogenesis and the immune response in this review and describe the pharmacological targets of Notch signaling in BC, which may serve as a theoretical foundation for future research into exploring this pathway for novel BC therapies.

A phenotypic rescue approach identifies lineage regionalization defects in a mouse model of DiGeorge syndrome

TBX1 is a key regulator of pharyngeal apparatus (PhAp) development. Vitamin B12 (vB12) treatment partially rescues aortic arch patterning defects of Tbx1^+/− embryos. Here, we show that it also improves cardiac outflow tract septation and branchiomeric muscle anomalies of Tbx1 hypomorphic mutants. At the molecular level, in vivo vB12 treatment enabled us to identify genes that were dysregulated by Tbx1 haploinsufficiency and rescued by treatment. We found that SNAI2, also known as SLUG, encoded by the rescued gene Snai2, identified a population of mesodermal cells that was partially overlapping with, but distinct from, ISL1⁺ and TBX1⁺ populations. In addition, SNAI2⁺ cells were mislocalized and had a greater tendency to aggregate in Tbx1^+/− and Tbx1^−/− embryos, and vB12 treatment restored cellular distribution. Adjacent neural crest-derived mesenchymal cells, which do not express TBX1, were also affected, showing enhanced segregation from cardiopharyngeal mesodermal cells. We propose that TBX1 regulates cell distribution in the core mesoderm and the arrangement of multiple lineages within the PhAp.

The regulation of yes-associated protein/transcriptional coactivator with PDZ-binding motif and their roles in vascular endothelium

Normal endothelial function plays a pivotal role in maintaining cardiovascular homeostasis, while endothelial dysfunction causes the occurrence and development of cardiovascular diseases. Yes-associated protein (YAP) and its homolog transcriptional co-activator with PDZ-binding motif (TAZ) serve as crucial nuclear effectors in the Hippo signaling pathway, which are regulated by mechanical stress, extracellular matrix stiffness, drugs, and other factors. Increasing evidence supports that YAP/TAZ play an important role in the regulation of endothelial-related functions, including oxidative stress, inflammation, and angiogenesis. Herein, we systematically review the factors affecting YAP/TAZ, downstream target genes regulated by YAP/TAZ and the roles of YAP/TAZ in regulating endothelial functions, in order to provide novel potential targets and effective approaches to prevent and treat cardiovascular diseases.

[JAG1 promotes migration, invasion, and adhesion of triple-negative breast cancer cells by promoting angiogenesis]

OBJECTIVE

To investigate the effect of JAG1 on the malignant phenotype of triple-negative breast cancer (TNBC) and its role in angiogenesis in breast cancer microenvironment.

METHODS

The expressions of Notch molecules were detected in human TNBC 231 and 231B cells using RT-qPCR. Five female nude mice were inoculated with 231 cells and another 5 with 231B cells into the mammary fat pads, and 4-6 weeks later, the tumors were collected for immunohistochemical and immunofluorescence tests. 231 cells and 231B cells were treated with recombinant JAG (rJAG) protein and DAPT, respectively, and changes in their malignant phenotypes were assessed using CCK-8 assay, Hoechst 33258 staining, wound healing assay, Transwell chamber assay and endothelial cell adhesion assay. Western blotting was used to detect the changes in the expressions of proteins related with the malignant phenotypes of 231 and 231B cells. The effects of conditioned medium (CM) derived from untreated 231 and 231 B cells, rJAG1-treated 231 cells and DAPT-treated 231B cells on proliferation and tube formation ability of cultured human umbilical vein endothelial cells (HUVECs) were evaluated using CCK-8 assay and tube-forming assay.

RESULTS

The expression of JAG1 was higher in 231B cells than in 231 cells (P < 0.05). Tumor 231B showed higher expression of VEGFA and CD31. Compared with 231-Blank group, the migration, invasion and adhesion of 231 cells in 231-rJAG1 were significantly enhanced (P < 0.05). Protein levels of Twist1 and Snail increased (P < 0.01), anti-apoptotic protein Bcl-2 increased (P < 0.05), while DAPT inhibited the related phenomena and indicators of 231B. The 231-rJAG1-CM increased the cell number and tubule number of HUVEC (P < 0.05).

