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The relationship between in-vitro endothelial permeability and molecules of the intercellular junctionBudworth, Rachel Ann January 2003 (has links)
Changes in endothelial permeability are known to contribute to many pathologies, including inflammation seen in skin irritation. The regulation of permeability has been linked to inter-endothelial junctions, specifically the tight and adherens junctions (TJ and AJ). The functional state of the junction is thought to be associated with numerous factors including cytoskeletal changes and the interactions between junctional components. How these factors interact and respond to inflammatory stimuli is still not fully understood. This project examined two human endothelial cell-lines for use in in-vitro permeability studies, ECV304 and HMEC-1. Changes in permeability along with arrangement of the F-actin cytoskeleton and the adherens junction molecule VE-cadherin were studied in response to a variety of compounds. Macromolecular permeability was assessed by measuring the leakage of fluorescently labelled dextrans of varying molecular weights. The F-actin and VE-cadherin were visualised using immunocytochemical techniques. TEM was undertaken to examine the ultrastructure of the junctions The ECV304 cells, whilst showing an increased permeability to a variety to vaso-active mediators, did not express some of the pertinent junctional molecules of the endothelium and thus are not recommended for use. The basal permeability of the HMEC-l cell-line was shown to act in predictable fashion, giving comparable permeability coefficients to other endothelial cells. The increase in permeability following exposure to A23187, CAPB, EGTA and PMA was shown to correlate to an altered expression of VE-cadherin and F-actin. These observations were furthered using histamine, where a quantifiable change in the levels of continuous and stitch VE-cadherin staining was demonstrated. The permeability response to histamine occurred much later than the VE-cadherin and F-actin changes. This could be due to methodology and/or the cells lack of TJs. The apparent lack of mature AJs was approached by exposing the cultures to cAMP-raising media. This significantly reduced the basal permeability and increased the expression of AJ components, apart from β-catenin, at the cell-cell contacts. Indeed α-catenin was redistributed from the triton-soluble fraction of the cells to the triton-insoluble fraction, which is proposed to contain the junctional components. These results demonstrate additional information on the role that the adherens junction molecules play in endothelial permeability and characterise the HMEC-1 cell-line for further use in this field.
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Assessing adipose tissue depot differences in thermogenesis during early life in sheep and browning response in humans with pheochromocytomaDavies, Graeme R. January 2017 (has links)
Obesity and associated comorbidities such as diabetes are currently major global health problems. It has been shown that individual sites or depots of fat have different properties and effects on whole body physiology. Of particular interest are depots that display thermogenic characteristics, known as brown or beige adipose tissue, which may be able to increase energy expenditure and clear excess glucose and lipids from the circulation. The aim of this thesis was to compare adipose tissue depots in terms of their capacity for thermogenesis in early life using sheep as an animal model and browning response to chronic adrenergic stress in humans with pheochromocytoma. Epicardial and paracardial adipose tissues were focused on in the sheep study as they have been described as thermogenic in some adult humans but these findings have been inconclusive. The characterisation of these depots and their capacity for thermogenesis in early life has not been established, especially in comparison to other known depots of white and brown adipose tissue. My results show that epicardial and paracardial adipose tissue have increased thermogenic gene expression and uncoupling protein 1 in comparison to omental white adipose tissue suggesting they may play a role in thermogenesis in early life. These depots undergo remodelling over the first 28 days changing from brown to white adipose tissue. In sheep, this adipose tissue transition occurs without evidence of apoptosis and which may suggest other cellular mechanisms are responsible for this process. The browning capacity of different fat depots is important for targeting therapeutic interventions. As a model of catecholamine excess, samples of human periadrenal and subcutaneous adipose tissue were collected from patients with pheochromocytoma as well as patients undergoing adrenalectomy for benign tumours (control group). The data suggests periadrenal adipose tissue can undergo browning in some patients with pheochromocytoma. These patients had the highest plasma catecholamine concentrations suggesting a possible threshold is required to elicit browning. Subcutaneous adipose tissue did not display signs of browning suggesting that this depot does not respond to chronic adrenergic stress. It may therefore have a lack of browning capacity compared to visceral depots. In conclusion, both studies suggest differences between adipose tissue depots in thermogenic capacity both in development in early life and capacity for browning in later life.
