Human endothelial cell life extension by telomerase expression

Therapeutic targeting of telomerase ameliorates experimental choroidal neovascularization

Choroidal neovascularization (CNV) is the principal driver of blindness in neovascular age-related macular degeneration (nvAMD). Increased activity of telomerase, has been associated with endothelial cell proliferation, survival, migration, and invasion in the context of tumor angiogenesis. Expanding on this knowledge, we investigated the role of telomerase in the development of CNV in mouse model. We observed increased gene expression and activity of telomerase in mouse CNV. Genetic deficiency of the telomerase components, telomerase reverse transcriptase (Tert) and telomerase RNA component (Terc) suppressed laser-induced CNV in mice. Similarly, a small molecule inhibitor of TERT (BIBR 1532), and antisense oligonucleotides (ASOs) targeting Tert and Terc reduced CNV growth. Bone marrow chimera studies suggested that telomerase activity in non-bone marrow-derived cells is crucial for the development of CNV. Comparison of BIBR 1532 with VEGF neutralizing therapeutic strategy in mouse revealed a comparable level of angiosuppressive activity. However, when BIBR and anti-VEGF antibodies were administered as a combination at sub-therapeutic doses, a statistically significant suppression of CNV was observed. These findings underscore the potential benefits of combining sub-therapeutic doses of BIBR and anti-VEGF antibodies for developing newer therapeutic strategies for NV-AMD. Telomerase inhibition with BIBR 1532 suppressed induction of multiple cytokines and growth factors critical for neovascularization. In conclusion, our study identifies telomerase as a promising therapeutic target for treating neovascular disease of the eye and thus provides a proof of principle for further exploration of telomerase inhibition as a novel treatment strategy for nvAMD.

Vascular organs-on-chip made with patient-derived endothelial cells: technologies to transform drug discovery and disease modeling

INTRODUCTION

Vascular diseases impart a tremendous burden on healthcare systems in the United States and across the world. Efforts to improve therapeutic interventions are hindered by limitations of current experimental models. The integration of patient-derived cells with organ-on-chip (OoC) technology is a promising avenue for preclinical drug screening that improves upon traditional cell culture and animal models.

AREAS COVERED

The authors review induced pluripotent stem cells (iPSC) and blood outgrowth endothelial cells (BOEC) as two sources for patient-derived endothelial cells (EC). They summarize several studies that leverage patient-derived EC and OoC for precision disease modeling of the vasculature, with a focus on applications for drug discovery. They also highlight the utility of patient-derived EC in other translational endeavors, including ex vivo organogenesis and multi-organ-chip integration.

EXPERT OPINION

Precision disease modeling continues to mature in the academic space, but end-use by pharmaceutical companies is currently limited. To fully realize their transformative potential, OoC systems must balance their complexity with their ability to integrate with the highly standardized and high-throughput experimentation required for drug discovery and development.

Interleukin-15 in kidney disease and therapeutics

PURPOSE OF REVIEW

Interleukin 15 (IL-15) is a member of the IL-2 family of common gamma chain receptor cytokines with well described anti-inflammatory, pro-survival and pro-proliferative signaling properties. The cytoprotective role of IL-15 in the kidney is now coming into focus with recent reports of its beneficial actions in various forms of kidney disease. This review will summarize what is currently known about IL-15 signaling in the kidney and highlight recent evidence of its beneficial effects on kidney physiology.

RECENT FINDINGS

IL-15 and its heterotrimeric receptor are expressed throughout the kidney. Like all IL-2 family cytokines, IL-15 can activate signaling through the Janus Kinase (JAK)/Signal transducer of activated T-cells (STAT), phosphoinositol-3 kinase (PI-3K)/AKT and mitogen activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathways and recent evidence suggests that STAT5B is an essential transcriptional mediator of prosurvival signaling in glomerular visceral epithelial cells (i.e. podocytes). IL-15 has also been shown to suppress pro-apoptotic signaling in models of acute kidney injury and pro-fibrotic signaling in models of chronic kidney disease.

SUMMARY

The cytoprotective properties of IL-15 suggest that it may have potential as a nonimmunosuppresive therapeutic for kidney disease. A novel class of IL-15 immunotherapies has emerged for the treatment cancer and some have demonstrated efficacy in clinical trials. These well tolerated IL-15 agonists could possibly be repurposed for the treatment of kidney disease and warrant further exploration.

Serum IgA augments adhesiveness of cultured lung microvascular endothelial cells and suppresses angiogenesis

Immunoglobulin A (IgA) is important in local immunity and is also abundant in the blood. This study aimed to evaluate the effects of serum IgA on cultured lung microvascular endothelial cells (HMVEC-Ls), which are involved in the pathogenesis of inflammatory lung diseases. Serum IgA induced adhesion molecules and inflammatory cytokine production from HMVEC-Ls, and enhanced adhesion of peripheral blood mononuclear cells to HMVEC-Ls. In contrast, migration, proliferation, and tube formation of HMVEC-Ls were significantly suppressed by serum IgA. Experiments with siRNAs and western blotting revealed that two known IgA receptors, β1,4-galactosyltransferase 1 (b4GALT1) and asialoglycoprotein receptor 1 (ASGR1), and mitogen-activated protein kinase and nuclear factor-kappa B pathways were partly involved in serum IgA-induced cytokine production by HMVEC-Ls. Collectively, serum IgA enhanced cytokine production and adhesiveness of HMVEC-L, with b4GALT1 and ASGR1 partially being involved, and suppressed angiogenesis. Thus, serum IgA may be targeted to treat inflammatory lung diseases.

Senescent Cells: A Therapeutic Target in Cardiovascular Diseases

Senescent cell accumulation has been observed in age-associated diseases including cardiovascular diseases. Senescent cells lack proliferative capacity and secrete senescence-associated secretory phenotype (SASP) factors that may cause or worsen many cardiovascular diseases. Therapies targeting senescent cells, especially senolytic drugs that selectively induce senescent cell removal, have been shown to delay, prevent, alleviate, or treat multiple age-associated diseases in preclinical models. Some senolytic clinical trials have already been completed or are underway for a number of diseases and geriatric syndromes. Understanding how cellular senescence affects the various cell types in the cardiovascular system, such as endothelial cells, vascular smooth muscle cells, fibroblasts, immune cells, progenitor cells, and cardiomyocytes, is important to facilitate translation of senotherapeutics into clinical interventions. This review highlights: (1) the characteristics of senescent cells and their involvement in cardiovascular diseases, focusing on the aforementioned cardiovascular cell types, (2) evidence about senolytic drugs and other senotherapeutics, and (3) the future path and clinical potential of senotherapeutics for cardiovascular diseases.

Endothelial senescence in vascular diseases: current understanding and future opportunities in senotherapeutics

Senescence compromises the essential role that the endothelium plays in maintaining vascular homeostasis, so promoting endothelial dysfunction and the development of age-related vascular diseases. Their biological and clinical significance calls for strategies for identifying and therapeutically targeting senescent endothelial cells. While senescence and endothelial dysfunction have been studied extensively, distinguishing what is distinctly endothelial senescence remains a barrier to overcome for an effective approach to addressing it. Here, we review the mechanisms underlying endothelial senescence and the evidence for its clinical importance. Furthermore, we discuss the current state and the limitations in the approaches for the detection and therapeutic intervention of target cells, suggesting potential directions for future research.

