Transfection of macrophages by collagen hollow spheres loaded with polyplexes: a step towards modulating inflammation

Biodegradable Microparticles for Regenerative Medicine: A State of the Art and Trends to Clinical Application

Tissue engineering and cell therapy are very attractive in terms of potential applications but remain quite challenging regarding the clinical aspects. Amongst the different strategies proposed to facilitate their implementation in clinical practices, biodegradable microparticles have shown promising outcomes with several advantages and potentialities. This critical review aims to establish a survey of the most relevant materials and processing techniques to prepare these micro vehicles. Special attention will be paid to their main potential applications, considering the regulatory constraints and the relative easiness to implement their production at an industrial level to better evaluate their application in clinical practices.

The Collagen Suprafamily: From Biosynthesis to Advanced Biomaterial Development

Collagen is the oldest and most abundant extracellular matrix protein that has found many applications in food, cosmetic, pharmaceutical, and biomedical industries. First, an overview of the family of collagens and their respective structures, conformation, and biosynthesis is provided. The advances and shortfalls of various collagen preparations (e.g., mammalian/marine extracted collagen, cell-produced collagens, recombinant collagens, and collagen-like peptides) and crosslinking technologies (e.g., chemical, physical, and biological) are then critically discussed. Subsequently, an array of structural, thermal, mechanical, biochemical, and biological assays is examined, which are developed to analyze and characterize collagenous structures. Lastly, a comprehensive review is provided on how advances in engineering, chemistry, and biology have enabled the development of bioactive, 3D structures (e.g., tissue grafts, biomaterials, cell-assembled tissue equivalents) that closely imitate native supramolecular assemblies and have the capacity to deliver in a localized and sustained manner viable cell populations and/or bioactive/therapeutic molecules. Clearly, collagens have a long history in both evolution and biotechnology and continue to offer both challenges and exciting opportunities in regenerative medicine as nature's biomaterial of choice.

Three-dimensional hepatocyte culture system for the study of Echinococcus multilocularis larval development

Background

Hepatocyte-based metacestode culture is an attractive method to study alveolar echinococcosis (AE), but it is limited by the relatively short lifespan of cultured hepatocytes in maintaining their normal function.

Methodology/principal findings

We describe a three-dimensional (3D) hepatic culture system developed from co-cultured hepatocytes and mesenchymal stem cells using a collagen scaffold to study the development of Echinococcus multilocularis larvae. This 3D culture system preserved the function of hepatocytes for a longer period of time than their monolayer counterparts, with albumin secretion, 7-ethoxyresorufin O-deethylation activity, urea synthesis, CYP3A4 and CYP2D6 activity being highly preserved for 21–28 days. The expression levels of hepatocyte-specific genes including CLDN-3, Bsep, AFP, G6P, A1AT, CYP3A4 and NR1I3 were significantly higher in the 3D cultured system compared with their monolayer counterparts after 14-days in culture. Additionally, in the presence of 3D cultured hepatocytes, 81.2% of E. multilocularis protoscoleces rapidly de-differentiated into infective vesicles within eight weeks. Transcriptomic analyses revealed 807 differentially expressed genes between cultured vesicles and protoscoleces, including 119 genes uniquely expressed in protoscoleces, and 242 genes uniquely expressed in vesicles. These differentially expressed genes were mainly involved in parasite growth relating to the G-protein coupled receptor activity pathway, substrate-specific transmembrane transporter activity, cell-cell adhesion process, and potentially with neuroactive ligand-receptor interaction.

Conclusions/significance

This culture system provides a valuable advance in prolonging hepatocyte functionality, a foundation for future in-depth analysis of the host-parasite interaction in AE, and a useful model to evaluate potential therapeutic strategies to treat AE.

Alveolar echinococcosis (AE) is one of the world’s most dangerous zoonoses. Although there have been recent advances in some aspects of the molecular biology of E. multilocularis, larval development is far from understood. An in vitro hepatocyte based cultivation system for the metacestode stage of E. multilocularis has been developed to improve our understanding of AE. However, in two-dimensional conventional cultures, hepatocytes rapidly lose key phenotypic and functional characteristics after only approximately seven days. This hinders long-term in vitro studies of E. multilocularis larvae, which require several months for development. Thus, in this paper, a three-dimensional (3D) hepatic model was developed for simulating the organotropism of E. multilocularis toward the liver of its intermediate host. This 3D model can preserve the functions of hepatocytes and results in rapidly developed E. multilocularis larva. Genes uniquely expressed in protoscoleces and vesicles provided key information for the further study of AE. The 3D hepatic model provides a new foundation for E. multilocularis developmental studies and in-depth analysis of the host-parasite interaction in AE.

