Successful endothelial monolayer formation on melt electrowritten scaffolds under dynamic conditions to mimic tunica intima

The lack of transplantable tissues and organs as well as the limitations of synthetic implants highlight the need for tissue-engineered constructs to obtain safe, long-lasting, and limitless tissue replacements. Scaffolds for cardiovascular applications, such as for a tissue-engineered vascular graft (TEVG), are thus highly required. For TEVGs, tubular scaffolds should support the formation of confluent endothelial layers in particular under dynamic conditions to prevent thrombosis and maintain hemostasis. For that purpose, a porous and highly diffusible scaffold structure is necessary to allow optimal cell adhesion as well as oxygen and nutrient exchange with the surrounding tissue. Here, we present a three-dimensional-printed scaffold made by a combination of fused deposition modeling (FDM) and melt electrowriting (MEW) out of polycaprolactone that enables monolayer formation and alignment of endothelial cells in the direction of medium flow under a shear stress of up to 10 dyn cm-2. Pore size and coating with human fibrin were optimized to enable confluent endothelial layers on the printed scaffold structures. Cell orientation and shape analysis showed a characteristic alignment and elongation of the tested endothelial cells with the direction of flow after dynamic cultivation. In contrast, melt electrospun scaffolds based on the same CAD design under comparable printing and cultivation conditions were not sufficient to form gapless cell layers. Thus, the new scaffold fabricated by MEW/FDM approach appears most suitable for TEVGs as a template for the innermost vascular wall layer, the tunica intima

Ink-structing the future of vascular tissue engineering: a review of the physiological bioink design

Three-dimensional (3D) printing and bioprinting have come into view for a plannable and standardizable generation of implantable tissue-engineered constructs that can substitute native tissues and organs. These tissue-engineered structures are intended to integrate with the patient’s body. Vascular tissue engineering (TE) is relevant in TE because it supports the sustained oxygenization and nutrition of all tissue-engineered constructs. Bioinks have a specific role, representing the necessary medium for printability and vascular cell growth. This review aims to understand the requirements for the design of vascular bioinks. First, an in-depth analysis of vascular cell interaction with their native environment must be gained. A physiological bioink suitable for a tissue-engineered vascular graft (TEVG) must not only ensure good printability but also induce cells to behave like in a native vascular vessel, including self-regenerative and growth functions. This review describes the general structure of vascular walls with wall-specific cell and extracellular matrix (ECM) components and biomechanical properties and functions. Furthermore, the physiological role of vascular ECM components for their interaction with vascular cells and the mode of interaction is introduced. Diverse currently available or imaginable bioinks are described from physiological matrix proteins to nonphysiologically occurring but natural chemical compounds useful for vascular bioprinting. The physiological performance of these bioinks is evaluated with regard to biomechanical properties postprinting, with a view to current animal studies of 3D printed vascular structures. Finally, the main challenges for further bioink development, suitable bioink components to create a self-assembly bioink concept, and future bioprinting strategies are outlined. These concepts are discussed in terms of their suitability to be part of a TEVG with a high potential for later clinical use

Clinical applicability of optogenetic gene regulation

The field of optogenetics is rapidly growing in relevance and number of developed tools. Among other things, the optogenetic repertoire includes light-responsive ion channels and methods for gene regulation. This review will be confined to the optogenetic control of gene expression in mammalian cells as suitable models for clinical applications. Here optogenetic gene regulation might offer an excellent method for spatially and timely regulated gene and protein expression in cell therapeutic approaches. Well-known systems for gene regulation, such as the LOV-, CRY2/CIB-, PhyB/PIF-systems, as well as other, in mammalian cells not yet fully established systems, will be described. Advantages and disadvantages with regard to clinical applications are outlined in detail. Among the many unanswered questions concerning the application of optogenetics, we discuss items such as the use of exogenous chromophores and their effects on the biology of the cells and methods for a gentle, but effective gene transfection method for optogenetic tools for in vivo applications

Vascular implants – new aspects for in situ tissue engineering

Conventional synthetic vascular grafts require ongoing anticoagulation, and autologous venous grafts are often not available in elderly patients. This review highlights the development of bioartificial vessels replacing brain-dead donor- or animal-deriving vessels with ongoing immune reactivity. The vision for such bio-hybrids exists in a combination of biodegradable scaffolds and seeding with immune-neutral cells, and here different cells sources such as autologous progenitor cells or stem cells are relevant. This kind of in situ tissue engineering depends on a suitable bioreactor system with elaborate monitoring systems, three-dimensional (3D) visualization and a potential of cell conditioning into the direction of the targeted vascular cell phenotype. Necessary bioreactor tools for dynamic and pulsatile cultivation are described. In addition, a concept for design of vasa vasorum is outlined, that is needed for sustainable nutrition of the wall structure in large caliber vessels. For scaffold design and cell adhesion additives, different materials and technologies are discussed. 3D printing is introduced as a relatively new field with promising prospects, for example, to create complex geometries or micro-structured surfaces for optimal cell adhesion and ingrowth in a standardized and custom designed procedure. Summarizing, a bio-hybrid vascular prosthesis from a controlled biotechnological process is thus coming more and more into view. It has the potential to withstand strict approval requirements applied for advanced therapy medicinal products

Recent advances in melt electro writing for tissue engineering for 3D printing of microporous scaffolds for tissue engineering

