Endothelial Progenitor Cells Senescence Research Articles

Role of NOX2 in mediating doxorubicin-induced senescence in human endothelial progenitor cells

Senescence exerts a great impact on both biological and functional properties of circulating endothelial progenitor cells (EPCs), especially in cardiovascular diseases where the physiological process of aging is accelerated upon clinical administration of certain drugs such as doxorubicin. EPC impairment contributes to doxorubicin-induced cardiotoxicity. Doxorubicin accelerates EPC aging, although mechanisms underlying this phenomenon remain to be fully clarified. Here we investigated if Nox2 activity is able to modulate the premature senescence induced in vitro by doxorubicin in human EPCs. Results showed that in conditioned media obtained from late EPC cultures, the levels of interleukin-6, isoprostanes and nitric oxide bioavailability were increased and reduced respectively after 3h of doxorubicin treatment. These derangements returned to physiological levels when cells were co-treated with apocynin or gp91ds-tat (antioxidant and specific Nox2 inhibitors, respectively). Accordingly, Nox2 activity resulted to be activated by doxorubicin. Importantly, we found that Nox2 inhibition reduced doxorubicin-induced EPC senescence, as indicated by a lower percentage of β-gal positive EPCs. In conclusion, Nox2 activity efficiently contributes to the mechanism of oxidative stress-induced increase in premature aging conferred by doxorubicin. The importance of modulation of Nox2 in human EPCs could reveal a useful tool to restore EPC physiological function and properties.

Non-muscle myosin light chain promotes endothelial progenitor cells senescence and dysfunction in pulmonary hypertensive rats through up-regulation of NADPH oxidase

Non-muscle myosin regulatory light chain (nmMLC20) is reported to exert transcriptional function in regulation of gene expression, and NADPH oxidase (NOX)-derived reactive oxygen species contribute to vascular remodeling of pulmonary artery hypertension (PAH). This study aims to determine if nmMLC20 can promote endothelial progenitor cells (EPCs) senescence and dysfunction through up-regulation of NOX in PAH rats. The rats were exposed to10% hypoxia for 3 weeks to establish a PAH model, which showed an increase in right ventricle systolic pressure, right ventricular and pulmonary vascular remodeling, and the accelerated senescence and impaired functions in EPCs, accompanied by an increase in Rho-kinase (ROCK) and NOX activities, p-nmMLC20 level, NOX expression and H2O2 content; these phenomena were reversed by fasudil, a selective inhibitor of ROCK. Next, normal EPCs were cultured under hypoxia to induce senescence in vitro. Consistent with the in vivo findings, hypoxia increased the senescence and dysfunction of EPCs concomitant with an increase in ROCK and NOX activities, p-nmMLC20 level, NOX expression and H2O2 content; these phenomena were reversed by fasudil. Knockdown of nmMLC20 showed similar results to that of fasudil except no effect on ROCK activity. Based on these observations, we conclude that nmMLC20 could promote the senescence and dysfunctions of EPCs in PAH through up-regulation of NOX in a phosphorylation-dependent manner.

Stress-Induced Premature Senescence of Endothelial and Endothelial Progenitor Cells.

This brief overview of premature senescence of dysfunctional endothelial and endothelial progenitor cells provides information on endothelial cell differentiation and specialization, their ontogeny, and controversies related to endothelial stem and progenitor cells. Stressors responsible for the dysfunction of endothelial and endothelial progenitor cells, as well as cellular mechanisms and consequences of endothelial cell dysfunction are presented. Metabolic signatures of dysfunctional endothelial cells and senescence pathways are described. Emerging strategies to rejuvenate endothelial and endothelial progenitor cells conclude the review.

Involvement of NADPH oxidases and non-muscle myosin light chain in senescence of endothelial progenitor cells in hyperlipidemia.

