Joanna Rejman

The Use of Inhibitors to Study Endocytic Pathways of Gene Carriers: Optimization and Pitfalls

Nonviral gene complexes can enter mammalian cells through different endocytic pathways. For efficient optimization of the gene carrier it is important to profile its cellular uptake, because this largely determines its intracellular processing and subsequent transfection efficiency. Most of the current information on uptake of these gene-delivery vehicles is based on data following the use of chemical inhibitors of endocytic pathways. Here, we have performed a detailed characterization of four commonly used endocytosis inhibitors [chlorpromazine, genistein, methyl-beta-cyclodextrin (MbetaCD), and potassium depletion] on cell viability and endocytosis in five well-described cell lines. We found that chlorpromazine and to a lesser extent MbetaCD significantly decreased cell viability of some cell lines even after short incubation periods and at concentrations that are routinely used to inhibit endocytosis. Through analyzing the uptake and subcellular distribution of two fluorescent endocytic probes transferrin and lactosylceramide (LacCer) that are reported to enter cells via clathrin-dependent (CDE) and clathrin-independent (CIE) mechanisms, respectively, we showed poor specificity of these agents for inhibiting distinct endocytic pathways. Finally, we demonstrate that any inhibitory effects are highly cell line dependent. Overall, the data question the significance of performing endocytosis studies with these agents in the absence of very stringent controls.

mRNA as gene therapeutic: how to control protein expression.

For many years, it was generally accepted that mRNA is too unstable to be efficiently used for gene therapy purposes. In the last decade, however, several research groups faced this challenge and not only proved the feasibility of mRNA-mediated transfection with surprising results regarding transfection efficiency and duration of protein expression, but also were able to demonstrate major advantages over the use of pDNA. These advantages will be the first issue discussed in this review, which first of all addresses the notions that mRNA does not need to cross the nuclear barrier to exert its biological activity and in addition lacks CpG motifs, which reduces its immunogenicity. Secondly, it provides insight in the (in)stability of the mRNA molecule, in how mRNA can be modified to increase its half-life and in the necessities of exogenously produced mRNA to be successfully used in transfection protocols. Furthermore, this review gives an in-depth overview of the different techniques and vehicles for intracellular mRNA delivery exploited by us and other groups, comprising electroporation, gene gun injection, lipo- and polyplexes. Finally, it covers recent literature describing specific applications for mRNA based gene delivery, showing that until now most attention has been paid to vaccination strategies. This review offers a comprehensive overview of current knowledge of the major theoretical as well as practical aspects of mRNA-mediated transfection, showing both its possibilities and its pitfalls and should therefore be useful for a diverse scientific audience.

Particulate vaccines: on the quest for optimal delivery and immune response.

Subunit vaccines offer a safer alternative to traditional organism-based vaccines, but their immunogenicity is impaired. This hurdle might be overcome by the use of micro- and nanodelivery systems carrying the antigen(s). This review discusses the rationale for the use of particulate vaccines and provides an overview of antigen-delivery vehicles currently under investigation. It further highlights the cellular uptake, antigen processing and the presentation by antigen-presenting cells because these processes are partially governed by particle characteristics and eventually determine the immunological outcome. Finally, we address the attractive concept of concomitant delivery of antigens and immunopotentiators. The condensed knowledge could be an asset for rationally designing antigen-delivery vehicles to obtain safe and efficacious vaccines.

In vivo integrity of polymer-coated gold nanoparticles

Inorganic nanoparticles are frequently engineered with an organic surface coating to improve their physicochemical properties, and it is well known that their colloidal properties may change upon internalization by cells. While the stability of such nanoparticles is typically assayed in simple in vitro tests, their stability in a mammalian organism remains unknown. Here, we show that firmly grafted polymer shells around gold nanoparticles may degrade when injected into rats. We synthesized monodisperse radioactively labelled gold nanoparticles ((198)Au) and engineered an (111)In-labelled polymer shell around them. Upon intravenous injection into rats, quantitative biodistribution analyses performed independently for (198)Au and (111)In showed partial removal of the polymer shell in vivo. While (198)Au accumulates mostly in the liver, part of the (111)In shows a non-particulate biodistribution similar to intravenous injection of chelated (111)In. Further in vitro studies suggest that degradation of the polymer shell is caused by proteolytic enzymes in the liver. Our results show that even nanoparticles with high colloidal stability can change their physicochemical properties in vivo.

Gene Transfer by Means of Lipo- and Polyplexes: Role of Clathrin and Caveolae-Mediated Endocytosis

In this paper we address the contribution of different endocytic pathways to the intracellular uptake and processing of differently sized latex particles and of plasmid DNA complexes by means of fluorescence microscopy and FACS analysis. By using a number of specific inhibitors of either clathrin-dependent or caveolae-dependent endocytosis we were able to discriminate between these two pathways. Latex particles smaller than 200 nm were internalized exclusively by clathrin-mediated endocytosis, whereas larger particles entered the cells via a caveolae-dependent pathway. The route of uptake of plasmid DNA complexes appears strongly dependent on the nature of the complexes. Thus, lipoplexes containing the cationic lipid DOTAP, were exclusively internalized by a clathrin-dependent mechanism, while polyplexes prepared from the cationic polymer polyethyleneimine (PEI) were internalized in roughly equal proportions by both pathways. Upon incubation of cells with lipoplexes containing the luciferase gene abundant luciferase expression was observed, which was effectively blocked by inhibitors of clathrin-dependent endocytosis but not by inhibitors of the caveolae-dependent uptake mechanism. By contrast, luciferase transfection of the cells with polyplexes was unaffected by inhibition of clathrin-mediated endocytosis, but was nearly completely blocked by inhibitors interfering with the caveolae pathway. The results are discussed with respect to possible differences in the mechanism by which plasmid DNA is released from lipoplexes and polyplexes into the cytosol and to the role of size in the uptake and processing of the complexes. Our data suggest that improvement of non-viral gene transfection could very much benefit from controlling particle size, which would allow targeting of particle internalization via a non-degradative pathway, involving caveolae-mediated endocytosis.