Melt electro writing (MEW) is a high-resolution 3D printing technique that combines elements of electro-hydrodynamic fiber attraction and melts extrusion. The ability to precisely deposit micro- to nanometer strands of biocompatible polymers in a layer-by-layer fashion makes MEW a promising scaffold fabrication method for all kinds of tissue engineering applications. This review describes possibilities to optimize multi-parametric MEW processes for precise fiber deposition over multiple layers and prevent printing defects. Printing protocols for nonlinear scaffolds structures, concrete MEW scaffold pore geometries and printable biocompatible materials for MEW are introduced. The review discusses approaches to combining MEW with other fabrication techniques with the purpose to generate advanced scaffolds structures. The outlined MEW printer modifications enable customizable collector shapes or sacrificial materials for non-planar fiber deposition and nozzle adjustments allow redesigned fiber properties for specific applications. Altogether, MEW opens a new chapter of scaffold design by 3D printing

High unawareness of chronic kidney disease in Germany

Chronic kidney disease (CKD) is associated with an increased risk for cardiovascular events, hospitalizations, end stage renal disease and mortality. Main risk factors for CKD are diabetes, hypertension, and older age. Although CKD prevalence is about 10%, awareness for CKD is generally low in patients and physicians, hindering early diagnosis and treatment. We analyzed baseline data of 3305 participants with CKD Stages 1–4 from German cohorts and registries collected in 2010. Prevalence of CKD unawareness and prevalence ratios (PR) (each with 95%-confidence intervals) were estimated in categories of age, sex, CKD stages, BMI, hypertension, diabetes and other relevant comorbidities. We used a log-binomial regression model to estimate the PR for CKD unawareness for females compared to males adjusting for CKD stage and CKD risk factors. CKD unawareness was high, reaching 71% (68–73%) in CKD 3a, 49% (45–54%) in CKD 3b and still 30% (24–36%) in CKD4. Prevalence of hypertension, diabetes or cardiovascular comorbidities was not associated with lower CKD unawareness. Independent of CKD stage and other risk factors unawareness was higher in female patients (PR = 1.06 (1.01; 1.10)). Even in patients with CKD related comorbidities, CKD unawareness was high. Female sex was strongly associated with CKD unawareness. Guideline oriented treatment of patients at higher risk for CKD could increase CKD awareness. Patient–physician communication about CKD might be amendable. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

A promising protocol for the endothelialization of vascular grafts in an instrumented rotating bioreactor towards clinical application

Pre-endothelialization of a tissue-engineered vascular graft before implantation aims to prevent thrombosis and immunoreactions. This work demonstrates a standardized cultivation process to build a confluent monolayer with human aortal endothelial cells on xenogenous scaffolds. Pre-tested dynamic cultivation conditions in flow slides with pulsatile flow (1 Hz) representing arterial wall conditions were transferred to a newly designed multi-featured rotational bioreactor system. The medium was thickened with 1% methyl cellulose simulating a non-Newtonian fluid comparable to blood. Computational fluid dynamics was used to estimate the optimal volume flow and medium distribution inside the bioreactor chamber for defined wall-near shear stress levels. Flow measurements were performed during cultivation for constant monitoring of the process. Three decellularized porcine arteries were seeded and cultivated in the bioreactor over six days. 1% MC turned out to be the optimal percentage to achieve shear stress values ranging up to 10 dyn/cm2. Vascular endothelial cells formed a continuous monolayer with significant cell alignment in the direction of flow. The presented cultivation protocol in the bioreactor system thus displays a promising template for graft endothelialization and cultivation. Therefore, establishing a key step for future tissue-engineered vascular graft development with a view towards clinical application

Mobile Corona-Analytik made in Hannover : Universitäre Forschungslabore im Einsatz zur Pandemiebekämpfung

An der Leibniz Universität Hannover wurden in enger Kooperation mit dem NIFE und der Medizinischen Hochschule Hannover mobile SARS-CoV-2 Teststationen entwickelt und betrieben. Dank dieses Projekts konnten wichtige Bereiche öffentlicher Institutionen, medizinischer Einrichtungen und kritischer Infrastruktur im südlichen Niedersachsen ihren Betrieb fortführen und Forschungsfragen unter anderem zur Verbreitung des Corona-Virus untersucht werden

Lebensretter Nierentransplantation : Zur Entwicklung von Schnelltests, die eine frühzeitige Abstoßung erkennen

Für eine eindeutige Diagnostik nach einer Nierentransplantation sind bisher schmerzhafte Biopsien notwendig. Wissenschaftlerinnen vom Institut für Technische Chemie arbeiten in Kooperation mit Sartorius und der Fassisi GmbH an Schnelltests, die ohne Eingriff in den Körper spezifische und immunologisch bedeutsame Biomarker identifizieren können

Smart multifunctional nanoparticles in nanomedicine

Recent advances in nanotechnology caused a growing interest using nanomaterials in medicine to solve a number of issues associated with therapeutic agents. The fabricated nanomaterials with unique physical and chemical properties have been investigated for both diagnostic and therapeutic applications. Therapeutic agents have been combined with the nanoparticles to minimize systemic toxicity, increase their solubility, prolong the circulation half-life, reduce their immunogenicity and improve their distribution. Multifunctional nanoparticles have shown great promise in targeted imaging and therapy. In this review, we summarized the physical parameters of nanoparticles for construction of "smart" multifunctional nanoparticles and their various surface engineering strategies. Outlook and questions for the further researches were discussed. © 2016 by De Gruyter