Ross J, Scott Herron G. Genetic and Epigenetic Influences on Cutaneous Cellular Senescence

Skin is the largest human organ system, and its protective function is critical to survival. The epithelial, dermal, and subcutaneous compartments are heterogeneous mixtures of cell types, yet they all display age-related skin dysfunction through the accumulation of an altered phenotypic cellular state called senescence. Cellular senescence is triggered by complex and dynamic genetic and epigenetic processes. A senescence steady state is achieved in different cell types under various and overlapping conditions of chronological age, toxic injury, oxidative stress, replicative exhaustion, DNA damage, metabolic dysfunction, and chromosomal structural changes. These inputs lead to outputs of cell-cycle withdrawal and the appearance of a senescence-associated secretory phenotype, both of which accumulate as tissue pathology observed clinically in aged skin. This review details the influence of genetic and epigenetic factors that converge on normal cutaneous cellular processes to create the senescent state, thereby dictating the response of the skin to the forces of both intrinsic and extrinsic aging. From this work, it is clear that no single biomarker or process leads to senescence, but that it is a convergence of factors resulting in an overt aging phenotype.

Tieing together loose ends: telomere instability in cancer and aging

Telomere maintenance is essential for maintaining genome integrity in both normal and cancer cells. Without functional telomeres, chromosomes lose their protective structure and undergo fusion and breakage events that drive further genome instability, including cell arrest or death. One means by which this loss can be overcome in stem cells and cancer cells is via re‐addition of G‐rich telomeric repeats by the telomerase reverse transcriptase (TERT). During aging of somatic tissues, however, insufficient telomerase expression leads to a proliferative arrest called replicative senescence, which is triggered when telomeres reach a critically short threshold that induces a DNA damage response. Cancer cells express telomerase but do not entirely escape telomere instability as they often possess short telomeres; hence there is often selection for genetic alterations in the TERT promoter that result in increased telomerase expression. In this review, we discuss our current understanding of the consequences of telomere instability in cancer and aging, and outline the opportunities and challenges that lie ahead in exploiting the reliance of cells on telomere maintenance for preserving genome stability.

Advanced Respiratory Models for Hazard Assessment of Nanomaterials—Performance of Mono-, Co- and Tricultures

Advanced in vitro models are needed to support next-generation risk assessment (NGRA), moving from hazard assessment based mainly on animal studies to the application of new alternative methods (NAMs). Advanced models must be tested for hazard assessment of nanomaterials (NMs). The aim of this study was to perform an interlaboratory trial across two laboratories to test the robustness of and optimize a 3D lung model of human epithelial A549 cells cultivated at the air–liquid interface (ALI). Potential change in sensitivity in hazard identification when adding complexity, going from monocultures to co- and tricultures, was tested by including human endothelial cells EA.hy926 and differentiated monocytes dTHP-1. All models were exposed to NM-300K in an aerosol exposure system (VITROCELL^® cloud-chamber). Cyto- and genotoxicity were measured by AlamarBlue and comet assay. Cellular uptake was investigated with transmission electron microscopy. The models were characterized by confocal microscopy and barrier function tested. We demonstrated that this advanced lung model is applicable for hazard assessment of NMs. The results point to a change in sensitivity of the model by adding complexity and to the importance of detailed protocols for robustness and reproducibility of advanced in vitro models.

DNA-RNA hybrid G-quadruplex tends to form near the 3' end of telomere overhang

Telomeric repeat-containing RNA (TERRA) has been suggested to participate in telomere maintenance. TERRA consisting of UUAGGG repeats is capable of forming an intermolecular G-quadruplex (GQ) with single-stranded TTAGGG-repeat DNA in the telomere 3' overhang. To explore the structural features and potential functions of this DNA-RNA hybrid GQ (HGQ), we used single-molecule FRET to study the folding patterns of DNA with four to seven telomeric tandem repeats annealed with a short RNA consisting of two or five telomeric repeats. Our data highlight that RNA prefers to form DNA-RNA HGQ near the 3' end of telomeric DNA. Furthermore, the unfolding of secondary structures by a complementary C-rich sequence was observed for DNA GQ but not for DNA-RNA HGQ, which demonstrated the enhanced stability of the telomere 3' end via hybridization with RNA. These conformational and physical properties of telomeric DNA-RNA HGQ suggest that TERRA might limit access to the 3' end of the telomeric DNA overhang, which is known to be critical for the interaction with telomerase and other telomere-associated proteins.

Gene Therapy Strategies Targeting Aging-Related Diseases

Rapid advancements have taken place in gene therapy technology. However, effective methods for treating aging- or age-related chronic diseases, which are often closely related to genes or even multiple genes, are still lacking. The path to developing cures is winding, while gene therapy that targets genes related to aging represents an exciting research direction with tremendous potential. Among aging-related genes, some candidates have been studied at different levels, from cell to organismal levels (e.g., mammalian models) with different methods, from overexpression to gene editing. The TERT and APOE have even entered the stage of clinical trials. Even those displaying only a preliminary association with diseases have potential applications. This article discusses the foundations and recent breakthroughs in the field of gene therapy, providing a summary of current mainstream strategies and gene therapy products with clinical and preclinical applications. Finally, we review representative target genes and their potential for treating aging or age-related diseases.

Melatonin Alleviates Age-Associated Endothelial Injury of Atherosclerosis via Regulating Telomere Function

Background

Atherosclerosis is an aging-related disease, partly attributed to telomerase dysfunction. This study aims to investigate whether telomere dysfunction-related vascular aging is involved in the protection mechanism of melatonin (MLT) in atherosclerosis.

Methods

Young and aged ApoE^−/− mice were used to establish atherosclerotic mice model. H&E staining and immunofluorescence assay were performed to detect endothelial cell injury and apoptosis. Inflammatory cytokines and oxidative stress-related factors were determined using corresponding commercial assay kits. Telomerase activity was detected by TRAP assay, and SA-β-gal staining was conducted to evaluate cellular senescence. HUVECs were treated with H₂O₂ for 1 h to induce senescence. Western blot was performed to measure protein expression.

Results

An obvious vascular endothelial injury, reflected by excessive production of inflammatory cytokines, elevated ROS, MDA and SOD levels, and more apoptotic endothelial cells, was found in atherosclerotic mice, especially in aged mice, which were then greatly suppressed by MLT. In addition, telomere dysfunction and senescence occurred in atherosclerosis, especially in aged mice, while MLT significantly alleviated the conditions. CYP1A1, one of the targeted genes of MLT, was verified to be upregulated in atherosclerotic mice but downregulated by MLT. Furthermore, H₂O₂ induced a senescence model in HUVECs, which was accompanied with a remarkably increased cell viability loss and apoptosis rate, and a downregulated telomerase activity of HUVECs, and this phenomenon was strengthened by RHPS4, an inhibitor of telomerase activity. However, MLT could partly abolish these changes in H₂O₂- and RHPS4-treated HUVECs, demonstrating that MLT alleviated vascular endothelial injury by regulating senescence and telomerase activity.

Conclusions

Collectively, this study provided evidence for the protective role of MLT in atherosclerosis through regulating telomere dysfunction-related vascular aging.

Deficiency of lncRNA SNHG12 impairs ischemic limb neovascularization by altering an endothelial cell cycle pathway

SNHG12, a long noncoding RNA (lncRNA) dysregulated in atherosclerosis, is known to be a key regulator of vascular senescence in endothelial cells (ECs). However, its role in angiogenesis and peripheral artery disease has not been elucidated. Hind-limb ischemia studies using femoral artery ligation (FAL) in mice showed that SNHG12 expression falls readily in the acute phase of the response to limb ischemia in gastrocnemius muscle and recovers to normal when blood flow recovery is restored to ischemic muscle, indicating that it likely plays a role in the angiogenic response to ischemia. Gain- and loss-of-function studies demonstrated that SNHG12 regulated angiogenesis — SNHG12 deficiency reduced cell proliferation, migration, and endothelial sprouting, whereas overexpression promoted these angiogenic functions. We identified SNHG12 binding partners by proteomics that may contribute to its role in angiogenesis, including IGF-2 mRNA–binding protein 3 (IGF2BP3, also known as IMP3). RNA-Seq profiling of SNHG12-deficient ECs showed effects on angiogenesis pathways and identified a strong effect on cell cycle regulation, which may be modulated by IMP3. Knockdown of SNHG12 in mice undergoing FAL using injected gapmeRs) decreased angiogenesis, an effect that was more pronounced in a model of insulin-resistant db/db mice. RNA-Seq profiling of the EC and non-EC compartments in these mice revealed a likely role of SNHG12 knockdown on Wnt, Notch, and angiopoietin signaling pathways. Together, these findings indicate that SNHG12 plays an important role in the angiogenic EC response to ischemia.

