Angiocrine functions of organ-specific endothelial cells

A streamlined method to generate endothelial cells from human pluripotent stem cells via transient doxycycline-inducible ETV2 activation

The development of reliable methods for producing functional endothelial cells (ECs) is crucial for progress in vascular biology and regenerative medicine. In this study, we present a streamlined and efficient methodology for the differentiation of human induced pluripotent stem cells (iPSCs) into induced ECs (iECs) that maintain the ability to undergo vasculogenesis in vitro and in vivo using a doxycycline-inducible system for the transient expression of the ETV2 transcription factor. This approach mitigates the limitations of direct transfection methods, such as mRNA-mediated differentiation, by simplifying the protocol and enhancing reproducibility across different stem cell lines. We detail the generation of iPSCs engineered for doxycycline-induced ETV2 expression and their subsequent differentiation into iECs, achieving over 90% efficiency within four days. Through both in vitro and in vivo assays, the functionality and phenotypic stability of the derived iECs were rigorously validated. Notably, these cells exhibit key endothelial markers and capabilities, including the formation of vascular networks in a microphysiological platform in vitro and in a subcutaneous mouse model. Furthermore, our results reveal a close transcriptional and proteomic alignment between the iECs generated via our method and primary ECs, confirming the biological relevance of the differentiated cells. The high efficiency and effectiveness of our induction methodology pave the way for broader application and accessibility of iPSC-derived ECs in scientific research, offering a valuable tool for investigating endothelial biology and for the development of EC-based therapies.

Exposure to acifluorfen induces developmental toxicity in the early life stage of zebrafish

Acifluorfen, a selective herbicide from the diphenyl ether family, targets broad leaf weeds. Diphenyl ether inhibits chlorophyll production in green plants by inhibiting protoporphyrinogen oxidase (PPO), causing cellular damage. Despite its known impacts on plants, the influence of acifluorfen on zebrafish embryo development remains unclear. In this study, we explored the LC50 of acifluorfen in early-stage wild-type zebrafish, determining it to be 54.99 mg/L. Subsequent examinations revealed morphological changes in zebrafish, including reduced body length. Using the cmlc2:dsRED transgenic model, we observed heart dysfunction in acifluorfen-exposed zebrafish, marked by an enlarged heart area, edema, and decreased heart rate. In response to dose-dependent acifluorfen exposure, the inhibition of angiogenesis in the brain was observed in transgenic zebrafish models (fli1a:eGFP). Organ malformations, specifically in the liver and pancreas, were noted, in lfabp:dsRED;elastase:eGFP transgenic models, indicating reduced organ size in acifluorfen-exposed zebrafish. Furthermore, acifluorfen heightened the expression of apoptosis-related genes (casp8, casp9, and tp53) in zebrafish embryos. We then determined whether acifluorfen affected the viability of zebrafish liver (ZFL) cells based on its effects on liver development in vivo. The results indicated that the proliferation of ZFL cells decreased significantly in a dose-dependent manner. Additionally, acifluorfen-treated ZFL cells exhibited a slight increase in apoptotic cells stained with annexin V and propidium iodide. In summary, these findings establish a baseline concentration for acifluorfen's effects on aquatic ecosystems and non-target organisms.

Role of liver sinusoidal endothelial cell in metabolic dysfunction-associated fatty liver disease

Liver sinusoidal endothelial cells (LSECs) are highly specialized endothelial cells that represent the interface between blood cells on one side and hepatocytes on the other side. LSECs not only form a barrier within the hepatic sinus, but also play important physiological functions such as regulating hepatic vascular pressure, anti-inflammatory and anti-fibrotic. Pathologically, pathogenic factors can induce LSECs capillarization, that is, loss of fenestra and dysfunction, which are conducive to early steatosis, lay the foundation for the progression of metabolic dysfunction-associated fatty liver disease (MAFLD), and accelerate metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. The unique localization, phenotype, and function of LSECs make them potential candidates for reducing liver injury, inflammation, and preventing or reversing fibrosis in the future.

A genetically inducible endothelial niche enables vascularization of human kidney organoids with multilineage maturation and emergence of renin expressing cells

Vascularization plays a critical role in organ maturation and cell type development. Drug discovery, organ mimicry, and ultimately transplantation hinge on achieving robust vascularization of in vitro engineered organs. Here, focusing on human kidney organoids, we overcame this hurdle by combining a human induced pluripotent stem cell (iPSC) line containing an inducible ETS translocation variant 2 (ETV2) (a transcription factor playing a role in endothelial cell development) that directs endothelial differentiation in vitro, with a non-transgenic iPSC line in suspension organoid culture. The resulting human kidney organoids show extensive endothelialization with a cellular identity most closely related to human kidney endothelia. Endothelialized kidney organoids also show increased maturation of nephron structures, an associated fenestrated endothelium with de novo formation of glomerular and venous subtypes, and the emergence of drug-responsive renin expressing cells. The creation of an engineered vascular niche capable of improving kidney organoid maturation and cell type complexity is a significant step forward in the path to clinical translation. Thus, incorporation of an engineered endothelial niche into a previously published kidney organoid protocol allowed the orthogonal differentiation of endothelial and parenchymal cell types, demonstrating the potential for applicability to other basic and translational organoid studies.

Processing of angiocrine alarmin IL-1α in endothelial cells promotes lung and liver fibrosis

BACKGROUND

Fibrosis results from excessive scar formation after tissue injury. Injured cells release alarmins such as interleukin 1 (IL-1) α and β as primary mediators initiating tissue repair. However, how alarmins from different cell types differentially regulate fibrosis remains to be explored.

METHODS

Here, we used tissue specific knockout strategy to illustrate a unique contribution of endothelial cell-derived IL-1α to lung and liver fibrosis. The two fibrotic animal model triggered by bleomycin and CCl4 were used to study the effects of endothelial paracrine/angiocrine IL-1α in fibrotic progression. Human umbilical vein endothelial cells (HUVEC) were performed to explore the production of angiocrine IL-1α at both transcriptional and post-transcriptional levels in vitro.

RESULTS

We found that endothelial paracrine/angiocrine IL-1α primarily promotes lung and liver fibrosis during the early phase of organ repair. By contrast, myeloid cell-specific ablation of IL-1α in mice resulted in little influence on fibrosis, suggesting the specific pro-fibrotic role of IL-1α from endothelial cell but not macrophage. In vitro study revealed a coordinated regulation of IL-1α production in human primary endothelial cells at both transcriptional and post-transcriptional levels. Specifically, the transcription of IL-1α is regulated by RIPK1, and after caspase-8 (CASP8) cleaves the precursor form of IL-1α, its secretion is triggered by ion channel Pannexin 1 upon CASP8 cleavage.

CONCLUSIONS

Endothelial cell-produced IL-1α plays a unique role in promoting organ fibrosis. Furthermore, the release of this angiocrine alarmin relies on a unique molecular mechanism involving RIPK1, CASP8, and ion channel Pannexin 1.

S1PR3 inhibition protects against LPS-induced ARDS by inhibiting NF-κB and improving mitochondrial oxidative phosphorylation

BACKGROUND

Inflammation and endothelial barrier dysfunction are the major pathophysiological changes in acute respiratory distress syndrome (ARDS). Sphingosine-1-phosphate receptor 3 (S1PR3), a G protein-coupled receptor, has been found to mediate inflammation and endothelial cell (EC) integrity. However, the function of S1PR3 in ARDS has not been fully elucidated.

METHODS

We used a murine lipopolysaccharide (LPS)-induced ARDS model and an LPS- stimulated ECs model to investigate the role of S1PR3 in anti-inflammatory effects and endothelial barrier protection during ARDS.

RESULTS

We found that S1PR3 expression was increased in the lung tissues of mice with LPS-induced ARDS. TY-52156, a selective S1PR3 inhibitor, effectively attenuated LPS-induced inflammation by suppressing the expression of proinflammatory cytokines and restored the endothelial barrier by repairing adherens junctions and reducing vascular leakage. S1PR3 inhibition was achieved by an adeno-associated virus in vivo and a small interfering RNA in vitro. Both the in vivo and in vitro studies demonstrated that pharmacological or genetic inhibition of S1PR3 protected against ARDS by inhibiting the NF-κB pathway and improving mitochondrial oxidative phosphorylation.

CONCLUSIONS

S1PR3 inhibition protects against LPS-induced ARDS via suppression of pulmonary inflammation and promotion of the endothelial barrier by inhibiting NF-κB and improving mitochondrial oxidative phosphorylation, indicating that S1PR3 is a potential therapeutic target for ARDS.