CONCLUSION

JAG1 may affect the malignant phenotype of TNBC and promote angiogenesis in the tumor microenvironment.

ERK5 Is a Major Determinant of Chemical Sarcomagenesis: Implications in Human Pathology

Simple Summary

Sarcoma is a heterogeneous group of tumors poorly studied with few therapeutic opportunities. Interestingly, the role of MAPKs still remains unclear in sarcomatous pathology. Here, we describe for the first time the critical role of ERK5 in the biology of soft tissue sarcoma by using in vitro and in vivo approaches in a murine experimental model of chemical sarcomagenesis. Indeed, our observations were extrapolated to a short series of human leiomyosarcoma and rhabdomyosarcomas. Furthermore, transcriptome analysis allows us to demonstrate the critical role of KLF2 in the biological effects of ERK5. Therefore, the data presented here open new windows in the diagnosis and therapy of soft tissue sarcomas.

Abstract

Sarcomas are a heterogeneous group of tumors in which the role of ERK5 is poorly studied. To clarify the role of this MAPK in sarcomatous pathology, we used a murine 3-methyl-cholanthrene (3MC)-induced sarcoma model. Our data show that 3MC induces pleomorphic sarcomas with muscle differentiation, showing an increased expression of ERK5. Indeed, this upregulation was also observed in human sarcomas of muscular origin, such as leiomyosarcoma or rhabdomyosarcoma. Moreover, in cell lines derived from these 3MC-induced tumors, abrogation of Mapk7 expression by using specific shRNAs decreased in vitro growth and colony-forming capacity and led to a marked loss of tumor growth in vivo. In fact, transcriptomic profiling in ERK5 abrogated cell lines by RNAseq showed a deregulated gene expression pattern for key biological processes such as angiogenesis, migration, motility, etc., correlating with a better prognostic in human pathology. Finally, among the various differentially expressed genes, Klf2 is a key mediator of the biological effects of ERK5 as indicated by its specific interference, demonstrating that the ERK5–KLF2 axis is an important determinant of sarcoma biology that should be further studied in human pathology.

Danhong injection combined with tPA protects the BBB through Notch-VEGF signaling pathway on long-term outcomes of thrombolytic therapy

Current therapy for ischemic stroke primarily relies on tissue plasminogen activator (tPA), but it is limited by narrow treatment time window, bleeding complications and neurotoxicity. The preliminary study of tPA plus Danhong injection (DHI) shows that it can significantly reduce the side effects of tPA and improve its thrombolytic effect, but the mechanism of this action has not been further studied. In this study, the rats were randomly divided into sham group, vehicle group, DHI group (4 mL/kg), tPA group (5 mg/kg) and DHI+tPA group (4 mL/kg+ 2.5 mg/kg), administered intravenously 4.5 h since focal embolic stroke modeling. After 3 days and 7 days of cerebral ischemia, the neurological function of each treatment group was significantly improved compared with the vehicle group. The combination of DHI and tPA significantly reduced Evans blue (EB) penetration as well as the expressions of the proteins MMP-9, PAI-1 and P-selectin, while upregulating the expressions of claudin-5, occludin, and ZO-1 mRNA. Furthermore, the effect of continuous 7-day treatment was more conspicuous than 3-day treatment. Then, it significantly reduced the expressions of the proteins DLL-4 and VEGFR-2, increased the expressions of Notch-1, HIF-1α and HES-1 mRNA, and promoted the expressions of VEGF/HIF-1α-positive cells at 14 days following stroke. Hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM) also showed that it improved pathological changes of ischemic brain tissue and the cerebral cortex micro-structure. These indicate that DHI combined with tPA may significantly ameliorate blood-brain barrier (BBB) disruption by activating Notch-VEGF signaling pathway to promote angiogenesis for long-term outcomes.

