Mechano-Biological Interactions of Endothelial Cells

Atherosclerosis is an ever-increasing cause of morbidity in the western world. Current surgical treatments include bypass grafts and coronary artery stents. However, there is still a need for alternative approaches especially for those who cannot receive conventional therapy. Tissue engineering is one such approach that may hold the key to the repair and regeneration. Tissue engineering is one such approach that may hold the key to the repair and regeneration of coronary arteries. Nevertheless, many questions need to be answered before a vialbe vascular tissie with the inherent properties of native tissue becomes a real contender with the surgical therapies in use today

A Collagen‐Glycosaminoglycan‐Fibrin Scaffold For Heart Valve Tissue Engineering Applications

The field of heart valve biology and tissue engineering a heart valve continue to expand. The presentatio ns at this meeting reflect the advances made in both areas due to the multi-disciplinary approach taken by many laboratories

A New Reinforced Fibrin Collagen Glycosaminoglycan Material to Resist Tissue Contraction in Heart Valves

A crosslinked, multicomponent scaffold of collagen, GAG and fibrin has been characterised for heart valve applications. Fibrin gels reinforced with a 0.75% collagen, 0.044% GAG scaffolds can resist VSMC induced contraction significantly more than fibrin-only gels, while allowing cell proliferation and maintaining excellent cell viability. This improvement in structural integrity may facilitate the use of fibrin based materials for heart valve tissue engineering

The Effect of Physiological Cyclic Stretch on the Cell Morphology, Cell Orientation and Protein Expression of Endothelial Cells

In vivo, endothelial cells are constantly exposed to pulsatile shear and tensile stresses. The main aim of this study was to design and build a physiological simulator, which reproduced homogenous strain profiles of the tensile strain experienced in vivo, and to investigate the effect of this cyclic tensile strain on the cell morphology, cell orientation and protein expression of endothelial cells. The biological response of human umbilical vein endothelial cells to a uniaxial cyclic stretch, in this newly developed simulator, was examined experimentally using immunohistostaining and confocal imaging and it was found that the cells elongated and oriented at 58.9± 4.5. This value was compared to a mathematical model where it was revealed that endothelial cells would orient at an angle of 60. This model also revealed that endothelial cells have an axial strain threshold value of 1.8% when exposed to a 10% cyclic strain at 1 Hz for 3 h. Cells cultured under conditions of cyclic strain showed increased ICAM-1 immunostaining when compared to static cells whereas, a marked decrease in the levels of VCAM-1 receptor staining was also observed. Haemodynamic stresses can modulate the endothelial cell adhesion response in vivo thus, taken together; this data validates the bioreactor as replicating the physiological environment

Towards 3D in vitro models for the study of cardiovascular tissues and disease

The field of tissue engineering is developing biomimetic biomaterial scaffolds which are showing increasing therapeutic potential for the repair of cardiovascular tissues. However, a major opportunity exists to use them as 3D in vitro models for the study of cardiovascular tissues and disease in addition to drug development and testing. These in vitro models can span the gap between 2D culture and in vivo testing thus reducing cost, time and the ethical burden of current approaches. This review outlines the progress to date and requirements for the development of ideal in vitro 3D models for blood vessels, heart valves and myocardial tissue

Freeze-Drying as a Novel Biofabrication Method for Achieving a Controlled Microarchitecture within Large, Complex Natural Biomaterial Scaffolds

The biofabrication of large scaffolds from natural biomaterials into complex 3D shapes with controllable microarchitecture remains a major challenge. Freeze-drying (or lyophilization) is a technique used to create bioactive scaffolds with a porous architecture and is typically only used to generate scaffolds in planar 3D geometries. Here we report the development of a new biofabrication process to form a collagen-based scaffold into a large, complex geometry which has a large height to width ratio, and a controlled porous microarchitecture. This biofabrication process was validated through the successful development of a heart valve shaped scaffold, fabricated from a collagen-glycosaminoglycan co-polymer. Notably, despite the significant challenges in using freeze-drying to create such a structure, the resultant scaffold had a uniform, homogeneous pore architecture throughout. This was achieved through optimization of the freeze-drying mold and freezing parameters. We believe this to be the first demonstration of using freeze-drying to create a large, complex scaffold geometry with a controlled, porous architecture using natural materials. This study validates the potential of using freeze-drying for development of organ-specific scaffold geometries for tissue engineering applications, which up until now might not have been considered feasible

