Proteomics: a reality-check for putative stem cells

Stem cell therapy in pulmonary hypertension: current practice and future opportunities

Pulmonary hypertension (PH) is a progressive disease characterised by elevated pulmonary arterial pressure and right-sided heart failure. While conventional drug therapies, including prostacyclin analogues, endothelin receptor antagonists and phosphodiesterase type 5 inhibitors, have been shown to improve the haemodynamic abnormalities of patients with PH, the 5-year mortality rate remains high. Thus, novel therapies are urgently required to prolong the survival of patients with PH. Stem cell therapies, including mesenchymal stem cells, endothelial progenitor cells and induced pluripotent stem cells, have shown therapeutic potential for the treatment of PH and clinical trials on stem cell therapies for PH are ongoing. This review aims to present the latest preclinical achievements of stem cell therapies, focusing on the therapeutic effects of clinical trials and discussing the challenges and future perspectives of large-scale applications.

Platelet Microparticles Regulate Neutrophil Extracellular Traps in Acute Pancreatitis

OBJECTIVE

This study aimed to explore the clinical significance of the increase of platelet microparticles (PMPs) in acute pancreatitis (AP).

METHODS

Clinical data and plasma samples from patients with AP were collected, and healthy subjects were controls. The PMPs were detected by flow cytometry; meanwhile, the ability to promote neutrophil extracellular traps (NETs) formation was investigated. Neutrophils from healthy subjects were co-cultured with PMPs from AP patients. The NETs were visualized by confocal laser scanning microscopy. In the supernatant of cell co-culture, myeloperoxidase, neutrophil elastase, and histone H3 were detected by enzyme-linked immunosorbent assay.

RESULTS

Patients with AP had elevated plasma levels of PMPs compared with controls; moreover, there were significantly higher PMPs levels in severe AP than mild AP and moderately severe AP. Healthy subjects' neutrophils were stimulated with PMPs from AP patients to release NETs. It was observed that NETs formed in AP group, but not in the controls. Correspondingly, there were higher levels of myeloperoxidase, neutrophil elastase, and histone H3 in AP group than in controls.

CONCLUSIONS

The level of PMPs is a positive correlation with AP severity, which may be related to PMPs-NETs interaction. Platelet microparticles may be a potential predictor of severe AP and promising novel therapeutic target for AP.

Novel Risk Markers and Risk Assessments for Cardiovascular Disease

The use of risk markers has transformed cardiovascular medicine, exemplified by the routine assessment of troponin, for both diagnosis and assessment of prognosis in patients with chest pain. Clinical risk factors form the basis for risk assessment of cardiovascular disease and the addition of biochemical, cellular, and imaging parameters offers further refinement. Identifying novel risk factors may allow greater risk stratification and a steady, but gradual progression toward precision medicine. Indeed, the generation of data in this area of research is explosive and when combined with new technologies and techniques provides the potential for more refined, targeted approaches to cardiovascular medicine. Although discussing the most recent developments in this field, this review article aims to strike a balance between novelty and validity by focusing on recent large sample-size studies that have been validated in a separate cohort in most cases. Risk markers related to atherosclerosis, thrombosis, inflammation, cardiac injury, and fibrosis are introduced in the context of their pathophysiology. Rapidly developing new areas, such as assessment of micro-RNA, are also explored. Subsequently the prognostic ability of these risk markers in coronary artery disease, heart failure, and atrial fibrillation is discussed in detail.

MicroRNA Biomarkers and Platelet Reactivity: The Clot Thickens

Over the last few years, several groups have evaluated the potential of microRNAs (miRNAs) as biomarkers for cardiometabolic disease. In this review, we discuss the emerging literature on the role of miRNAs and other small noncoding RNAs in platelets and in the circulation, and the potential use of miRNAs as biomarkers for platelet activation. Platelets are a major source of miRNAs, YRNAs, and circular RNAs. By harnessing multiomics approaches, we may gain valuable insights into their potential function. Because not all miRNAs are detectable in the circulation, we also created a gene ontology annotation for circulating miRNAs using the gene ontology term extracellular space as part of blood plasma. Finally, we share key insights for measuring circulating miRNAs. We propose ways to standardize miRNA measurements, in particular by using platelet-poor plasma to avoid confounding caused by residual platelets in plasma or by adding RNase inhibitors to serum to reduce degradation. This should enhance comparability of miRNA measurements across different cohorts. We provide recommendations for future miRNA biomarker studies, emphasizing the need for accurate interpretation within a biological and methodological context.

