Passage Number-Induced Replicative Senescence Modulates the Endothelial Cell Response to Protein-Bound Uremic Toxins

Quantitative analysis of human umbilical vein endothelial cell morphology and tubulogenesis

Primary human umbilical vein endothelial cells can grow as both a monolayer in culture and also as a capillary-like network making them an ideal model system in order to study vascular remodelling. Image-based analysis can allow assessment of cell morphology and motility but is dependent on accurate cell segmentation which requires high-contrast images not normally achievable without fluorescent markers. Here, ptychography is employed as a label-free image-based modality in order to extract quantitative metrics of morphology and tubulogenesis from cultured HUVECs over time in an automated multiwell assay. Phase-specific parameters of dry mass, optical thickness and sphericity were extracted and assessed alongside other metrics of cell number and shape. Tubulogenesis could be captured dynamically without any imaging artefacts from use of a basement membrane matrix and metrics of tube number, growth and branching exported alongside morphology metrics at early time-points. Utilising ptychography-based image analysis, all VEGF165a isoforms studied, elicited a concentration-dependent effect on cell elongation and survival within a HUVEC monolayer. Pharmacologically relevant parameters of potency (EC50) and efficacy were derived, exemplifying this label-free approach for the multiparameter and multiwell quantitative study of vascular remodelling in physiologically relevant cells at 37°C.

Nicotinamide mononucleotide restores impaired metabolism, endothelial cell proliferation and angiogenesis in old sedentary male mice

Aging is accompanied by a decline in neovascularization potential and increased susceptibility to ischemic injury. Here, we confirm the age-related impaired neovascularization following ischemic leg injury and impaired angiogenesis. The age-related deficits in angiogenesis arose primarily from diminished EC proliferation capacity, but not migration or VEGF sensitivity. Aged EC harvested from the mouse skeletal muscle displayed a pro-angiogenic gene expression phenotype, along with considerable changes in metabolic genes. Metabolomics analysis and 13C glucose tracing revealed impaired ATP production and blockade in glycolysis and TCA cycle in late passage HUVECs, which occurred at nicotinamide adenine dinucleotide (NAD⁺)-dependent steps, along with NAD+ depletion. Supplementation with nicotinamide mononucleotide (NMN), a precursor of NAD⁺, enhances late-passage EC proliferation and sprouting angiogenesis from aged mice aortas. Taken together, our study illustrates the importance of NAD+-dependent metabolism in the maintenance of EC proliferation capacity with age, and the therapeutic potential of NAD precursors.

Advances in the mechanisms of vascular calcification in chronic kidney disease

Vascular calcification (VC) is common in patients with advanced chronic kidney disease (CKD).A series of factors, such as calcium and phosphorus metabolism disorders, uremic toxin accumulation, inflammation and oxidative stress and cellular senescence, cause osteoblast-like differentiation of vascular smooth muscle cells, secretion of extracellular vesicles, and imbalance of calcium regulatory factors, which together promote the development of VC in CKD. Recent advances in epigenetics have provided better tools for the investigation of VC etiology and new approaches for finding more accurate biomarkers. These advances have not only deepened our understanding of the pathophysiological mechanisms of VC in CKD, but also provided valuable clues for the optimization of clinical predictors and the exploration of potential therapeutic targets. The aim of this article is to provide a comprehensive overview of the pathogenesis of CKD VC, especially the new advances made in recent years, including the various key factors mentioned above. Through the comprehensive analysis, we expect to provide a solid theoretical foundation and research direction for future studies targeting the specific mechanisms of CKD VC, the establishment of clinical predictive indicators and the development of potential therapeutic strategies.

Syndecan 4 is a marker of endothelial inflammation in pathological aging and predicts long-term cardiovascular outcomes in type 2 diabetes

BACKGROUND

Endothelial cellular senescence is emerging as a key mechanism of age-related vascular dysfunction. Disruption of the endothelium glycocalyx and shedding of the syndecan (SDC) ectodomains have been associated with several age-related diseases. Although SDC4 is highly expressed in endothelial cells, its levels and shedding in senescent endothelial cells and vascular endothelial dysfunction associated with aging are still unknown.

METHODS

To assess whether SDC4 expression was affected by inflammatory conditions, we evaluated its levels in young human umbilical vein endothelial cells (HUVECs) treated with TNF-α at a concentration of 50 ng/mL for 24 h and in cells undergoing replicative senescence. Plasma levels of SDC4 were evaluated in two previously recruited cohorts of (i) subjects with type 2 diabetes (T2D, n = 110) followed for a median of 16.8 years and age- and gender-matched healthy subjects (n = 100), and (ii) middle-aged subjects with mild-to-moderate dyslipidemia. Binomial logistic regression was used to assess whether SDC4 levels could be prognostic for major adverse cardiovascular events (MACE).