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Investigating potential biochemical properties of fetal membrane spongy layer for clinical application at the ocular surfaceLazutina, Elena January 2017 (has links)
The amniotic membrane, well known scaffolding tissue, which widely uses and benefits of having anti-inflammatory, anti-microbial, anti-fibrosis, anti-scarring with low immunogenicity and reasonable mechanical properties. Amniotic Membrane Transplantation (AMT) is an established treatment modality, which favourably influence ocular surface re-epithelisation and prevents angiogenesis, thus promoting healing and minimising scarring. It is also used at several other sites of the body. Despite its widespread use, key elements of the membrane and its precise mechanism(s) of action remain to be elucidated. Unfortunately, over the years conflicting clinical reports have suggested variations in the efficacy of AM utility. Conventional methods for amnion preparation do not acknowledge the presence of the SL. My project is a continuation of previous PhD completed in the department, which mentioned the Spongy Layer as one of the important layers in Amniotic Membrane, which had not been look for in any previous work and Dr A Hopkinson, the author of previously mentioned PhD, accidentally discovered possibility to separate that layer from the amnion, it had been decided to take a close look at the layer and investigate properties. Researchers at the University of Nottingham have developed and improved techniques of manufacturing clinical grade the amnion and they have identified the SL as a substance that is variably present in conventional amnion. They have developed techniques to entirely isolate the SL, which allows comprehensive characterisation of its composition and biological properties. The project originally designed to investigate all layers of Amniotic Membrane separately in comparison with amniotic membrane which is completely free from Spongy Layer (SL detached) as well as Spongy Layer attached to the amniotic membrane (classically used layer) and identify a layer which is richest in proteins and growth factors. So, three different samples were investigated: 1) Isolated Spongy Layer; 2) Isolated Amniotic Membrane; 3) Amniotic Membrane with Spongy Layer attached (classical layer, which well- known used). I used technique developed in the department. This technique allows separating the SL without unnecessary mechanical tissue disturbance and isolated SL was used to investigate comprehensive characterisation of the composition and biological properties. Our technique of removing SL is simple and could be easily adapted. The SL imbibes water well and significantly expands, which makes it thick and easy to pull using forceps or using blunt edge of the scalpel blade to push the SL from the amnion surface without mechanical interruption. Investigation of origin of the Spongy Layer during gestation period done through intensive literature search and came to conclusion that the Spongy Layer developed from the extraembryonic endoderm. It is well known that the SL acts as a barrier between vascular amnion and avascular chorion. Also, question was about similarities and differences of embryological origin of the Wharton Jelly and the Spongy Layer. The present in which of TGFb1 (immunofluorescent staining) could be result of cross link during the embryological development. As previously, reported by Dr A Hopkinson et al in 2006, that the Spongy Layer’s biochemical composition is containing TGF-b1, EGF and HGF. The structure of SL is reported to be composed of Collagen types I-VIII, the SL contains high level of hyaluronan, which is a major carbohydrate component of the ECM. To extract proteins from the SL, a few different techniques were used, first of all the tissue weighted, freeze dried and lyophilised in buffers, which were different and depended on the experiment planned. After, proteins were analysed through the Searchlight protein array analysis, 2-D protein quantitation, the Bradford (Commassie staining) assay, the mass spectrometry, had been discovered that the SL contains angiogenic factors, biomarkers, cell adhesions factors, cytokine proteins, growth factors, metalloproteinases, chemokine proteins, neurotrophic factors and cellular components. Experiments show that the level of those factors and proteins in fresh AM, the Transplant Ready Amniotic Membrane (TRAM) and the SL shows that significant amount of proteins was simply washed out during preparation from the TRAM, however the SL is holding those proteins in significant level probably due to imbibing while absorbing water. The important discovery of this project was the cytotoxic effect of the SL and its antimicrobial properties. Some fractions of the SL with high molecular weight proteins show apoptotic activity to corneal keratofibroblasts by necrosis rather than apoptosis. However, cells occurred apoptosis after treatment with lower molecular weight proteins. As preliminary data shows the SL to be cytotoxic, this could lead to some understanding of different outcome in the Amniotic Membrane transplantation (AMT). However, this area needs further investigation. Well known antimicrobial properties of the amniotic membrane