Effects of senescence on the tumour microenvironment and response to therapy

Cellular senescence is a state of durable cell arrest that has been identified both in vitro and in vivo. It is associated with profound changes in gene expression and a specific secretory profile that includes pro-inflammatory cytokines, growth factors and matrix-remodelling enzymes, referred to as the senescence-associated secretory phenotype (SASP). In cancer, senescence can have anti- or pro-tumour effects. On one hand, it can inhibit tumour progression in a cell autonomous manner. On the other hand, senescence can also promote tumour initiation, progression, metastatic dissemination and resistance to therapy in a paracrine manner. Therefore, despite efforts to target senescence as a potential strategy to inhibit tumour growth, senescent cancer and microenvironmental cells can eventually lead to uncontrolled proliferation and aggressive tumour phenotypes. This can happen either through overcoming senescence growth arrest or through SASP-mediated effects in adjacent tumour cells. This review will discuss how senescence affects the tumour microenvironment, including extracellular matrix remodelling, the immune system and the vascular compartment, to promote tumourigenesis, metastasis and resistance to DNA-damaging therapies. It will also discuss current approaches used in the field to target senescence: senolytics, improving the immune clearance of senescent cells and targeting the SASP.

Understanding the Role of Endothelial Cells in Glioblastoma: Mechanisms and Novel Treatments

Glioblastoma is a highly aggressive neoplasm and the most common primary malignant brain tumor. Endothelial tissue plays a critical role in glioblastoma growth and progression, facilitating angiogenesis, cellular communication, and tumorigenesis. In this review, we present an up-to-date and comprehensive summary of the role of endothelial cells in glioblastomas, along with an overview of recent developments in glioblastoma therapies and tumor endothelial marker identification.

The pioneer transcription factor Zelda facilitates the exit from regeneration and restoration of patterning in Drosophila

For a damaged tissue to regenerate, the injured site must repair the wound, proliferate, and restore the correct patterning and cell types. We found that Zelda, a pioneer transcription factor largely known for its role in embryonic zygotic genome activation, is dispensable for normal wing development but crucial for wing disc patterning during regeneration. Impairing Zelda function during disc regeneration resulted in adult wings with a plethora of cell fate errors, affecting the veins, margins, and posterior compartment identity. Using CUT&RUN, we identified and validated targets of Zelda including the cell fate genes cut, Delta and achaete, which failed to return to their normal expression patterns upon loss of Zelda. In addition, Zelda controls expression of factors previously established to preserve cell fate during regeneration like taranis and osa, which stabilizes engrailed expression during regeneration, thereby preserving posterior identity. Finally, Zelda ensures proper expression of the integrins encoded by multiple edematous wings and myospheroid during regeneration to prevent blisters in the resuting adult wing. Thus, Zelda is crucial for maintaining cell fate and structural architecture of the regenerating tissue.

FGD5 in basal cells induces CXCL14 secretion that initiates a feedback loop to promote murine mammary epithelial growth and differentiation

The interactions of environmental compartments with epithelial cells are essential for mammary gland development and homeostasis. Currently, the direct crosstalk between the endothelial niche and mammary epithelial cells remains poorly understood. Here, we show that faciogenital dysplasia 5 (FGD5) is enriched in mammary basal cells (BCs) and mediates critical interactions between basal and endothelial cells (ECs) in the mammary gland. Conditional deletion of Fgd5 reduced, whereas conditional knockin of Fgd5 increased, the engraftment and expansion of BCs, regulating ductal morphogenesis in the mammary gland. Mechanistically, murine mammary BC-expressed FGD5 inhibited the transcriptional activity of activating transcription factor 3 (ATF3), leading to subsequent transcriptional activation and secretion of CXCL14. Furthermore, activation of CXCL14/CXCR4/ERK signaling in primary murine mammary stromal ECs enhanced the expression of HIF-1α-regulated hedgehog ligands, which initiated a positive feedback loop to promote the function of BCs. Collectively, these findings identify functionally important interactions between BCs and the endothelial niche that occur through the FGD5/CXCL14/hedgehog axis.

Advances in ex vivo expansion of hematopoietic stem and progenitor cells for clinical applications

As caretakers of the hematopoietic system, hematopoietic stem cells assure a lifelong supply of differentiated populations that are responsible for critical bodily functions, including oxygen transport, immunological protection and coagulation. Due to the far-reaching influence of the hematopoietic system, hematological disorders typically have a significant impact on the lives of individuals, even becoming fatal. Hematopoietic cell transplantation was the first effective therapeutic avenue to treat such hematological diseases. Since then, key use and manipulation of hematopoietic stem cells for treatments has been aspired to fully take advantage of such an important cell population. Limited knowledge on hematopoietic stem cell behavior has motivated in-depth research into their biology. Efforts were able to uncover their native environment and characteristics during development and adult stages. Several signaling pathways at a cellular level have been mapped, providing insight into their machinery. Important dynamics of hematopoietic stem cell maintenance were begun to be understood with improved comprehension of their metabolism and progressive aging. These advances have provided a solid platform for the development of innovative strategies for the manipulation of hematopoietic stem cells. Specifically, expansion of the hematopoietic stem cell pool has triggered immense interest, gaining momentum. A wide range of approaches have sprouted, leading to a variety of expansion systems, from simpler small molecule-based strategies to complex biomimetic scaffolds. The recent approval of Omisirge, the first expanded hematopoietic stem and progenitor cell product, whose expansion platform is one of the earliest, is predictive of further successes that might arise soon. In order to guarantee the quality of these ex vivo manipulated cells, robust assays that measure cell function or potency need to be developed. Whether targeting hematopoietic engraftment, immunological differentiation potential or malignancy clearance, hematopoietic stem cells and their derivatives need efficient scaling of their therapeutic potency. In this review, we comprehensively view hematopoietic stem cells as therapeutic assets, going from fundamental to translational.

Vascular endothelial-derived SPARCL1 exacerbates viral pneumonia through pro-inflammatory macrophage activation

Inflammation induced by lung infection is a double-edged sword, moderating both anti-viral and immune pathogenesis effects; the mechanism of the latter is not fully understood. Previous studies suggest the vasculature is involved in tissue injury. Here, we report that expression of Sparcl1, a secreted matricellular protein, is upregulated in pulmonary capillary endothelial cells (EC) during influenza-induced lung injury. Endothelial overexpression of SPARCL1 promotes detrimental lung inflammation, with SPARCL1 inducing 'M1-like' macrophages and related pro-inflammatory cytokines, while SPARCL1 deletion alleviates these effects. Mechanistically, SPARCL1 functions through TLR4 on macrophages in vitro, while TLR4 inhibition in vivo ameliorates excessive inflammation caused by endothelial Sparcl1 overexpression. Finally, SPARCL1 expression is increased in lung ECs from COVID-19 patients when compared with healthy donors, while fatal COVID-19 correlates with higher circulating SPARCL1 protein levels in the plasma. Our results thus implicate SPARCL1 as a potential prognosis biomarker for deadly COVID-19 pneumonia and as a therapeutic target for taming hyperinflammation in pneumonia.

Shear stress and pathophysiological PI3K involvement in vascular malformations

Molecular characterization of vascular anomalies has revealed that affected endothelial cells (ECs) harbor gain-of-function (GOF) mutations in the gene encoding the catalytic α subunit of PI3Kα (PIK3CA). These PIK3CA mutations are known to cause solid cancers when occurring in other tissues. PIK3CA-related vascular anomalies, or "PIKopathies," range from simple, i.e., restricted to a particular form of malformation, to complex, i.e., presenting with a range of hyperplasia phenotypes, including the PIK3CA-related overgrowth spectrum. Interestingly, development of PIKopathies is affected by fluid shear stress (FSS), a physiological stimulus caused by blood or lymph flow. These findings implicate PI3K in mediating physiological EC responses to FSS conditions characteristic of lymphatic and capillary vessel beds. Consistent with this hypothesis, increased PI3K signaling also contributes to cerebral cavernous malformations, a vascular disorder that affects low-perfused brain venous capillaries. Because the GOF activity of PI3K and its signaling partners are excellent drug targets, understanding PIK3CA's role in the development of vascular anomalies may inform therapeutic strategies to normalize EC responses in the diseased state. This Review focuses on PIK3CA's role in mediating EC responses to FSS and discusses current understanding of PIK3CA dysregulation in a range of vascular anomalies that particularly affect low-perfused regions of the vasculature. We also discuss recent surprising findings linking increased PI3K signaling to fast-flow arteriovenous malformations in hereditary hemorrhagic telangiectasias.