NADPH oxidase (NOX)-derived reactive oxygen species (ROS) is involved in endothelial dysfunction of hyperlipidemia, and non-muscle myosin regulatory light chain (nmMLC20) is reported to have a transcriptional function in regulation of gene expression. The purposes of this study are to determine whether NOX-derived ROS can promote endothelial progenitor cell (EPC) senescence and whether nmMLC20 can regulate NOX expression through a phosphorylation-dependent manner. The rats were subjected to 8 weeks of high-fat diet feeding to establish a hyperlipidemic model, which showed an increase in plasma lipids and the accelerated senescence and reduced number of circulating EPCs, accompanied by an increase in myosin light chain kinase (MLCK) and NOX activities, p-nmMLC20 level, NOX (NOX2, NOX4) expression, and H2O2 content. Next, EPCs isolated from normal rats were incubated with ox-LDL (100 μg/mL) for 24 h to establish a senescent model in vitro. Consistent with our in vivo findings, ox-LDL treatment increased the senescence of EPCs concomitant with an increase in MLCK and NOX activities, p-nmMLC20 level (in total or nuclear proteins), NOX expression, and H2O2 content; these phenomena were reversed by MLCK inhibitor. NOX inhibitor achieved similar results to that of MLCK inhibitor except that there is no effect on MLCK activity and p-nmMLC20 level. Furthermore, knockdown of nmMLC20, NOX2, or NOX4 led to a down-regulation in NOX and a reduction in ox-LDL-induced EPC senescence. These results suggest that NOX-derived ROS promotes the senescence of circulating EPCs in hyperlipidemia and nmMLC20 may play a transcriptional role in the upregulation of NOX through a phosphorylation-dependent manner.

Bradykinin inhibits oxidative stress-induced senescence of endothelial progenitor cells through the B2R/AKT/RB and B2R/EGFR/RB signal pathways.

Circulating endothelial progenitor cells (EPCs) have multiple protective effects that facilitate repair of damage to tissues and organs. However, while various stressors are known to impair EPC function, the mechanisms of oxidative stress-induced EPC senescence remains unknown. We demonstrated that B2 receptor (B2R) expression on circulating CD34(+) cells was significantly reduced in patients with diabetes mellitus (DM) as compared to healthy controls. Furthermore, CD34(+) cell B2R expression in patients with DM was inversely correlated with plasma myeloperoxidase concentrations. Bradykinin (BK) treatment decreased human EPC (hEPC) senescence and intracellular oxygen radical production, resulting in reduced retinoblastoma 1 (RB) RNA expression in H2O2-induced senescent hEPCs and a reversal of the B2R downregulation that is normally observed in senescent cells. Furthermore, BK treatment of H2O2-exposed cells leads to elevated phosphorylation of RB, AKT, and cyclin D1 compared with H2O2-treatment alone. Antagonists of B2R, PI3K, and EGFR signaling pathways and B2R siRNA blocked BK protective effects. In summary, this study demonstrates that BK significantly inhibits oxidative stress-induced hEPC senescence though B2R-mediated activation of PI3K and EGFR signaling pathways.

Anthocyanins-rich chokeberry fruit extract reduces endothelial progenitor cells senescence and protects against oxidative stress induced by angiotensin II

Anthocyanins-rich chokeberry fruit extract reduces endothelial progenitor cells senescence and protects against oxidative stress induced by angiotensin II

Stromal cell-derived factor-1α prevents endothelial progenitor cells senescence and enhances re-endothelialization of injured arteries via human telomerase reverse transcriptase.

Recent studies have suggested that endothelial progenitor subpopulation (EPCs) number and activity were associated with EPCs senescence. Our previous study had shown that stromal cell-derived factor-1alpha (SDF-1α) could prevent EPCs senescence, which may be via telomerase. In this study, we further investigated the role of human telomerase reverse transcriptase (h-TERT) on the protective effect of SDF-1α against senescence. Knockdown h-TERT abrogated the protective effect of SDF-1α and abolished the effects of SDF-1α on migration and proliferation. Moreover, it inhibited EPCs recruitment. In conclusion, h-TERT served a critical role in the progress that SDF-1α prevented EPCs senescence and enhanced re-endothelialization of the injured arteries.

