Persistent epigenetic signals propel a senescence-associated secretory phenotype and trained innate immunity in CD34+ hematopoietic stem cells from diabetic patients

BACKGROUND

Diabetes-induced trained immunity contributes to the development of atherosclerosis and its complications. This study aimed to investigate in humans whether epigenetic signals involved in immune cell activation and inflammation are initiated in hematopoietic stem/progenitor cells (HSPCs) and transferred to differentiated progeny.

METHODS AND RESULTS

High glucose (HG)-exposure of cord blood (CB)-derived HSPCs induced a senescent-associated secretory phenotype (SASP) characterized by cell proliferation lowering, ROS production, telomere shortening, up-regulation of p21 and p27genes, upregulation of NFkB-p65 transcription factor and increased secretion of the inflammatory cytokines TNFα and IL6. Chromatin immunoprecipitation assay (ChIP) of p65 promoter revealed that H3K4me1 histone mark accumulation and methyltransferase SetD7 recruitment, along with the reduction of repressive H3K9me3 histone modification, were involved in NFkB-p65 upregulation of HG-HSPCs, as confirmed by increased RNA polymerase II engagement at gene level. The differentiation of HG-HSPCs into myeloid cells generated highly responsive monocytes, mainly composed of intermediate subsets (CD14hiCD16+), that like the cells from which they derive, were characterized by SASP features and similar epigenetic patterns at the p65 promoter. The clinical relevance of our findings was confirmed in sternal BM-derived HSPCs of T2DM patients. In line with our in vitro model, T2DM HSPCs were characterized by SASP profile and SETD7 upregulation. Additionally, they generated, after myeloid differentiation, senescent monocytes mainly composed of proinflammatory intermediates (CD14hiCD16+) characterized by H3K4me1 accumulation at NFkB-p65 promoter.

CONCLUSIONS

Hyperglycemia induces marked chromatin modifications in HSPCs, which, once transmitted to the cell progeny, contributes to persistent and pathogenic changes in immune cell function and composition.

High Phosphate-Induced JAK-STAT Signalling Sustains Vascular Smooth Muscle Cell Inflammation and Limits Calcification

Vascular calcification (VC) is an age-related complication characterised by calcium-phosphate deposition in the arterial wall driven by the osteogenic transformation of vascular smooth muscle cells (VSMCs). The JAK-STAT pathway is an emerging target in inflammation. Considering the relationship between VC and inflammation, we investigated the role of JAK-STAT signalling during VSMC calcification. Human aortic smooth muscle cells (HASMCs) were cultured in high-inorganic phosphate (Pi) medium for up to 7 days; calcium deposition was determined via Alizarin staining and colorimetric assay. Inflammatory factor secretion was evaluated via ELISA and JAK-STAT members' activation using Western blot or immunohistochemistry on HASMCs or calcified aortas of Vitamin D-treated C57BL6/J mice, respectively. The JAK-STAT pathway was blocked by JAK Inhibitor I and Von Kossa staining was used for calcium deposits in murine aortic rings. During Pi-induced calcification, HASMCs released IL-6, IL-8, and MCP-1 and activated JAK1-JAK3 proteins and STAT1. Phospho-STAT1 was detected in murine calcified aortas. Blocking of the JAK-STAT cascade reduced HASMC proliferation and pro-inflammatory factor expression and release while increasing calcium deposition and osteogenic transcription factor RUNX2 expression. Consistently, JAK-STAT pathway inhibition exacerbates mouse aortic ring calcification ex vivo. Intriguingly, our results suggest an alternative link between VSMC inflammation and VC.

Human Hematopoietic Stem/Progenitor Cells in Type One Diabetes Mellitus Treatment: Is There an Ideal Candidate?

Type 1 diabetes mellitus (T1DM) is a highly prevalent autoimmune disease causing the destruction of pancreatic islet β-cells. The resulting insulin production deficiency leads to a lifelong need for insulin re-placement therapy, systemic complications, and reduced life quality and expectancy. Cell therapy has been extensively attempted to restore insulin independence (IID), and autologous nonmyeloablative hematopoietic stem cell transplantation (AHST) has appeared to give the most promising results, but with a highly variable quote of patients achieving IID across the studies. We performed a comprehensive review of the trials involving stem cells, and in particular AHST, for the treatment of T1DM. We then pooled the patients enrolled in the different trials and looked for the patient characteristics that could be associated with the achievement of IID. We found a significantly higher probability of achieving IID in older patients (OR 1.17, 95%CI 1.06–1.33, p = 0.002) and a significantly lower probability in patients with a history of ketoacidosis (OR 0.23, 95%CI 0.06–0.78, p = 0.023). This suggests that there could be a population of patients more likely to benefit from AHST, but further data would be required to depict the profile of the ideal candidate.

Effects of RAGE Deletion on the Cardiac Transcriptome during Aging

Cardiac aging is characterized by increased cardiomyocyte hypertrophy, myocardial stiffness, and fibrosis, which enhance cardiovascular risk. The receptor for advanced glycation end-products (RAGE) is involved in several age-related diseases. RAGE knockout (Rage−/−) mice show an acceleration of cardiac dimension changes and interstitial fibrosis with aging. This study identifies the age-associated cardiac gene expression signature induced by RAGE deletion. We analyzed the left ventricle transcriptome of 2.5-(Young), 12-(Middle age, MA), and 21-(Old) months-old female Rage−/− and C57BL/6N (WT) mice. By comparing Young, MA, and Old Rage−/− versus age-matched WT mice, we identified 122, 192, and 12 differently expressed genes, respectively. Functional inference analysis showed that RAGE deletion is associated with: (i) down-regulation of genes involved in antigen processing and presentation of exogenous antigen, adaptive immune response, and cellular responses to interferon beta and gamma in Young animals; (ii) up-regulation of genes related to fatty acid oxidation, cardiac structure remodeling and cellular response to hypoxia in MA mice; (iii) up-regulation of few genes belonging to complement activation and triglyceride biosynthetic process in Old animals. Our findings show that the age-dependent cardiac phenotype of Rage−/− mice is associated with alterations of genes related to adaptive immunity and cardiac stress pathways.