Buffering Mechanism in Aortic Arch Artery Formation and Congenital Heart Disease

BACKGROUND

The resiliency of embryonic development to genetic and environmental perturbations has been long appreciated; however, little is known about the mechanisms underlying the robustness of developmental processes. Aberrations resulting in neonatal lethality are exemplified by congenital heart disease arising from defective morphogenesis of pharyngeal arch arteries (PAAs) and their derivatives.

METHODS

Mouse genetics, lineage tracing, confocal microscopy, and quantitative image analyses were used to investigate mechanisms of PAA formation and repair.

RESULTS

The second heart field (SHF) gives rise to the PAA endothelium. Here, we show that the number of SHF-derived endothelial cells (ECs) is regulated by VEGFR2 (vascular endothelial growth factor receptor 2) and Tbx1. Remarkably, when the SHF-derived EC number is decreased, PAA development can be rescued by the compensatory endothelium. Blocking such compensatory response leads to embryonic demise. To determine the source of compensating ECs and mechanisms regulating their recruitment, we investigated 3-dimensional EC connectivity, EC fate, and gene expression. Our studies demonstrate that the expression of VEGFR2 by the SHF is required for the differentiation of SHF-derived cells into PAA ECs. The deletion of 1 VEGFR2 allele (VEGFR2SHF-HET) reduces SHF contribution to the PAA endothelium, while the deletion of both alleles (VEGFR2SHF-KO) abolishes it. The decrease in SHF-derived ECs in VEGFR2SHF-HET and VEGFR2SHF-KO embryos is complemented by the recruitment of ECs from the nearby veins. Compensatory ECs contribute to PAA derivatives, giving rise to the endothelium of the aortic arch and the ductus in VEGFR2SHF-KO mutants. Blocking the compensatory response in VEGFR2SHF-KO mutants results in embryonic lethality shortly after mid-gestation. The compensatory ECs are absent in Tbx1+/- embryos, a model for 22q11 deletion syndrome, leading to unpredictable arch artery morphogenesis and congenital heart disease. Tbx1 regulates the recruitment of the compensatory endothelium in an SHF-non-cell-autonomous manner.

CONCLUSIONS

Our studies uncover a novel buffering mechanism underlying the resiliency of PAA development and remodeling.

Bioengineering toolkits for potentiating organoid therapeutics

Organoids are three-dimensional, multicellular constructs that recapitulate the structural and functional features of specific organs. Because of these characteristics, organoids have been widely applied in biomedical research in recent decades. Remarkable advancements in organoid technology have positioned them as promising candidates for regenerative medicine. However, current organoids still have limitations, such as the absence of internal vasculature, limited functionality, and a small size that is not commensurate with that of actual organs. These limitations hinder their survival and regenerative effects after transplantation. Another significant concern is the reliance on mouse tumor-derived matrix in organoid culture, which is unsuitable for clinical translation due to its tumor origin and safety issues. Therefore, our aim is to describe engineering strategies and alternative biocompatible materials that can facilitate the practical applications of organoids in regenerative medicine. Furthermore, we highlight meaningful progress in organoid transplantation, with a particular emphasis on the functional restoration of various organs.

Microvascular changes following exposure to iodinated contrast media in vitro. A qualitative comparison to serum creatinine concentrations in post-cardiac catheterization patients

INTRODUCTION

Contrast-associated acute kidney injury (CA-AKI) is characterized as a loss of renal function following radiological contrast media administration. While all contrast media induce variable changes in microvascular endothelial cells in vitro, only few studies report clinical significance of their findings. A comprehensive assessment of the effect of iodinated contrast media on the renal function in vitro and in vivo is essential. The aim of our study was to morphometrically quantify the effect of two different contrast media (Iobitridol and Iodixanol) on vascular endothelial capillaries in vitro and to analyze their effect on the renal function of patients who underwent cardiac catheterization including the intra-arterial administration of contrast media, by measuring serum creatinine concentration (SCr), a byproduct of muscle metabolism, primarily excreted by the kidneys. Our hypothesis suggests that conducting a qualitative comparison of both outcomes will enable identification of differences and similarities between in vitro and in vivo exposure.

MATERIAL AND METHODS

In vitro, co-cultures of human dermal fibroblasts and human dermal microvascular endothelial cells forming capillary beds were exposed to a mixture of phosphate buffered saline and either Iobitridol, Iodixanol, or one of their supplements EDTA or Trometamol for 1.5 or 5 min. Negative control co-cultures were exposed exclusively to phosphate buffered saline. Co-cultures were either directly fixed or underwent a regeneration time of 1, 3 or 7 days. An artificial intelligence software was trained for detection of labeled endothelial capillaries (CD31) on light microscope images and measurements of morphometric parameters. In vivo, we retrospectively analyzed data from patients who underwent intra-arterial administration of contrast media and for whom SCr values were available pre- and post-contrast exposition (1, 3, and 7 days following procedure). Temporal development of SCr and incidence of CA-AKI were assessed. Both exposure types were qualitatively compared.

RESULTS

In vitro, Iobitridol, Iodixanol and EDTA induced a strong decrease of two morphometric parameters after 3 days of regeneration. In vivo, a significant increase of SCr and incidence of CA-AKI was observed 3 days following procedure in the post-contrast media patients. No difference was observed between groups.

DISCUSSION

Two of the morphometric parameters were inversely proportional to the SCr of the patients. If the endothelial damages observed in vitro occur in vivo, it may result in renal hypoxia, inducing a loss of kidney function clinically translated into an increase of SCr. Further development of our in vitro model could allow closer replication of the internal structure of a kidney and bridge the gap between in vitro studies and their clinical findings.

Role of mitochondrial potassium channels in ageing

Ageing is described as an inevitable decline in body functions over time and an increase in susceptibility to age-related diseases. Therefore, the increase of life expectancy is also viewed as a condition in which many elderly will develop age-related diseases and disabilities, such as cardiovascular, metabolic, neurological and oncological ones. Currently, several recognized cellular hallmarks of senescence are taken in consideration to evaluate the level of biological ageing and are the topic to plan preventive/curative anti-ageing interventions, including genomic instability, epigenetic alterations, and mitochondrial dysfunction. In this scenario, alterations in the function/expression of mitochondrial ion channels have been found in ageing and associated to an impairment of calcium cycling and a reduced mitochondrial membrane potential. Although several ion channels have been described at mitochondrial level, undoubtedly the mitochondrial potassium (mitoK) channels are the most investigated. Therefore, this review summarized the evidence that sheds to light a correlation between age-related diseases and alteration of mitoK channels, focusing the attention of the main age-related diseases, i.e. cardiovascular, neurological and oncological ones.

The protective role of endothelial GLUT1 in ischemic stroke

OBJECTIVE

To provide thorough insight on the protective role of endothelial glucose transporter 1 (GLUT1) in ischemic stroke.

METHODS

We comprehensively review the role of endothelial GLUT1 in ischemic stroke by narrating the findings concerning biological characteristics of GLUT1 in brain in depth, summarizing the changes of endothelial GLUT1 expression and activity during ischemic stroke, discussing how GLUT1 achieves its neuroprotective effect via maintaining endothelial function, and identifying some outstanding blind spots in current studies.

RESULTS

Endothelial GLUT1 maintains persistent high glucose and energy requirements of the brain by transporting glucose through the blood-brain barrier, which preserves endothelial function and is beneficial to stroke prognosis.

CONCLUSION

This review underscores the potential involvement of GLUT1 trafficking, activity modulation, and degradation, and we look forward to more clinical and animal studies to illuminate these mechanisms.

VC-resist glioblastoma cell state: vessel co-option as a key driver of chemoradiation resistance

Glioblastoma (GBM) is a highly lethal type of cancer. GBM recurrence following chemoradiation is typically attributed to the regrowth of invasive and resistant cells. Therefore, there is a pressing need to gain a deeper understanding of the mechanisms underlying GBM resistance to chemoradiation and its ability to infiltrate. Using a combination of transcriptomic, proteomic, and phosphoproteomic analyses, longitudinal imaging, organotypic cultures, functional assays, animal studies, and clinical data analyses, we demonstrate that chemoradiation and brain vasculature induce cell transition to a functional state named VC-Resist (vessel co-opting and resistant cell state). This cell state is midway along the transcriptomic axis between proneural and mesenchymal GBM cells and is closer to the AC/MES1-like state. VC-Resist GBM cells are highly vessel co-opting, allowing significant infiltration into the surrounding brain tissue and homing to the perivascular niche, which in turn induces even more VC-Resist transition. The molecular and functional characteristics of this FGFR1-YAP1-dependent GBM cell state, including resistance to DNA damage, enrichment in the G2M phase, and induction of senescence/stemness pathways, contribute to its enhanced resistance to chemoradiation. These findings demonstrate how vessel co-option, perivascular niche, and GBM cell plasticity jointly drive resistance to therapy during GBM recurrence.

