Short Overview of ROS as Cell Function Regulators and Their Implications in Therapy Concepts

The importance of reactive oxygen species (ROS) has been gradually acknowledged over the last four decades. Initially perceived as unwanted products of detrimental oxidative stress, they have been upgraded since, and now ROS are also known to be essential for the regulation of physiological cellular functions through redox signaling. In the majority of cases, metabolic demands, along with other stimuli, are vital for ROS formation and their actions. In this review, we focus on the role of ROS in regulating cell functioning and communication among themselves. The relevance of ROS in therapy concepts is also addressed here

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS).

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.The EU-ROS consortium (COST Action BM1203) was supported by the European Cooperation in Science and Technology (COST). The present overview represents the final Action dissemination summarizing the major achievements of COST Action BM1203 (EU-ROS) as well as research news and personal views of its members. Some authors were also supported by COST Actions BM1005 (ENOG) and BM1307 (PROTEOSTASIS), as well as funding from the European Commission FP7 and H2020 programmes, and several national funding agencies

Engineering of osteochondral grafts by electrospinning

Articular cartilage (AC) morbidity represents a substantial burden to global and public health, and continues to afflict millions of people in the UK. This costs the economy more than billion annually and requires approximately 80,000 knee replacements every year. To avoid these radical surgery procedures, various strategies have been recently developed to repair or restore AC through implantation of osteochondral grafts. However, their success remains limited, mainly with respect to the quality of the newly formed cartilage. To contribute to the development of improved treatment options, this thesis explored a tissue engineering approach towards the potential use of the electrospinning technique to build osteochondral grafts. The main objectives of the research were to produce and characterise a range of electrospun membranes with various compositions, to construct three-dimensional (3D) scaffolds seeded with cells, and to study the release of therapeutic agents from electrospun materials. Poly(lactic-co-glycolic acid) (PLGA) and Poly-epsilon-caprolactone (PCL) were the two FDA-approved polymers used to create the electrospun membranes. Collagen and hydroxyapatite were also added to increase the biocompatibility of the scaffolds. Tissue constructs were created by layering electrospun membranes with seeded sheets of human mesenchymal stem cells. Bovine Serum Albumin (BSA) and recombinant Transforming Growth Factor beta 3 (TGF-beta3) were also incorporated into the fibres and used as model proteins to study the release of therapeutic agents from the core of co-axial electrospun fibres. Results suggest that minor alterations in composition cause gradual but significant changes in morphology, surface properties, mechanical characteristics and biocompatibility of the scaffold. The combination of electrospinning and cell sheet engineering presents a unique and effective strategy that can be used to create 3D tissue constructs with high cell density and viability. Differentiation results also indicate that intrinsic properties of PLGA and PCL affect the chondrocyte phenotype. With regard to drug delivery, BSA and TGF-beta3 were successfully incorporated into electrospun materials and subsequently released into an aqueous environment. The release profiles recorded exhibited a pronounced initial burst release that was significantly reduced by mineral deposition onto the membranes. To conclude, this thesis presents several contributions that demonstrate the use of multilayered electrospun scaffolds as a successful approach for the generation of tissue engineered osteochondral grafts. Furthermore, this work supports the use of electrospinning as a key technology for future AC repair.</p

Preclinical comparison of novel rotator cuff repair scaffolds

-This thesis is not currently available via ORA

Effect of annealing on the mechanical properties and the degradation of electrospun polydioxanone filaments