were established only in the TRAM and in the samples of the SL which were prepared in the same way as TRAM (washed in gentamicin), however samples of the SL which were not washed in gentamicin did not show antimicrobial properties. One of the next steps of investigation properties of Spongy Layer was the measurement of the thickness of the layer in normal physiological situation, during gestation. As the SL is imbibing the water quickly, in vitro it was difficult to measure “real” thickness of the membrane; this gave an idea to measure it in vivo. To answer the question of “real” (physiological) thickness of the Spongy Layer, different methods were used, however the Ultrasound technique was our method of interest, as it gave the possibility to see the layer during gestation without any interruption and see changes in thickness prior to delivery. These measurements were done in the Fetal Maternal Medicine Department by very experienced sonographer. The Spongy Layer has a variable thickness in three different areas (cervical part, mid region and apical part of the uterus) the SL regions had been divided accordingly. The Spongy Layer has a variable thickness depending on the anatomical location. The difference of the SL thickness had been measured in vivo (ultrasound technic – described below) and in vitro (this work published by JJ Gicquel) the compared results matched. The major problem of the project was the separation of proteins and to break hyaluronic chains to extract clean proteins. In my project, I used two different techniques to separate proteins according the molecular weight of proteins presented in the sample. 1) Revers Phase Solid Phase Extraction (RP-SPE) isolation of proteins; and 2) Soluble Protein Fractionation using Vivaspin columns The second technique in my hands was more successful and I decided to use this for all my samples. To minimise the possibility of sample variations from the point of sample preparation of the SL and the AM itself, I used the same technique for all experiments and combined samples. Nevertheless, my samples were not 100% clear due to different protein structure and shape. This layer therefore has the potential to be exploited clinically for the treatment of several indications. However, before it can be employed, the layer requires further investigation to determine characterise the content of potential factors. In addition, as the spongy layer is predominantly composed of mucin and proteoglycans resulting in a gelatinous/viscous substance, a processing procedure must be developed to either modify the substance in a usable format, or to extract the beneficial factors, for clinical use. Being able to demonstrate the isolated SL and its derivatives can be exploited as potential therapeutic agents in the treatment of many ocular surface disorders, would have significant translational potential. / The control of inflammation caused by disease (e.g. Ocular cicatricial pemphigoid) and any injury (e.g. Chemical burns) and the limitation of scarring and vascularisation would preserve sight or allow successful secondary intervention such as corneal drafting, which otherwise has a high risk of failure in such situations, the potential for preventing visual impairment and promoting quality of life in all age groups in therefore immense. My work proved that the SL is a separate layer and is having a vast number of different factors in a significantly high amount compare to amnion itself.
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Development of biomimetic platforms to investigate the influence of the extra-cellular environment on immunological responsesDonaldson, Amy Rose January 2017 (has links)
The immune system comprises highly sophisticated networks of cells and signalling molecules which function in concert to protect the body against pathogens. Within this system a role for the extra-cellular microenvironment as a crucial mediator of immune responses is becoming increasingly apparent. Conventional in vitro cultures lack physiologically relevant extra-cellular cues, such as extracellular matrix (ECM) and shear flow. Tissue engineering can be used to simulate features of the natural microenvironment for the development of biologically relevant platforms. It is anticipated that this will enable the study of the influence of the extra-cellular environment on immune responses. This thesis describes the development and characterisation of tissue-engineered platforms for immune cell culture which incorporate the ECM and shear flow. This work goes on to apply these platforms for the study of the effect of the extra-cellular environment on dendritic cells and their interactions with T cells in the context of immunological stimulation. The ECM defines the three-dimensional architecture of the natural microenvironment. It provides structural support and also promotes cell motility in tissues. This is important for the function of the immune system as it directs the organisation and interactions of immune cells which ultimately contributes to the modulation of immune responses. Candidate synthetic and natural biomaterials were assessed for their suitability to provide an in vitro extracellular matrix (ECM) platform for human immune cell culture. The