Tumor endothelial cell-derived Sfrp1 supports the maintenance of cancer stem cells via Wnt signaling

Cancer stem cells (CSCs), which are critical targets for cancer therapy as they are involved in drug resistance to anticancer drugs, and metastasis, are maintained by angiocrine factors produced by particular niches that form within tumor tissue. Secreted frizzled-related protein 1 (Sfrp1) is an extracellular protein that modulates Wnt signaling. However, the cells that produce Sfrp1 in the tumor environment and its function remain unclear. We aimed to elucidate angiocrine factors related to CSC maintenance, focusing on Sfrp1. Although Sfrp1 is a Wnt pathway-related factor, its impact on tumor tissues remains unknown. We investigated the localization of Sfrp1 in tumors and found that it is expressed in some tumor vessels. Analysis of mice lacking Sfrp1 showed that tumor growth was suppressed in Sfrp1-deficient tumor tissues. Flow cytometry analysis indicated that CSCs were maintained in the early tumor growth phase in the Sfrp1 knockout (KO) mouse model of tumor-bearing cancer. However, tumor growth was inhibited in the late tumor growth phase because of the inability to maintain CSCs. Real-time PCR results from tumors of Sfrp1 KO mice showed that the expression of Wnt signaling target genes significantly decreased in the late stage of tumor growth. This suggests that Sfrp1, an angiocrine factor produced by the tumor vascular niche, is involved in Wnt signaling-mediated mechanisms in tumor tissues.

HIV Infection, Antiretroviral Drugs, and the Vascular Endothelium

Endothelial cell activation, injury, and dysfunction underlies the pathophysiology of vascular diseases and infections associated with vascular dysfunction, including human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome. Despite viral suppression with combination antiretroviral therapy (ART), people living with HIV (PLWH) are prone to many comorbidities, including neurological and neuropsychiatric complications, cardiovascular and metabolic diseases, premature aging, and malignancies. HIV and viral proteins can directly contribute to the development of these comorbidities. However, with the continued high prevalence of these comorbidities despite viral suppression, it is likely that ART or some antiretroviral (ARVs) drugs contribute to the development and persistence of comorbid diseases in PLWH. These comorbid diseases often involve vascular activation, injury, and dysfunction. The purpose of this manuscript is to review the current literature on ARVs and the vascular endothelium in PLWH, animal models, and in vitro studies. I also summarize evidence of an association or lack thereof between ARV drugs or drug classes and the protection or injury/dysfunction of the vascular endothelium and vascular diseases.

Parenchymal cues define Vegfa-driven venous angiogenesis by activating a sprouting competent venous endothelial subtype

Formation of organo-typical vascular networks requires cross-talk between differentiating parenchymal cells and developing blood vessels. Here we identify a Vegfa driven venous sprouting process involving parenchymal to vein cross-talk regulating venous endothelial Vegfa signaling strength and subsequent formation of a specialized angiogenic cell, prefabricated with an intact lumen and pericyte coverage, termed L-Tip cell. L-Tip cell selection in the venous domain requires genetic interaction between vascular Aplnra and Kdrl in a subset of venous endothelial cells and exposure to parenchymal derived Vegfa and Apelin. Parenchymal Esm1 controls the spatial positioning of venous sprouting by fine-tuning local Vegfa availability. These findings may provide a conceptual framework for understanding how Vegfa generates organo-typical vascular networks based on the selection of competent endothelial cells, induced via spatio-temporal control of endothelial Kdrl signaling strength involving multiple parenchymal derived cues generated in a tissue dependent metabolic context.

JunB condensation attenuates vascular endothelial damage under hyperglycemic condition

Endothelial damage is the initial and crucial factor in the occurrence and development of vascular complications in diabetic patients, contributing to morbidity and mortality. Although hyperglycemia has been identified as a damaging effector, the detailed mechanisms remain elusive. In this study, identified by ATAC-seq and RNA-seq, JunB reverses the inhibition of proliferation and the promotion of apoptosis in human umbilical vein endothelial cells treated with high glucose, mainly through the cell cycle and p53 signaling pathways. Furthermore, JunB undergoes phase separation in the nucleus and in vitro, mediated by its intrinsic disordered region and DNA-binding domain. Nuclear localization and condensation behaviors are required for JunB-mediated proliferation and apoptosis. Thus, our study uncovers the roles of JunB and its coacervation in repairing vascular endothelial damage caused by high glucose, elucidating the involvement of phase separation in diabetes and diabetic endothelial dysfunction.

Endothelial H2S-AMPK dysfunction upregulates the angiocrine factor PAI-1 and contributes to lung fibrosis

Dysfunction of the vascular angiocrine system is critically involved in regenerative defects and fibrosis of injured organs. Previous studies have identified various angiocrine factors and found that risk factors such as aging and metabolic disorders can disturb the vascular angiocrine system in fibrotic organs. One existing key gap is what sense the fibrotic risk to modulate the vascular angiocrine system in organ fibrosis. Here, using human and mouse data, we discovered that the metabolic pathway hydrogen sulfide (H2S)-AMP-activated protein kinase (AMPK) is a sensor of fibrotic stress and serves as a key mechanism upregulating the angiocrine factor plasminogen activator inhibitor-1 (PAI-1) in endothelial cells to participate in lung fibrosis. Activation of the metabolic sensor AMPK was inhibited in endothelial cells of fibrotic lungs, and AMPK inactivation was correlated with enriched fibrotic signature and reduced lung functions in humans. The inactivation of endothelial AMPK accelerated lung fibrosis in mice, while the activation of endothelial AMPK with metformin alleviated lung fibrosis. In fibrotic lungs, endothelial AMPK inactivation led to YAP activation and overexpression of the angiocrine factor PAI-1, which was positively correlated with the fibrotic signature in human fibrotic lungs and inhibition of PAI-1 with Tiplaxtinin mitigated lung fibrosis. Further study identified that the deficiency of the antioxidative gas metabolite H2S accounted for the inactivation of AMPK and activation of YAP-PAI-1 signaling in endothelial cells of fibrotic lungs. H2S deficiency was involved in human lung fibrosis and H2S supplement reversed mouse lung fibrosis in an endothelial AMPK-dependent manner. These findings provide new insight into the mechanism underlying the deregulation of the vascular angiocrine system in fibrotic organs.

Fibrosis-on-Chip: A Guide to Recapitulate the Essential Features of Fibrotic Disease

Fibrosis, which is primarily marked by excessive extracellular matrix (ECM) deposition, is a pathophysiological process associated with many disorders, which ultimately leads to organ dysfunction and poor patient outcomes. Despite the high prevalence of fibrosis, currently there exist few therapeutic options, and importantly, there is a paucity of in vitro models to accurately study fibrosis. This review discusses the multifaceted nature of fibrosis from the viewpoint of developing organ-on-chip (OoC) disease models, focusing on five key features: the ECM component, inflammation, mechanical cues, hypoxia, and vascularization. The potential of OoC technology is explored for better modeling these features in the context of studying fibrotic diseases and the interplay between various key features is emphasized. This paper reviews how organ-specific fibrotic diseases are modeled in OoC platforms, which elements are included in these existing models, and the avenues for novel research directions are highlighted. Finally, this review concludes with a perspective on how to address the current gap with respect to the inclusion of multiple features to yield more sophisticated and relevant models of fibrotic diseases in an OoC format.

Endovascular biopsy in neurointerventional surgery: A systematic review

INTRODUCTION

Endothelial cells (ECs) continuously line the cerebrovasculature. Molecular aberrations in the ECs are hallmarks and contributory factors to the development of cerebrovascular diseases, including intracranial aneurysms and arteriovenous malformations (AVMs). Endovascular biopsy has been introduced as a method to harvest ECs and obtain relevant biologic information. We aimed to summarize the literature on endovascular biopsy in neurointerventional surgery.