Stimuli-responsive electrospun fibers and their applications

Stimuli-responsive electrospun nanofibers are gaining considerable attention as highly versatile tools which offer great potential in the biomedical field. In this critical review, an overview is given on recent advances made in the development and application of stimuli-responsive fibers. The specific features of these electrospun fibers are highlighted and discussed in view of the properties required for the diverse applications. Furthermore, several novel biomedical applications are discussed and the respective advantages and shortcomings inherent to stimuli-responsive electrospun fibers are addressed (136 references).

Type I IFN Counteracts the Induction of Antigen-Specific Immune Responses by Lipid-Based Delivery of mRNA Vaccines

The use of DNA and viral vector-based vaccines for the induction of cellular immune responses is increasingly gaining interest. However, concerns have been raised regarding the safety of these immunization strategies. Due to the lack of their genome integration, mRNA-based vaccines have emerged as a promising alternative. In this study, we evaluated the potency of antigen-encoding mRNA complexed with the cationic lipid 1,2-dioleoyl-3trimethylammonium-propane/1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOTAP/DOPE ) as a novel vaccination approach. We demonstrate that subcutaneous immunization of mice with mRNA encoding the HIV-1 antigen Gag complexed with DOTAP/DOPE elicits antigen-specific, functional T cell responses resulting in specific killing of Gag peptide-pulsed cells and the induction of humoral responses. In addition, we show that DOTAP/DOPE complexed antigen-encoding mRNA displays immune-activating properties characterized by secretion of type I interferon (IFN) and the recruitment of proinflammatory monocytes to the draining lymph nodes. Finally, we demonstrate that type I IFN inhibit the expression of DOTAP/DOPE complexed antigen-encoding mRNA and the subsequent induction of antigen-specific immune responses. These results are of high relevance as they will stimulate the design and development of improved mRNA-based vaccination approaches.

On the cellular processing of non-viral nanomedicines for nucleic acid delivery: Mechanisms and methods

In the field of nanomedicine, ample attention has been paid to the development of nanocarriers for the intracellular delivery of therapeutic cargo, such as nucleic acids for gene therapy. The efficiency with which these non-viral carriers deliver their payload at the required intracellular site of action remains low. Despite extensive research on cellular attachment, endocytosis and intracellular trafficking of nanocarriers, clear-cut rules for the design of effective nanocarriers to improve nucleic acid transfer are still lacking. This is mainly caused by the cell type-dependence of this highly dynamic cellular processing, and to the lack of reliable methods to study these events. For these reasons there is a strong demand for the development and standardization of such methods in order to better understand the intracellular dynamics of nanomedicine processing and validate cellular and intracellular targeting strategies. This review aims at providing an overview of the different processes that are currently known to be involved in the cellular processing of nanomedicines, with a focus on cellular internalization mechanisms, as this has received a great deal of attention in the last couple of years. Furthermore, the intracellular hurdles that need to be overcome to allow efficient NA transfer will be critically discussed. In addition, an overview will be given of various methodologies that have been applied to unravel these cellular processing mechanisms, with a discussion on their strengths and weaknesses.

Electrospun cellulose acetate phthalate fibers for semen induced anti-HIV vaginal drug delivery

Despite many advances in modern medicine, human immunodeficiency virus (HIV) still affects the health of millions of people world-wide and much effort is put in developing methods to either prevent infection or to eradicate the virus after infection has occurred. Here, we describe the potential use of electrospun cellulose acetate phthalate (CAP) fibers as a tool to prevent HIV transmission. During the electrospinning process, anti-viral drugs can easily be incorporated in CAP fibers. Interestingly, as a result of the pH-dependent solubility of CAP, the fibers are stable in vaginal fluid (the healthy vaginal flora has a pH of below 4.5), whereas the addition of small amounts of human semen (pH between 7.4 and 8.4) immediately dissolves the fibers which results in the release of the encapsulated drugs. The pH-dependent release properties have been carefully studied and we show that the released anti-viral drugs, together with the CAP which has been reported to have intrinsic antimicrobial activity, efficiently neutralize HIV in vitro.

In vitro interaction of colloidal nanoparticles with mammalian cells: What have we learned thus far?

Summary The interfacing of colloidal nanoparticles with mammalian cells is now well into its second decade. In this review our goal is to highlight the more generally accepted concepts that we have gleaned from nearly twenty years of research. While details of these complex interactions strongly depend, amongst others, upon the specific properties of the nanoparticles used, the cell type, and their environmental conditions, a number of fundamental principles exist, which are outlined in this review.