Angelica sinensis polysaccharides inhibit endothelial progenitor cell senescence through the reduction of oxidative stress and activation of the Akt/hTERT pathway

Context: Angelica sinensis (Oliv.) Diels (Apiaceae) polysaccharides (ASP) may play a key role in anti-ischemic activity. However, the anti-atherosclerotic activity and mechanism are unknown.Objective: This study investigated the protective effects of ASP against ox-LDL-induced senescence of EPCs and explored its underlying molecular mechanisms.Materials and methods: Mononuclear cells were isolated from bone marrow (BM) of SD rats and differentiated to EPCs. EPCs were exposed to oxidized low-density lipoprotein (ox-LDL, 10 µg/mL, 24 h) and incubated with or without high-dose (100 µg/mL, 48 h) or low-dose (20 µg/mL, 48 h) ASP. Another group of EPCs was pre-treated with Wortmannin (100 nM, 45 min), a PI3K/Akt inhibitor. EPC senescence, telomerase activity, and superoxide anion levels were assessed using SA-β-galactosidase staining, telomerase PCR-ELISA analysis, and DHE staining, respectively. The expression of related proteins, including Akt, p-Akt, hTERT, p-hTERT, and gp91phox, were detected using western blot.Results: EPCs (47.3%) were SA-β-gal positive after treatment by ox-LDL, additionally, ox-LDL significantly increased superoxide anion levels (375% versus 100%), and inhibited telomerase activity (42% versus 100%). However, the pro-senescent effect of ox-LDL was attenuated about three-fold (16.7%), superoxide anion levels were decreased more than two-fold (148%), and telomerase activity was recovered partly (88% versus 42%) in the EPCs when treated with ASP (100 µg/mL). The immunoblotting confirmed that ASP attenuated inhibition of phosphorylation of Akt and hTERT induced by ox-LDL and down-regulated increased the expression of gp91-phox. Moreover, some effects of ASP were partially abrogated in the presence of Wortmannin.Discussion: Ox-LDL induced senescence of EPCs via inhibition of telomerase activity, which was influenced by oxidative stress and the Akt/hTERT pathway. The inhibition of EPC senescence by ASP could be important for potential therapeutics.Conclusion: Treatment of EPCs with ASP remarkably attenuates the harmful effects of ox-LDL via augmentation of Akt/hTERT phosphorylation and inhibition of oxidative stress.

MicroRNA-34a: a new player in arterial inflammaging

Arterial inflammaging highly contributes to cardiovascular morbidity and mortality. As vascular cells age they become senescent and sustain a chronic low grade sterile inflammation by acquiring a senescence-associated secretory phenotype (SASP). The molecular mechanisms leading to the phenotypic changes affecting endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are also relevant for the pathogenesis of vascular diseases, such as atherosclerosis and hypertension. Therefore, unravelling the etiology of vascular inflammaging becomes of crucial importance. MicroRNAs (miRNAs) are small non-coding negative post-transcriptional regulator that are emerging as promising drug targets. MicroRNA-34a (miR-34a) had been implicated in tissues aging and endothelial and endothelial progenitor cells senescence. Our recent work showed that this miRNA is upregulated in aged mouse aortas as well as in senescent VSMCs. Conversely, its target SIRT1 is downregulated in the same specimens. We also found that miR-34a can inhibit VSMCs proliferation and induce VSMCs senescence, the latter by the direct regulation of SIRT1. Notably, for the first time, we demonstrated that miR-34a is also able to modulate the SASP by inducing the transcriptional expression of a subset of pro-inflammatory factors in a SIRT1-independent manner. These data support a model in which the age-dependent upregulation of miR-34a, by affecting senescence and inflammation of vascular cells, could play a causal role to arterial dysfunctions. Hence, further studies are necessary to unravel miR-34a-dependent mechanisms leading to arterial inflammaging in order to develop an effective strategy to age-related cardiovascular complications.

Accelerated onset of senescence of endothelial progenitor cells in patients with type 2 diabetes mellitus: Role of dimethylarginine dimethylaminohydrolase 2 and asymmetric dimethylarginine