Circulating levels of AGEs and soluble RAGE isoforms are associated with all-cause mortality and development of cardiovascular complications in type 2 diabetes: a retrospective cohort study

BACKGROUND

Advanced glycation end-products (AGEs) and their interaction with the receptor for advanced glycation end-products (RAGE) play a pivotal role in the development and progression of type 2 diabetes. In this retrospective cohort study, we explored the association of circulating levels of soluble RAGE (sRAGE) isoforms, i.e., endogenous secretory esRAGE and cleaved cRAGE, AGEs and their respective ratios with 15-year all-cause mortality in type 2 diabetes.

METHODS

Baseline AGEs and sRAGE isoforms concentration were measured by ELISA in 362 patients with type 2 diabetes and in 125 age- and gender-matched healthy control subjects (CTR). Independent predictors of mortality were determined using Cox proportional-hazards models and used to build and validate a nomogram for all-cause mortality prediction in type 2 diabetes.

RESULTS

AGEs, total sRAGE, cRAGE and the AGEs/sRAGE and AGEs/esRAGE ratios were significantly increased in patients with type 2 diabetes compared to CTR (p < 0.001). In CTR subjects, but not in type 2 diabetes patients, a significant negative correlation between cRAGE and age was confirmed (p = 0.003), whereas the AGEs/sRAGE (p = 0.032) and AGEs/cRAGE (p = 0.006) ratios were positively associated with age. At an average follow-up of 15 years (4,982 person-years), 130 deaths were observed. The increase in the AGEs/cRAGE ratio was accompanied by a higher risk of all-cause mortality in patients with type 2 diabetes (HR per each SD increment = 1.30, 95% CI 1.15-1.47; p < 0.001). Moreover, sRAGE was associated with the development of major adverse cardiovascular events (MACE) in type 2 diabetes patients without previous MACE (OR for each SD increase: 1.48, 95% CI 1.11-1.89). A nomogram based on age, sex, HbA1c, systolic blood pressure, and the AGEs/cRAGE ratio was built to predict 5-, 10- and 15-year survival in type 2 diabetes. Patients were categorized into quartiles of the monogram scores and Kaplan-Meier survival curves confirmed the prognostic accuracy of the model (log-rank p = 6.5 × 10- 13).

CONCLUSIONS

The ratio between AGEs and the cRAGE isoform is predictive of 15-year survival in patients with type 2 diabetes. Our data support the assessment of circulating AGEs and soluble RAGE isoforms in patients with type 2 diabetes as predictors of MACE and all-cause mortality.

Liraglutide preserves CD34+ stem cells from dysfunction Induced by high glucose exposure

Background

Glucagon like peptide-1 receptor agonists (GLP-1RAs) have shown to reduce mortality and cardiovascular events in patients with type 2 diabetes mellitus (T2DM). Since the impairment in number and function of vasculotrophic circulating CD34⁺ hematopoietic stem progenitor cells (HSPCs) in T2D has been reported to increase cardiovascular (CV) risk, we hypothesized that one of the mechanisms whereby GLP-1 RAs exert CV protective effects may be related to the ability to improve CD34⁺ HSPC function.

Methods

In cord blood (CB)-derived CD34⁺ HSPC, the expression of GLP-1 receptor (GLP-1R) mRNA, receptor protein and intracellular signaling was evaluated by RT-qPCR and Western Blot respectively. CD34⁺ HSPCs were exposed to high glucose (HG) condition and GLP-1RA liraglutide (LIRA) was added before as well as after functional impairment. Proliferation, CXCR4/SDF-1α axis activity and intracellular ROS production of CD34⁺ HSPC were evaluated.

Results

CD34⁺ HSPCs express GLP-1R at transcriptional and protein level. LIRA treatment prevented and rescued HSPC proliferation, CXCR4/SDF-1α axis activity and metabolic imbalance from HG-induced impairment. LIRA stimulation promoted intracellular cAMP accumulation as well as ERK1/2 and AKT signaling activation. The selective GLP-1R antagonist exendin (9–39) abrogated LIRA-dependent ERK1/2 and AKT phosphorylation along with the related protective effects.

Conclusion

We provided the first evidence that CD34⁺ HSPC express GLP-1R and that LIRA can favorably impact on cell dysfunction due to HG exposure. These findings open new perspectives on the favorable CV effects of GLP-1 RAs in T2DM patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01486-9.

The Role of Glycemic Variability in Cardiovascular Disorders

Diabetes mellitus (DM) is one of the most common and costly disorders that affect humans around the world. Recently, clinicians and scientists have focused their studies on the effects of glycemic variability (GV), which is especially associated with cardiovascular diseases. In healthy subjects, glycemia is a very stable parameter, while in poorly controlled DM patients, it oscillates greatly throughout the day and between days. Clinically, GV could be measured by different parameters, but there are no guidelines on standardized assessment. Nonetheless, DM patients with high GV experience worse cardiovascular disease outcomes. In vitro and in vivo studies showed that high GV causes several detrimental effects, such as increased oxidative stress, inflammation, and apoptosis linked to endothelial dysfunction. However, the evidence that treating GV is beneficial is still scanty. Clinical trials aiming to improve the diagnostic and prognostic accuracy of GV measurements correlated with cardiovascular outcomes are needed. The present review aims to evaluate the clinical link between high GV and cardiovascular diseases, taking into account the underlined biological mechanisms. A clear view of this challenge may be useful to standardize the clinical evaluation and to better identify treatments and strategies to counteract this DM aspect.

Doxorubicin induces an alarmin-like TLR4-dependent autocrine/paracrine action of Nucleophosmin in human cardiac mesenchymal progenitor cells

Background

Doxorubicin (Dox) is an anti-cancer anthracycline drug that causes double-stranded DNA breaks. It is highly effective against several types of tumours; however, it also has adverse effects on regenerative populations of normal cells, such as human cardiac mesenchymal progenitor cells (hCmPCs), and its clinical use is limited by cardiotoxicity. Another known effect of Dox is nucleolar disruption, which triggers the ubiquitously expressed nucleolar phosphoprotein Nucleophosmin (NPM) to be released from the nucleolus into the cell, where it participates in the orchestration of cellular stress responses. NPM has also been observed in the extracellular space in response to different stress stimuli; however, the mechanism behind this and its functional implications are as yet largely unexplored. The aim of this study was to establish whether Dox could elicit NPM secretion in the extracellular space and to elucidate the mechanism of secretion and the effect of extracellular NPM on hCmPCs.