CD34+ VEGFR-3+ progenitor cells have a potential to differentiate towards lymphatic endothelial cells

Endothelial progenitor cells (EPCs) play an important role in postnatal neovascularization. However, it is poorly understood whether EPCs contribute to lymphangiogenesis. Here, we assessed differentiation of a novel population of EPCs towards lymphatic endothelial cells and their lymphatic formation. CD34(+) VEGFR-3(+) EPCs were isolated from mononuclear cells of human cord blood by fluorescence-activated cell sorting. These cells expressed CD133 and displayed the phenotype of the endothelial cells. Cell colonies appeared at 7-10 days after incubation. The cells of the colonies grew rapidly and could be repeatedly subcultured. After induction with VEGF-C for 2 weeks, CD34(+) VEGFR-3(+) EPCs could differentiate into lymphatic endothelial cells expressing specific markers 5'-nucleotidase, LYVE-1 and Prox-1. The cells also expressed hyaluronan receptor CD44. The differentiated cells had properties of proliferation, migration and formation of lymphatic capillary-like structures in three-dimensional collagen gel and Matrigel. VEGF-C enhanced VEGFR-3 mRNA expression. After interfering with VEGFR-3 siRNA, the effects of VEGF-C were diminished. These results demonstrate that there is a population of CD34(+) VEGFR-3(+) EPCs with lymphatic potential in human cord blood. VEGF-C/VEGFR-3 signalling pathway mediates differentiation of CD34(+) VEGFR-3(+) EPCs towards lymphatic endothelial cells and lymphangiogenesis. Cord blood-derived CD34(+) VEGFR-3(+) EPCs may be a reliable source in transplantation therapy for lymphatic regenerative diseases.

A systematic approach to the establishment and characterization of endothelial progenitor cells for gene therapy

It has been recently demonstrated that endothelial progenitor cells (EPCs) have increasing potential for gene therapy or regenerative cell therapy for cardiovascular diseases and cancer. However, current therapies involving EPCs are inefficient because of the very low level of EPCs in the available sources, for example, in blood. One solution is to derive in vitro an expanded population of EPCs from circulation. In addition, EPCs like other progenitor cells have an intrinsic predisposition of differentiating into mature cell types, for example, mature endothelial cells; therefore, establishing a sufficient amount of EPCs alongside maintaining the EPC characteristic phenotype during genetic modification and long-term culture presents a significant challenge to the field of gene and cell therapies. In this study, we have systematically investigated EPCs from different sources and used multiple parameters, including cell surface markers and a tubule formation assay to identify factors that influence the establishment, characteristics, and vector transduction capability of EPCs. Our results show the considerable promise, as well as certain limitations in the establishment and manipulation of genetically modified EPCs for gene therapy. While obtaining high transduction efficiency and robust in vitro tubule formation of EPCs using lentiviral vectors, we also observed that lentiviral vector transduction significantly altered EPC phenotype as demonstrated by an increased percentage of CD34(+) progenitor cells and increased expression of adhesion molecule CD144 (VE-cadherin). Taking account of the increased expression of CD144 reported in cancer patients, the altered expression of EPC-related markers, for example, VE-cadherin and the enrichment of CD34(+) cells, after vector transduction indicates the importance of extensive characterization and vigorous safety control of genetically modified EPCs before they are accepted for clinical use.

Proteomics: from single molecules to biological pathways

The conventional reductionist approach to cardiovascular research investigates individual candidate factors or linear signalling pathways but ignores more complex interactions in biological systems. The advent of molecular profiling technologies that focus on a global characterization of whole complements allows an exploration of the interconnectivity of pathways during pathophysiologically relevant processes, but has brought about the issue of statistical analysis and data integration. Proteins identified by differential expression as well as those in protein–protein interaction networks identified through experiments and through computational modelling techniques can be used as an initial starting point for functional analyses. In combination with other ‘-omics’ technologies, such as transcriptomics and metabolomics, proteomics explores different aspects of disease, and the different pillars of observations facilitate the data integration in disease-specific networks. Ultimately, a systems biology approach may advance our understanding of cardiovascular disease processes at a ‘biological pathway’ instead of a ‘single molecule’ level and accelerate progress towards disease-modifying interventions.