The risk of cardiovascular complications in diabetic patients is mainly associated with endothelial dysfunction. Reduced number of EPCs and impaired function of EPCs in diabetes result in imbalance of endothelial homeostasis and dysfunction of vessels. In patients with diabetes mellitus, plasma levels of asymmetric dimethylarginine (ADMA) were elevated, while the expression and activity of dimethylarginine dimethylaminohydrolase (DDAH) were reduced. In the present study, we investigated the role of the DDAH2/ADMA pathway in the senescence of EPCs in type 2 diabetic patients and cultured EPCs treated with high glucose. The results showed that the percentage of senescent EPCs increased while the expression of DDAH2 decreased concomitantly with an increase in the plasma levels of ADMA in patients with type 2 diabetes mellitus (T2DM). Similar results were seen in cultured EPCs treated with high glucose. Exogenous application of ADMA accelerated the senescence of EPCs in a dose-dependent manner, and overexpression of DDAH2 inhibited high glucose-induced EPCs senescence. In addition, it has also been reported that DDAH/ADMA pathway is regulated by silent information regulator 1 (SIRT1) in endothelial cell. In the present study, we found decreased expression of SIRT1 both in T2DM patients and EPCs pretreated with high glucose. And resveratrol (activating SIRT1) inhibited high glucose-induced EPCs senescence by upregulating the expression of DDAH2 and decreasing the levels of ADMA. Taken together, we concluded that DDAH2/ADMA is involved in the accelerated senescence of EPCs in diabetes, which is associated with the activation of SIRT1.

Abstract 20452: Microrna-200b Induces Endothelial Progenitor Cell Apoptosis and Senescence by Targeting Cjun Expression

Introduction: Lineage negative bone marrow cells (Lin - BMCs) mediate vascular repair. Aging-associated apoptosis and senescence result in reduced number and impair Lin - BMCs’s pro-repair capacity. Molecular mechanisms underlying lin - BMCs apoptosis and senescence remain poorly understood. MicroRNAs (miRNAs) regulate many important biological processes. The identification of miRNA-mRNA networks that modulate the health and functionality of lin - BMCs is a critical step in understanding the process of vascular repair. Hypothesis: miR-200b-cJun network plays a vital role in regulating Lin - BMCs apoptosis, senescence and self renewal in angiogenesis. Methods: Lin - BMCs were isolated from young (3-week-old) wild type (WT), young apoE -/- , aged WT (29-month-old) and aged apoE -/- (12 month-old) C57BL/6 mice. Global miRNA and gene expression profiling were analyzed. Results: Transcriptome analysis in Lin - BMCs isolated from young and aged WT and apoE -/- mice showed a significant aging-associated increase in miR-200b expression. We found that C-Jun was predicted to be a miR-200b target and c-Jun expression was reversely correlated with miR-200b levels. Luciferase reporter assays confirmed c-Jun as a direct target of miR-200b. MiR-200b overexpression in young lin-BMCs inhibited c-Jun expression, resulting in increased senescence and apoptosis in vitro and impaired angiogenic capacity in vivo . In contrast, suppression of miR-200b or overexpression of c-Jun in aged lin - BMCs increased c-Jun expression rejuvenated Lin - BMCs with decreased senescence and apoptosis, leading to improved angiogenesis in vitro and in vivo . Conclusions: Using genomic and functional studies, we discovered that miR-200b regulates apoptosis and senescence of age-associated lin - BMCs by suppressing c-Jun expression, thus negatively affecting vascular repair capacity of those cells in atherogenesis. Modulation of miR-200b and/or its target c-Jun may suggest a potential therapeutic intervention to improve Lin - BMCs-mediated angiogenesis and vascular repair.

Homocysteine accelerates senescence of endothelial cells via DNA hypomethylation of human telomerase reverse transcriptase.

Homocysteine can accelerate the senescence of endothelial progenitor cells or endothelial cells (ECs) via telomerase inactivation and length shortening. However, the underlying mechanism is unclear. Here, we investigated whether homocysteine promotes endothelial senescence by reducing the expression and activity of human telomerase reverse transcriptase (hTERT) by DNA methylation to reduce ECs telomerase activity. When compared with primary human umbilical vein endothelial cells grown under standard conditions, ECs with chronic homocysteine treatment showed accelerated upregulation of p16, p21, and p53, markers of cellular senescence, during 6 to 10 passages. Interestingly, homocysteine-stimulated but not angiotensin II-stimulated ECs senescence could be reversed by hypermethylation induced by folic acid or s-adenosylmethionine supplementation. Meanwhile, homocysteine promoted the shortening of telomere length specifically related to restoration of hTERT transcriptional expression and CCCTC-binding factor binding sites with hTERT promoter hypomethylation, as detected by quantitative real-time polymerase chain reaction, Western blot, methylation-specific polymerase chain reaction, and bisulfite sequencing assay. Electrophoretic mobility shift assay and chromatin immunoprecipitation results showed that homocysteine-reduced telomere activity and homocysteine-induced EC senescence might contribute to hTERT promoter demethylation by increasing CCCTC-binding factor repression and interfering in the SP1 binding to the demethylated hTERT promoter, which might relate with reduced of DNA methyltransferase 1. Furthermore, the CCCTC-binding factor-dependent mechanism of homocysteine-reduced hTERT expression via DNA demethylation was confirmed in aortic endothelia of mice with hyperhomocysteine levels. CCCTC-binding factor and SP1 cross talk may contribute to homocysteine-reduced hTERT DNA methylation and expression in endothelial senescence.