Annealing, or heat treatment, has traditionally been used as a treatment to improve the strength and stiffness of electrospun materials. Understanding the extent to which annealing can improve the mechanical properties and alter the degradation rate of electrospun polydioxanone filaments could influence the range of its potential clinical applications. In this study, we investigated the effect of annealing electrospun polydioxanone filaments at varying times and temperatures and subsequently subjecting them to in vitro degradation in phosphate buffer saline for up to 6 weeks. Fibre alignment, tensile strength and thermal properties were assessed. It was determined that annealing at 65 °C for 3 h only marginally improved the tensile strength (9±2%) but had a significant effect on reducing strain and rate of degradation, as well as maintaining fibre alignment within the filament. The filament retained significantly more of its force at failure after 4 weeks (82±15%, compared to 61±20% for non annealed filaments) and after 6 weeks of degradation (81±9%, compared to 55±13% for non annealed filaments). Conversely, annealing filaments at 75°C improved the initial tensile strength of the filament (17±6%), but over 6 weeks, both samples annealed at 75 °C and 85 °C otherwise performed similarly or mechanically worse than those not annealed. These findings suggest that annealing at low temperatures is more useful as a method to tailor degradation rate than to improve mechanical properties. The ability to modulate the degradation profile with annealing may become useful to tailor the properties of electrospun materials without altering the chemistry of the polymer used. This might better match the degradation of the implant and gradual loss of mechanical properties with the new matrix deposition within the structure, enabling multiple regenerative strategies within a singl

From chain growth to step growth polymerization of photoreactive poly-epsilon-caprolactone : the network topology of bioresorbable networks as tool in tissue engineering

Control of the network topology by selection of an appropriate cross-linking chemistry is introduced as a new strategy to improve the elasticity and toughness of bioresorbable networks. The development of novel photocross-linkable and bioresorbable oligomers is essential for the application of light-based 3D-printing techniques in the context of tissue engineering. Although light-based 3D-printing techniques are characterized by an increased resolution and manufacturing speed as compared to extrusion-based 3D-printing, their application remains limited. Via chemical modification, poly-epsilon-caprolactone (PCL) is functionalized with photoreactive end groups such as acrylates, alkenes, and alkynes. Based on these precursors, networks with different topologies are designed via chain growth polymerization, step growth polymerization, or a combination thereof. The influence of the network topology and the concomitant cross-linking chemistry on the thermal, mechanical, and biological properties are elucidated together with their applicability in digital light processing (DLP). Photocross-linkable PCL with an elongation at break of 736.3 +/- 47% and an ultimate strength of 21.3 +/- 0.8 MPa is realized, which is approximately tenfold higher compared to the current state-of-the-art. Finally, extremely elastic DLP-printed dog bones are developed which can fully retrieve their initial length upon stress relieve at an elongation of 1000%

Time-dependent ECM alterations of young tendons in response to stress relaxation – a model for the Ponseti method

The Ponseti method corrects a clubfoot by manipulation and casting which causes stress relaxation on the tendons. Here, we examined the effect of long-term stress relaxation on tendon extracellular matrix (ECM) by an (1) ex vivo stress relaxation test, (2) an in vitro tenocyte culture with stress relaxation, and (3) an in vivo rabbit study. Time-dependent tendon lengthening and ECM alterations including crimp angle reduction and cleaved elastin were observed, which illustrated the mechanism of tissue lengthening behind the treatment – a material-based crimp angle reduction resulted from elastin cleavage. Additionally, in vitro and in vivo results observed restoration of these ECM alterations along with increased elastin level after 7 days of treatment, and the existence of neovascularization and inflammation, indicating the recovery and adaptation from the tendon in reaction to the treatment. Overall, this study provides the scientific background and information that helps explain the Ponseti method

Pyridine as an additive to improve the deposition of continuous electrospun filaments.

Electrospun filaments are leading to a new generation of medical yarns that have the ability to enhance tissue healing through their biophysical cues. We have recently developed a technology to fabricate continuous electrospun filaments by depositing the submicron fibres onto a thin wire. Here we investigate the influence of pyridine on the fibre deposition. We have added pyridine to polydioxanone solutions at concentrations ranging from 0 to 100 ppm, increasing the conductivity of the solutions almost linearly from 0.04 uS/cm to 7 uS/cm. Following electrospinning, this led to deposition length increasing from 1 cm to 14 cm. The samples containing pyridine easily underwent cold drawing. The strength of drawn filaments increased from 0.8 N to 1.5 N and this corresponded to a decrease in fibre diameter, with values dropping from 2.7 μm to 1 μm. Overall, these findings are useful to increase the reliability of the manufacturing process of continuous electrospun filaments and to vary their biophysical properties required for their application as medical yarns such as surgical sutures