RESULTS

In the in vitro study, we showed that HUVECs, when exposed to TNF-α or undergoing replicative senescence, exhibited elevated expression levels of SDC4 and matrix metallopeptidase 9 (MMP-9), as well as increased shedding of SDC4 into the extracellular microenvironment, in comparison to actively proliferating young HUVECs. Analysis of human samples revealed that patients with T2D without complications exhibited higher SDC4 levels compared to healthy controls and those with T2D vascular complications. In particular, patients with a history of major adverse cardiovascular events (MACE) had lower SDC4 levels. The longitudinal evaluation revealed that higher SDC4 levels predict the onset of new MACE during a 16.8-year follow-up. In the second cohort, no significant association was observed between SDC4 and endothelial dysfunction, assessed by flow-mediated dilation (FMD) or nitric oxide metabolites. SDC4 levels correlated positively with C-reactive protein (CRP) in both cohorts and with PAI-1 in the cohort of patients with T2D.

CONCLUSION

Overall, we conclude that the shedding of SDC4 from endothelial cells increases under acute (TNF-α treatment) and chronic (senescence) inflammatory conditions and that increased circulating SDC4 levels are associated with systemic inflammation in pathological aging.

Proteomic analysis of endothelial cells and extracellular vesicles in response to indoxyl sulfate: Mechanisms of endothelial dysfunction in chronic kidney disease

AIMS

Cardiovascular pathology is the main cause of death in chronic kidney disease (CKD) patients. CKD is associated with the accumulation of uremic toxins in the bloodstream, and indoxyl sulfate (IS) is one of the most abundant uremic toxins found in the blood of CKD patients. We conducted an in vitro study to assess the mechanisms underlying the IS-induced endothelial dysfunction that could lead to cardiovascular diseases. We also studied their extracellular vesicles (EVs) owing to their capacity to act as messengers that transmit signals through their cargo.

MAIN METHODS

EVs were characterized by nanoparticle tracking analysis, transmission electron microscopy, flow cytometry, and tetraspanin expression. Cell lysates and isolated EVs were analyzed using liquid chromatography coupled with mass spectrometry, followed by Gene Set Enrichment Analysis to identify the altered pathways.

KEY FINDINGS

Proteomic analysis of endothelial cells revealed that IS causes an increase in proteins related to adipogenesis, inflammation, and xenobiotic metabolism and a decrease in proliferation. Extracellular matrix elements, as well as proteins associated with myogenesis, response to UV irradiation, and inflammation, were found to be downregulated in IS-treated EVs. Fatty acid metabolism was also found to be increased along with adipogenesis and inflammation observed in cells.

SIGNIFICANCE

The treatment of endothelial cells with IS increased the expression of proteins related to adipogenesis, inflammation, and xenobiotic metabolism and was less associated with proliferation. Furthermore, EVs from cells treated with IS may mediate endothelial dysfunction, since they present fewer extracellular matrix elements, myogenesis, inflammatory factors, and proteins downregulated in response to UV radiation.

The functional role of cellular senescence during vascular calcification in chronic kidney disease

Vascular calcification (VC) has emerged as a key predictor of cardiovascular events in patients with chronic kidney disease (CKD). In recent years, an expanding body of research has put forth the concept of accelerated vascular aging among CKD patients, highlighting the significance of vascular cells senescence in the process of VC. Within the milieu of uremia, senescent vascular endothelial cells (VECs) release extracellular microvesicles (MV) that promote vascular smooth muscle cells (VSMCs) senescence, thereby triggering the subsequent osteogenic phenotypic switch and ultimately contributing to the VC process. In addition, senescent vascular progenitor or stem cells with diminished ability to differentiate into VECs and VSMCS, compromise the repair of vascular integrity, on the other hand, release a cascade of molecules associated with senescence, collectively known as the senescence-associated secretory phenotype (SASP), perpetuating the senescence phenomenon. Furthermore, SASP triggers the recruitment of monocytes and macrophages, as well as adjacent VECs and VSMCs into a pro-adhesive and pro-inflammatory senescent state. This pro-inflammatory microenvironment niche not only impacts the functionality of immune cells but also influences the differentiation of myeloid immune cells, thereby amplifying the reduced ability to effectively clear senescent cells of senescent macrophages, promoted calcification of VSMCs. The objective of this paper is to provide a comprehensive review of the contribution of vascular cell senescence to the emergence and advancement of VC. Gaining a comprehensive understanding of the involvement of cellular senescence within the vessel wall is pivotal, especially when it comes to its intersection with VC. This knowledge is essential for advancing groundbreaking anti-aging therapies, aiming to effectively mitigate cardiovascular diseases.