Results

We found that following the double-strand break formation in hCmPCs caused by Dox, NPM was rapidly secreted in the extracellular space by an active mechanism, in the absence of either apoptosis or necrosis. Extracellular release of NPM was similarly seen in response to ultraviolet radiation (UV). Furthermore, we observed an increase of NPM levels in the plasma of Dox-treated mice; thus, NPM release also occurred in vivo. The treatment of hCmPCs with extracellular recombinant NPM induced a decrease of cell proliferation and a response mediated through the Toll-like receptor (TLR)4. We demonstrated that NPM binds to TLR4, and via TLR4, and nuclear factor kappa B (NFkB) activation/nuclear translocation, exerts proinflammatory functions by inducing IL-6 and COX-2 gene expression. Finally, we found that in hCmPCs, NPM secretion could be driven by an autophagy-dependent unconventional mechanism that requires TLR4, since TLR4 inhibition dramatically reduced Dox-induced secretion.

Conclusions

We hypothesise that the extracellular release of NPM could be a general response to DNA damage since it can be elicited by either a chemical agent such as Dox or a physical genotoxic stressor such as UV radiation. Following genotoxic stress, NPM acts similarly to an alarmin in hCmPCs, being rapidly secreted and promoting cell cycle arrest and a TLR4/NFκB-dependent inflammatory response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01058-5.

Digital PCR for high sensitivity viral detection in false-negative SARS-CoV-2 patients

Patients requiring diagnostic testing for coronavirus disease 2019 (COVID-19) are routinely assessed by reverse-transcription quantitative polymerase chain reaction (RT-qPCR) amplification of Sars-CoV-2 virus RNA extracted from oro/nasopharyngeal swabs. Despite the good specificity of the assays certified for SARS-CoV-2 molecular detection, and a theoretical sensitivity of few viral gene copies per reaction, a relatively high rate of false negatives continues to be reported. This is an important challenge in the management of patients on hospital admission and for correct monitoring of the infectivity after the acute phase. In the present report, we show that the use of digital PCR, a high sensitivity method to detect low amplicon numbers, allowed us to correctly detecting infection in swab material in a significant number of false negatives. We show that the implementation of digital PCR methods in the diagnostic assessment of COVID-19 could resolve, at least in part, this timely issue.

New Strategies to Enhance Myocardial Regeneration: Expectations and Challenges from Preclinical Evidence

Nowadays, cardiac regeneration is an emerging topic in the cardiovascular field because of the compelling need for effective therapies for repairing or replacing cardiac tissue damaged by pathological or physiological conditions. Indeed, irreversible myocardial remodeling which follows acute myocardial infarction represents a serious burden of this century. In this context, a great improvement in pharmacological and interventional techniques is accompanied by a big challenge of cardiac regenerative medicine. In the last 20 years, several clinical trials tried to investigate the role of different types of stem cells in promoting cardiac repair. However, the promising results obtained in the preclinical trials have not yet been reproduced in patients. Thus, the development of novel strategies to improve stem cell efficiency became imperative. Here, an overview of the more recent cell types proposed for cardiac regeneration is presented, together with the most interesting approaches to enhance cell regenerative potential as well as cell-free approaches.

Differences in Mitochondrial Membrane Potential Identify Distinct Populations of Human Cardiac Mesenchymal Progenitor Cells

Adult human cardiac mesenchymal progenitor cells (hCmPC) are multipotent resident populations involved in cardiac homeostasis and heart repair. Even if the mechanisms have not yet been fully elucidated, the stem cell differentiation is guided by the mitochondrial metabolism; however, mitochondrial approaches to identify hCmPC with enhanced stemness and/or differentiation capability for cellular therapy are not established. Here we demonstrated that hCmPCs sorted for low and high mitochondrial membrane potential (using a lipophilic cationic dye tetramethylrhodamine methyl ester, TMRM), presented differences in energy metabolism from preferential glycolysis to oxidative rates. TMRM-high cells are highly efficient in terms of oxygen consumption rate, basal and maximal respiration, and spare respiratory capacity compared to TMRM-low cells. TMRM-high cells showed characteristics of pre-committed cells and were associated with higher in vitro differentiation capacity through endothelial, cardiac-like, and, to a lesser extent, adipogenic and chondro/osteogenic cell lineage, when compared with TMRM-low cells. Conversely, TMRM-low showed higher self-renewal potential. To conclude, we identified two hCmPC populations with different metabolic profile, stemness maturity, and differentiation potential. Our findings suggest that metabolic sorting can isolate cells with higher regenerative capacity and/or long-term survival. This metabolism-based strategy to select cells may be broadly applicable to therapies.

Abnormal DNA Methylation Induced by Hyperglycemia Reduces CXCR 4 Gene Expression in CD 34+ Stem Cells

Background CD 34⁺ stem/progenitor cells are involved in vascular homeostasis and in neovascularization of ischemic tissues. The number of circulating CD 34⁺ stem cells is a predictive biomarker of adverse cardiovascular outcomes in diabetic patients. Here, we provide evidence that hyperglycemia can be "memorized" by the stem cells through epigenetic changes that contribute to onset and maintenance of their dysfunction in diabetes mellitus. Methods and Results Cord-blood-derived CD 34⁺ stem cells exposed to high glucose displayed increased reactive oxygen species production, overexpression of p66^shc gene, and downregulation of antioxidant genes catalase and manganese superoxide dismutase when compared with normoglycemic cells. This altered oxidative state was associated with impaired migration ability toward stromal-cell-derived factor 1 alpha and reduced protein and mRNA expression of the C-X-C chemokine receptor type 4 ( CXCR 4) receptor. The methylation analysis by bisulfite Sanger sequencing of the CXCR 4 promoter revealed a significant increase in DNA methylation density in high-glucose CD 34⁺ stem cells that negatively correlated with mRNA expression (Pearson r=-0.76; P=0.004). Consistently, we found, by chromatin immunoprecipitation assay, a more transcriptionally inactive chromatin conformation and reduced RNA polymerase II engagement on the CXCR 4 promoter. Notably, alteration of CXCR 4 DNA methylation, as well as transcriptional and functional defects, persisted in high-glucose CD 34⁺ stem cells despite recovery in normoglycemic conditions. Importantly, such an epigenetic modification was thoroughly confirmed in bone marrow CD 34⁺ stem cells isolated from sternal biopsies of diabetic patients undergoing coronary bypass surgery. Conclusions CD 34⁺ stem cells "memorize" the hyperglycemic environment in the form of epigenetic modifications that collude to alter CXCR 4 receptor expression and migration.