[Effects of transient receptor potential vanilloid type 4-specific activator on human vascular endothelial cell functions and blood supply of rat perforator flap and its mechanism]

Objective: To analyze the effects of transient receptor potential vanilloid type 4 (TRPV4) activation on the function and endothelial-to-mesenchymal transition (EndMT) of human umbilical vein endothelial cells (HUVECs), as well as to explore the effects of TRPV4 activation on blood perfusion and survival of rat perforator flap and the mechanism. Methods: The experimental research methods were used. The 3rd to 6th passages of HUVECs were used for experiments and divided into 0.5 μmol/L 4α-phorbol 12, 13-didecanoate (4αPDD) group, 1.0 μmol/L 4αPDD group, 3.0 μmol/L 4αPDD group, 10.0 μmol/L 4αPDD group, and phosphate buffer solution (PBS) group, which were cultivated in corresponding final molarity of 4αPDD and PBS, respectively. The cell proliferation activity at 6 and 12 h of culture was detected using cell counting kit-8 (CCK-8). Another batch of cells was acquired and divided into PBS group, 1 μmol/L 4αPDD group, and 3 μmol/L 4αPDD group, which were treated similarly as described before and then detected for cell proliferation activity at 6, 12, 24, and 48 h of culture. The residual scratch area of cells at post scratch hour (PSH) 12, 24, and 48 was detected by scratch test, and the percentage of the residual scratch area was calculated. The number of migrated cells at 24 and 48 h of culture was detected by Transwell experiment. The tube-formation assay was used to measure the number of tubular structures at 4 and 8 h of culture. The protein expressions of E-cadherin, N-cadherin, Slug, and Snail at 24 h of culture were detected by Western blotting. All the sample numbers in each group at each time point in vitro experiments were 3. A total of 36 male Sprague-Dawley rats aged 8 to 10 weeks were divided into delayed flap group, 4αPDD group, and normal saline group according to the random number table, with 12 rats in each group, and iliolumbar artery perforator flap models on the back were constructed. The flap surgical delay procedure was only performed in the rats in delayed flap group one week before the flap transfer surgery. Neither rats in 4αPDD group nor normal saline group had flap surgical delay; instead, they were intraperitoneally injected with 4αPDD and an equivalent mass of normal saline, respectively, at 10 min before, 24 h after, and 48 h after the surgery. The general state of flap was observed on post surgery day (PSD) 0 (immediately), 1, 4, and 7. The flap survival rates were assessed on PSD 7. The flap blood perfusion was detected by laser speckle contrast imaging technique on PSD 1, 4, and 7. The microvascular density in the flap's choke vessel zone was detected by immunohistochemical staining. All the sample numbers in each group at each time point in vivo experiments were 12. Data were statistically analyzed with analysis of variance for factorial design, analysis of variance for repeated measurement, one-way analysis of variance, least significant difference t test, and Bonferroni correction. Results: At 6 and 12 h of culture, there were no statistically significant differences in cell proliferation activity in the overall comparison among PBS group, 0.5 μmol/L 4αPDD group, 1.0 μmol/L 4αPDD group, 3.0 μmol/L 4αPDD group, and 10.0 μmol/L 4αPDD group (P>0.05). At 6, 12, 24, and 48 h of culture, there were no statistically significant differences in cell proliferation activity in the overall comparison among PBS group, 1 μmol/L 4αPDD group, and 3 μmol/L 4αPDD group (P>0.05). At PSH 12, the percentages of the residual scratch area of cells in 1 μmol/L 4αPDD group and 3 μmol/L 4αPDD group were close to that in PBS group (P>0.05). At PSH 24 and 48, compared with those in PBS group, the percentages of the residual scratch area of cells in 3 μmol/L 4αPDD group were significantly decreased (with t values of 2.83 and 2.79, respectively, P<0.05), while the percentages of the residual scratch area of cells in 1 μmol/L 4αPDD group showed no significant differences (P>0.05). At 24 h of culture, the number of migrated cells in 1 μmol/L 4αPDD group