Uremic Toxins Induce THP-1 Monocyte Endothelial Adhesion and Migration through Specific miRNA Expression

Atherosclerosis is initiated by the activation of endothelial cells that allows monocyte adhesion and transmigration through the vascular wall. The accumulation of uremic toxins such as indoxyl sulphate (IS) and p-cresol (PC) has been associated with atherosclerosis. Currently, miRNAs play a crucial role in the regulation of monocyte activation, adhesion, and trans-endothelial migration. The aim of the present study is to evaluate the effect of IS and PC on monocyte adhesion and migration processes in monocytes co-cultured with endothelial cells as well as to determine the underlying mechanisms. The incubation of HUVECs and THP-1 cells with both IS and PC toxins resulted in an increased migratory capacity of THP-1 cells. Furthermore, the exposure of THP-1 cells to both uremic toxins resulted in the upregulation of BMP-2 and miRNAs-126-3p, -146b-5p, and -223-3p, as well as the activation of nuclear factor kappa B (NF-κB) and a decrease in its inhibitor IĸB. Uremic toxins, such as IS and PC, enhance the migratory and adhesion capacity of THP-1 cells to the vascular endothelium. These toxins, particularly PC, contribute significantly to uremia-associated vascular disease by increasing in THP-1 cells the expression of BMP-2, NF-κB, and key miRNAs associated with the development of atherosclerotic vascular diseases.

miR-143-3p Promotes Ovarian Granulosa Cell Senescence and Inhibits Estradiol Synthesis by Targeting UBE2E3 and LHCGR

The ovary is a highly susceptible organ to senescence, and granulosa cells (GCs) have a crucial role in oocyte development promotion and overall ovarian function maintenance. As age advances, GCs apoptosis and dysfunction escalate, leading to ovarian aging. However, the molecular mechanisms underpinning ovarian aging remain poorly understood. In this study, we observed a correlation between the age-related decline of fertility and elevated expression levels of miR-143-3p in female mice. Moreover, miR-143-3p was highly expressed in senescent ovarian GCs. The overexpression of miR-143-3p in GCs not only hindered their proliferation and induced senescence-associated secretory phenotype (SASP) but also impeded steroid hormone synthesis by targeting ubiquitin-conjugating enzyme E2 E3 (Ube2e3) and luteinizing hormone and human chorionic gonadotropin receptor (Lhcgr). These findings suggest that miR-143-3p plays a substantial role in senescence and steroid hormone synthesis in GCs, indicating its potential as a therapeutic target for interventions in the ovarian aging process.

Gut Enterobacteriaceae and uraemic toxins - Perpetrators for ageing

Ageing is a complex process that is associated with changes in the composition and functions of gut microbiota. Reduction of gut commensals is the hallmarks of ageing, which favours the expansion of pathogens even in healthy centenarians. Interestingly, gut Enterobacteriaceae have been found to be increased with age and also consistently observed in the patients with metabolic diseases. Thus, they are associated with all-cause mortality, regardless of genetic origin, lifestyle, and fatality rate. Moreover, Enterobacteriaceae are also implicated in accelerating the ageing process through telomere attrition, cellular senescence, inflammasome activation and impairing the functions of mitochondria. However, acceleration of ageing is likely to be determined by intrinsic interactions between Enterobacteriaceae and other associated gut bacteria. Several studies suggested that Enterobacteriaceae possess genes for the synthesis of uraemic toxins. In addition to intestine, Enterobacteriaceae and their toxic metabolites have also been found in other organs, such as adipose tissue and liver and that are implicated in multiorgan dysfunction and age-related diseases. Therefore, targeting Enterobacteriaceae is a nuance approach for reducing inflammaging and enhancing the longevity of older people. This review is intended to highlight the current knowledge of Enterobacteriaceae-mediated acceleration of ageing process.

[Relationship between gut microbiota-derived substances and vascular function: focus on indoxyl sulfate and trimethylamine-N-oxide]

Emerging evidences suggest that gut microbiota-derived substances play a pivotal role in the regulation of host homeostasis including vascular function. Actually, these substances and/or their metabolites can be presented in circulation and local tissue and their levels are often abnormal in the pathophysiological states. Therefore, to determine the role of them in physiological function is important in human health. On the other hand, vascular dysfunction is a key event in the initiation and progression of systematic complications of cardiovascular, kidney and metabolic diseases including hypertension, dyslipidemia, diabetes, and atherosclerosis. Although abnormalities in endothelial and vascular smooth muscle cells play an important role on vascular dysfunction, emerging evidences has suggested that gut microbiota-derived substances can directly or indirectly affect these cellular functions. The present review will focus on the relationship between vascular function and indoxyl sulfate or trimethylamine-N-oxide (TMAO).