When Good Guys Turn Bad: Bone Marrow's and Hematopoietic Stem Cells' Role in the Pathobiology of Diabetic Complications

Diabetes strongly contributes to the development of cardiovascular disease, the leading cause of mortality and morbidity in these patients. It is widely accepted that hyperglycemia impairs hematopoietic stem/progenitor cell (HSPC) mobilization from the bone marrow (BM) by inducing stem cell niche dysfunction. Moreover, a recent study demonstrated that type 2 diabetic patients are characterized by significant depletion of circulating provascular progenitor cells and increased frequency of inflammatory cells. This unbalance, potentially responsible for the reduction of intrinsic vascular homeostatic capacity and for the establishment of a low-grade inflammatory status, suggests that bone BM-derived HSPCs are not only victims but also active perpetrators in diabetic complications. In this review, we will discuss the most recent literature on the molecular mechanisms underpinning hyperglycemia-mediated BM dysfunction and differentiation abnormality of HSPCs. Moreover, a section will be dedicated to the new glucose-lowering therapies that by specifically targeting the culprits may prevent or treat diabetic complications.

Sensitive and quantitative method to evaluate DNA methylation of the positive regulatory domains (PRDI, PRDII) and cAMP response element (CRE) in human endothelial nitric oxide synthase promoter

Nitric oxide plays a prominent role in the cardiovascular system and much attention has been devoted in the last years on deciphering the regulation of human endothelial nitric oxide synthase (eNOS) expression. Epigenetic-based mechanisms have a key role in the eNOS expression and their pathologic perturbations may have profound effects on the steady state RNA levels in the endothelium. The human eNOS promoter lacks a canonical TATA box and it does not contain a proximal CpG island. A differentially DNA methylated region (DMR) in the native eNOS proximal promoter is involved in gene expression regulation. Here we describe a quantitative, sensitive and cost-effective method that, relying on a novel normalization strategy, allows the quantification of DNA methylation status of the positive regulatory domains (PRDI, PRDII) and cAMP response element (CRE) in human eNOS promoter. This technique will enable to explore the functional relevance of DNA methylation perturbations of eNOS promoter both under pathological and physiological conditions.

P2252Hyperglycemia drives myeloid CD34+ stem cells differentiation towards pro-inflammatory and senescent monocyte subpopulations

Background/Introduction

Diabetes is characterized by a chronic low-grade inflammatory status mediated by cellular senescence and alterations of the circulating cytokine profile and of innate immune system cell components. An abnormal expansion of intermediate (CD14++CD16+) and non-classical (CD14+CD16++) monocyte subpopulations with highly inflammatory and senescent-associated secretory phenotype (SASP) have been observed in T2DM patients with cardiovascular (CV) complications. It is unknown whether CD34+ hematopoietic stem cells (HSCs), players of CV prognosis, are involved in this process.

Purpose

To assess whether hyperglycemia might induce a pro-inflammatory priming of hematopoietic CD34+ HSCs that through senescence and acquisition of SASP skew their myeloid differentiation into more aggressive monocyte populations.

Methods

CD34+ cells were purified from cord blood of healthy donors and expanded in normal-glucose (NG; with 30 mM mannitol for osmotic control) or high-glucose (HG; 30 mM) serum-free medium plus cytokines. The cell were counted after 10, 20 and 30 days. The expression of p27, p21 RELA/p65, IL6, TNFα genes and telomere length was assessed by qPCR and secreted cytokines by ELISA. Apoptosis, ROS and monocyte subpopulations were evaluated by flow cytometry after Annexin V, CellRox and CD14/CD16 staining respectively.

Results

CD34+ HSCs cultured in HG (HG-CD34+) displayed a significant proliferation impairment when compared to their osmotic control (NG-CD34+). This loss of glucose tolerance was associated with a significant increase in mitochondrial ROS production (n=6; p≤0.01) without induction of apoptosis as showed by flow cytometry analysis for Annexin V. Moreover, qPCR assay revealed a significant telomere shortening (n=4; p≤0.05) and up-regulation of cyclin-dependent kinase inhibitors p27 and p21 in HG-CD34+cells (n=13; p≤0.05) along with an enhanced expression and secretion of TNFα (n=9; p≤0.05) and IL6 (n=10; p≤0.05) in HG-CD34+ when compared with NG-CD34+. SASP phenotype in HG-CD34+ was associated to a significant up-regulation of RELA/p65 gene in HG-CD34+ when compared with NG-CD34+ (n=8; p≤0.05). Furthermore, we found that in vitro HG-CD34+ differentiation into myeloid lineage generated higher levels of pro-inflammatory intermediate (n=3; p≤0.05) and non-classical (n=3; p≤0.01) monocyte subsets when compared with the normoglycemic counterpart.

Conclusion(s)

These data suggest that HG exposure primes HSCs myeloid differentiation towards inflammatory and senescent monocyte subpopulations.

Acknowledgement/Funding

This work was supported by Ricerca Finalizzata, Ministero della Salute [PE-2011-02348537]

Evaluating the methylation status of CXCR4 promoter: A cost-effective and sensitive two-step PCR method

The chemokine receptor CXCR4 plays a key role in the bone marrow microenvironment maintenance and in the hematopoietic stem and progenitor cells migration. In addition, CXCR4 is expressed in a broad spectrum of solid tumors where its methylation state has been recently proposed as a biomarker for cancer prognosis. To evaluate methylation status of CXCR4 promoter we developed a sensitive, accurate, specific and cost-effective two-step PCR method that does not require any specific equipment other than a conventional real-time PCR instrument. The principle of the technique relies on a novel normalization strategy which allows the detection and quantification of small methylation differences among pre-amplified DNA samples deriving from low amount of starting material. In addition, the analysis of melting curve profiles of PCR products provides additional information about the methylation status of CpG sites in between the primers. Finally, the principle of this technique can potentially be adapted for the investigation of the methylation status of any other DNA region.