METHODS

We conducted a comprehensive literature search in multiple databases, identifying eligible studies focusing on neurosurgical applications of endovascular biopsy. The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The relevant information was collected, including study characteristics, biopsy techniques, and key findings.

RESULTS

Nine studies met the inclusion criteria and were included. The studies involved the collection of ECs using various endovascular devices including coils, guide wires, different stents, and forceps. Endothelial-enrichment techniques, such fluorescence-activated cell sorting (FACS), collected ECs and facilitated downstream applications of bulk or single-cell RNA sequencing (scRNAseq). The studies provided insights into gene expression profiles and identified potential biomarkers associated with intracranial aneurysms. However, challenges were observed in obtaining an adequate number of ECs and identifying consistent biomarkers.

CONCLUSION

Endovascular biopsy of endothelial cells (ECs) in cerebrovascular pathologies shows promise for gene expression profiling. However, many studies have been limited in sample size and underpowered to identify "signature genes" for aneurysm growth or rupture. Advancements in minimally invasive biopsy methods have potential to facilitate applications of precision medicine in the treatment of cerebrovascular disorders.

Brain-derived endothelial cells are neuroprotective in a chronic cerebral hypoperfusion mouse model

Whether organ-specific regeneration is induced by organ-specific endothelial cells (ECs) remains unelucidated. The formation of white matter lesions due to chronic cerebral hypoperfusion causes cognitive decline, depression, motor dysfunction, and even acute ischemic stroke. Vascular ECs are an important target for treating chronic cerebral hypoperfusion. Brain-derived ECs transplanted into a mouse chronic cerebral hypoperfusion model showed excellent angiogenic potential. They were also associated with reducing both white matter lesions and brain dysfunction possibly due to the high expression of neuroprotective humoral factors. The in vitro coculture of brain cells with ECs from several diverse organs suggested the function of brain-derived endothelium is affected within a brain environment due to netrin-1 and Unc 5B systems. We found brain CD157-positive ECs were more proliferative and beneficial in a mouse model of chronic cerebral hypoperfusion than CD157-negative ECs upon inoculation. We propose novel methods to improve the symptoms of chronic cerebral hypoperfusion using CD157-positive ECs.

Endothelial Dysfunction in Psoriasis: An Integrative Review

Vascular endothelial cells (ECs), the inner layer of blood vessels, were previously considered to be a passive lining that facilitates cellular and molecular exchange. However, recent studies have revealed that ECs can respond to various stimuli and actively regulate vascular function and skin inflammation. Specific subtypes of ECs are known to have significant roles in a diverse range of physiological and pathological processes in the skin. This review suggests that EC dysfunction is both causal and consequential in the pathogenesis of psoriasis. Further investigations into dysregulated pathways in EC dysfunction may provide new insights for the treatment of psoriasis.

Crosstalk between endothelial cells with a non-canonical EndoMT phenotype and cardiomyocytes/fibroblasts via IGFBP5 aggravates TAC-induced cardiac dysfunction

Heart failure (HF) is a complex chronic condition characterized by structural and functional impairments. The differentiation of endothelial cells into myofibroblasts (EndoMT) in response to cardiac fibrosis is controversial, and the relative contribution of endothelial plasticity remains to be explored. Single-cell RNA sequencing was used to identify endothelial cells undergoing fibrotic differentiation within 2 weeks of transverse aortic constriction (TAC). This subset of endothelial cells transiently expressed fibrotic genes but had low expression of alpha-smooth muscle actin, indicating a non-canonical EndoMT, which we named a transient fibrotic-like phenotype (EndoFP). The role of EndoFP in pathological cardiac remodeling may be correlated with increased levels of osteopontin. Cardiomyocytes and fibroblasts co-cultured with EndoFP exhibited heightened pro-hypertrophic and pro-fibrotic effects. Mechanistically, we found that the upregulated expression of insulin-like growth factor-binding protein 5 may be a key mediator of EndoFP-induced cardiac dysfunction. Furthermore, our findings suggested that Rab5a is a novel regulatory gene involved in the EndoFP process. Our study suggests that the specific endothelial subset identified in TAC-induced pressure overload plays a critical role in the cellular interactions that lead to cardiac fibrosis and hypertrophy. Additionally, our findings provide insight into the mechanisms underlying EndoFP, making it a potential therapeutic target for early heart failure.

Endothelial cells regulate alveolar morphogenesis by constructing basement membranes acting as a scaffold for myofibroblasts

Alveologenesis is a spatially coordinated morphogenetic event, during which alveolar myofibroblasts surround the terminal sacs constructed by epithelial cells and endothelial cells (ECs), then contract to form secondary septa to generate alveoli in the lungs. Recent studies have demonstrated the important role of alveolar ECs in this morphogenetic event. However, the mechanisms underlying EC-mediated alveologenesis remain unknown. Herein, we show that ECs regulate alveologenesis by constructing basement membranes (BMs) acting as a scaffold for myofibroblasts to induce septa formation through activating mechanical signaling. Rap1, a small GTPase of the Ras superfamily, is known to stimulate integrin-mediated cell adhesions. EC-specific Rap1-deficient (Rap1iECKO) mice exhibit impaired septa formation and hypo-alveolarization due to the decreased mechanical signaling in myofibroblasts. In Rap1iECKO mice, ECs fail to stimulate integrin β1 to recruit Collagen type IV (Col-4) into BMs required for myofibroblast-mediated septa formation. Consistently, EC-specific integrin β1-deficient mice show hypo-alveolarization, defective mechanical signaling in myofibroblasts, and disorganized BMs. These data demonstrate that alveolar ECs promote integrin β1-mediated Col-4 recruitment in a Rap1-dependent manner, thereby constructing BMs acting as a scaffold for myofibroblasts to induce mechanical signal-mediated alveologenesis. Thus, this study unveils a mechanism of organ morphogenesis mediated by ECs through intrinsic functions.

Vascular development, remodeling and maturation

The development of the vascular system is crucial in supporting the growth and health of all other organs in the body, and vascular system dysfunction is the major cause of human morbidity and mortality. This chapter discusses three successive processes that govern vascular system development, starting with the differentiation of the primitive vascular system in early embryonic development, followed by its remodeling into a functional circulatory system composed of arteries and veins, and its final maturation and acquisition of an organ specific semi-permeable barrier that controls nutrient uptake into tissues and hence controls organ physiology. Along these steps, endothelial cells forming the inner lining of all blood vessels acquire extensive heterogeneity in terms of gene expression patterns and function, that we are only beginning to understand. These advances contribute to overall knowledge of vascular biology and are predicted to unlock the unprecedented therapeutic potential of the endothelium as an avenue for treatment of diseases associated with dysfunctional vasculature.

Single-Cell Transcriptomic Analysis of Salivary Gland Endothelial Cells

Vascular endothelial cells have important tissue-specific functions in fibrosis and regeneration. In the salivary gland, endothelial cells are required for proper development, but their roles within adult glands are largely unknown. To identify ligand-receptor interactions between endothelial cells and other cell types that may be important during fibrosis and regeneration, we used a reversible ductal ligation injury. To induce injury, a clip was applied to the primary ducts for 14 d, and to induce a regenerative response, the clip was subsequently removed for 5 d. To identify endothelial cell-produced factors, we used single-cell RNA sequencing of stromal-enriched cells from adult female submandibular and sublingual salivary glands. Transcriptional profiles of homeostatic salivary gland endothelial cells were compared to endothelial cells of other organs. Salivary gland endothelial cells expressed many unique genes and displayed the highest overlap in gene expression with other fenestrated endothelial cells from the colon, small intestine, and kidney. Comparison of the 14-d ligated, mock-ligated, and 5-d deligated stromal-enriched transcripts and lineage tracing revealed that endothelial cells retain their identity following ligation and recovery from injury. CellChat and NATMI were used to predict changes in ligand-receptor interactions from endothelial cells to other cells in response to ligation and deligation. CellChat and NATMI predicted that after ligation, interactions with fibroblasts, epithelial cells, and glial cells were increased, and following deligation, interactions with pericyte, glia, fibroblasts, and immune cells were increased. Some of the highest-ranked interactions predicted in ligated compared to mock endothelial cells were between glial cells via Col4a2-Cd93 and Jag2-Notch1, as well as epithelial cells via Pecam1-Cd38, while in deligated compared to ligated endothelial cells, the top interactions were between fibroblasts via Ntf3-Ntrk2, glial cells via Hspg2-Itgb1, and pericytes via Jam2-F11r. Understanding salivary gland endothelial cell signaling will inform future endothelial cell-based regenerative therapies.