The GroEL protein of Porphyromonas gingivalis accelerates tumor growth by enhancing endothelial progenitor cell function and neovascularization.

Porphyromonas gingivalis is a bacterial species that causes destruction of periodontal tissues. Additionally, previous evidence indicates that GroEL from P. gingivalis may possess biological activities involved in systemic inflammation, especially inflammation involved in the progression of periodontal diseases. The literature has established a relationship between periodontal disease and cancer. However, it is unclear whether P. gingivalis GroEL enhances tumor growth. Here, we investigated the effects of P. gingivalis GroEL on neovasculogenesis in C26 carcinoma cell-carrying BALB/c mice and chick eggs in vivo as well as its effect on human endothelial progenitor cells (EPC) in vitro. We found that GroEL treatment accelerated tumor growth (tumor volume and weight) and increased the mortality rate in C26 cell-carrying BALB/c mice. GroEL promoted neovasculogenesis in chicken embryonic allantois and increased the circulating EPC level in BALB/c mice. Furthermore, GroEL effectively stimulated EPC migration and tube formation and increased E-selectin expression, which is mediated by eNOS production and p38 mitogen-activated protein kinase activation. Additionally, GroEL may enhance resistance against paclitaxel-induced cell cytotoxicity and senescence in EPC. In conclusion, P. gingivalis GroEL may act as a potent virulence factor, contributing to the neovasculogenesis of tumor cells and resulting in accelerated tumor growth.

MicroRNA-34a Induces Vascular Smooth Muscle Cells Senescence by SIRT1 Downregulation and Promotes the Expression of Age-Associated Pro-inflammatory Secretory Factors.

Arterial aging is a major risk factor for the occurrence of cardiovascular diseases. The aged artery is characterized by endothelial dysfunction and vascular smooth muscle cells altered physiology together with low-grade chronic inflammation. MicroRNA-34a (miR-34a) has been recently implicated in cardiac, endothelial, and endothelial progenitor cell senescence; however, its contribution to aging-associated vascular smooth muscle cells phenotype has not been explored so far. We found that miR-34a was highly expressed in aortas isolated from old mice. Moreover, its well-known target, the longevity-associated protein SIRT1, was significantly downregulated during aging in both endothelial cells and vascular smooth muscle cells. Increased miR-34a as well as decreased SIRT1 expression was also observed in replicative-senescent human aortic smooth muscle cells. miR-34a overexpression in proliferative human aortic smooth muscle cells caused cell cycle arrest along with enhanced p21 protein levels and evidence of cell senescence. Furthermore, miR-34a ectopic expression induced pro-inflammatory senescence-associated secretory phenotype molecules. Finally, SIRT1 protein significantly decreased upon miR-34a overexpression and restoration of its levels rescued miR-34a-dependent human aortic smooth muscle cells senescence, but not senescence-associated secretory phenotype factors upregulation. Taken together, our findings suggest that aging-associated increase of miR-34a expression levels, by promoting vascular smooth muscle cells senescence and inflammation through SIRT1 downregulation and senescence-associated secretory phenotype factors induction, respectively, may lead to arterial dysfunctions.

Endothelial progenitor cells in diabetic patients with myocardial infarction – Can statins improve their function?