Methylation profiling by bisulfite sequencing analysis of the mtDNA Non-Coding Region in replicative and senescent Endothelial Cells

The regulation and function of Mitochondrial DNA (mtDNA) cytosine methylation (5 mC) are largely unexplored. Mitochondria, Endothelial Cell (EC) senescence, and cardiovascular dysfunction are closely related. We extensively investigated the mtDNA Non-Coding Region (NCR) methylation pattern and its variations in EC replicative senescence. We observed previously undescribed 5 mC clusters and a biased distribution of 5 mC among DNA sites and throughout the NCR. The methylation pattern in senescent EC showed non-random variations, including the hypo-methylation of mtDNA replication regulatory sites. Additional experiments opened to a possible role for 5 mC in D-loop formation, rather than in mitochondrial gene expression.

Inflammatory environment and oxidized LDL convert circulating human proangiogenic cells into functional antigen-presenting cells

The function of human circulating PACs has been described extensively. However, little focus has been placed on understanding how these cells differ in their functions in the presence of microenvironments mimicking vascular inflammation. We hypothesized that exposure to proinflammatory cytokines or the oxLDL, an autoantigen abundant in advanced atherosclerotic plaques, converts PACs into immune-modulating/proinflammatory cells. Hence, we examined the effect of oxLDL and inflammatory stimuli on their phenotype by use of a functional genomics model based on secretome and whole genome transcriptome profiling. PACs obtained from culturing a PBMC fraction in angiogenic medium were primed with DC differentiation cytokines and then exposed to proinflammatory cytokines or oxLDL. Under these conditions, PACs converted into APCs, expressed maturation markers CD80 and CD83, and showed an increased up-regulation of CD86. APCcy and APCox induced a robust T cell BrdU incorporation. Despite a similar ability to induce lymphocyte proliferation, APCcy and APCox differed for the secretory pathway and mRNA expression. Analysis of the differentially expressed genes identified 4 gene "clusters," showing reciprocal modulation in APCcy vs. APCox, justifying, according to functional genomics analyses, a different putative function of the cells in antigen processing. Together, these data show that treatment with inflammatory cytokines or oxLDL converts human PAC phenotypes and functions into that of APCs with similar lymphocyte-activating ability but distinct maturation degree and paracrine functions.

Feasibility of pig and human-derived aortic valve interstitial cells seeding on fixative-free decellularized animal pericardium

Glutaraldehyde-fixed pericardium of animal origin is the elective material for the fabrication of bio-prosthetic valves for surgical replacement of insufficient/stenotic cardiac valves. However, the pericardial tissue employed to this aim undergoes severe calcification due to chronic inflammation resulting from a non-complete immunological compatibility of the animal-derived pericardial tissue resulting from failure to remove animal-derived xeno-antigens. In the mid/long-term, this leads to structural deterioration, mechanical failure, and prosthesis leaflets rupture, with consequent need for re-intervention. In the search for novel procedures to maximize biological compatibility of the pericardial tissue into immunocompetent background, we have recently devised a procedure to decellularize the human pericardium as an alternative to fixation with aldehydes. In the present contribution, we used this procedure to derive sheets of decellularized pig pericardium. The decellularized tissue was first tested for the presence of 1,3 α-galactose (αGal), one of the main xenoantigens involved in prosthetic valve rejection, as well as for mechanical tensile behavior and distensibility, and finally seeded with pig- and human-derived aortic valve interstitial cells. We demonstrate that the decellularization procedure removed the αGAL antigen, maintained the mechanical characteristics of the native pig pericardium, and ensured an efficient surface colonization of the tissue by animal- and human-derived aortic valve interstitial cells. This establishes, for the first time, the feasibility of fixative-free pericardial tissue seeding with valve competent cells for derivation of tissue engineered heart valve leaflets.

Adventitial vessel growth and progenitor cells activation in an ex vivo culture system mimicking human saphenous vein wall strain after coronary artery bypass grafting

Saphenous vein graft disease is a timely problem in coronary artery bypass grafting. Indeed, after exposure of the vein to arterial blood flow, a progressive modification in the wall begins, due to proliferation of smooth muscle cells in the intima. As a consequence, the graft progressively occludes and this leads to recurrent ischemia. In the present study we employed a novel ex vivo culture system to assess the biological effects of arterial-like pressure on the human saphenous vein structure and physiology, and to compare the results to those achieved in the presence of a constant low pressure and flow mimicking the physiologic vein perfusion. While under both conditions we found an activation of Matrix Metallo-Proteases 2/9 and of microRNAs-21/146a/221, a specific effect of the arterial-like pressure was observed. This consisted in a marked geometrical remodeling, in the suppression of Tissue Inhibitor of Metallo-Protease-1, in the enhanced expression of TGF-β₁ and BMP-2 mRNAs and, finally, in the upregulation of microRNAs-138/200b/200c. In addition, the veins exposed to arterial-like pressure showed an increase in the density of the adventitial vasa vasorum and of cells co-expressing NG2, CD44 and SM22α markers in the adventitia. Cells with nuclear expression of Sox-10, a transcription factor characterizing multipotent vascular stem cells, were finally found in adventitial vessels. Our findings suggest, for the first time, a role of arterial-like wall strain in the activation of pro-pathologic pathways resulting in adventitial vessels growth, activation of vasa vasorum cells, and upregulation of specific gene products associated to vascular remodeling and inflammation.