* Collagen Cross-Linking: Biophysical, Biochemical, and Biological Response Analysis

Extracted forms of collagen are subjected to chemical cross-linking to enhance their stability. However, traditional cross-linking approaches are associated with toxicity and inflammation. This work investigates the stabilization capacity, cytotoxicity and inflammatory response of collagen scaffolds cross-linked with glutaraldehyde (GTA), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, 4-arm polyethylene glycol (PEG) succinimidyl glutarate (4SP), genipin (GEN), and oleuropein. Although all cross-linking methods reduced free amine groups, variable data were obtained with respect to denaturation temperature, resistance to collagenase digestion, and mechanical properties. With respect to biological analysis, fibroblast cultures showed no significant difference between the treatments. Although direct cultures with human-derived leukemic monocyte cells (THP-1) clearly demonstrated the cytotoxic effect of GTA, THP-1 cultures supplemented with conditioned medium from the various groups showed no significant difference between the treatments. With respect to cytokine profile, no significant difference in secretion of proinflammatory (e.g., interleukin [IL]-1β, IL-8, tumor necrosis factor-α) and anti-inflammatory (e.g., vascular endothelial growth factor) cytokines was observed between the noncross-linked and the 4SP and GEN cross-linked groups, suggesting the suitability of these agents as collagen cross-linkers.

Fibrin-genipin annulus fibrosus sealant as a delivery system for anti-TNFα drug

BACKGROUND CONTEXT

Intervertebral discs (IVDs) are attractive targets for local drug delivery because they are avascular structures with limited transport. Painful IVDs are in a chronic inflammatory state. Although anti-inflammatories show poor performance in clinical trials, their efficacy treating IVD cells suggests that sustained, local drug delivery directly to painful IVDs may be beneficial.

PURPOSE

The purpose of this study was to determine if genipin cross-linked fibrin (FibGen) with collagen Type I hollow spheres (CHS) can serve as a drug-delivery carrier for infliximab, the anti-tumor necrosis factor α (TNFα) drug. Infliximab was chosen as a model drug because of the known role of TNFα in increasing downstream production of several pro-inflammatory cytokines and pain mediators. Genipin cross-linked fibrin was used as drug carrier because it is adhesive, injectable, and slowly degrading hydrogel with the potential to seal annulus fibrosus (AF) defects. CHS allow simple and nondamaging drug loading and could act as a drug reservoir to improve sustained delivery.

STUDY DESIGN/SETTING

This is a study of biomaterials and human AF cell culture to determine drug release kinetics and efficacy.

METHODS

Infliximab was delivered at low and high concentrations using FibGen with and without CHS. Gels were analyzed for structure, drug release kinetics, and efficacy treating human AF cells after release.

RESULTS

Fibrin showed rapid infliximab drug release but degraded quickly. CHS alone showed a sustained release profile, but the small spheres may not remain in a degenerated IVD with fissures. Genipin cross-linked fibrin showed steady and low levels of infliximab release that was increased when loaded with higher drug concentrations. Infliximab was bound in CHS when delivered within FibGen and was only released after enzymatic degradation. The infliximab released over 20 days retained its bioactivity as confirmed by the sustained reduction of interleukin (IL)-1β, IL-6, IL-8, and TNFα concentrations produced by AF cells.

CONCLUSIONS

Direct mixing of infliximab into FibGen was the simplest drug-loading protocol capable of sustained release. Results show feasibility of using drug-loaded FibGen for delivery of infliximab and, in the context with the literature, show potential to seal AF defects and partially restore IVD biomechanics. Future investigations are required to determine if drug-loaded FibGen can effectively deliver drugs, seal AF defects, and promote IVD repair or prevent further IVD degeneration in vivo.

Biomaterial-mediated modification of the local inflammatory environment

Inflammation plays a major role in the rejection of biomaterial implants. In addition, despite playing an important role in the early stages of wound healing, dysregulated inflammation has a negative impact on the wound healing processes. Thus, strategies to modulate excessive inflammation are needed. Through the use of biomaterials to control the release of anti-inflammatory therapeutics, increased control over inflammation is possible in a range of pathological conditions. However, the choice of biomaterial (natural or synthetic), and the form it takes (solid, hydrogel, or micro/nanoparticle) is dependent on both the cause and tissue location of inflammation. These considerations also influence the nature of the anti-inflammatory therapeutic that is incorporated into the biomaterial to be delivered. In this report, the range of biomaterials and anti-inflammatory therapeutics that have been combined will be discussed, as well as the functional benefit observed. Furthermore, we point toward future strategies in the field that will bring more efficacious anti-inflammatory therapeutics closer to realization.

