Endothelial Progenitors as Tools to Study Vascular Disease

Endothelial progenitor cells (EPCs) have great clinical value because they can be used as diagnostic biomarkers and as a cellular therapy for promoting vascular repair of ischaemic tissues. However, EPCs also have an additional research value in vascular disease modelling to interrogate human disease mechanisms. The term EPC is used to describe a diverse variety of cells, and we have identified a specific EPC subtype called outgrowth endothelial cell (OEC) as the best candidate for vascular disease modelling because of its high-proliferative potential and unambiguous endothelial commitment. OECs are isolated from human blood and can be exposed to pathologic conditions (forward approach) or be isolated from patients (reverse approach) in order to study vascular human disease. The use of OECs for modelling vascular disease will contribute greatly to improving our understanding of endothelial pathogenesis, which will potentially lead to the discovery of novel therapeutic strategies for vascular diseases

Endothelial cell-derived Pentraxin 3 limits the vasoreparative therapeutic potential of Circulating Angiogenic Cells

AIMS: Circulating angiogenic cells (CACs) promote revascularization of ischaemic tissues although their underlying mechanism of action and the consequences of delivering varying number of these cells for therapy remain unknown. This study investigates molecular mechanisms underpinning CAC modulation of blood vessel formation. METHODS AND RESULTS: CACs at low (2 × 10(5) cells/mL) and mid (2 × 10(6) cells/mL) cellular densities significantly enhanced endothelial cell tube formation in vitro, while high density (HD) CACs (2 × 10(7) cells/mL) significantly inhibited this angiogenic process. In vivo, Matrigel-based angiogenesis assays confirmed mid-density CACs as pro-angiogenic and HD CACs as anti-angiogenic. Secretome characterization of CAC-EC conditioned media identified pentraxin 3 (PTX3) as only present in the HD CAC-EC co-culture. Recombinant PTX3 inhibited endothelial tube formation in vitro and in vivo. Importantly, our data revealed that the anti-angiogenic effect observed in HD CAC-EC co-cultures was significantly abrogated when PTX3 bioactivity was blocked using neutralizing antibodies or PTX3 siRNA in endothelial cells. We show evidence for an endothelial source of PTX3, triggered by exposure to HD CACs. In addition, we confirmed that PTX3 inhibits fibroblast growth factor (FGF) 2-mediated angiogenesis, and that the PTX3 N-terminus, containing the FGF-binding site, is responsible for such anti-angiogenic effects. CONCLUSION: Endothelium, when exposed to HD CACs, releases PTX3 which markedly impairs the vascular regenerative response in an autocrine manner. Therefore, CAC density and accompanying release of angiocrine PTX3 are critical considerations when using these cells as a cell therapy for ischaemic disease

Therapeutic revascularisation of ischaemic tissue: the opportunities and challenges for therapy using vascular stem/progenitor cells.

Ischaemia-related diseases such as peripheral artery disease and coronary heart disease constitute a major issue in medicine as they affect millions of individuals each year and represent a considerable economic burden to healthcare systems. If the underlying ischaemia is not sufficiently resolved it can lead to tissue damage, with subsequent cell death. Treating such diseases remains difficult and several strategies have been used to stimulate the growth of blood vessels and promote regeneration of ischaemic tissues, such as the use of recombinant proteins and gene therapy. Although these approaches remain promising, they have limitations and results from clinical trials using these methods have had limited success. Recently, there has been growing interest in the therapeutic potential of using a cell-based approach to treat vasodegenerative disorders. In vascular medicine, various stem cells and adult progenitors have been highlighted as having a vasoreparative role in ischaemic tissues. This review will examine the clinical potential of several stem and progenitor cells that may be utilised to regenerate defunct or damaged vasculature and restore blood flow to the ischaemic tissue. In particular, we focus on the therapeutic potential of endothelial progenitor cells as an exciting new option for the treatment of ischaemic diseases.This work was supported by the Medical Research Council, by Fight for Sight, D.E.L. (NI), by the Juvenile Diabetes Research Foundation, by The Royal Society and by the Sir Jules Thorn Trust

Reduced Amygdala and Ventral Striatal Activity to Happy Faces in PTSD Is Associated with Emotional Numbing

There has been a growing recognition of the importance of reward processing in PTSD, yet little is known of the underlying neural networks. This study tested the predictions that (1) individuals with PTSD would display reduced responses to happy facial expressions in ventral striatal reward networks, and (2) that this reduction would be associated with emotional numbing symptoms. 23 treatment-seeking patients with Posttraumatic Stress Disorder were recruited from the treatment clinic at the Centre for Traumatic Stress Studies, Westmead Hospital, and 20 trauma-exposed controls were recruited from a community sample. We examined functional magnetic resonance imaging responses during the presentation of happy and neutral facial expressions in a passive viewing task. PTSD participants rated happy facial expression as less intense than trauma-exposed controls. Relative to controls, PTSD participants revealed lower activation to happy (-neutral) faces in ventral striatum and and a trend for reduced activation in left amygdala. A significant negative correlation was found between emotional numbing symptoms in PTSD and right ventral striatal regions after controlling for depression, anxiety and PTSD severity. This study provides initial evidence that individuals with PTSD have lower reactivity to happy facial expressions, and that lower activation in ventral striatal-limbic reward networks may be associated with symptoms of emotional numbing