SOX2 regulates self-renewal and tumorigenicity of human melanoma-initiating cells

Melanoma is one of the most aggressive types of human cancer, characterized by enhanced heterogeneity and resistance to conventional therapy at advanced stages. We and others have previously shown that HEDGEHOG-GLI (HH-GLI) signaling is required for melanoma growth and for survival and expansion of melanoma-initiating cells (MICs). Recent reports indicate that HH-GLI signaling regulates a set of genes typically expressed in embryonic stem cells, including SOX2 (sex-determining region Y (SRY)-Box2). Here we address the function of SOX2 in human melanomas and MICs and its interaction with HH-GLI signaling. We find that SOX2 is highly expressed in melanoma stem cells. Knockdown of SOX2 sharply decreases self-renewal in melanoma spheres and in putative melanoma stem cells with high aldehyde dehydrogenase activity (ALDH(high)). Conversely, ectopic expression of SOX2 in melanoma cells enhances their self-renewal in vitro. SOX2 silencing also inhibits cell growth and induces apoptosis in melanoma cells. In addition, depletion of SOX2 progressively abrogates tumor growth and leads to a significant decrease in tumor-initiating capability of ALDH(high) MICs upon xenotransplantation, suggesting that SOX2 is required for tumor initiation and for continuous tumor growth. We show that SOX2 is regulated by HH signaling and that the transcription factors GLI1 and GLI2, the downstream effectors of HH-GLI signaling, bind to the proximal promoter region of SOX2 in primary melanoma cells. In functional studies, we find that SOX2 function is required for HH-induced melanoma cell growth and MIC self-renewal in vitro. Thus SOX2 is a critical factor for self-renewal and tumorigenicity of MICs and an important mediator of HH-GLI signaling in melanoma. These findings could provide the basis for novel therapeutic strategies based on the inhibition of SOX2 for the treatment of a subset of human melanomas.

Hypoxia-resistant profile implies vulnerability of cancer stem cells to physiological agents, which suggests new therapeutic targets

We have previously shown that peculiar metabolic features of cell adaptation and survival in hypoxia imply growth restriction points that are typical of embryonic stem cells and disappear with differentiation. Here we provide evidence that such restrictions can be exploited as specific antiblastic targets by physiological factors such as pyruvate, tetrahydrofolate, and glutamine. These metabolites act as powerful cytotoxic agents on cancer stem cells (CSCs) when supplied at doses that perturb the biochemical network, sustaining the resumption of aerobic growth after the hypoxic dormant state. Experiments were performed in vivo and in vitro using CSCs obtained from various anaplastic tumors: human melanoma, leukemia, and rat hepatoma cells. Pretreatment of melanoma CSCs with pyruvate significantly reduces their self-renewal in vitro and tumorigenicity in vivo. The metabolic network underlying the cytotoxic effect of the physiological factors was thoroughly defined, principally using AH130 hepatoma, a tumor spontaneously reprogrammed to the embryonic stem stage. This network, based on a tight integration of aerobic glycolysis, cellular redox state, and folate metabolism, is centered on the cellular NADP/NADPH ratio that controls the redox pathway of folate utilization in purine synthesis. On the whole, this study indicates that pyruvate, FH 4, and glutamine display anticancer activity, because CSCs are committed to survive and maintain their stemness in hypoxia. When CSC need to differentiate and proliferate, they shift from anaerobic to aerobic status, and the few mitochondria available makes them susceptible to the injury of the above physiological factors. This vulnerability might be exploited for novel therapeutic treatments.

Mechanical compliance and immunological compatibility of fixative-free decellularized/cryopreserved human pericardium

BACKGROUND

The pericardial tissue is commonly used to produce bio-prosthetic cardiac valves and patches in cardiac surgery. The procedures adopted to prepare this tissue consist in treatment with aldehydes, which do not prevent post-graft tissue calcification due to incomplete xeno-antigens removal. The adoption of fixative-free decellularization protocols has been therefore suggested to overcome this limitation. Although promising, the decellularized pericardium has not yet used in clinics, due to the absence of proofs indicating that the decellularization and cryopreservation procedures can effectively preserve the mechanical properties and the immunologic compatibility of the tissue.

PRINCIPAL FINDINGS

The aim of the present work was to validate a procedure to prepare decellularized/cryopreserved human pericardium which may be implemented into cardiovascular homograft tissue Banks. The method employed to decellularize the tissue completely removed the cells without affecting ECM structure; furthermore, uniaxial tensile loading tests revealed an equivalent resistance of the decellularized tissue to strain, before and after the cryopreservation, in comparison with the fresh tissue. Finally, immunological compatibility, showed a minimized host immune cells invasion and low levels of systemic inflammation, as assessed by tissue transplantation into immune-competent mice.

CONCLUSIONS

Our results indicate, for the first time, that fixative-free decellularized pericardium from cadaveric tissue donors can be banked according to Tissue Repository-approved procedures without compromising its mechanical properties and immunological tolerance. This tissue can be therefore treated as a safe homograft for cardiac surgery.

The involvement of a Nanog, Klf4 and c-Myc transcriptional circuitry in the intertwining between neoplastic progression and reprogramming

One undisputed milestone of traditional oncology is neoplastic progression, which consists of a progressive selection of dedifferentiated cells driven by a chance sequence of genetic mutations. Recently it has been demonstrated that the overexpression of well-defined transcription factors reprograms somatic cells to the pluripotent stem status. The demonstration raises crucial questions as to whether and to what extent this reprogramming contributes to tumorigenesis, and whether the epigenetic changes involved in it are reversible. Here, we show for the first time that a tumor produced in vivo by a chemical carcinogen is the product of the interaction between neoplastic progression and reprogramming. The experimental model employed the prototype of ascites tumors, the Yoshida AH130 hepatoma and other neoplasias, including human melanoma. AH130 hepatoma was started in the liver by the carcinogen o-aminoazotoluene. This compound binds to and abolishes the p53 protein, producing a genomic instability that promotes both the neoplastic progression and the hepatoma reprogramming. Eventually this tumor contained 100% CD133(+) elements and pO(2)-dependent percentages of the three embryonic transcription factors Nanog, Klf4 and c-Myc. Once transferred into aerobic cultures, the minor cellular fraction expressing this triad generates various types of adherent cells, which are progressively substituted by non-tumorigenic elements committed to fibromuscular, neuronal and glial differentiation. This reprogramming appears to be accomplished stepwise, with the assembly of the triad into a sophisticated transcriptional, oxygen-dependent circuitry, in which Nanog and Klf4 antagonistically regulate c-Myc, and hence, cell hypoxia survival and cell cycle activation.

Heterogeneous expression of cyclooxygenase-2 and inducible nitric oxide synthase within colorectal tumors: correlation with tumor angiogenesis

BACKGROUND

Recent studies have shown that the cyclooxygenase (COX) and the inducible nitric oxide synthase (iNOS) pathways are involved in the development of tumor angiogenesis in human cancers.

AIMS

To investigate whether a different pattern of COX-2 and iNOS expression/activity exists within different areas of colorectal tumors and to analyze the relationship between these two enzymes and tumor angiogenesis.