To cross-link or not to cross-link? Cross-linking associated foreign body response of collagen-based devices

Collagen-based devices, in various physical conformations, are extensively used for tissue engineering and regenerative medicine applications. Given that the natural cross-linking pathway of collagen does not occur in vitro, chemical, physical, and biological cross-linking methods have been assessed over the years to control mechanical stability, degradation rate, and immunogenicity of the device upon implantation. Although in vitro data demonstrate that mechanical properties and degradation rate can be accurately controlled as a function of the cross-linking method utilized, preclinical and clinical data indicate that cross-linking methods employed may have adverse effects on host response, especially when potent cross-linking methods are employed. Experimental data suggest that more suitable cross-linking methods should be developed to achieve a balance between stability and functional remodeling.

Collagen microsphere serving as a cell carrier supports oligodendrocyte progenitor cell growth and differentiation for neurite myelination in vitro

Introduction

Microspheres fabricated from natural materials serve as a promising biodegradable and biocompatible carrier in a small volume for efficient cell delivery to the lesion of the injured neural tissue to generate biological functions. As the major component of extracellular matrix and due to its natural abundance within the body, collagen may be fabricated into microspheres and improve the ability of pre-seeded cells on the microspheres to encounter the hostile micro-environment in the lesion.

Methods

In this study, collagen microspheres were fabricated using the water-in-oil emulsion technique and cross-linked with 1-ethyl-3-(3-dimethylaminopropryl) carbodiimide. Oligodendrocyte progenitor cells isolated from postnatal day P1 to 2 rats were cultured and differentiated on the microspheres. The microspheres carrying the oligodendrocyte progenitor cells were co-cultured with dorsal root ganglions from 15-day-old rat embryos. The myelination formation was studied for the co-culture of oligodendrocyte progenitor cells and dorsal root ganglions.

Results

We showed that the viability of oligodendrocyte progenitor cells, B104 cells and PC12 cells grown on microspheres was not significantly different with those in cell culture plates. Oligodendrocyte progenitor cells differentiated into oligodendrocytes on collagen microspheres. The oligodendrocytes grown on microspheres extended processes that wrapped the axons of dorsal root ganglion neurons and the formation of myelin sheath was observed in the co-culture.

Conclusions

This study demonstrates the feasibility of collagen microspheres in further applications for the delivery of neural progenitor cells for neural regeneration.

Influence of sterilisation methods on collagen-based devices stability and properties

Sterilisation is essential for any implantable medical device in order to prevent infection in patients. The selection of the most appropriate sterilisation method depends on the nature and the physical state of the material to be sterilised; the influence of the sterilisation method on the properties of the device; and the type of the potential contaminant. In this context, herein we review the influence of ethylene oxide, γ-irradiation, e-beam irradiation, gas plasma, peracetic acid and ethanol on structural, biomechanical, biochemical and biological properties of collagen-based devices. Data to-date demonstrate that chemical approaches are associated with cytotoxicity, whilst physical methods are associated with degradation, subject to the device physical characteristics. Thus, the sterilisation method of choice is device dependent.

Assembly of protein-based hollow spheres encapsulating a therapeutic factor

Neurotrophins, as important regulators of neural development, function, and survival, have a therapeutic potential to repair damaged neurons. However, a controlled delivery of therapeutic molecules to injured tissue remains one of the greatest challenges facing the translation of novel drug therapeutics field. This study presents the development of an innovative protein-protein delivery technology of nerve growth factor (NGF) by an electrostatically assembled protein-based (collagen) reservoir system that can be directly injected into the injury site and provide long-term release of the therapeutic. A protein-based biomimetic hollow reservoir system was fabricated using a template method. The capability of neurotrophins to localize in these reservoir systems was confirmed by confocal images of fluorescently labeled collagen and NGF. In addition, high loading efficiency of the reservoir system was proven using ELISA. By comparing release profile from microspheres with varying cross-linking, highly cross-linked collagen spheres were chosen as they have the slowest release rate. Finally, biological activity of released NGF was assessed using rat pheochromocytoma (PC12) cell line and primary rat dorsal root ganglion (DRG) cell bioassay where cell treatment with NGF-loaded reservoirs induced significant neuronal outgrowth, similar to that seen in NGF treated controls. Data presented here highlights the potential of a high capacity reservoir-growth factor technology as a promising therapeutic treatment for neuroregenerative applications and other neurodegenerative diseases.