The effect of statins on endothelial progenitor cells (EPCs) function derived from diabetic patients (DMpts) with acute myocardial infarction (AMI) is unknown. In this study we assess the response of early and late EPCs from diabetic versus non-diabetic patients (NDMpts) with AMI to statins. EPCs were obtained from 10 diabetic and 10 age-matched non-diabetic male patients with AMI. For each patient, cultures of early and late EPCs were performed under 4 different conditions: normal glucose concentration (control); high glucose concentration; normal glucose concentration with atorvastatin supplementation and normal glucose concentration with pravastatin supplementation. To compare the effect of these treatments on EPC function in DMpts versus NDMpts, we performed in vitro: EPC colony-forming units (CFU) assay; cell cycle analysis; viability assessment and expression of the surface markers CXCR4, CD133, CD34 and KDR. Under control conditions, CFU numbers were reduced in DMpts-derived EPCs when compared to those of NDMpts (1.4±0.8 vs 2.6±1.2 CFU/well, P=0.021). When early EPCs from DMpts were cultured in the presence of statins, CFU capacity was restored, surmounting that of NDMpts under control conditions. Statins significantly improved viability of early EPCs and delayed the onset of late EPCs senescence, even in cells from DMpts. In addition, statins induced approximately a 2-fold increase in the proportion of late EPCs in S-phase of the cell cycle (P<0.05). Statins have a beneficial effect on both early and late EPCs from DMpts with AMI. Despite the functional impairment of EPCs from DMpts, they exhibit similar responsiveness to statins as equivalent cells from NDMpts.

Cleaved high molecular weight kininogen stimulates JNK/FOXO4/MnSOD pathway for induction of endothelial progenitor cell senescence

ObjectiveRecently we have reported that cleaved high molecular weight kininogen (HKa) accelerates the onset of endothelial progenitor cells (EPCs) senescence by induction of reactive oxygen species (ROS). However, the mechanisms by which HKa induces production of ROS remain unknown. In this study, we have shown that HKa induces EPC senescence via stimulation of c-Jun N-terminal kinases (JNK)-related pathway. Methods and resultsTreatment of human EPCs with HKa for 72h stimulated JNK phosphorylation at Thr183/Tyr185, and FOXO4 phosphorylation at Thr451, Concomitantly, upregulated the expression of MnSOD at protein and mRNA levels in a concentration-dependent manner. HKa increased intracellular level of H2O2, without affecting the expression of catalase. To narrow down the functional domain of HKa, recombinant proteins of human HK heavy chain (HC, 19–380aa) and light chain (LC, 390–644aa) were generated. HC, but not LC, increased senescence of EPCs and intracellular ROS levels, to a similar extent with HKa. Moreover, HC at 50nM increased FOXO4 phosphorylation at Thr451 and the protein level of MnSOD in EPCs. ConclusionThese results demonstrate that HKa accelerates the onset of EPC senescence by stimulating JNK/FOXO4/MnSOD pathway, its effect is mediated by the HC.

Regulation of endothelial progenitor cell differentiation and function by dimethylarginine dimethylaminohydrolase 2 in an asymmetric dimethylarginine-independent manner.

Endothelial progenitor cells (EPCs) are involved in the repair of vessels and angiogenesis and are useful in the treatment of ischemic diseases. The dimethylarginine dimethylaminohydrolase (DDAH)/asymmetric dimethylarginine (ADMA) pathway is regulated by silent information regulator 1 (SIRT1), leading to the senescence of endothelial cells (ECs). Here, we demonstrated that peripheral blood EPCs predominantly expressed DDAH2 that increased with EPC differentiation. EPC senescence and dysfunction were induced on interruption of DDAH2 expression, whereas the mRNA expression of vascular endothelial growth factor (VEGF) and kinase-domain insert containing receptor (KDR) were downregulated. Moreover, SIRT1 expression increased with EPC differentiation. Interruption of SIRT1 inhibited DDAH2, VEGF, and KDR expression, but had no effect on the level of ADMA. From our data, we concluded that DDAH2 is involved in the differentiation of EPCs and regulates the senescence and function of EPCs through the VEGF/KDR pathway by activation of SIRT1.