METHODS

Microvessel density (MVD) and COX-2, iNOS, vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR-2) protein expression were evaluated at both the invasive front (IF) and the tumor center (TC) in 46 human colorectal cancer specimens. We also investigated the concentration of PGE2 and NO at the same sites.

RESULTS

COX-2 and iNOS protein expression and activity were significantly higher within the IF than the TC of the tumor specimens. Similarly, MVD and VEGF/VEGFR-2 expression significantly increased from the TC to the IF. Only COX-2 expression was significantly correlated with MVD and VEGF/VEGFR-2 expression at both the TC and the IF.

CONCLUSION

Our study shows a heterogeneous expression of COX-2 and iNOS in colorectal cancer. The up-regulation of COX-2 at the IF parallels an increase in vessel density and VEGF/VEGFR-2 expression, thus supporting the hypothesis that the tumor periphery is the most aggressive portion of a colorectal tumor.

Human mature endothelial cells modulate peripheral blood mononuclear cell differentiation toward an endothelial phenotype

Circulating endothelial progenitor cells (EPCs) can contribute to neovascularization, even if the mechanisms by which they interact with mature endothelial cells remain unclear. The interactions between human coronary artery endothelial cells (HCAECs) and peripheral blood mononuclear cells (PBMCs) during their early differentiation towards an EPC phenotype were investigated. A co-culture model, in which the two cell types share the same culture medium in the absence of any exogenous angiogenic stimulus, was used. The role of hypoxia was assessed by pretreating HCAECs with 3% O(2) before co-culture setting. Since we have previously shown that both adherent and suspended PBMCs display a significant increase in endothelial marker expression within the 2nd day of culture in an angiogenic environment, the role of HCAECs on early PBMC differentiation was evaluated in both adherent and suspended cell fractions. A 3-day co-culture period increased the expression of VEGF-R2, VE-cadherin, alpha(v)beta(3)- and alpha(5)-integrin in both the adherent and suspended PBMCs, assessed by cytofluorimetric analysis, and up-regulated VEGF-R1 mRNA assessed by real-time RT-PCR. HCAECs influenced PBMC adhesion, transendothelial migration and cell organization on Matrigel. Hypoxia modulated either PBMC differentiation or their functional properties. These data strongly suggest that endothelium may support the differentiation of PBMCs into EPCs.

Trophic effects induced by α1D-adrenoceptors on endothelial cells are potentiated by hypoxia

Catecholamines have been shown to be involved in vascular remodeling through the stimulation of α1-adrenoceptors (α1-ARs). Recently, it has been demonstrated that catecholamines can stimulate angiogenesis in pathological conditions, even if the mechanisms and the AR subtypes involved still remain unclear. We investigated the influence of hypoxia (3% O2) on the ability of picomolar concentrations of phenylephrine (PHE), which are unable to induce any vascular contraction, to induce a trophic effect in human endothelial cells through stimulation of the α1D-subtype ARs. PHE, at picomolar concentrations, significantly promoted pseudocapillary formation from fragments of human mature vessels in vitro. Exposure to hypoxia significantly potentiated this effect, which was inhibited by the selective α1D-AR antagonist BMY-7378 and by the nitric oxide synthase inhibitor l-NAME, suggesting that α1D-ARs were involved in this effect through activation of the nitric oxide pathway. Proliferation and migration of HUVEC were also affected by picomolar PHE concentrations. Again, these effects were significantly potentiated in cells exposed to hypoxia and were inhibited by BMY-7378 and by NG-nitro-l-arginine methyl ester. Conversely, the α1A-AR-selective antagonist ( S)-(+)-niguldipine hydrochloride and the α1B-AR antagonist chloroethylclonidine dihydrochloride did not modify endothelial cell migration and proliferation in response to PHE. These results demonstrate that the stimulation of α1D-ARs, triggered by picomolar PHE concentrations devoid of any contractile vascular effects, induces a proangiogenic phenotype in human endothelial cells that is enhanced in a hypoxic environment. The role of α1D-ARs may become more prominent in the adaptive responses to hypoxic vasculature injury.

Intracellular pathways triggered by the selective FLT-1-agonist placental growth factor in vascular smooth muscle cells exposed to hypoxia

We have previously shown that hypoxia makes vascular smooth muscle cells (VSMCs) responsive to placental growth factor (PlGF) through the induction of functional fms-like tyrosine kinase (Flt-1) receptors. The aim of this study was to investigate the molecular mechanisms involved in the PlGF effects on proliferation and contraction of VSMCs previously exposed to hypoxia (3% O2). In cultured rat VSMCs exposed to hypoxia, PlGF increased the phosphorylation of protein kinase B (Akt), p38 and STAT3; activation of STAT3 was higher than that of other kinases. In agreement with this finding, the proliferation of hypoxia-treated VSMCs in response to PlGF was significantly impaired by the p38 and the phosphatidylinositol 3-kinase inhibitors SB202190 and LY294002, respectively, and was almost completely prevented by AG490, a janus tyrosine kinase (JAK)/signal transducer and activator of transcription (STAT) inhibitor. Since hypoxia was able to reverse the vasorelaxant effect of PlGF into a vasoconstrictor response, the mechanism of this latter effect was also investigated. Significant Flt-1 activity was measured in isolated preparations from rat aorta exposed to hypoxia. Inhibitors of mitogen-activated protein kinase kinase, Akt and STAT3 induced a modest inhibition of the vasoconstrictor response to PlGF, while the p38 inhibitor SB202190 markedly impaired the PlGF-induced contractile response. These effects were selectively mediated by Flt-1 without any involvement of foetal liver kinase-1 receptors. These data are the first evidence that different intracellular pathways activated by Flt-1 receptor in VSMCs are involved in diverse biological effects of PlGF: while mitogen activated protein kinase kinase/extracellular signal regulated kinase(1/2) and JAK/STAT play a role in VSMC proliferation, p38 is involved in VSMC contraction. These findings may highlight the role of PlGF in vascular pathology.