suitability of these materials to provide an artificial ECM platform was based on the viability, resting immune state and immune competence of the cells. The synthetic biomaterials tested were a thermo-responsive colloidal gel and electrospun PET and PLGA scaffolds coated with a thermo-responsive polymer. An important finding from the work done with the colloidal gel was that the human dendritic cells, which were incorporated into the gel at the beginning of the experiment, could not be separated from the material for flow cytometric analysis. Therefore, characterisation of the colloidal gel for immune cell culture could not be completed. Regarding the characterisation of the electrospun PET and PLGA scaffolds, although they did not significantly impair cell viability of dendritic cells they were found to induce cell maturation. As a result, none of the synthetic biomaterials were found to be a suitable ECM surrogate. A semi-natural biomaterial, gelatin methacryloyl (GelMA) hydrogel, was included in the investigation. The results from the characterisation of GelMA for human immune cell culture indicated that the hydrogel induced a pro-inflammatory immune response due to the profile of secreted cytokines. Based on this, GelMA was also discounted as an appropriate material for the development of the ECM platform. The final ECM candidate was a collagen hydrogel, which is a naturally-derived biomaterial. The collagen hydrogel was shown to support immune cell survival and human dendritic cells maintained an immature phenotype in culture. In addition, typical responses to immunological stimuli by human dendritic cells and T cells were observed in collagen hydrogel cultures. This work demonstrated that out of the biomaterials which were characterised, the collagen hydrogel was the most suitable biomaterial for the development of the ECM platform. The influence of the collagen hydrogel ECM platform on antigen-specific immune responses was investigated in the context of autologous human dendritic cell and T cell co-cultures stimulated with the model antigen Mycobacterium tuberculosis purified protein derivative, also referred to as PPD. The results from these experiments indicated that the presence of the collagen hydrogel increased the sensitivity and specificity of the immune response, compared to conventional tissue culture conditions. An attempt was made at utilising the ECM platform to investigate immune responses to chemical sensitisers to address the requirement for in vitro alternatives to replace current animal testing methods. In this work, innate and adaptive immune responses to sensitisers were detected using the ECM platform. However, the reproducibility of these experiments was low due to large donor variation. Therefore the effect of the ECM platform on immune responses to sensitisers could not be evaluated. This difficulty likely reflects the complexity of the molecular and cellular mechanisms which lead to the acquisition of chemical sensitisation. Shear flow is a type of physiological stress to which immune cells are exposed in vivo due to the movement of blood and lymph fluid. Recent studies have implicated flow as an immunologically relevant stimulus, capable of inducing changes in the expression of receptors and chemokines involved in regulating immune cell migration, and activating immune receptor signalling. A fluidic cell culture platform was developed to recapitulate the effect of shear flow. Two different prototypes were constructed, one of which was taken forward and characterised for immune cell culture applications. The fluidic platform taken forward had a paper-based cell culture scaffold which was coated with collagen hydrogel. The scaffold was found to induce maturation of human dendritic cells which was attributed to the possibility of incomplete coverage of the scaffold by the collagen hydrogel. The viability of dendritic cells was slightly impaired by flow, however not significantly. Interestingly, when exposed to shear flow, dendritic cells maintained a less mature phenotype compared to their static counterparts. Antigen-specific immune responses were studied on the fluidic platform by setting up co-cultures comprising PPD-stimulated autologous human dendritic cells and T cells. Typical T cell activation was observed on the platform and the sensitivity and specificity of immune responses was found to be greater under flow conditions, compared with static cultures. In conclusion, this thesis demonstrates the value of developing biomimetic platforms for studying the influence of the extra-cellular environment on immune responses. Finally, the ability to mimic extra-cellular cues to which cells are exposed in vivo has the potential to generate more realistic immune responses in the lab. This presents huge opportunities for advancing understanding in immunology. It also has implications for methods used in research, drug discovery and safety testing, where currently only animals provide a representative system for the study of immune reactions. It is anticipated that enhancing the physiological relevance of in vitro cell culture will ultimately contribute to the reduction of animals used in research and testing.
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