Bradykinin Protects Human Endothelial Progenitor Cells from High-Glucose-Induced Senescence through B2 Receptor-Mediated Activation of the Akt/eNOS Signalling Pathway

BACKGROUND

Circulating endothelial progenitor cells (EPCs) play important roles in vascular repair. However, the mechanisms of high-glucose- (HG-) induced cord blood EPC senescence and the role of B2 receptor (B2R) remain unknown.

METHODS

Cord blood samples from 26 patients with gestational diabetes mellitus (GDM) and samples from 26 healthy controls were collected. B2R expression on circulating CD34+ cells of cord blood mononuclear cells (CBMCs) was detected using flow cytometry. The plasma concentrations of 8-isoprostaglandin F2α (8-iso-PGF2α) and nitric oxide (NO) were measured. EPCs were treated with HG (40 mM) alone or with bradykinin (BK) (1 nM). The B2R and eNOS small interfering RNAs (siRNAs) and the PI3K antagonist LY294002 were added to block B2R, eNOS, and PI3K separately. To determine the number of senescent cells, senescence-associated β-galactosidase (SA-β-gal) staining was performed. The level of mitochondrial reactive oxygen species (ROS) in EPCs was assessed by Mito-Sox staining. Cell viability was evaluated by Cell Counting Kit-8 (CCK-8) assays. Mitochondrial DNA (mtDNA) copy number and the relative length of telomeres were detected by real time-PCR. The distribution of human telomerase reverse transcriptase (hTERT) in the nucleus, cytosol, and mitochondria of EPCs was detected by immunofluorescence. The expression of B2R, p16, p21, p53, P-Ser473AKT, T-AKT, eNOS, and hTERT was demonstrated by Western blot.

RESULTS

B2R expression on circulating CD34+ cells of CBMCs was significantly reduced in patients with GDM compared to healthy controls. Furthermore, B2R expression on circulating CD34+ cells of CBMCs was inversely correlated with plasma 8-iso-PGF2α concentrations and positively correlated with plasma NO levels. BK treatment decreased EPC senescence and ROS generation. Furthermore, BK treatment of HG-exposed cells led to elevated P-Ser473AKT and eNOS protein expression compared with HG treatment alone. BK reduced hTERT translocation in HG-induced senescent EPCs. B2R siRNA, eNOS siRNA, and antagonist of the PI3K signalling pathway blocked the protective effects of BK.

CONCLUSION

BK, acting through PI3K-AKT-eNOS signalling pathways, reduced hTERT translocation, increased the relative length of telomeres while reducing mtDNA copy number, and finally protected against EPC senescence induced by HG.

Telomere Length and Oxidative Stress and Its Relation with Metabolic Syndrome Components in the Aging

Simple Summary

A link between telomere length and some age-related diseases has been identified, including metabolic syndrome. So far, there is no mechanism to explain the origin or cause of telomere shortening in this syndrome; however, oxidative stress is a constant factor. Therefore, we reviewed scientific evidence that supported the association between oxidative stress and telomere length dynamics, also examining how each of the metabolic syndrome components individually affects the length. In this regard, there is strong scientific evidence that an increase in the number of metabolic syndrome components is associated with a shorter telomere length, oxidative damage at the lipid and DNA level, and inflammation, as well as its other components, such as obesity, hyperglycemia, and hypertension, while for dyslipidemia, there is a little more discrepancy. The difficulty for the correct treatment of metabolic syndrome lies in its multifactorial nature. Hence, there is a need to carry out more studies on healthy lifestyles during aging to prevent and reduce oxidative damage and telomere wear during aging, and consequently the progression of chronic degenerative diseases, thus improving the living conditions of older people.

Abstract

A great amount of scientific evidence supports that Oxidative Stress (OxS) can contribute to telomeric attrition and also plays an important role in the development of certain age-related diseases, among them the metabolic syndrome (MetS), which is characterised by clinical and biochemical alterations such as obesity, dyslipidaemia, arterial hypertension, hyperglycaemia, and insulin resistance, all of which are considered as risk factors for type 2 diabetes mellitus (T2DM) and cardiovascular diseases, which are associated in turn with an increase of OxS. In this sense, we review scientific evidence that supports the association between OxS with telomere length (TL) dynamics and the relationship with MetS components in aging. It was analysed whether each MetS component affects the telomere length separately or if they all affect it together. Likewise, this review provides a summary of the structure and function of telomeres and telomerase, the mechanisms of telomeric DNA repair, how telomere length may influence the fate of cells or be linked to inflammation and the development of age-related diseases, and finally, how the lifestyles can affect telomere length.

Endothelial Cells as Tools to Model Tissue Microenvironment in Hypoxia-Dependent Pathologies

Endothelial cells (ECs) lining the blood vessels are important players in many biological phenomena but are crucial in hypoxia-dependent diseases where their deregulation contributes to pathology. On the other hand, processes mediated by ECs, such as angiogenesis, vessel permeability, interactions with cells and factors circulating in the blood, maintain homeostasis of the organism. Understanding the diversity and heterogeneity of ECs in different tissues and during various biological processes is crucial in biomedical research to properly develop our knowledge on many diseases, including cancer. Here, we review the most important aspects related to ECs’ heterogeneity and list the available in vitro tools to study different angiogenesis-related pathologies. We focus on the relationship between functions of ECs and their organo-specificity but also point to how the microenvironment, mainly hypoxia, shapes their activity. We believe that taking into account the specific features of ECs that are relevant to the object of the study (organ or disease state), especially in a simplified in vitro setting, is important to truly depict the biology of endothelium and its consequences. This is possible in many instances with the use of proper in vitro tools as alternative methods to animal testing.

Telomere length and human hippocampal neurogenesis

Short telomere length is a risk factor for age-related disease, but it is also associated with reduced hippocampal volumes, age-related cognitive decline and psychiatric disorder risk. The current study explored whether telomere shortening might have an influence on cognitive function and psychiatric disorder pathophysiology, via its hypothesised effects on adult hippocampal neurogenesis. We modelled telomere shortening in human hippocampal progenitor cells in vitro using a serial passaging protocol that mimics the end-replication problem. Serially passaged progenitors demonstrated shorter telomeres (P ≤ 0.05), and reduced rates of cell proliferation (P ≤ 0.001), with no changes in the ability of cells to differentiate into neurons or glia. RNA-sequencing and gene-set enrichment analyses revealed an effect of cell ageing on gene networks related to neurogenesis, telomere maintenance, cell senescence and cytokine production. Downregulated transcripts in our model showed a significant overlap with genes regulating cognitive function (P ≤ 1 × 10^-5), and risk for schizophrenia (P ≤ 1 × 10^-10) and bipolar disorder (P ≤ 0.005). Collectively, our results suggest that telomere shortening could represent a mechanism that moderates the proliferative capacity of human hippocampal progenitors, which may subsequently impact on human cognitive function and psychiatric disorder pathophysiology.