Biomaterial constructs for delivery of multiple therapeutic genes: a spatiotemporal evaluation of efficacy using molecular beacons

Gene therapy is emerging as a potential therapeutic approach for cardiovascular pathogenesis. An appropriate therapy may require multiple genes to enhance therapeutic outcome by modulating inflammatory response and angiogenesis in a controlled and time-dependent manner. Thus, the aim of this research was to assess the spatiotemporal efficacy of a dual-gene therapy model based on 3D collagen scaffolds loaded with the therapeutic genes interleukin 10 (IL-10), a potent anti-inflammatory cytokine, and endothelial nitric oxide synthase (eNOS), a promoter of angiogenesis. A collagen-based scaffold loaded with plasmid IL-10 polyplexes and plasmid eNOS polyplexes encapsulated into microspheres was used to transfect HUVECs and HMSCs cells.The therapeutic efficacy of the system was monitored at 2, 7 and 14 days for eNOS and IL-10 mRNA expression using RT-PCR and live cell imaging molecular beacon technology. The dual gene releasing collagen-based scaffold provided both sustained and delayed release of functional polyplexes in vitro over a 14 day period which was corroborated with variation in expression levels seen using RT-PCR and MB imaging. Maximum fold increases in IL-10 mRNA and eNOS mRNA expression levels occurred at day 7 in HMSCs and HUVECs. However, IL-10 mRNA expression levels seemed dependent on frequency of media changes and/or ease of transfection of the cell type. It was demonstrated that molecular beacons are able to monitor changes in mRNA levels at various time points, in the presence of a 3D scaffolding gene carrier system and the results complemented those of RT-PCR.

Collagen: finding a solution for the source

Extracellular matrix (ECM)-based scaffolds, through their inherent bioactivity and molecular recognition signals, provide the ideal substrate for tissue engineering and regenerative applications. Collagen, the most abundant ECM protein, has proven itself to be a very versatile material with applications in many fields, including the leather and food industries, cosmetics, drug delivery, and tissue engineering. However, doubts persist about the optimal source of collagen for tissue engineering applications, given possible immunogenicity and disease transmission associated with animal sources and reduced bioactivity and availability of recombinant technologies. In this special edition, an attempt is made to elucidate the advantages of plant-derived human recombinant collagen and its applications in tissue engineering, particularly skin and wound healing. While results are promising, the widespread use of animal-derived collagen means that recombinant technologies may find applications in niche areas.

The neurotoxicity of gene vectors and its amelioration by packaging with collagen hollow spheres

Over the last twenty years there have been several reports on the use of nonviral vectors to facilitate gene transfer in the mammalian brain. Whilst a large emphasis has been placed on vector transfection efficiency, the study of the adverse effects upon the brain, caused by the vectors themselves, remains completely overshadowed. To this end, a study was undertaken to study the tissue response to three commercially available transfection agents in the brain of adult Sprague Dawley rats. The response to these transfection agents was compared to adeno-associated viral vector (AAV), PBS and naked DNA. Furthermore, the use of a collagen hollow sphere (CHS) sustained delivery system was analysed for its ability to reduce striatal toxicity of the most predominantly studied polymer vector, polyethyleneimine (PEI). The size of the gross tissue loss at the injection site was analysed after immunohistochemical staining and was used as an indication of acute toxicity. Polymeric vectors showed similar levels of acute brain toxicity as seen with AAV, and CHS were able to significantly reduce the toxicity of the PEI vector. In addition; the host response to the vectors was measured in terms of reactive astrocytes and microglial cell recruitment. To understand whether this gross tissue loss was caused by the direct toxicity of the vectors themselves an in vitro study on primary astrocytes was conducted. All vectors reduced the viability of the cells which is brought about by direct necrosis and apoptosis. The CHS delivery system reduced cell necrosis in the early stages of post administration. In conclusion, whilst polymeric gene vectors cause acute necrosis, administration in the brain causes adverse effects no worse than that of an AAV vector. Furthermore, packaging the PEI vector with CHS reduces surface charge and direct toxicity without elevating the host response.