Towards a biofunctionalized vascular prosthesis: immune cell trapping via a growth factor receptor.

To improve the clinical performance of vascular prostheses, which is inacceptably low for implants with small diameters (< 6 mm), biofunctionalization of synthetic implants by endothelialization has become a major, although still unreached, aim. In order to be able to recruit native endothelial progenitor cells (EPCs) to luminal implant surfaces from the blood stream, we generated monoclonal antibodies against the EPC-specific vascular endothelial growth factor receptor 2 (VEGFR-2). Employing the very efficient genetic immunization strategy, > 10 000 hybridoma clones were generated.

Fine-tuned PEGylation of chitosan to maintain optimal siRNA-nanoplex bioactivity.

Polyethylene glycol (PEG) is a widely used modification for drug delivery systems. It reduces undesired interaction with biological components, aggregation of complexes and serves as a hydrophilic linker of ligands for targeted drug delivery. However, PEGylation can also lead to undesired changes in physicochemical characteristics of chitosan/siRNA nanoplexes and hamper gene silencing.

Immunoliposomes for Targeted Delivery of an Antifibrotic Drug.

Excessive extracellular matrix formation in organs and tissues arises from an imbalance between the synthesis and degradation of matrix proteins, especially collagen. This condition interferes with proper wound healing and regeneration, and to date, no specific treatment is available. In the present study, we propose a targeted drug delivery system consisting of cell-specific immunoliposomes (ILs) loaded with deferoxamine (DFO) as an antifibrotic drug.

miR-124 disinhibits neurite outgrowth in an inflammatory environment.

Lesions of the central nervous system elicit inflammatory responses that counteract the regeneration of neurites. Microglia and infiltrating macrophages that were activated by trauma have been identified as cellular sources of inhibitory factors. We examine cultured macrophage (RAW264.

Cell-type specific four-component hydrogel.

In the field of regenerative medicine we aim to develop implant matrices for specific tissue needs. By combining two per se, cell-permissive gel systems with enzymatic crosslinkers (gelatin/transglutaminase and fibrinogen/thrombin) to generate a blend (technical term: quattroGel), an unexpected cell-selectivity evolved. QuattroGels were porous and formed cavities in the cell diameter range, possessed gelation kinetics in the minute range, viscoelastic properties and a mechanical strength appropriate for general cell adhesion, and restricted diffusion.

Hyaluronic acid/chitosan multilayer coatings on neuronal implants for localized delivery of siRNA nanoplexes.

Binding, stabilizing and promoting cellular uptake of siRNA are all critical efforts in creating matrices for the localized delivery of siRNA molecules to target cells. In this study, we describe the generation of chitosan imidazole/siRNA nanoplexes (NPs) embedded in nano scope polyelectrolyte multilayers (PEMs) composed of hyaluronic acid and chitosan for sustained and localized drug delivery. Regular PEM build-up, successful integration of NPs and controlled release under physiological conditions were shown.

Prostate carcinoma cell growth-inhibiting hydrogel supports axonal regeneration in vitro.

Prostate cancer is the most common malignant tumor in men. Radical prostatectomy, the most common surgical therapy, is typically accompanied by erectile dysfunction and incontinence due to severing of the axons of the plexus prostaticus. To date, no reconstructive therapy is available as the delicate network of severed nerve fibers preclude the transplantation of autologous nerves or synthetic tube implants.

Bioactive coronary stent coating based on layer-by-layer technology for siRNA release.

One procedure to treat stenotic coronary arteries is the percutaneous transluminal coronary angioplasty (PTCA). In recent years, drug-eluting stents (DESs) have demonstrated elaborate ways to improve outcomes of intravascular interventions. To enhance DESs, the idea has evolved to design stents that elute specific small interfering RNA (siRNA) for better vascular wall regeneration.

The recombinant bifunctional protein αCD133-GPVI promotes repair of the infarcted myocardium in mice.

Background: Bone-marrow-derived progenitor cells are important in myocardial repair mechanisms following prolonged ischemia. Cell-based therapy of diseased myocardium is limited by a low level of tissue engraftment.

Objectives: The aim of this study was the development of the bifunctional protein αCD133-glycoprotein (GP)VI as an effective treatment for supporting vascular and myocardial repair mechanisms.

The bispecific SDF1-GPVI fusion protein preserves myocardial function after transient ischemia in mice.

Background: CXCR4-positive bone marrow cells (BMCs) are critically involved in cardiac repair mechanisms contributing to preserved cardiac function. Stromal cell-derived factor-1 (SDF-1) is the most prominent BMC homing factor known to augment BMC engraftment, which is a limiting step of stem cell-based therapy. After myocardial infarction, SDF-1 expression is rapidly upregulated and promotes myocardial repair.

Telomerase-based immortalization modifies the angiogenic/inflammatory responses of human coronary artery endothelial cells.

Telomerase reverse transcriptase (TERT) is fundamental in determining the life span by regulating telomere length of chromosomes. To address the question whether the enhancement of the proliferative potential hampers cell differentiation, we generated TERT-over-expressing endothelial cells (ECs) and analyzed in vitro their (1) barrier function; (2) low-density lipoprotein uptake; (3) expression pattern of six selected marker proteins; (4) angiogenic potential in four assays; and (5) inflammatory responses. In contrast to investigations with focus on other cell parameters, we demonstrate that immortalization of ECs by over-expression of TERT resulted in different angiogenic and inflammatory behavior in comparison to cells with low native telomerase levels.

Bioartificial reconstruction of peripheral nerves using the rat median nerve model.

Different bioartificial tubes were recommended for peripheral nerve reconstruction in the past. In order to replace autologous nerve grafts this materials are still under review in different animal studies. Most of them are dealing with the rodent peripheral nerves.

