GPMVs in variable physiological conditions: could they be used for therapy delivery?

Cell Line and Media Composition Influence the Production of Giant Plasma Membrane Vesicles

Giant plasma membrane vesicles (GPMVs) have been utilized as a model to study phase separation in the plasma membrane. Additionally, GPMVs have been employed as vehicle for delivering molecular cargo, including small molecule drugs and nanoparticles. Nearly all examples of GPMV production use a defined salt buffer that is a stark contrast to typical cell culture medium. In this study, we demonstrate that the addition of formaldehyde and dithiothreitol to a standard culture medium was capable of generating GPMVs at a concentration equal to or higher than the traditional production buffer. These methods were evaluated for two human cell lines: kidney endothelial and Schwann cells (SCs). Morphological properties of the resultant GPMVs exhibited no significant differences between the two formulations. Factors such as pH and seeding density significantly influenced the production of GPMVs in both mediums. The cell type and seeding density was shown to influence the number of GPMVs to the greatest extent. SCs yield more GPMVs at higher seeding densities compared to endothelial cells. Stability of the membrane of the GPMVs produced in both mediums was evaluated by monitoring passive diffusion of two fluorescently tagged dextrans (3 and 10 kDa). Regardless of the production formulation or cell type, approximately 85% GPMVs are impermeable to either dextran. Cold storage for on-demand use and shipping are essential for broader use of GPMVs. Toward this aim, we have evaluated the GMPV number and morphologies following storage at -80 °C and in liquid nitrogen. A significant loss of the GPMV number, ∼30%, was observed following storage across production formulations as well as cell types. Our results indicate that smaller GMPVs, <5 μm are more stable for preservation. In conclusion, GPMVs can be produced in a broad range of formulations, exhibit a high degree of stability, and can undergo cold storage for further adoption.

Development of Cell-Derived Plasma Membrane Vesicles as a Nanoparticle Encapsulation and Delivery System

Background

Developing non-invasive delivery platforms with a high level of structural and/or functional similarity to biological membranes is highly desirable to reduce toxicity and improve targeting capacity of nanoparticles. Numerous studies have investigated the impacts of physicochemical properties of engineered biomimetic nanoparticles on their interaction with cells, yet technical difficulties have led to the search for better biomimetics, including vesicles isolated directly from live cells. Cell-derived giant plasma membrane vesicles (GPMVs), in particular, offer a close approximation of the intact cell plasma membrane by maintaining the latter's compositional complexity, protein positioning in a fluid-mosaic pattern, and physical and mechanical properties. Thus, to overcome technical barriers of prior nanoparticle delivery approaches, we aimed to develop a novel method using GPMVs to encapsulate a variety of engineered nanoparticles, then use these core-shell, nanoparticle-GPMV vesicle structures to deliver cargo to other cells.

Results

The GPMV system in this study was generated by chemically inducing vesiculation in A549 cells, a model human alveolar epithelial line. These cell-derived GPMVs retained encapsulated silica nanoparticles (50 nm diameter) for at least 48 hours at 37 °C. GPMVs showed nearly identical lipid and protein membrane profiles as the parental cell plasma membrane, with or without encapsulation of nanoparticles. Notably, GPMVs were readily endocytosed in the parental A549 cell line as well as the human monocytic THP-1 cell line. Higher cellular uptake levels were observed for GPMV-encapsulated nanoparticles compared to control groups, including free nanoparticles. Further, GPMVs delivered a variety of nanoparticles to parental cells with reduced cytotoxicity compared to free nanoparticles at concentrations that were otherwise significantly toxic.

Conclusions

We have introduced a novel technique to load nanoparticles within the cell plasma membrane during the GPMV vesiculation process. These GPMVs are capable of (a) encapsulating different types of nanoparticles (including larger and not highly-positively charged bodies that have been technically challenging cargoes) using a parental cell uptake technique, and (b) improving delivery of nanoparticles to cells without significant cytotoxicity. Ultimately, endogenous surface membrane proteins and lipids can optimize the physicochemical properties of cell membrane-derived vesicles, which could lead to highly effective cell membrane-based nanoparticle/drug delivery systems.