Fibroblasts and endothelial cells interplay drives hypertrophic scar formation: Insights from in vitro and in vivo models

Hypertrophic scar formation is influenced by the intricate interplay between fibroblasts and endothelial cells. In this study, we investigated this relationship using in vitro and in vivo models. Clinical observations revealed distinct morphological changes and increased vascularity at pathological scar sites. Further analysis using OCTA, immunohistochemistry, and immunofluorescence confirmed the involvement of angiogenesis in scar formation. Our indirect co-culture systems demonstrated that endothelial cells enhance the proliferation and migration of fibroblasts through the secretion of cytokines including VEGF, PDGF, bFGF, and TGF-β. Additionally, a suspended co-culture multicellular spheroid model revealed molecular-level changes associated with extracellular matrix remodeling, cellular behaviors, inflammatory response, and pro-angiogenic activity. Furthermore, KEGG pathway analysis identified the involvement of TGF-β, IL-17, Wnt, Notch, PI3K-Akt, and MAPK pathways in regulating fibroblasts activity. These findings underscore the critical role of fibroblasts-endothelial cells crosstalk in scar formation and provide potential targets for therapeutic intervention. Understanding the molecular mechanisms underlying this interplay holds promise for the development of innovative approaches to treat tissue injuries and diseases.

Epithelial stem cells and niches in lung alveolar regeneration and diseases

Alveoli serve as the functional units of the lungs, responsible for the critical task of blood-gas exchange. Comprising type I (AT1) and type II (AT2) cells, the alveolar epithelium is continuously subject to external aggressors like pathogens and airborne particles. As such, preserving lung function requires both the homeostatic renewal and reparative regeneration of this epithelial layer. Dysfunctions in these processes contribute to various lung diseases. Recent research has pinpointed specific cell subgroups that act as potential stem or progenitor cells for the alveolar epithelium during both homeostasis and regeneration. Additionally, endothelial cells, fibroblasts, and immune cells synergistically establish a nurturing microenvironment-or "niche"-that modulates these epithelial stem cells. This review aims to consolidate the latest findings on the identities of these stem cells and the components of their niche, as well as the molecular mechanisms that govern them. Additionally, this article highlights diseases that arise due to perturbations in stem cell-niche interactions. We also discuss recent technical innovations that have catalyzed these discoveries. Specifically, this review underscores the heterogeneity, plasticity, and dynamic regulation of these stem cell-niche systems. It is our aspiration that a deeper understanding of the fundamental cellular and molecular mechanisms underlying alveolar homeostasis and regeneration will open avenues for identifying novel therapeutic targets for conditions such as chronic obstructive pulmonary disease (COPD), fibrosis, coronavirus disease 2019 (COVID-19), and lung cancer.

Identification of novel buffering mechanisms in aortic arch artery development and congenital heart disease

Rationale

The resiliency of embryonic development to genetic and environmental perturbations has been long appreciated; however, little is known about the mechanisms underlying the robustness of developmental processes. Aberrations resulting in neonatal lethality are exemplified by congenital heart disease (CHD) arising from defective morphogenesis of pharyngeal arch arteries (PAA) and their derivatives.

Objective

To uncover mechanisms underlying the robustness of PAA morphogenesis.

Methods and Results

The second heart field (SHF) gives rise to the PAA endothelium. Here, we show that the number of SHF-derived ECs is regulated by VEGFR2 and Tbx1 . Remarkably, when SHF-derived EC number is decreased, PAA development can be rescued by the compensatory endothelium. Blocking such compensatory response leads to embryonic demise. To determine the source of compensating ECs and mechanisms regulating their recruitment, we investigated three-dimensional EC connectivity, EC fate, and gene expression. Our studies demonstrate that the expression of VEGFR2 by the SHF is required for the differentiation of SHF-derived cells into PAA ECs. The deletion of one VEGFR2 allele (VEGFR2 SHF-HET ) reduces SHF contribution to the PAA endothelium, while the deletion of both alleles (VEGFR2 SHF-KO ) abolishes it. The decrease in SHF-derived ECs in VEGFR2 SHF-HET and VEGFR2 SHF-KO embryos is complemented by the recruitment of ECs from the nearby veins. Compensatory ECs contribute to PAA derivatives, giving rise to the endothelium of the aortic arch and the ductus in VEGFR2 SHF-KO mutants. Blocking the compensatory response in VEGFR2 SHF-KO mutants results in embryonic lethality shortly after mid-gestation. The compensatory ECs are absent in Tbx1 +/- embryos, a model for 22q11 deletion syndrome, leading to unpredictable arch artery morphogenesis and CHD. Tbx1 regulates the recruitment of the compensatory endothelium in an SHF-non-cell-autonomous manner.

Conclusions

Our studies uncover a novel buffering mechanism underlying the resiliency of PAA development and remodeling.

Nonstandard Abbreviations and Acronyms in Alphabetical Order

CHD - congenital heart disease; ECs - endothelial cells; IAA-B - interrupted aortic arch type B; PAA - pharyngeal arch arteries; RERSA - retro-esophageal right subclavian artery; SHF - second heart field; VEGFR2 - Vascular endothelial growth factor receptor 2.

Identification of myeloid-derived growth factor as a mechanically-induced, growth-promoting angiocrine signal for human hepatocytes

Recently, we have shown that after partial hepatectomy (PHx), an increased hepatic blood flow initiates liver growth in mice by vasodilation and mechanically-triggered release of angiocrine signals. Here, we use mass spectrometry to identify a mechanically-induced angiocrine signal in human hepatic endothelial cells, that is, myeloid-derived growth factor (MYDGF). We show that it induces proliferation and promotes survival of primary human hepatocytes derived from different donors in two-dimensional cell culture, via activation of mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3). MYDGF also enhances proliferation of human hepatocytes in three-dimensional organoids. In vivo, genetic deletion of MYDGF decreases hepatocyte proliferation in the regenerating mouse liver after PHx; conversely, adeno-associated viral delivery of MYDGF increases hepatocyte proliferation and MAPK signaling after PHx. We conclude that MYDGF represents a mechanically-induced angiocrine signal and that it triggers growth of, and provides protection to, primary mouse and human hepatocytes.

Disturbed endothelial cell signaling in tumor progression and therapy resistance

Growth of new blood vessels is considered requisite to cancer progression. Recent findings revealed that in addition to inducing angiogenesis, tumor-derived factors alter endothelial cell gene transcription within the tumor mass but also systemically throughout the body. This subsequently contributes to immunosuppression, altered metabolism, therapy resistance and metastasis. Clinical studies demonstrated that targeting the endothelium can increase the success rate of immunotherapy. Single-cell technologies revealed remarkable organ-specific endothelial heterogeneity that becomes altered by the presence of a tumor. In metastases, endothelial transcription differs remarkably between newly formed and co-opted vessels which may provide a basis for developing new therapies to target endothelial cells and overcome therapy resistance more effectively. This review addresses how cancers impact the endothelium to facilitate tumor progression.

Lung regeneration: diverse cell types and the therapeutic potential

Lung tissue has a certain regenerative ability and triggers repair procedures after injury. Under controllable conditions, lung tissue can restore normal structure and function. Disruptions in this process can lead to respiratory system failure and even death, causing substantial medical burden. The main types of respiratory diseases are chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and acute respiratory distress syndrome (ARDS). Multiple cells, such as lung epithelial cells, endothelial cells, fibroblasts, and immune cells, are involved in regulating the repair process after lung injury. Although the mechanism that regulates the process of lung repair has not been fully elucidated, clinical trials targeting different cells and signaling pathways have achieved some therapeutic effects in different respiratory diseases. In this review, we provide an overview of the cell type involved in the process of lung regeneration and repair, research models, and summarize molecular mechanisms involved in the regulation of lung regeneration and fibrosis. Moreover, we discuss the current clinical trials of stem cell therapy and pharmacological strategies for COPD, IPF, and ARDS treatment. This review provides a reference for further research on the molecular and cellular mechanisms of lung regeneration, drug development, and clinical trials.