β(2)-Integrin and Notch-1 differentially regulate CD34(+)CD31(+) cell plasticity in vascular niches

AIMS

The implication of circulating haematopoietic CD34(+) progenitors in the vasculature is unclear due to the lack of understanding of their characteristics and plasticity mediated by their cellular microenvironment. We investigated how vascular smooth muscle cells (SMCs) and their interactions with endothelial cells (ECs) affect the behaviour and plasticity of CD34(+)CD31(+) progenitors and the underlying mechanisms.

METHODS AND RESULTS

Human peripheral blood-derived CD34(+)CD31(+) cells were directly transplanted into injured arteries in vivo and co-cultured with ECs and SMCs in vitro. CD34(+)CD31(+) progenitors injected into wire-injured mouse arteries differentiate into ECs and macrophages in the neoendothelial layer and neointima, respectively. SMC-co-culture increases CD34(+)CD31(+) cell mobility and adhesion to and transmigration across ECs. Sorted CD34(+)CD31(+) progenitors that adhered to ECs co-cultured with SMCs have the capacity to form capillary-like structures in Matrigel and chimeric blood vessels in vivo. Sorted transmigrated progenitors give rise to macrophages with increased pro-angiogenic activity. These differentiations of CD34(+)CD31(+) progenitors into ECs and macrophages are mediated by β(2)-integrin and Notch-1, respectively. β(2)-Integrin and Notch-1 are activated by their counterligands, intercellular adhesion molecule-1 (ICAM-1) and jagged-1, which are highly expressed in the neoendothelium and neointima in injured arteries. Intra-arterial injection of β(2)-integrin-activated CD34(+)CD31(+) progenitors into wire-injured mouse arteries inhibits neointima formation.

CONCLUSION

Our findings indicate that the peripheral vascular niches composed of ECs and SMCs may predispose haematopoietic CD34(+)CD31(+) progenitors to differentiate into ECs and macrophages through the activations of the ICAM-1/β(2)-integrin and jagged-1/Notch-1 cascades, respectively.

Platelet-associated angiogenesis regulating factors: a pharmacological perspective

Platelets, in addition to maintaining hemostasis, also stimulate angiogenesis by generating and releasing, upon activation, factors that promote the growth of new blood vessels. To date, at least 20 angiogenesis-regulating factors have been identified in platelets, including both promoters and inhibitors. Platelet-derived angiogenesis regulators promote angiogenesis during wound healing, tumor growth, and in response to ischemia. Within platelets, angiogenesis regulators are primarily stored in α-granules, but are also found in the cytosol or derived from membrane lipids. Their release can be inhibited pharmacologically by anti-platelet agents, which consequently suppress platelet-stimulated angiogenesis. Several years ago, our research group discovered that platelets generate the angiogenesis inhibitor angiostatin independent of the activation state of platelets, and that platelet-derived angiostatin serves to limit the angiogenesis-stimulating effects of platelets. In this review, we summarize the current knowledge of platelet-associated angiogenesis regulators, how they impact angiogenesis, and how they are controlled pharmacologically.

MicroRNAs in vascular and metabolic disease

Recent findings demonstrated the importance of microRNAs (miRNAs) in the vasculature and the orchestration of lipid metabolism and glucose homeostasis. MiRNA networks represent an additional layer of regulation for gene expression that absorbs perturbations and ensures the robustness of biological systems. This function is very elegantly demonstrated in cholesterol metabolism where miRNAs reducing cellular cholesterol export are embedded in the very same genes that increase cholesterol synthesis. Often their alteration does not affect normal development but changes under stress conditions and in disease. A detailed understanding of the molecular and cellular mechanisms of miRNA-mediated effects on metabolism and vascular pathophysiology could pave the way for the development of novel diagnostic markers and therapeutic approaches. In the first part of this review, we summarize the role of miRNAs in vascular and metabolic diseases and explore potential confounding effects by platelet miRNAs in preclinical models of cardiovascular disease. In the second part, we discuss experimental strategies for miRNA target identification and the challenges in attributing miRNA effects to specific cell types and single targets.

Endothelial progenitor cells: a new player in lupus?

Patients with systemic lupus erythematosus (SLE) have a greatly increased risk of cardiovascular disease. There is growing interest in the link between vascular damage and lupus-specific inflammatory factors. Impaired endothelial repair could account for the endothelial dysfunction in this patient group. This review describes the contribution that endothelial progenitor cells could play in the pathogenesis of premature vascular damage in this disease. The methods of isolation, detection, and characterization of endothelial progenitor cells, together with their potential role in repair of the endothelium and as a therapeutic target in SLE, are discussed.