Cytotoxic responses of the anticancer drug cyclophosphamide in the mussel Mytilus galloprovincialis and comparative sensitivity with human cells lines

The rise of cancer cases worldwide led to an increase in production and consumption of anticancer drugs, that ultimately end up in the marine environment and are accumulated in aquatic organisms. Cyclophosphamide (CP) is a cytotoxic alkylating agent frequently prescribed in cancer treatments. This study assess ecotoxicological effects of CP on mussels Mytilus galloprovincialis, through in vivo and ex vivo approaches and compares the sensitivity of mussel haemocytes with well-established human cell lines (RPE and HeLa). Mussels were exposed in vivo to CP (1000 ng L^-1) and several biomarkers analysed in gills and digestive glands namely neurotoxicity (AChE activity), oxidative stress (GPx activity), biotransformation (GST activity), lipid peroxidation (LPO) and apoptosis (caspase activity), whereas genotoxicity was determined in mussels' haemocytes. Cytotoxicity was also assessed in haemocytes (in vivo and ex vivo) and human cell lines (in vitro) exposed to a range of CP concentrations (50, 100, 250, 500 and 1000 ng L^-1) over 24 h, via neutral red assay. In in vivo exposure, detoxification of CP did not efficiently occur in the gills while in digestive glands GPx and GST activities were induced, jointly with a decrease in lipid peroxidation, indicating a potential outcome of the protective antioxidant mechanisms, whereas no apoptosis was noted. Moreover, cytotoxicity and DNA damage were detected in haemocytes. The ex vivo exposure haemocytes to CP caused cytotoxicity (from 100 ng L^-1), whereas no effects occurred in human cell lines. This suggests that, at relevant environmental concentrations, CP cause subtle and irreversible impacts on M. galloprovincialis.

Telomerase activation in the treatment of aging or degenerative diseases: a systematic review

Telomeres are protective structures that are shortened during the lifetime, resulting in aging and degenerative diseases. Subjects experiencing aging and degenerative disorders present smaller telomeres than young and healthy ones. The size of these structures can be stabilized by telomerase, an enzyme which is inactive in adult tissues but functional in fetal and newborn tissues and adult testes and ovaries. The aim of this study was to perform a systematic review to evaluate the effect of telomerase activation in the treatment of degenerative and aging disorders. We accomplished the search using the Pubmed interface for papers published from September 1985 to April 16th, 2020. We found twenty one studies that matched our eligibility criteria. I concluded that telomerase is probably a potential and safe treatment for aging and degenerative diseases, demonstrating neither side effects nor risk of cancer in the selected studies. Further studies in humans are needed to confirm safety and efficiency of this treatment.

High glucose concentration produces a short-term increase in pERK1/2 and p85 proteins, having a direct angiogenetic effect by an action similar to VEGF

AIMS

Excessive glucose serum concentration, endothelial dysfunction and microangiopathy are key features of diabetes mellitus, being both diagnostic parameters and pathogenetic mechanisms. Vascular endothelial growth factor (VEGF) is importantly implicated in the physiology and pathology of blood vessels, including diabetic vascular damage.

METHODS

These factors certainly affect endothelial cells, and to evaluate mechanisms involved, we took advantage of telomerase-immortalized human microvascular endothelial (TIME) cells. TIME cells were exposed to different glucose concentrations and to VEGF treatments. Culture conditions also included the use of basement membrane extract, as an in vitro differentiation model. Cell morphology was then evaluated in the different conditions, and cellular proteins were extracted to analyze specific protein products by Western blot.

RESULTS

High glucose concentrations and VEGF did substantially affect neither morphology nor growth of cultured TIME cells, while both considerably increased differentiation into "capillary-like" structures when cells were cultured on basement membrane extract.

CONCLUSIONS

Under these conditions, high glucose concentration and VEGF also produced a short-term increase in pERK1/2 and p85 proteins, while total and phosphorylated AKT were not affected. These data suggest a direct angiogenetic effect of glucose, affecting intracellular transduction mechanisms with an action similar to that of VEGF. This effect on endothelial cell proliferation and differentiation could be part of pathogenetic mechanisms producing diabetic microvascular alterations.

Immortalized normal human lung epithelial cell models for studying lung cancer biology

Primary cultures of human lung epithelial cells are ideal representatives of normal lung epithelial cells, and while there are certain novel approaches for the long-term culture of lung epithelial cells, the cells eventually undergo irreversible growth arrest, limiting their experimental utility, particularly the ability to widely distribute these cultures and their clonal derivatives to the broader research community. Therefore, the establishment of immortalized normal human lung epithelial cell strains has garnered considerable attention. The number and type of oncogenic changes necessary for the tumorigenic transformation of normal cells could be determined using "normal" cell lines immortalized with the simian virus 40 (SV40) large T antigen (LT). A primary report suggested that LT, human telomerase reverse transcriptase (hTERT), and oncogenic RAS transformed normal lung epithelial cells into tumorigenic cells. Since LT inactivates the tumor suppressors p53 and RB, at least four alterations would be necessary. However, the SV40 small T antigen (ST), a different oncoprotein, was also introduced simultaneously with LT in the above-mentioned study. Furthermore, the possible uncharacterized functions of LT remained largely obscure. Therefore, no definitive conclusion could be arrived in these studies. Subsequent studies used methods that did not involve the use of oncoproteins and revealed that at least five genetic changes were necessary for full tumorigenic transformation. hTERT-immortalized normal human lung epithelial cell lines established without using viral oncoproteins were also used for investigating several aspects of lung cancer, such as epithelial to mesenchymal transition and the cancer stem cell theory. The use of immortalized normal lung epithelial cell models has improved our understanding of lung cancer pathogenesis and these models can serve as valuable research tools.

Evolutionary optimization of image processing for cell detection in microscopy images

In this paper, we present a new evolution-based algorithm that optimizes cell detection image processing workflows in a self-adaptive fashion. We use evolution strategies to optimize the parameters for all steps of the image processing pipeline and improve cell detection results. The algorithm reliably produces good cell detection results without the need for extensive domain knowledge. Our algorithm also needs no labeled data to produce good cell detection results compared to the state-of-the-art neural network approaches. Furthermore, the algorithm can easily be adapted to different applications by modifying the processing steps in the pipeline and has high scalability since it supports multithreading and computation on graphical processing units (GPUs).

Cardiac tissue remodeling in healthy aging: the road to pathology

This review aims to highlight the normal physiological remodeling that occurs in healthy aging hearts, including changes that occur in contractility, conduction, valve function, large and small coronary vessels, and the extracellular matrix. These "normal" age-related changes serve as the foundation that supports decreased plasticity and limited ability for tissue remodeling during pathophysiological states such as myocardial ischemia and heart failure. This review will identify populations at greater risk for poor tissue remodeling in advanced age along with present and future therapeutic strategies that may ameliorate dysfunctional tissue remodeling in aging hearts.

Feed‑back loops integrating RELA, SOX18 and FAK mediate the break‑down of the lymph‑endothelial barrier that is triggered by 12(S)‑HETE

Metastatic cancer cells cross endothelial barriers and travel through the blood or lymphatic fluid to pre‑metastatic niches, leading to their colonisation. 'S' stereoisomer 12S‑hydroxy‑5Z,8Z,10E,14Z‑eicosatetraenoic acid [12(S)‑HETE] is secreted by a variety of cancer cell types and has been indicated to open up these barriers. In the present study, another aspect of the endothelial unlocking mechanism was elucidated. This was achieved by investigating 12(S)‑HETE‑treated lymph endothelial cells (LECs) with regard to their expression and mutual interaction with v‑rel avian reticuloendotheliosis viral oncogene homolog A (RELA), intercellular adhesion molecule 1, SRY‑box transcription factor 18 (SOX18), prospero homeobox 1 (PROX1) and focal adhesion kinase (FAK). These key players of LEC retraction, which is a prerequisite for cancer cell transit into vasculature, were analysed using western blot analysis, reverse transcription‑quantitative PCR and transfection with small interfering (si)RNA. The silencing of a combination of these signalling and executing molecules using siRNA, or pharmacological inhibition with defactinib and Bay11‑7082, extended the mono‑culture experiments to co‑culture settings using HCT116 colon cancer cell spheroids that were placed on top of LEC monolayers to measure their retraction using the validated 'circular chemorepellent‑induced defect' assay. 12(S)‑HETE was indicated to induce the upregulation of the RELA/SOX18 feedback loop causing the subsequent phosphorylation of FAK, which fed back to RELA/SOX18. Therefore, 12(S)‑HETE was demonstrated to be associated with circuits involving RELA, SOX18 and FAK, which transduced signals causing the retraction of LECs. The FAK‑inhibitor defactinib and the NF‑κB inhibitor Bay11‑7082 attenuated LEC retraction additively, which was similar to the suppression of FAK and PROX1 (the target of SOX18) by the transfection of respective siRNAs. FAK is an effector molecule at the distal end of a pro‑metastatic signalling cascade. Therefore, targeting the endothelial‑specific activity of FAK through the pathway demonstrated herein may provide a potential therapeutic method to combat cancer dissemination via vascular routes.