and 3 μmol/L 4αPDD group were close to that in PBS group (P>0.05). At 48 h of culture, the number of migrated cells in 1 μmol/L 4αPDD group and 3 μmol/L 4αPDD groups were significantly greater than that in PBS group (with t values of 6.20 and 9.59, respectively, P<0.01). At 4 h of culture, the numbers of tubular structures of cells in 1 μmol/L 4αPDD group and 3 μmol/L 4αPDD group were significantly greater than that in PBS group (with t values of 4.68 and 4.95, respectively, P<0.05 or <0.01). At 8 h of culture, the numbers of tubular structures of cells in 1 μmol/L 4αPDD and 3 μmol/L 4αPDD groups were similar to that in PBS group (P>0.05). At 24 h of culture, compared with those in PBS group, the protein expression level of E-cadherin of cells in 3 μmol/L 4αPDD group was significantly decreased (t=5.13, P<0.01), whereas there was no statistically significant difference in the protein expression level of E-cadherin of cells in 1 μmol/L 4αPDD group (P>0.05); the protein expression level of N-cadherin of cells in 3 μmol/L 4αPDD group was significantly increased (t=4.93, P<0.01), whereas there was no statistically significant difference in the protein expression level of N-cadherin of cells in 1 μmol/L 4αPDD group (P>0.05); the protein expression levels of Slug of cells in 1 μmol/L 4αPDD group and 3 μmol/L 4αPDD group were significantly increased (with t values of 3.85 and 6.52, respectively, P<0.05 or P<0.01); and the protein expression level of Snail of cells in 3 μmol/L 4αPDD group was significantly increased (t=4.08, P<0.05), whereas there was no statistically significant difference in the protein expression level of Snail of cells in 1 μmol/L 4αPDD group (P>0.05). There were no statistically significant differences in the protein expression levels of E-cadherin, N-cadherin, Slug, or Snail of cells between 1 μmol/L 4αPDD group and 3 μmol/L 4αPDD group (P>0.05). The general condition of flaps of rats in the three groups was good on PSD 0. On PSD 1, the flaps of rats in the three groups were basically similar, with bruising and swelling at the distal end. On PSD 4, the swelling of flaps of rats in the three groups subsided, and the distal end turned dark brown and necrosis occurred, with the area of necrosis in flaps of rats in normal saline group being larger than the areas in 4αPDD group and delayed flap group. On PSD 7, the necrotic areas of flaps of rats in the 3 groups were fairly stable, with the area of necrosis at the distal end of flap of rats in delayed flap group being the smallest. On PSD 7, the flap survival rates of rats in 4αPDD group ((80±13)%) and delayed flap group ((87±9)%) were similar (P>0.05), and both were significantly higher than (70±11)% in normal saline group (with t values of 2.24 and 3.65, respectively, P<0.05 or P<0.01). On PSD 1, the overall blood perfusion signals of rats in the 3 groups were basically the same, and the blood perfusion signals in the choke vessel zone were relatively strong, with a certain degree of underperfusion at the distal end. On PSD 4, the boundary between the surviving and necrotic areas of flaps of rats in the 3 groups became evident, and the blood perfusion signals in the choke vessel zone were improved, with the normal saline group's distal hypoperfused area of flap being larger than the areas in delayed flap group and 4αPDD group. On PSD 7, the blood perfusion signals of overall flap of rats had generally stabilized in the 3 groups, with the intensity of blood perfusion signal in the choke vessel zone and overall flap of rats in delayed flap group and 4αPDD group being significantly greater than that in normal saline group. On PSD 7, the microvascular density in the choke vessel zone of flap of rats in 4αPDD group and delayed flap group were similar (P>0.05), and both were significantly higher than that in normal saline group (with t values of 4.11 and 5.38, respectively, P<0.01). Conclusions: After activation, TRPV4 may promote the migration and tubular formation of human vascular endothelial cells via the EndMT pathway, leading to the enhanced blood perfusion of perforator flap and microvascular density in the choke vessel zone, and therefore increase the flap survival rate.