Neuronal and glial responses to siRNA-coated nerve guide implants in vitro.

The manipulation of gene expression by RNA interference could play a key role in future neurotherapies, for example in the development of biohydrid implants to bridge nerve and spinal cord lesion gaps. Such resorbable biomaterial prostheses could serve as growth substrates together with specific siRNA to foster neuronal regeneration. To the best of our knowledge, we are the first to biofunctionalize neuronal prostheses with siRNA.

Chitosan/siRNA nanoparticles biofunctionalize nerve implants and enable neurite outgrowth.

Microstructured 20 μm thick polymer filaments used as nerve implants were loaded with chitosan/siRNA nanoparticles to promote nerve regeneration and ensure local delivery of nanotherapeutics. The stable nanoparticles were rapidly internalized by cells and did not affect cell viability. Target mRNA was successfully reduced by 65-75% and neurite outgrowth was enhanced even in an inhibitory environment.

Bioengineered glial strands for nerve regeneration.

Nerve guide implants approved for human application in the peripheral nervous system generally fail to bridge lesion gaps longer than 2 cm and cannot match the clinical performance of autologous nerve transplants. Since current synthetic implants are simply hollow tubes, we aim to recreate the native microarchitecture of nerves inside the tubular implants. Most importantly, in the regenerating nerve, dedifferentiated Schwann cells align to form thousands of long glial strands, which act as guiding structures for the regrowing axons.

Suppression of adverse angiogenesis in an albumin-based hydrogel for articular cartilage and intervertebral disc regeneration.

An injectable polyethylene glycol-crosslinked albumin gel (AG) supplemented with hyaluronic acid as a matrix for autologous chondrocyte implantation was evaluated with regard to its impact on angiogenesis. Healthy articular cartilage and intervertebral discs (IVD) are devoid of blood vessels, whereas pathological blood vessel formation augments degeneration of both theses tissues. In contrast to human endothelial cells, primary human articular chondrocytes encapsulated in the AG retained their viability.

A novel gelatin sponge for accelerated hemostasis.

To more effectively manage the substantial bleeding encountered during surgical procedures in oto-rhino-laryngology, we developed a novel hemostatic sponge made of pharmaceutical grade, chemically cross-linked gelatin. The sponge is characterized by a high pore density, reduced ligaments, and a high nanoscale roughness of lamella surfaces in the matrix. In vitro blood uptake assays revealed a very rapid absorption of human blood, which was two to three times faster than that measured with comparative hemostyptic devices.

A novel microsurgical nerve implantation technique preserving outer nerve layers.

A novel epineural tube implantation paradigm in the adult rat was designed for the analysis of regulatory cell interactions in peripheral nerves and for the development of therapeutic implants. The aim was to allow the integration of synthetic regenerative structures and cells into the nerve interior while preserving an outer nerve tissue layer with a supportive vasculature. The microsurgical technique allowed us to remove the interfascicular epineurium, leaving behind an epineural tube with an intact tissue wall of about 0.

Does telomerase reverse transcriptase induce functional de-differentiation of human endothelial cells?

By counteracting the shortening of chromosome telomeres, telomerase reverse transcriptase (hTERT) prevents senescence and age-related cell death. Embryonic cells display a high telomerase activity that declines rapidly with cell differentiation. Conversely, de-differentiated tumor cells tend to re-express telomerase.

Strategies for inducing the formation of bands of Büngner in peripheral nerve regeneration.

Peripheral human nerves fail to regenerate across longer tube implants (>2 cm), most likely because implants lack the microarchitecture of native nerves, including bands of Büngner. Bands of Büngner comprise longitudinally aligned Schwann cell strands that guide selectively regrowing axons. We aim to optimize tubular implants by integrating artificial bands of Büngner.

Nerve fibroblast impact on Schwann cell behavior.

In order to reveal non-neuronal cell interactions after peripheral nerve lesions, we began to analyze the impact of sciatic nerve fibroblasts on Schwann cells in vitro. Both cell types are considered to have opposite effects on axonal regeneration. Few data are available on how repulsive nerve fibroblasts affect neuritotrophic Schwann cells and thus might indirectly influence axonal regrowth.

Electrical stimulation-induced release of beta-endorphin from genetically modified neuro-2a cells.

The quantity of therapeutic gene products released from genetically engineered cells can be controlled externally at different levels. The widely used approach of controlling expression, however, generally has the disadvantage that chemical substances must be applied for stimulation. An alternative strategy aims at controlling gene products at posttranslational levels such as secretion.

Permeability testing of biomaterial membranes.

The permeability characteristics of biomaterials are critical parameters for a variety of implants. To analyse the permeability of membranes made from crosslinked ultrathin gelatin membranes and the transmigration of cells across the membranes, we combined three technical approaches: (1) a two-chamber-based permeability assay, (2) cell culturing with cytochemical analysis and (3) biochemical enzyme electrophoresis (zymography). Based on the diffusion of a coloured marker molecule in conjunction with photometric quantification, permeability data for a gelatin membrane were determined in the presence or absence of gelatin degrading fibroblasts.

Comparative neuro tissue engineering using different nerve guide implants.

At the moment autologous nerve grafting remains the only reasonable technique for reconstruction of peripheral nerve defects. Unfortunately, this technique has a lot of complications and disadvantages. These problems are related to the autologous nerve that is harvested for this procedure.

The pro-angiogenic characteristics of a cross-linked gelatin matrix.

To overcome limitations on regeneration in the nervous system and other organs caused by insufficient blood supply, we have developed a gelatin sponge material which stimulates blood vessel formation, i.e. angiogenesis.