Molecular docking, antiproliferative and anticonvulsant activities of swertiamarin isolated from Enicostemma axillare

Present study aimed for molecular docking, antiproliferative and anticonvulsant activities of swertiamarin isolated from the successive methanol extract of Enicostemma axillare. Molecular docking of swertiamarin on telomerase targets (PDB ID: 5UGW, 3DU6 and 4ERD), followed by antiproliferative activity on HEp2 and HT-29 cells by MTT and SRB assays. Also tested for anticonvulsant activity by pentylenetetrazole (PTZ, 80 mg/kg bw) induced convulsant. Molecular docking study predicted good total score of the swertiamarin with the selected targets. Swertiamarin possesses antiproliferative activity on HEp-2 and HT-29 cells with lower CTC₅₀ values. It also served as significant anticonvulsant agent with prolonged onset and reduced duration of the seizures. These results confirm that swertiamarin exhibited potential antiproliferative and anticonvulsant activities.

Development of Immortalized Human Tumor Endothelial Cells from Renal Cancer

Tumor angiogenesis research and antiangiogenic drug development make use of cultured endothelial cells (ECs) including the human microvascular ECs among others. However, it has been reported that tumor ECs (TECs) are different from normal ECs (NECs). To functionally validate antiangiogenic drugs, cultured TECs are indispensable tools, but are not commercially available. Primary human TECs are available only in small quantities from surgical specimens and have a short life span in vitro due to their cellular senescence. We established immortalized human TECs (h-imTECs) and their normal counterparts (h-imNECs) by infection with lentivirus producing simian virus 40 large T antigen and human telomerase reverse transcriptase to overcome the replication barriers. These ECs exhibited an extended life span and retained their characteristic endothelial morphology, expression of endothelial marker, and ability of tube formation. Furthermore, h-imTECs showed their specific characteristics as TECs, such as increased proliferation and upregulation of TEC markers. Treatment with bevacizumab, an antiangiogenic drug, dramatically decreased h-imTEC survival, whereas the same treatment failed to alter immortalized NEC survival. Hence, these h-imTECs could be a valuable tool for drug screening to develop novel therapeutic agents specific to TECs or functional biological assays in tumor angiogenesis research.

Structural Insight into the In Vitro Anti-Intravasative Properties of Flavonoids

We investigated the effect of 21 flavonoids in a three-dimensional in vitro system for their ability to inhibit gap formation by MCF-7 breast cancer spheroids in monolayers of lymphendothelial cells. Different representatives of the classes of flavones, flavonols, and flavanones were tested in the circular chemorepellent-induced defects (CCID)-assay. Bay11-7082, a known inhibitor of CCID formation served as the positive control. This study provides the first comparison of the potential of flavonoids to suppress features influencing the intravasation of MCF-7 breast cancer cells aggregates through the lymph endothelial barrier. The most significant effects were seen after incubation with the flavones luteolin, chrysin, and apigenin. Additional hydroxylation or methoxylation in positions 6 or 8, as expected, resulted in decreased activity. The tested flavanones remained without or low efficacy.

Matrix Production in Chondrocytes Transfected with Sex Determining Region Y-Box 9 and Telomerase Reverse Transcriptase Genes: An In Vitro Evaluation from Monolayer Culture to Three-Dimensional Culture

Background

This study aimed to observe the cartilaginous matrix production in SRY (sex determining region Y)-box 9 (SOX9)- and/or telomerase reverse transcriptase (TERT)-transfected chondrocytes from monolayer to three-dimensional (3D) culture.

Methods

The genes were transferred into chondrocytes at passage-1 (P1) via lipofection. The post-transfected chondrocytes (SOX9-, TERT- and SOX9/TERT) were analysed at P1, P2 and P3. The non-transfected group was used as control. The 3D culture was established using the chondrocytes seeded in a disc-shaped PLGA/fibrin and PLGA scaffolds. The resulting 3D "cells-scaffolds" constructs were analysed at week-1, -2 and -3. The histoarchitecture was evaluated using haematoxylin and eosin, alcian blue and safranin o stains. The quantitative sulphated glycosaminoglycan (sGAG) content was measured using biochemical assay. The cartilage-specific markers expression were analysed via real-time polymerase chain reaction.

Results

All monolayer cultured chondrocytes showed flattened, fibroblast-like appearance throughout passages. Proteoglycan and sGAG were not detected at the pericellular matrix region of the chondrocytes. The sGAG content assay indicated the matrix production depletion in the culture. The cartilage-specific markers, COL2A1 and ACAN, were downregulated. However, the dedifferentiation marker, COL1A1 was upregulated. In 3D "cells-scaffolds" constructs, regardless of transfection groups, chondrocytes seeded in PLGA/fibrin showed a more uniform distribution and produced denser matrix than the PLGA group especially at week-3. Both sGAG and proteoglycan were clearly visualised in the constructs, supported by the increment of sGAG content, quantitatively. Both COL2A1 and ACAN were upregulated in SOX9/TERT-PLGA and SOX9/TERT-PLGA/fibrin respectively. While, COL1A1 was downregulated in SOX9/TERT-PLGA.

Conclusion

These findings indicated that the SOX9/TERT-transfected chondrocytes incorporation into 3D scaffolds facilitates the cartilage regeneration which is viable structurally and functionally.

Endothelial Cell Aging: How miRNAs Contribute?

Endothelial cells (ECs) form monolayers and line the interior surfaces of blood vessels in the entire body. In most mammalian systems, the capacity of endothelial cells to divide is limited and endothelial cells are prone to be senescent. Aging of ECs and resultant endothelial dysfunction lead to a variety of vascular diseases such as atherosclerosis, diabetes mellites, hypertension, and ischemic injury. However, the mechanism by which ECs get old and become senescent and the impact of endothelial senescence on the vascular function are not fully understood. Recent research has unveiled the crucial roles of miRNAs, which are small non-coding RNAs, in regulating endothelial cellular functions, including nitric oxide production, vascular inflammation, and anti-thromboformation. In this review, how senescent-related miRNAs are involved in controlling the functions of ECs will be discussed.

A pumpless body-on-a-chip model using a primary culture of human intestinal cells and a 3D culture of liver cells

We describe an expanded modular gastrointestinal (GI) tract-liver system by co-culture of primary human intestinal epithelial cells (hIECs) and 3D liver mimic. The two organ body-on-chip design consisted of GI and liver tissue compartments that were connected by fluidic medium flow driven via gravity. The hIECs and HepG2 C3A liver cells in the co-culture system maintained high viability for at least 14 days in which hIECs differentiated into major cell types found in native human intestinal epithelium and the HepG2 C3A cells cultured on 3D polymer scaffold formed a liver micro-lobe like structure. Moreover, the hIECs formed a monolayer on polycarbonate membranes with a tight junction and authentic TEER values of approximately 250 Ω cm2 for the native gut. The hIEC permeability was compared to a conventional permeability model using Caco-2 cell response for drug absorption by measuring the uptake of propranolol, mannitol and caffeine. Metabolic rates (urea or albumin production) of the cells in the co-culture GI-liver system were comparable to those of HepG2 C3A cells in a single-organ fluidic culture system, while induced CYP activities were significantly increased in the co-culture GI tract-liver system compared to the single-organ fluidic culture system. These results demonstrated potential of the low-cost microphysiological GI-liver model for preclinical studies to predict human response.