A Step Closer to Elastogenesis on Demand; Inducing Mature Elastic Fibre Deposition in a Natural Biomaterial Scaffold

Elastic fibres play a key role in bodily functions where fatigue resistance and elastic recovery are necessary while regulating phenotype, proliferation and migration in cells. While in vivo elastic fibres are created at a late foetal stage, a major obstacle in the development of engineered tissue is that human vascular smooth muscle cells (hVSMCs), one of the principal elastogenic cells, are unable to spontaneously promote elastogenesis in vitro. Therefore, the overall aim of this study was to activate elastogenesis in vitro by hVSMCs seeded in fibrin, collagen, glycosaminoglycan (FCG) scaffolds, following the addition of recombinant human tropoelastin. This combination of scaffold, tropoelastin and cells induced the deposition of elastin and formation of lamellar maturing elastic fibres, similar to those found in skin, blood vessels and heart valves. Furthermore, higher numbers of maturing branched elastic fibres were synthesised when a higher cell density was used and by drop-loading tropoelastin onto cell-seeded FCG scaffolds prior to adding growth medium. The addition of tropoelastin showed no effect on cell proliferation or mechanical properties of the scaffold which remained dimensionally stable throughout. With these results, we have established a natural biomaterial scaffold that can undergo controlled elastogenesis on demand, suitable for tissue engineering applications

Impact of Tumour Epithelial Subtype on Circulating MicroRNAs in Breast Cancer Patients

While a range of miRNAs have been shown to be dysregulated in the circulation of patients with breast cancer, little is known about the relationship between circulating levels and tumour characteristics. The aim of this study was to analyse alterations in circulating miRNA expression during tumour progression in a murine model of breast cancer, and to detemine the clinical relevance of identified miRNAs at both tissue and circulating level in patient samples. Athymic nude mice received a subcutaneous or mammary fat pad injection of MDA-MB-231 cells. Blood sampling was performed at weeks 1, 3 and 6 following tumour induction, and microRNA extracted. MicroRNA microArray analysis was performed comparing samples harvested at week 1 to those collected at week 6 from the same animals. Significantly altered miRNAs were validated across all murine samples by RQ-PCR (n = 45). Three miRNAs of interest were then quantified in the circulation(n = 166) and tissue (n = 100) of breast cancer patients and healthy control individuals. MicroArray-based analysis of murine blood samples revealed levels of 77 circulating microRNAs to be changed during disease progression, with 44 demonstrating changes .2-fold. Validation across all samples revealed miR-138 to be significantly elevated in the circulation of animals during disease development, with miR-191 and miR-106a levels significantly decreased. Analysis of patient tissue and blood samples revealed miR-138 to be significantly up-regulated in the circulation of patients with breast cancer, with no change observed in the tissue setting. While not significantly changed overall in breast cancer patients compared to controls, circulating miR-106a and miR-191 were significantly decreased in patients with basal breast cancer. In tissue, both miRNAs were significantly elevated in breast cancer compared to normal breast tissue. The data demonstrates an impact of tumour epithelial subtype on circulating levels of miRNAs, and highlights divergent miRNA profiles between tissue and blood samples from breast cancer patients

Automatisierte Planung von digitalen Hochgeschwindigkeitsnetzen

Der Ausbau von digitalen Hochgeschwindigkeitsnetzen ist gekennzeichnet durch neuartige Anforderungen an den Planungsprozess. Diese Anforderungen erfordern wiederum den Einsatz von neuartigen Paradigmen, die eine effiziente und zugleich genaue Planung von flächendeckenden Glasfasernetzen ermöglichen. Hierbei können wiederkehrende Planungsaufgaben durch eine gezielte computergestützte Automatisierung effizienter und genauer ausgeführt, als es mit bisherigen Planungskonzepten möglich ist. Dieses Arbeitspapier beschreibt die computergestützte Ausführung eines Planungsprozesses auf Basis von fünf grundlegenden, iterativen Planungsschritten und gibt Empfehlungen für eine effiziente und genaue Planung von Glasfasernetzen. Der hier vorgestellte Ansatz ermöglicht es Netzbetreibern und Investoren, den Ausbau beliebiger Siedlungs- und Gewerbegebiete auf der zuverlässigen Basis von belastbarem Faktenwissen wirtschaftlich zu priorisieren