Accelerated senescence of cord blood endothelial progenitor cells in premature neonates is driven by SIRT1 decreased expression

AbstractEpidemiological and experimental studies indicate that early vascular dysfunction occurs in low-birth-weight subjects, especially preterm (PT) infants. We recently reported impaired angiogenic activity of endothelial colony-forming cells (ECFCs) in this condition. We hypothesized that ECFC dysfunction in PT might result from premature senescence and investigated the underlying mechanisms. Compared with ECFCs from term neonates (n = 18), ECFCs isolated from PT (n = 29) display an accelerated senescence sustained by growth arrest and increased senescence-associated β-galactosidase activity. Increased p16INK4a expression, in the absence of telomere shortening, indicates that premature PT-ECFC aging results from stress-induced senescence. SIRT1 level, a nicotinamide adenine dinucleotide-dependent deacetylase with anti-aging activities, is dramatically decreased in PT-ECFCs and correlated with gestational age. SIRT1 deficiency is subsequent to epigenetic silencing of its promoter. Transient SIRT1 overexpression or chemical induction by resveratrol treatment reverses senescence phenotype, and rescues in vitro PT-ECFC angiogenic defect in a SIRT1-dependent manner. SIRT1 overexpression also restores PT-ECFC capacity for neovessel formation in vivo. We thus demonstrate that decreased expression of SIRT1 drives accelerated senescence of PT-ECFCs, and acts as a critical determinant of the PT-ECFC angiogenic defect. These findings lay new grounds for understanding the increased cardiovascular risk in individuals born prematurely and open perspectives for therapeutic strategy.

Effect of lipopolysaccharide on the characteristics of endothelial progenitor cells from bone marrow in mice

Previous studies have shown that lipopolysaccharide (LPS) induces acute lung injury (ALI), and that endothelial progenitor cells (EPCs) participate in tissue repair. Therefore, in this study it was hypothesized that LPS influences the number and function of EPCs directly. In order to investigate this, an in vitro study was performed using EPCs. EPCs were cultured for seven days (early EPCs), and then treated with increasing concentrations of LPS (10 pg/ml, 100 pg/ml, 1 ng/ml, 10 ng/ml and 100 ng/ml) for 4, 8, 12, and 24 h. The proliferation, senescence and adhesion of EPCs was then assessed. Alongside this an in vivo study was also performed. Mice were administered LPS (2.5 mg/kg) via the trachea. After 4, 8, 12, and 24 h, EPCs were harvested and cultured for seven days, and the proliferation, senescence and adhesion of the EPCs were examined. The results showed that the rate of adhesion and senescence of EPCs decreased in vitro when treated with 10 and 100 ng/ml LPS. The adhesion and senescence rate also decreased after 12 and 24 h in vivo. Proliferation, however, was increased in vitro following treatment with 10 and 100 ng/ml LPS, but proliferation in vivo decreased after 8 and 12 h. The effects of LPS on EPCs were distinct in vivo and in vitro. In vitro, cells were sensitive to 100 ng/ml LPS. In the course of ALI induced by LPS, the proliferation and adhesion activity of the EPCs was activated in 8 h and then gradually decreased with time.

Early accelerated senescence of circulating endothelial progenitor cells in premature coronary artery disease patients in a developing country - a case control study

BackgroundThe decreased number and senescence of circulating endothelial progenitor cells (EPCs) are considered markers of vascular senescence associated with aging, atherosclerosis, and coronary artery disease (CAD) in elderly. In this study, we explore the role of vascular senescence in premature CAD (PCAD) in a developing country by comparing the numerical status and senescence of circulating EPCs in PCAD patients to controls.MethodsEPCs were measured by flow cytometry in 57 patients with angiographically documented CAD, and 57 controls without evidence of CAD, recruited from random patients ≤ 50 years of age at All India Institute of Medical Sciences. EPC senescence as determined by telomere length (EPC-TL) and telomerase activity (EPC-TA) was studied by real time polymerase chain reaction (q PCR) and PCR– ELISA respectively.ResultThe number of EPCs (0.18% Vs. 0.039% of total WBCs, p < 0.0001), and EPC-TL (3.83 Vs. 5.10 kb/genome, p = 0.009) were markedly lower in PCAD patients compared to controls. These differences persisted after adjustment for age, sex, BMI, smoking and medications. EPC-TA was reduced in PCAD patients, but was statistically significant only after adjustment for confounding factors (1.81 Vs. 2.20 IU/cell, unadjusted p = 0.057, adjusted p = 0.044).ConclusionsWe observed an association between increased vascular cell senescence with PCAD in a sample of young patients from India. This suggests that early accelerated vascular cell senescence may play an important mechanistic role in CAD epidemic in developing countries like India where PCAD burden is markedly higher compared to developed countries.