Apelin/APJ axis improves angiotensin II-induced endothelial cell senescence through AMPK/SIRT1 signaling pathway

INTRODUCTION

Previous studies have shown that endothelial cell senescence is involved in cardiovascular diseases such as cardiac fibrosis, atherosclerosis and heart failure. Accumulating evidence indicates that apelin exerts protective effects on ageing-related endothelial dysfunction. In this study, we aim to investigate the role of the apelin/APJ axis in angiotensin II (AngII)-induced endothelium senescence and its associated mechanisms.

MATERIAL AND METHODS

Senescence-related β-gal activity assay and western blot were used to evaluate human umbilical vein endothelial cell (HUVEC) senescence. In addition, DCFH-DA staining was carried out to detect the generation of reactive oxygen species (ROS). A validated, high-sensitivity real-time quantitative telomeric repeat amplification protocol (RQ-TRAP) was applied to determine telomerase activity in HUVECs, and a CCK-8 assay was employed to measure cellular viability.

RESULTS

AngII induced an increase in SA-β-Gal-positive cells and upregulation on expression of P21 and PAI-1 compared to the control group (p < 0.05), while apelin against this process (p < 0.05). The protective effects were attenuated when APJ, AMPK and SIRT1 expression was knocked down (p < 0.05). Furthermore, apelin reduced AngII-induced ROS generation and enhanced telomerase activity in HUVECs (p < 0.05), which contributed to increased HUVEC viability as assessed by the CCK-8 assay (p < 0.05).

CONCLUSIONS

The apelin/APJ axis improved AngII-induced HUVEC senescence via the AMPK/SIRT1 signaling pathway, and the underlying mechanisms might be associated with reduced ROS production and enhanced telomerase activity.

The Emerging Roles for Telomerase in the Central Nervous System

Telomerase, a specialized ribonucleoprotein enzyme complex, maintains telomere length at the 3′ end of chromosomes, and functions importantly in stem cells, cancer and aging. Telomerase exists in neural stem cells (NSCs) and neural progenitor cells (NPCs), at a high level in the developing and adult brains of humans and rodents. Increasing studies have demonstrated that telomerase in NSCs/NPCs plays important roles in cell proliferation, neuronal differentiation, neuronal survival and neuritogenesis. In addition, recent works have shown that telomerase reverse transcriptase (TERT) can protect newborn neurons from apoptosis and excitotoxicity. However, to date, the link between telomerase and diseases in the central nervous system (CNS) is not well reviewed. Here, we analyze the evidence and summarize the important roles of telomerase in the CNS. Understanding the roles of telomerase in the nervous system is not only important to gain further insight into the process of the neural cell life cycle but would also provide novel therapeutic applications in CNS diseases such as neurodegenerative condition, mood disorders, aging and other ailments.

12(S)-HETE induces lymph endothelial cell retraction in vitro by upregulation of SOX18

Metastasising breast cancer cells communicate with adjacent lymph endothelia, intravasate and disseminate through lymphatic routes, colonise lymph nodes and finally metastasize to distant organs. Thus, understanding and blocking intravasation may attenuate the metastatic cascade at an early step. As a trigger factor, which causes the retraction of lymph endothelial cells (LECs) and opens entry ports for tumour cell intravasation, MDA-MB231 breast cancer cells secrete the pro-metastatic arachidonic acid metabolite, 12S-hydroxy-5Z,8Z,10E,14Z-eicosatetraenoic acid [12(S)-HETE]. In the current study, treatment of LECs with 12(S)-HETE upregulated the expression of the transcription factors SRY-related HMG-box 18 (SOX18) and prospero homeobox protein 1 (PROX1), which determine endothelial development. Thus, whether they have a role in LEC retraction was determined using a validated intravasation assay, small interfering RNA mediated knockdown of gene expression, and mRNA and protein expression analyses. Specific inhibition of SOX18 or PROX1 significantly attenuated in vitro intravasation of MDA-MB231 spheroids through the LEC barrier and 12(S)-HETE-triggered signals were transduced by the high and low affinity receptors, 12(S)-HETE receptor and leukotriene B4 receptor 2. In addition, the current findings indicate that there is crosstalk between SOX18 and nuclear factor κ-light-chain-enhancer of activated B cells, which was demonstrated to contribute to MDA-MB231/lymph endothelial intravasation. The present data demonstrate that the endothelial-specific and lymph endothelial-specific transcription factors SOX18 and PROX1 contribute to LEC retraction.

Development and Characterisation of a Human Chronic Skin Wound Cell Line-Towards an Alternative for Animal Experimentation

Background: Chronic skin wounds are a growing financial burden for healthcare providers, causing discomfort/immobility to patients. Whilst animal chronic wound models have been developed to allow for mechanistic studies and to develop/test potential therapies, such systems are not good representations of the human chronic wound state. As an alternative, human chronic wound fibroblasts (CWFs) have permitted an insight into the dysfunctional cellular mechanisms that are associated with these wounds. However, such cells strains have a limited replicative lifespan and therefore a limited reproducibility/usefulness. Objectives: To develop/characterise immortalised cell lines of CWF and patient-matched normal fibroblasts (NFs). Methods and Results: Immortalisation with human telomerase resulted in both CWF and NF proliferating well beyond their replicative senescence end-point (respective cell strains senesced as normal). Gene expression analysis demonstrated that, whilst proliferation-associated genes were up-regulated in the cell lines (as would be expected), the immortalisation process did not significantly affect the disease-specific genotype. Immortalised CWF (as compared to NF) also retained a distinct impairment in their wound repopulation potential (in line with CWF cell strains). Conclusions: These novel CWF cell lines are a credible animal alternative and could be a valuable research tool for understanding both the aetiology of chronic skin wounds and for therapeutic pre-screening.

Administration of L-arginine plus L-citrulline or L-citrulline alone successfully retarded endothelial senescence

L-citrulline and L-arginine supplementation has been shown to have several beneficial effects on the cardiovascular system. Nitric oxide (NO) protects against the progression of atherosclerosis and is synthesized by nitric oxide synthase (NOS), which converts L-arginine (L-Arg) into L-citrulline (L-Cit). Our previous study revealed that chronic administration of a combination of L-Cit and L- Arg has a better therapeutic effect on high cholesterol-induced atherosclerosis in rabbits. We investigated how L-Arg and L-Cit affect endothelial function, aging and atherosclerosis. Following a 3-day stimulation of human umbilical venous endothelial cells (HUVECs) with high glucose (HG: 22 mM) and L-Arg (300 μM), L-Cit (300 μM) or L-Arg plus L-Cit (LALC: each 150 μM) supplementation, endothelial senescence and function were evaluated. These amino acids were also administered to dyslipidemic type 2 diabetic (ZDFM) rats fed a high cholesterol diet. They were fed L-Arg or L-Cit or LALC for four weeks. Aortic senescence was investigated by measuring senescence-associated ß-galactosidase (SA-ß-gal), telomerase activity, DNA damage and p16^INK4a protein expression. Only L-Cit and LALC supplementation retarded the HG-induced endothelial senescence, as evaluated by SA-ß-gal activity, a widely used marker of cellular senescence, p16^INK4a expression, a senescence-related protein, and DNA damage. Under HG conditions, L-Cit and LCLA restored telomerase activity to levels observed under normal glucose (NG) conditions. Under HG conditions, L-Cit decreased ROS production, as measured by CM-H₂DCFDA and the expression of p67^phox, a major component of NADPH oxidase. Under HG conditions, L-Cit and LALC increased NO production, as measured by DAF-2AM. Endothelial NO synthase (eNOS) and phosphorylated eNOS were decreased under HG conditions and L-Cit and LALC significantly increased these levels. Arginase 2 protein expression increased under the HG conditions, and L-Cit and LALC significantly attenuated this effect. In ZDFM rats, SA-ß-gal activity was detected on the aortic endothelial surface; however, L-Cit and LALC reduced these levels. L-Cit and LALC both decreased the proportion of senescent cells. Furthermore, treatment with LALC for 4 weeks increased plasma NO production. Therefore conclusively, L-citrulline supplementation rescued NO levels better than L-arginine supplementation by inhibiting ROS production and arginase 2 protein expression. Consequently, L-Cit and LCLA supplementation retaeded HG-induced endothelial senescence.