Age-related changes in rat myocardium involve altered capacities of glycosaminoglycans to potentiate growth factor functions and heparan sulfate-altered sulfation

Glycosaminoglycans (GAGs) are essential components of the extracellular matrix, the natural environment from which cell behavior is regulated by a number or tissue homeostasis guarantors including growth factors. Because most heparin-binding growth factor activities are regulated by GAGs, structural and functional alterations of these polysaccharides may consequently affect the integrity of tissues during critical physiological and pathological processes. Here, we investigated whether the aging process can induce changes in the myocardial GAG composition in rats and whether these changes can affect the activities of particular heparin-binding growth factors known to sustain cardiac tissue integrity. Our results showed an age-dependent increase of GAG levels in the left ventricle. Biochemical and immunohistological studies pointed out heparan sulfates (HS) as the GAG species that increased with age. ELISA-based competition assays showed altered capacities of the aged myocardial GAGs to bind FGF-1, FGF-2, and VEGF but not HB EGF. Mitogenic assays in cultured cells showed an age-dependent decrease of the elderly GAG capacities to potentiate FGF-2 whereas the potentiating effect on VEGF(165) was increased, as confirmed by augmented angiogenic cell proliferation in Matrigel plugs. Moreover, HS disaccharide analysis showed considerably altered 6-O-sulfation with modest changes in N- and 2-O-sulfations. Together, these findings suggest a physiological significance of HS structural and functional alterations during aging. This can be associated with an age-dependent decline of the extracellular matrix capacity to efficiently modulate not only the activity of resident or therapeutic growth factors but also the homing of resident or therapeutic cells.

The Use of High-Throughput Technologies to Investigate Vascular Inflammation and Atherosclerosis

The greatest challenge of scientific research is to understand the causes and consequences of disease. In recent years, great efforts have been devoted to unraveling the basic mechanisms of atherosclerosis (the underlying pathology of cardiovascular disease), which remains a major cause of morbidity and mortality worldwide. Because of the complex and multifactorial pathophysiology of cardiovascular disease, different research techniques have increasingly been combined to unravel genetic aspects, molecular pathways, and cellular functions involved in atherogenesis, vascular inflammation, and dyslipidemia to gain a multifaceted picture addressing this complexity. Thanks to the rapid evolution of high-throughput technologies, we are now able to generate large-scale data on the DNA, RNA, and protein levels. With the help of sophisticated computational tools, these data sets are integrated to enhance information extraction and are being increasingly used in a systems biology approach to model biological processes as interconnected and regulated networks. This review exemplifies the use of high-throughput technologies—such as genomics, transcriptomics, proteomics, and epigenomics—and systems biology to explore pathomechanisms of vascular inflammation and atherosclerosis.

Bone marrow-derived cells do not engraft into skeletal muscle microvasculature but promote angiogenesis after acute injury

The skeletal muscle is supported by a vast network of microvessels with the capacity to regenerate in response to injury. However, the dynamics of microvascular repair and the origin of reconstituted endothelial cells in the skeletal muscle are poorly understood. A growing body of literature exists to indicate bone marrow (BM)-derived cells engraft into regenerating vascular endothelium and muscle macrovasculature. Therefore, we investigated the extent of BM contribution to skeletal muscle microvasculature after acute injury. Because reporters and markers commonly used to trace donor BM cells are not endothelial specific but are also expressed by leukocytes, we generated novel BM chimeras utilizing Tie2-green fluorescent protein BM cells transplanted into CD31 and Caveolin-1 knockout recipients. In turn, we surveyed BM vascular contribution, not just by the presence of green fluorescent protein, but also CD31 and Caveolin-1, respectively. After stable BM reconstitution, chimera limb muscles were cardiotoxin (CTX) injured and examined 21 days post-injury for the presence of green fluorescent protein, CD31, and Caveolin-1. Acute muscle injury by CTX is characterized by initial microvasculature death followed by rapid endothelial regeneration within 14 days post-damage. Histological analysis of injured and uninjured contralateral limb muscles revealed a complete absence of BM engraftment in the muscle vasculature of wild-type and CD31/Caveolin-1 knockout chimeras. In contrast, F4/80(+) cells isolated from CTX-injured muscle, expressed endothelial-related markers and promoted angiogenesis in vitro. Therefore, despite the absence of BM engraftment to regenerated skeletal muscle microvasculature, macrophages recruited after injury promote angiogenesis and, in turn, vascular regeneration.