Endothelial anthrax toxin receptor 2 plays a protective role in liver fibrosis

Hepatocellular carcinoma is one of the leading cancers worldwide and is a potential consequence of fibrosis. Therefore, the identification of key cellular and molecular mechanisms involved in liver fibrosis is an important goal for the development of new strategies to control liver-related diseases. Here, single-cell RNA sequencing data (GSE136103 and GES181483) of clinical liver non-parenchymal cells were analyzed to identify cellular and molecular mechanisms of liver fibrosis. The proportion of endothelial subpopulations in cirrhotic livers was significantly higher than that in healthy livers. Gene ontology and gene set enrichment analysis of differentially expressed genes in the endothelial subgroups revealed that extracellular matrix (ECM)-related pathways were significantly enriched. Since anthrax toxin receptor 2 (ANTXR2) interacts with the ECM, the expression of ANTXR2 in the liver endothelium was analyzed. ANTXR2 expression in the liver endothelium of wild-type (WT) mice significantly decreased after a 4-time sequential injection of carbon tetrachloride (CCl4) to induce liver fibrosis. Next, conditional knockout mice selectively lacking Antxr2 in endothelial cells were generated. After endothelial-specific Antxr2 knockout mice were subjected to the CCl4 model, the degree of liver fibrosis in the knockout group was significantly more severe than that in the control group. In addition, ANTXR2 in human umbilical vein endothelial cells promoted matrix metalloproteinase 2 (MMP2) activation to degrade the ECM in vitro. Finally, endothelial-specific overexpression of Antxr2 alleviated the development of liver fibrosis following adeno-associated virus treatment. Collectively, these results suggested that endothelial ANTXR2 plays a protective role in liver fibrosis. This function of ANTXR2 may be achieved by promoting MMP2 activation to degrade the ECM.

YBX1 promotes type H vessel-dependent bone formation in an m5C-dependent manner

RNA-binding proteins (RBPs) interact with RNA and ubiquitously regulate RNA transcripts during their life cycle, playing a fundamental role in the progression of angiogenesis-related diseases. In the skeletal system, endothelium-dependent angiogenesis is indispensable for bone formation. However, the role of RBPs in endothelium-dependent bone formation is unclear. Here, we show that RBP-Y-box-binding protein 1 (YBX1) was strongly reduced in the bone vasculature of ovariectomy (OVX) mice. Endothelial cell-specific deletion of Ybx1 impaired CD31-high, endomucin-high (CD31hiEMCNhi) endothelium morphology and resulted in low bone mass whereas Ybx1 overexpression promoted angiogenesis-dependent osteogenesis and ameliorated bone loss. Mechanistically, YBX1 deletion disrupted CD31, EMCN, and bone morphogenetic protein 4 (BMP4) stability in an m5C-dependent manner and blocked endothelium-derived BMP4 release, thereby inhibiting osteogenic differentiation of bone mesenchymal stromal cells. Administration of recombinant BMP4 protein restored impaired bone formation in Ybx1 deletion mice. Tail vein injection of CD31-modified polyethylene glycol-poly (lactic-co-glycolic acid) carrying sciadopitysin, a natural YBX1 agonist, pharmacologically partially reversed CD31hiEMCNhi vessels' decline and improved bone mass in both OVX and aging animals. These findings demonstrated the role of RBP-YBX1 in angiogenesis-dependent bone formation and provided a therapeutic approach for ameliorating osteoporosis.

Radiation-induced multi-organ injury

PURPOSE

Natural history studies have been informative in dissecting radiation injury, isolating its effects, and compartmentalizing injury based on the extent of exposure and the elapsed time post-irradiation. Although radiation injury models are useful for investigating the mechanism of action in isolated subsyndromes and development of medical countermeasures (MCMs), it is clear that ionizing radiation exposure leads to multi-organ injury (MOI).

METHODS

The Radiation and Nuclear Countermeasures Program within the National Institute of Allergy and Infectious Diseases partnered with the Biomedical Advanced Research and Development Authority to convene a virtual two-day meeting titled 'Radiation-Induced Multi-Organ Injury' on June 7-8, 2022. Invited subject matter experts presented their research findings in MOI, including study of mechanisms and possible MCMs to address complex radiation-induced injuries.

RESULTS

This workshop report summarizes key information from each presentation and discussion by the speakers and audience participants.

CONCLUSIONS

Understanding the mechanisms that lead to radiation-induced MOI is critical to advancing candidate MCMs that could mitigate the injury and reduce associated morbidity and mortality. The observation that some of these mechanisms associated with MOI include systemic injuries, such as inflammation and vascular damage, suggests that MCMs that address systemic pathways could be effective against multiple organ systems.

A Preliminary Study of the Role of Endothelial-Mesenchymal Transitory Factor SOX 2 and CD147 in the Microvascularization of Oral Squamous Cell Carcinoma

INTRODUCTION

The aim of this study was to detect the possible endothelial expression of embryonic-type cancer stem cells (CSC) marker SOX2 and the stemness-type CSC marker CD147 in oral potential malignant disorders (OPMDs), oral leukoplakia (OL) in particular, and oral squamous cell carcinoma (OSCC).

METHODS

This study focuses on the immunohistochemical pattern of expression of CSC protein-biomarkers SOX2 and CD147 in paraffin-embedded samples of 21 OSCCs of different grades of differentiation and 30 cases of OLs with different grades of dysplasia, compared to normal oral mucosa.

RESULTS

The protein biomarker SOX2 was expressed in the endothelial cells, but without establishing any statistically significant correlation among OSCC, OL, and normal tissue specimens. However, SOX endothelial staining was noticed in 7/30 (23.3%) cases of OL (one non-dysplastic, one mildly dysplastic, one moderately dysplastic, and four severely dysplastic cases) and 5/21 (23.8%) cases of OSCC (two well-differentiated, one moderately differentiated, and two poorly differentiated cases). Although CD147 is expressed in normal oral epithelium, OL, and OSCC neoplastic cells, its vascular-endothelial expression was noticed in only 2/5 (40%) cases of normal oral epithelium, 1/30 (3.3%) cases of OL (one severely dysplastic case), and 4/21 (19%) cases of OSCC (two well-differentiated, one moderately differentiated, and one poorly differentiated case). Therefore, no statistically significant correlation among OSCC, OL, and normal tissue specimens was established.

CONCLUSION

The endothelial presence of SOX2 both in oral potentially malignant and malignant lesions suggests that SOX2 may be implicated in the microvascularization process and associated with the degree of dysplasia in OL. The expression of CD147 may be attributed both to local inflammation and tumorigenesis. The implementation of CD147 in larger groups of tissue samples will shed some light on its role in cancer and inflammation. The evidence so far supports the need for more studies, which may support the clinical significance of these novel cancer stem cell biomarkers.

Discovery of Transcription Factors Involved in the Maintenance of Resident Vascular Endothelial Stem Cell Properties

A resident vascular endothelial stem cell (VESC) population expressing CD157 has been identified recently in mice. Herein, we identified transcription factors (TFs) regulating CD157 expression in endothelial cells (ECs) that were associated with drug resistance, angiogenesis, and EC proliferation. In the first screening, we detected 20 candidate TFs through the CD157 promoter and gene expression analyses. We found that 10 of the 20 TFs induced CD157 expression in ECs. We previously reported that 70% of CD157 VESCs were side population (SP) ECs that abundantly expressed ATP-binding cassette (ABC) transporters. Here, we found that the 10 TFs increased the expression of several ABC transporters in ECs and increased the proportion of SP ECs. Of these 10 TFs, we found that six (Atf3, Bhlhe40, Egr1, Egr2, Elf3, and Klf4) were involved in the manifestation of the SP phenotype. Furthermore, the six TFs enhanced tube formation and proliferation in ECs. Single-cell RNA sequence data in liver ECs suggested that Atf3 and Klf4 contributed to the production of CD157+ VESCs in the postnatal period. We concluded that Klf4 might be important for the development and maintenance of liver VESCs. Our work suggests that a TF network is involved in the differentiation hierarchy of VESCs.

Cardiac and intestinal tissue conduct developmental and reparative processes in response to lymphangiocrine signaling

Lymphatic vessels conduct a diverse range of activities to sustain the integrity of surrounding tissue. Besides facilitating the movement of lymph and its associated factors, lymphatic vessels are capable of producing tissue-specific responses to changes within their microenvironment. Lymphatic endothelial cells (LECs) secrete paracrine signals that bind to neighboring cell-receptors, commencing an intracellular signaling cascade that preludes modifications to the organ tissue's structure and function. While the lymphangiocrine factors and the molecular and cellular mechanisms themselves are specific to the organ tissue, the crosstalk action between LECs and adjacent cells has been highlighted as a commonality in augmenting tissue regeneration within animal models of cardiac and intestinal disease. Lymphangiocrine secretions have been owed for subsequent improvements in organ function by optimizing the clearance of excess tissue fluid and immune cells and stimulating favorable tissue growth, whereas perturbations in lymphatic performance bring about the opposite. Newly published landmark studies have filled gaps in our understanding of cardiac and intestinal maintenance by revealing key players for lymphangiocrine processes. Here, we will expand upon those findings and review the nature of lymphangiocrine factors in the heart and intestine, emphasizing its involvement within an interconnected network that supports daily homeostasis and self-renewal following injury.