Cell-Derived Vesicles with Increased Stability and On-Demand Functionality by Equipping Their Membrane with a Cross-Linkable Copolymer

Cell-derived vesicles retain the cytoplasm and much of the native cell membrane composition. Therefore, they are attractive for investigations of membrane biophysics, drug delivery systems, and complex molecular factories. However, their fragility and aggregation limit their applications. Here, the mechanical properties and stability of giant plasma membrane vesicles (GPMVs) are enhanced by decorating them with a specifically designed diblock copolymer, cholesteryl-poly[2-aminoethyl methacrylate-b-poly(ethylene glycol) methyl ether acrylate]. When cross-linked, this polymer brush enhances the stability of the GPMVs. Furthermore, the pH-responsiveness of the copolymer layer allows for a controlled cargo loading/release, which may enable various bioapplications. Importantly, the cross-linked-copolymer GPMVs are not cytotoxic and preserve in vitro membrane integrity and functionality. This effective strategy to equip the cell-derived vesicles with stimuli-responsive cross-linkable copolymers is expected to open a new route to the stabilization of natural membrane systems and overcome barriers to biomedical applications.

Giant plasma membrane vesicles to study plasma membrane structure and dynamics

The plasma membrane (PM) is a highly heterogenous structure intertwined with the cortical actin cytoskeleton and extracellular matrix. This complex architecture makes it difficult to study the processes taking place at the PM. Model membrane systems that are simple mimics of the PM overcome this bottleneck and allow us to study the biophysical principles underlying the processes at the PM. Among them, cell-derived giant plasma membrane vesicles (GPMVs) are considered the most physiologically relevant system, retaining the compositional complexity of the PM to a large extent. GPMVs have become a key tool in membrane research in the last few years. In this review, I will provide a brief overview of this system, summarize recent applications and discuss the limitations.

Burkholderia cenocepacia transcriptome during the early contacts with giant plasma membrane vesicles derived from live bronchial epithelial cells

Burkholderia cenocepacia is known for its capacity of adherence and interaction with the host, causing severe opportunistic lung infections in cystic fibrosis patients. In this work we produced Giant Plasma Membrane Vesicles (GPMVs) from a bronchial epithelial cell line and validated their use as a cell-like alternative to investigate the steps involved in the adhesion process of B. cenocepacia. RNA-sequencing was performed and the analysis of the B. cenocepacia K56-2 transcriptome after the first contacts with the surface of host cells allowed the recognition of genes implicated in bacterial adaptation and virulence-associated functions. The sensing of host membranes led to a transcriptional shift that caused a cascade of metabolic and physiological adaptations to the host specific environment. Many of the differentially expressed genes encode proteins related with central metabolic pathways, transport systems, cellular processes, and virulence traits. The understanding of the changes in gene expression that occur in the early steps of infection can uncover new proteins implicated in B. cenocepacia-host cell adhesion, against which new blocking agents could be designed to control the progression of the infectious process.

Chemical manipulations to facilitate membrane blebbing and vesicle shedding on the cellular cortex

OBJECTIVES

Most attention has been focused on physiologically generated membrane blebs on the cellular cortex, whereas artificial membrane blebs induced by chemicals are studied to a lesser extent.

RESULTS

We found that exposure of HeLa human cervical cancer cells to paraformaldehyde (PFA), followed by incubation in phosphate-buffered saline (PBS) efficiently induced large membrane blebs on the cellular cortex. Intriguingly, sequential exposure of the PFA-treated cells to PBS containing dimethyl sulfoxide (DMSO) facilitated shedding of the blebs from the cellular cortex, yielding a high quantity of large extracellular vesicles in the supernatant, which was applicable to assess the potentials of compounds and proteins as membrane influencers. Similar effects of PFA and DMSO were detected on the cellular cortex of other human, mouse, and fish cells.

CONCLUSIONS

Our procedure to facilitate membrane blebbing and vesicle shedding by chemicals may be practical for the manipulation of membrane dynamics and the development of vesicle-inspired technologies using a wide variety of cell types.