Development and validation of immortalized bovine mammary epithelial cell line as an in vitro model for the study of mammary gland functions

This study aimed to develop a bovine mammary epithelial (BME) cell line model, which provides a possibility to determine functional properties of the bovine mammary gland. The primary cell culture was derived from bovine mammary gland tissues and processed enzymatically to obtain cell colonies with epithelial-like morphology. The cultures of BME cells were purified and optimally cultured at 37 °C in DMEM/F12 medium supplemented with 10% fetal bovine serum. The BME cells were identified as epithelial cell line by the evaluating the expression of keratin-18 using immunofluorescence staining. A novel gene expression system strongly enhances the expression of telomerase, has been used to immortalize BME cell line termed hTBME cell line. Interestingly, telomerase remained active even after over 60 passages of hTBME cell line, required for immortalization of BME cells. In addition, the hTBME cell line was continuously subcultured with a spontaneous epithelial-like morphology, with a great proliferation activity, and without evidence of apoptotic and necrotic effects. Further characterization showed that hTBME cell line can be continuously propagated in culture with constant chromosomal features and without tumorigenic properties. Finally, established hTBME cell line was evaluated for mammary gland specific functions. Our results demonstrated that the hTBME cell line was able to retain functional-morphological structure, and functional differentiation by expression of beta (β)-casein as in the bovine mammary gland in vivo. Taken together, our findings suggest that the established hTBME cell line can serve as a valuable tool for the study of bovine mammary gland functions.

Telomere Biology and Thoracic Aortic Aneurysm

Ascending aortic aneurysms are mostly asymptomatic and present a great risk of aortic dissection or perforation. Consequently, ascending aortic aneurysms are a source of lethality with increased age. Biological aging results in progressive attrition of telomeres, which are the repetitive DNA sequences at the end of chromosomes. These telomeres play an important role in protection of genomic DNA from end-to-end fusions. Telomere maintenance and telomere attrition-associated senescence of endothelial and smooth muscle cells have been indicated to be part of the pathogenesis of degenerative vascular diseases. This systematic review provides an overview of telomeres, telomere-associated proteins and telomerase to the formation and progression of aneurysms of the thoracic ascending aorta. A better understanding of telomere regulation in the vascular pathology might provide new therapeutic approaches. Measurements of telomere length and telomerase activity could be potential prognostic biomarkers for increased risk of death in elderly patients suffering from an aortic aneurysm.

Angiogenesis, Cancer, and Vascular Aging

Several lines of evidence have revealed that the angiogenic response to ischemic injury declines with age, which might account for the increased morbidity and mortality of cardiovascular disease (CVD) among the elderly. While impairment of angiogenesis with aging leads to delayed wound healing or exacerbation of atherosclerotic ischemic diseases, it also inhibits the progression of cancer. Age-related changes of angiogenesis have been considered to at least partly result from vascular aging or endothelial cell senescence. There is considerable evidence supporting the hypothesis that vascular cell senescence contributes to the pathogenesis of age-related CVD, suggesting that vascular aging could be an important therapeutic target. Since therapeutic angiogenesis is now regarded as a promising concept for patients with ischemic CVD, it has become even more important to understand the detailed molecular mechanisms underlying impairment of angiogenesis in older patients. To improve the usefulness of therapeutic angiogenesis, approaches are needed that can compensate for impaired angiogenic capacity in the elderly while not promoting the development or progression of malignancy. In this review, we briefly outline the mechanisms of angiogenesis and vascular aging, followed by a description of how vascular aging leads to impairment of angiogenesis. We also examine potential therapeutic approaches that could enhance angiogenesis and/or vascular function in the elderly, as well as discussing the possibility of anti-senescence therapy or reversal of endothelial cell senescence.

Cellular lifespan and senescence: a complex balance between multiple cellular pathways

The study of cellular senescence and proliferative lifespan is becoming increasingly important because of the promises of autologous cell therapy, the need for model systems for tissue disease and the implication of senescent cell phenotypes in organismal disease states such as sarcopenia, diabetes and various cancers, among others. Here, we explain the concepts of proliferative cellular lifespan and cellular senescence, and we present factors that have been shown to mediate cellular lifespan positively or negatively. We review much recent literature and present potential molecular mechanisms by which lifespan mediation occurs, drawing from the fields of telomere biology, metabolism, NAD(+) and sirtuin biology, growth factor signaling and oxygen and antioxidants. We conclude that cellular lifespan and senescence are complex concepts that are governed by multiple independent and interdependent pathways, and that greater understanding of these pathways, their interactions and their convergence upon specific cellular phenotypes may lead to viable therapies for tissue regeneration and treatment of age-related pathologies, which are caused by or exacerbated by senescent cells in vivo.

Telomere Biology of Human Hematopoietic Stem Cells

BACKGROUND

Telomeres are protein DNA structures present at the ends of chromosomes and are essential for genetic stability and cell replication. Telomerase is the enzyme complex that maintains telomere integrity. Hematopoietic stem cells express telomerase and contain long telomeres, which become shorter as cells differentiate and mature. The extent of telomere shortening and the level of telomerase activity often correlate with the presence and severity of some hematopoietic diseases.

METHODS

The fundamentals of telomeres and telomerase are reviewed, and the telomere biology of human hematopoietic cells is discussed.

RESULTS

Telomere length and telomerase activity are important in the self-renewal of hematopoietic stem cells. Changes within these compartments affect both normal hematopoietic cells and the generation of hematopoietic disease. Telomere length provides information pertaining to the proliferative history and potential of a hematopoietic cell.

CONCLUSIONS

The role of telomerase and telomeres within the hematopoietic compartment needs further clarification. Advances in our knowledge in this field may improve clinical outcomes for the treatment of hematologic disease.

Vascular aging: Molecular mechanisms and potential treatments for vascular rejuvenation

Aging is the main risk factor contributing to vascular dysfunction and the progression of vascular diseases. In this review, we discuss the causes and mechanisms of vascular aging at the tissue and cellular level. We focus on Endothelial Cell (EC) and Smooth Muscle Cell (SMC) aging due to their critical role in mediating the defective vascular phenotype. We elaborate on two categories that contribute to cellular dysfunction: cell extrinsic and intrinsic factors. Extrinsic factors reflect systemic or environmental changes which alter EC and SMC homeostasis compromising vascular function. Intrinsic factors induce EC and SMC transformation resulting in cellular senescence. Replenishing or rejuvenating the aged/dysfunctional vascular cells is critical to the effective repair of the vasculature. As such, this review also elaborates on recent findings which indicate that stem cell and gene therapies may restore the impaired vascular cell function, reverse vascular aging, and prolong lifespan.