Predicting Individuals' Learning Success from Patterns of Pre-Learning MRI Activity

Performance in most complex cognitive and psychomotor tasks improves with training, yet the extent of improvement varies among individuals. Is it possible to forecast the benefit that a person might reap from training? Several behavioral measures have been used to predict individual differences in task improvement, but their predictive power is limited. Here we show that individual differences in patterns of time-averaged T2*-weighted MRI images in the dorsal striatum recorded at the initial stage of training predict subsequent learning success in a complex video game with high accuracy. These predictions explained more than half of the variance in learning success among individuals, suggesting that individual differences in neuroanatomy or persistent physiology predict whether and to what extent people will benefit from training in a complex task. Surprisingly, predictions from white matter were highly accurate, while voxels in the gray matter of the dorsal striatum did not contain any information about future training success. Prediction accuracy was higher in the anterior than the posterior half of the dorsal striatum. The link between trainability and the time-averaged T2*-weighted signal in the dorsal striatum reaffirms the role of this part of the basal ganglia in learning and executive functions, such as task-switching and task coordination processes. The ability to predict who will benefit from training by using neuroimaging data collected in the early training phase may have far-reaching implications for the assessment of candidates for specific training programs as well as the study of populations that show deficiencies in learning new skills

A Specific and Rapid Neural Signature for Parental Instinct

Darwin originally pointed out that there is something about infants which prompts adults to respond to and care for them, in order to increase individual fitness, i.e. reproductive success, via increased survivorship of one's own offspring. Lorenz proposed that it is the specific structure of the infant face that serves to elicit these parental responses, but the biological basis for this remains elusive. Here, we investigated whether adults show specific brain responses to unfamiliar infant faces compared to adult faces, where the infant and adult faces had been carefully matched across the two groups for emotional valence and arousal, as well as size and luminosity. The faces also matched closely in terms of attractiveness. Using magnetoencephalography (MEG) in adults, we found that highly specific brain activity occurred within a seventh of a second in response to unfamiliar infant faces but not to adult faces. This activity occurred in the medial orbitofrontal cortex (mOFC), an area implicated in reward behaviour, suggesting for the first time a neural basis for this vital evolutionary process. We found a peak in activity first in mOFC and then in the right fusiform face area (FFA). In mOFC the first significant peak (p<0.001) in differences in power between infant and adult faces was found at around 130 ms in the 10–15 Hz band. These early differences were not found in the FFA. In contrast, differences in power were found later, at around 165 ms, in a different band (20–25 Hz) in the right FFA, suggesting a feedback effect from mOFC. These findings provide evidence in humans of a potential brain basis for the “innate releasing mechanisms” described by Lorenz for affection and nurturing of young infants. This has potentially important clinical applications in relation to postnatal depression, and could provide opportunities for early identification of families at risk

Endothelial progenitor cells : development of a cell-based therapy

Much interest currently surrounds the emerging field of regenerative medicine. Cell-based therapies represent a novel therapeutic platform for the treatment of ischaemic diseases, shifting the focus clinically from the management of disease symptoms to their potential cure. Endothelial progenitor cells (EPCs) contribute to vascular repair and angiogenesis. Despite controversy surrounding the heterogeneous nature of these cells in vitro and in vivo, their vasoreparative functions suggest that EPCs have potential clinical value. The aim of this thesis is to further define the precise phenotype, angiogenic properties and potential clinical development of two EPC subtypes and to further elucidate the optimal myeloid angiogenic cell (MAC) or outgrowth endothelial cell (OEC) transplant regimen that is safe and effective prior to large-scale clinical application of these cells for therapeutic angiogenesis. EPCs were isolated from human peripheral blood and cord blood by density gradient centrifugation. Mononuclear cells were cultured on fibronectin or collagen and two different isolation protocols were utilised to obtain MACs and OECs respectively. MACs, previously referred to as early EPCs (eEPCs), were found to be M2 alternatively activated macrophages, which induced angiogenesis via release of IL8 in a paracrine manner both in vitro and in vivo. OECs were also assessed in a similar manner, and the effect of high glucose conditions and senescence on their vasoreparative function was evaluated. The effect of cell density on MAC secretome and vascular contribution was also investigated in vitro, as this represents an important Issue in the clinical and commercial development of a cytotherapy This study has provided a complete analysis of both types of EPCs and shed further light on a number of issues associated with the development of a cell-based treatment strategy for autologous or allogeneic therapy. These findings have imp011ant implications in relation to the harnessing of these cells as a cell therapy for vascular repair of ischaemic tissues.EThOS - Electronic Theses Online ServiceGBUnited Kingdo