Effect of vascular endothelial growth factor and epidermal growth factor on iatrogenic apoptosis in human endothelial cells

To study the effect of growth factors on iatrogenic apoptosis, we examined the influence of vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) on staurosporine-induced apoptosis in primary cultures of human umbilical vein endothelial cells (HUVEC). Apoptosis was evaluated by a cell viability test, the TUNEL-POD assay and the activation of the pro-apoptotic caspase-3. Staurosporine (10-100nM) caused the activation of caspase-3. This effect was manifest after 2hr of incubation and reached its maximum after 5hr. Severe loss of viability followed within 18hr. VEGF or EGF (10-100ng/mL) added together with staurosporine decreased the activation of caspase-3. The loss of viability was 24hr delayed. The action of growth factors was observed at 1% serum concentration but also at concentration optimal for HUVEC survival (10%, v/v). Furthermore, the inhibition of PI-3 kinase (PI-3K) by wortmannin or LY294002 as well as the inhibition of MEK by PD098059 or U0126 prevented the protective effect of VEGF and EGF. Western blotting analysis showed that after 3hr of incubation with staurosporine the level of the anti-apoptotic protein Mcl-1 decreased and this effect was reverted by VEGF. It is concluded that VEGF and EGF antagonize the pro-apoptotic action of staurosporine by the combined signalling of PI-3K and ERKs pathways.

Expression and regulation of endothelin-1 and its receptors in human penile smooth muscle cells

We report for the first time that penile smooth muscle cells (SMC) not only respond to, but also synthesize, endothelin-1 (ET-1), one of the main regulators of SMC activity. Immunohistochemical studies indicated that, beside endothelial cells (EC), SMC of the human adult and fetal penis also express ET-1 and its converting enzyme, ECE-1. Accordingly, cultures of adult penile stromal cells express these genes. We also prepared and characterized penile SMC from human fetuses. These cells express SMC specific markers such as alpha smooth muscle actin and phosphodiesterase type 5A3 along with hallmarks of androgen-dependent cells (androgen receptor and 5alpha reductase type 2). Human fetal penile SMC (hfPSMC) are immunopositive for ET-1 and release ET-1. ET-1 expression in hfPSMC was strongly increased by several factors such as transforming growth factor-beta1 (TGF-beta1), interleukin-1alpha (IL-1alpha), ET-1 itself and prolonged (24 h) hypoxia. This latter condition not only affected ET-1 expression but also responsiveness. While at normal oxygen tension, hfPSMC responded to ET-1 with a decreased proliferation mediated by the endothelin-A receptors and TGF-beta1; however, during hypoxia, ET-1 stimulated cell growth. Accordingly, prolonged hypoxia up-regulated endothelin-B receptor mRNA expression. In conclusion, our results indicate that in penile tissues SMC produce ET-1 and that such production is modulated by factors involved in penile physiology and tissue remodelling. In addition, the hfPSMC we have characterized might be a useful model for studying biochemical aspects of the human erectile process in vitro.

Endothelin-1 production by prostate cancer cell lines is up-regulated by factors involved in cancer progression and down-regulated by androgens

BACKGROUND

Recent data demonstrate that endothelin-1 (ET-1) concentration increases in plasma of men with advanced, hormone-refractory prostate adenocarcinoma. In addition, ET-1 is involved in osteblastic remodelling and new bone formation, suggesting a role for this vasoactive peptide in the metastatic progression of prostate cancer to the bone.

METHODS

We investigated the regulation of ET-1 expression in androgen-sensitive and insensitive prostate cancer cell lines by androgens and several factors involved in progression of prostate cancer (EGF) and bone remodelling (TGFbeta-1, IL1-alpha and IGF-1).

RESULTS

Northern analysis and radio immunoassay demonstrated that all the ET-1 pathways are tuned off in the androgen-sensitive LNCaP cell line when compared to the androgen-insensitive PC-3 and DU145. In PC-3 cells transfected with a full-length androgen receptor expression vector (PC-3-AR), treatment with androgens reduced gene expression and secretion of ET-1 without affecting the gene expression of ET-3. Collectively, these data support a role for androgens in the regulation of ET-1 production by prostate adenocarcinoma cells. In PC-3 and DU145 cells, ET-1 gene expression and secretion were up-regulated by TGFbeta-1, EGF and IL1-alpha, whereas IGF-1 was ineffective. Conversely, none of the treatments affected ECE-1 or ET-3 gene expression.

CONCLUSIONS

In conclusion, ET-1 production by prostate adenocarcinoma cells is down-regulated by androgens and up-regulated by factors involved in tumour progression indicating a role for this peptide in the biology of prostate cancer. In view of the role exerted by ET-1 in the process of bone metastasis, our data suggest the use of ET-1 receptor antagonists in the treatment of advanced prostate cancer.

Role of potassium channels in the antinociception induced by agonists of alpha2-adrenoceptors

1. The effect of the administration of pertussis toxin (PTX) as well as modulators of different subtypes of K+ channels on the antinociception induced by clonidine and guanabenz was evaluated in the mouse hot plate test. 2. Pretreatment with pertussis toxin (0.25 microg per mouse i.c.v.) 7 days before the hot-plate test, prevented the antinociception induced by both clonidine (0.08-0.2 mg kg(-1), s.c.) and guanabenz (0.1-0.5 mg kg(-1), s.c.). 3. The administration of the K(ATP) channel openers minoxidil (10 microg per mouse, i.c.v.), pinacidil (25 microg per mouse, i.c.v.) and diazoxide (100 mg kg(-1), p.o.) potentiated the antinociception produced by clonidine and guanabenz whereas the K(ATP) channel blocker gliquidone (6 microg per mouse, i.c.v.) prevented the alpha2 adrenoceptor agonist-induced analgesia. 4. Pretreatment with an antisense oligonucleotide (aODN) to mKv1.1, a voltage-gated K+ channel, at the dose of 2.0 nmol per single i.c.v. injection, prevented the antinociception induced by both clonidine and guanabenz in comparison with degenerate oligonucleotide (dODN)-treated mice. 5. The administration of the Ca2+-gated K+ channel blocker apamin (0.5-2.0 ng per mouse, i.c.v.) never modified clonidine and guanabenz analgesia. 6. At the highest effective doses, none of the drugs used modified animals' gross behaviour nor impaired motor coordination, as revealed by the rota-rod test. 7. The present data demonstrate that both K(ATP) and mKv1.1 K+ channels represent an important step in the transduction mechanism underlying central antinociception induced by activation of alpha2 adrenoceptors.