The human vascular endothelial cell line HUV-EC-C harbors the integrated HHV-6B genome which remains stable in long term culture

Human herpes virus 6 (HHV-6) is a common human pathogen that is most often detected in hematopoietic cells. Although human cells harboring chromosomally integrated HHV-6 can be generated in vitro, the availability of such cell lines originating from in vivo tissues is limited. In this study, chromosomally integrated HHV-6B has been identified in a human vascular endothelial cell line, HUV-EC-C (IFO50271), derived from normal umbilical cord tissue. Sequence analysis revealed that the viral genome was similar to the HHV-6B HST strain. FISH analysis using a HHV-6 DNA probe showed one signal in each cell, detected at the distal end of the long arm of chromosome 9. This was consistent with a digital PCR assay, validating one copy of the viral DNA. Because exposure of HUV-EC-C to chemicals did not cause viral reactivation, long term cell culture of HUV-EC-C was carried out to assess the stability of viral integration. The growth rate was altered depending on passage numbers, and morphology also changed during culture. SNP microarray profiles showed some differences between low and high passages, implying that the HUV-EC-C genome had changed during culture. However, no detectable change was observed in chromosome 9, where HHV-6B integration and the viral copy number remained unchanged. Our results suggest that integrated HHV-6B is stable in HUV-EC-C despite genome instability.

Immortalization of chicken preadipocytes by retroviral transduction of chicken TERT and TR

The chicken is an important agricultural animal and model for developmental biology, immunology and virology. Excess fat accumulation continues to be a serious problem for the chicken industry. However, chicken adipogenesis and obesity have not been well investigated, because no chicken preadipocyte cell lines have been generated thus far. Here, we successfully generated two immortalized chicken preadipocyte cell lines through transduction of either chicken telomerase reverse transcriptase (chTERT) alone or in combination with chicken telomerase RNA (chTR). Both of these cell lines have survived >100 population doublings in vitro, display high telomerase activity and have no sign of replicative senescence. Similar to primary chicken preadipocytes, these two cell lines display a fibroblast-like morphology, retain the capacity to differentiate into adipocytes, and do not display any signs of malignant transformation. Isoenzyme analysis and PCR-based analysis confirmed that these two cell lines are of chicken origin and are free from inter-species contamination. To our knowledge, this is the first report demonstrating the generation of immortal chicken cells by introduction of chTERT and chTR. Our established chicken preadipocyte cell lines show great promise as an in vitro model for the investigation of chicken adipogenesis, lipid metabolism, and obesity and its related diseases, and our results also provide clues for immortalizing other avian cell types.

Low p16INK4a Expression in Early Passage Human Prostate Basal Epithelial Cells Enables Immortalization by Telomerase Expression Alone

BACKGROUND

There are two principal senescence barriers that must be overcome to successfully immortalize primary human epithelial cells in culture, stress-induced senescence, and replicative senescence. The p16^INK4a /retinoblastoma protein (p16/Rb) pathway mediates stress-induced senescence, and is generally upregulated by primary epithelial cells in response to the artificial conditions from tissue culture. Replicative senescence is associated with telomere loss. Following each round of cell division, telomeres progressively shorten. Once telomeres shorten to a critical length, the DNA damage response pathway is activated, and the tumor suppressor p53 pathway triggers replicative senescence. Exogenous expression of telomerase in normal human epithelial cells extends the replicative capacity of cells, and in some cases, immortalizes cells. However reliable immortalization of epithelial cells usually requires telomerase activity coupled with inactivation of the p16/Rb pathway.

METHODS

A lentiviral vector, pLOX-TERT-iresTK (Addgene #12245), containing a CMV promoter upstream of a bicistronic coding cassette that includes loxP sites flanking the catalytic subunit of human telomerase gene (TERT) and herpes simplex virus type-1 thymidine kinase gene (HSV1-tk) was used to transduce normal prostate basal epithelial cells (PrECs) initiated in cell culture from prostate cancer patients undergoing radical prostatectomies.

RESULTS

Transduction of early (i.e., <7) passage PrECs with TERT led to successful immortalization. However, attempts to immortalize late (i.e., >7) passage PrECs were unsuccessful. Late passage PrECs, which acquired elevated p16, were unable to overcome the senescence barrier. Immortalized PrECs (TERT-PrECs) retained a normal male karyotype and low p16 expression. Additionally, TERT-PrECs were non-tumorigenic when inoculated into intact male immunodeficient NSG mice.

CONCLUSIONS

The present studies document that early passage human PrECs have sufficiently low p16 to permit immortalization by TERT expression alone. TERT-PrECs developed using this transduction approach provides an appropriate and experimentally facile model for clarifying the molecular mechanism(s) involved in both immortalization of human PrECs, as well as identifying genetic/epigenetic "drivers" for conversion of these immortalized non-tumorigenic cells into fully lethal prostate cancers. Notably, loxP sites flank the exogenous TERT gene in the TERT-PrECs. Cre recombinase can be used to excise TERT, and resolve whether TERT expression is required for these cells to be fully transformed into lethal cancer. Prostate 77: 374-384, 2017. © 2016 Wiley Periodicals, Inc.

Detection of the Ubiquitinome in Cells Undergoing Oncogene-Induced Senescence

Senescent cells exhibit dramatic changes in protein post-translational modifications. Here, we describe a method, stable isotope labeling with amino acids in cell culture (SILAC) coupled to liquid chromatography tandem mass spectrometry (LC-MS/MS), to identify changes in the ubiquitinome in cells that have undergone oncogene-induced senescence.

Serum- and Glucocorticoid-Inducible Kinase 1 Delay the Onset of Endothelial Senescence by Directly Interacting with Human Telomerase Reverse Transcriptase

Endothelial senescence is characteristic of vascular aging. Serum- and glucocorticoid-inducible kinase (SGK)1 belongs to a family of serine/threonine kinases regulated by various external stimuli. SGK1 has been shown to be protective against reactive oxygen species (ROS) production and to be involved in processes regulating aging. However, data on the direct relationship between SGK1 and senescence are sparse. In the present study, we sought to investigate the role of SGK1 in cellular aging by using human umbilical vein endothelial cells (HUVECs) infected with different constructs. Senescence was measured at different cellular stages by senescence-associated β-galactosidase (SA-β-gal) activity, human telomerase reverse transcriptase (hTERT) activity, p21 protein levels, and ROS production. HUVECs over-expressing full-length SGK1 (wild-type SGK1 [SGK1WT]) showed a decrease in SA-β-gal and p21 expression and a corresponding increase in hTERT activity in the early stages of aging. Moreover, SGK1WT presented lower levels of ROS production. A direct interaction between SGK1WT and hTERT was also shown by co-immunoprecipitation. The SGK1Δ60 isoform, lacking the amino-terminal 60 amino acids, did not show interaction with hTERT, suggesting a pivotal role of this protein site for the SGK1 anti-aging function. The results from this study may be of particular importance, because SGK1WT over-expression by activating telomerase and reducing ROS levels may delay the processes of endothelial senescence.

Cell Electrical Impedance as a Novel Approach for Studies on Senescence Not Based on Biomarkers

Senescence of cardiac myocytes is frequently associated with heart diseases. To analyze senescence in cardiac myocytes, a number of biomarkers have been isolated. However, due to the complex nature of senescence, multiple markers are required for a single assay to accurately depict complex physiological changes associated with senescence. In single cells, changes in both cytoplasm and cell membrane during senescence can affect the changes in electrical impedance. Based on this phenomenon, we developed MEDoS, a novel microelectrochemical impedance spectroscopy for diagnosis of senescence, which allows us to precisely measure quantitative changes in electrical properties of aging cells. Using cardiac myocytes isolated from 3-, 6-, and 18-month-old isogenic zebrafish, we examined the efficacy of MEDoS and showed that MEDoS can identify discernible changes in electrical impedance. Taken together, our data demonstrated that electrical impedance in cells at different ages is distinct with quantitative values; these results were comparable with previously reported ones. Therefore, we propose that MEDoS be used as a new biomarker-independent methodology to obtain quantitative data on the biological senescence status of individual cells.