Unveiling the power of microenvironment in liver regeneration: an in-depth overview

The liver serves as a vital regulatory hub for various physiological processes, including sugar, protein, and fat metabolism, coagulation regulation, immune system maintenance, hormone inactivation, urea metabolism, and water-electrolyte acid-base balance control. These functions rely on coordinated communication among different liver cell types, particularly within the liver's fundamental hepatic lobular structure. In the early stages of liver development, diverse liver cells differentiate from stem cells in a carefully orchestrated manner. Despite its susceptibility to damage, the liver possesses a remarkable regenerative capacity, with the hepatic lobule serving as a secure environment for cell division and proliferation during liver regeneration. This regenerative process depends on a complex microenvironment, involving liver resident cells, circulating cells, secreted cytokines, extracellular matrix, and biological forces. While hepatocytes proliferate under varying injury conditions, their sources may vary. It is well-established that hepatocytes with regenerative potential are distributed throughout the hepatic lobules. However, a comprehensive spatiotemporal model of liver regeneration remains elusive, despite recent advancements in genomics, lineage tracing, and microscopic imaging. This review summarizes the spatial distribution of cell gene expression within the regenerative microenvironment and its impact on liver regeneration patterns. It offers valuable insights into understanding the complex process of liver regeneration.

Elucidating the Morphogenic and Signaling Roles of Defined Growth Factors Controlling Human Endothelial Cell Lumen Formation Versus Sprouting Behavior

Five growth factors [ie, insulin, fibroblast growth factor-2 (FGF-2), stem cell factor, IL-3, and stromal-derived factor 1α] in combination are necessary for human endothelial cells (ECs) to undergo tube morphogenesis, a process requiring both lumen formation and sprouting behavior. This study investigated why these factors are required by subdividing the factors into 4 separate groups: insulin-only, insulin and FGF-2, no FGF-2 (all factors but without FGF-2), and all factors. The study found that the insulin-only condition failed to support EC morphogenesis or survival, the insulin and FGF-2 condition supported primarily EC lumen formation, and the no FGF-2 condition supported EC sprouting behavior. By comparison, the all-factors condition more strongly stimulated both EC lumen formation and sprouting behavior, and signaling analysis revealed prolonged stimulation of multiple promorphogenic signals coupled with inhibition of proregressive signals. Pharmacologic inhibition of Jak kinases more selectively blocked EC sprouting behavior, whereas inhibition of Raf, phosphatidylinositol 3-kinase, and Akt kinases showed selective blockade of lumen formation. Inhibition of Src family kinases and Notch led to increased sprouting coupled to decreased lumen formation, whereas inhibition of Pak, Mek, and mammalian target of rapamycin kinases blocked both sprouting and lumen formation. These findings reveal novel downstream biological and signaling activities of defined factors that are required for the assembly of human EC-lined capillary tube networks.

Engineering Organ-on-a-Chip Systems for Vascular Diseases

Vascular diseases, such as atherosclerosis and thrombosis, are major causes of morbidity and mortality worldwide. Traditional in vitro models for studying vascular diseases have limitations, as they do not fully recapitulate the complexity of the in vivo microenvironment. Organ-on-a-chip systems have emerged as a promising approach for modeling vascular diseases by incorporating multiple cell types, mechanical and biochemical cues, and fluid flow in a microscale platform. This review provides an overview of recent advancements in engineering organ-on-a-chip systems for modeling vascular diseases, including the use of microfluidic channels, ECM (extracellular matrix) scaffolds, and patient-specific cells. We also discuss the limitations and future perspectives of organ-on-a-chip for modeling vascular diseases.

Endothelial heterogeneity and their relevance in cardiac development and coronary artery disease

Micro- and macrovascular endothelial cells (ECs) are characterized by structural and functional heterogeneity, which is also reflected in their secretory activity. The root of this heterogeneity and related regulatory mechanisms are still poorly understood. During embryogenesis, microvascular ECs participate in organogenesis prior to the development of the fetal circulation, suggesting that ECs are capable of releasing paracrine trophogens, termed angiocrine factors (AFs). These are angiocrine growth factors, adhesion molecules, and chemokines, which are intended to promote morphogenesis and repair of the adjacent parenchyma/stroma where the vessels are located. There is a tissue and organ-specificity of AFs that traces the heterogeneity of ECs. This AF heterogeneity also traces how ECs respond to pathological conditions or exposure to cardiovascular risk factors. The study of the mechanisms that regulate endothelial and paracrine heterogeneity and that contribute to endotheliopathy represents a broad and as yet understudied area of research. A better understanding of the cellular and molecular mechanisms that regulate this heterogeneity, leading to endotheliopathy is an exciting challenge. In this brief review we will discuss experimental advances in the heterogeneity of ECs and their AF, with a focus on their involvement in the pathogenesis of coronary artery disease.

Endothelial Notch Signaling Regulates the Function of the Retinal Pigment Epithelial Barrier via EC Angiocrine Signaling

The outer blood-retina barrier (oBRB), comprises tightly connected retinal pigment epithelium (RPE) cells, Bruch's membrane, and choroid blood vessels, and is essential for retinal health and normal visual function. Disruption of the RPE barrier and its dysfunction can lead to retinal disorders such as age-related macular degeneration (AMD). In the present study, we investigated the essential role of choroid endothelial cells (ECs) in the RPE barrier formation process and its dysfunction. We discovered that ECs promoted RPE barrier formation through angiocrine signaling. Through blocking or activating endothelial Notch signaling and conducting experiments in vitro and in vivo, we confirmed that endothelial Notch signaling regulated the expression of heparin-binding epidermal growth factor (HBEGF) and consequently impacted the expression and activity of matrix metalloproteinases (MMP)-9 in RPE cells. This modulation influenced the RPE extracellular matrix deposition, tight junctions and RPE barrier function. In in vivo experiments, the intravitreal administration of recombinant HBEGF (r-HBEGF) alleviated the RPE barrier disruption induced by subretinal injection (SI) or laser treatment and also rescued RPE barrier disruption in endothelial Notch-deficient mice. Our results showed that the endothelial Notch signaling drove HBEGF expression through angiocrine signaling and effectively improved RPE barrier function by regulating the MMP-9 expression in RPE cells. It suggests that the modulation of Notch signaling in the choroidal endothelium may offer a novel therapeutic strategy for retinal degenerative diseases.

Endothelial Cell-Derived Lactate Triggers Bone Mesenchymal Stem Cell Histone Lactylation to Attenuate Osteoporosis

Blood vessels play a role in osteogenesis and osteoporosis; however, the role of vascular metabolism in these processes remains unclear. The present study finds that ovariectomized mice exhibit reduced blood vessel density in the bone and reduced expression of the endothelial glycolytic regulator pyruvate kinase M2 (PKM2). Endothelial cell (EC)-specific deletion of Pkm2 impairs osteogenesis and worsens osteoporosis in mice. This is attributed to the impaired ability of bone mesenchymal stem cells (BMSCs) to differentiate into osteoblasts. Mechanistically, EC-specific deletion of Pkm2 reduces serum lactate levels secreted by ECs, which affect histone lactylation in BMSCs. Using joint CUT&Tag and RNA sequencing analyses, collagen type I alpha 2 chain (COL1A2), cartilage oligomeric matrix protein (COMP), ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), and transcription factor 7 like 2 (TCF7L2) as osteogenic genes regulated by histone H3K18la lactylation are identified. PKM2 overexpression in ECs, lactate addition, and exercise restore the phenotype of endothelial PKM2-deficient mice. Furthermore, serum metabolomics indicate that patients with osteoporosis have relatively low lactate levels. Additionally, histone lactylation and related osteogenic genes of BMSCs are downregulated in patients with osteoporosis. In conclusion, glycolysis in ECs fuels BMSC differentiation into osteoblasts through histone lactylation, and exercise partially ameliorates osteoporosis by increasing serum lactate levels.