Extracellular Vesicles Derived from Plasmodium-infected and Non-infected Red Blood Cells as Targeted Drug Delivery Vehicles

Among several factors behind drug resistance evolution in malaria is the challenge of administering overall doses that are not toxic for the patient but that, locally, are sufficiently high to rapidly kill the parasites. Thus, a crucial antimalarial strategy is the development of drug delivery systems capable of targeting antimalarial compounds to Plasmodium with high specificity. In the present study, extracellular vesicles (EVs) have been evaluated as a drug delivery system for the treatment of malaria. EVs derived from naive red blood cells (RBCs) and from Plasmodium falciparum-infected RBCs (pRBCs) were isolated by ultrafiltration followed by size exclusion chromatography. Lipidomic characterization showed that there were no significant qualitative differences between the lipidomic profiles of pRBC-derived EVs (pRBC-EVs) and RBC-derived EVs (RBC-EVs). Both EVs were taken up by RBCs and pRBCs, although pRBC-EVs were more efficiently internalized than RBC-EVs, which suggested their potential use as drug delivery vehicles for these cells. When loaded into pRBC-EVs, the antimalarial drugs atovaquone and tafenoquine inhibited in vitro P. falciparum growth more efficiently than their free drug counterparts, indicating that pRBC-EVs can potentially increase the efficacy of several small hydrophobic drugs used for the treatment of malaria

Modulation of tissue tropism and biological activity of exosomes and other extracellular vesicles : New nanotools for cancer treatment

Exosomes are naturally secreted nanovesicles that have recently aroused a great interest in the scientific and clinical community for their roles in intercellular communication in almost all physiological and pathological processes. These 30–100 nm sized vesicles are released from the cells into the extracellular space and ultimately into biofluids in a tightly regulated way. Their molecular composition reflects their cells of origin, may confer specific cell or tissue tropism and underlines their biological activity. Exosomes and other extracellular vesicles (EVs) carry specific sets of proteins, nucleic acids (DNA, mRNA and regulatory RNAs), lipids and metabolites that represent an appealing source of novel noninvasive markers through biofluid biopsies. Exosome-shuttled molecules maintain their biological activity and are capable of modulating and reprogramming recipient cells. This multi-faceted nature of exosomes hold great promise for improving cancer treatment featuring them as novel diagnostic sensors as well as therapeutic effectors and drug delivery vectors. Natural biological activity including the therapeutic payload and targeting behavior of EVs can be tuned via genetic and chemical engineering. In this review we describe the properties that EVs share with conventional synthetic nanoparticles, including size, liposome-like membrane bilayer with customizable surface, and multifunctional capacity. We also highlight unique characteristics of EVs, which possibly allow them to circumvent some limitations of synthetic nanoparticle systems and facilitate clinical translation. The latter are in particular correlated with their innate stability, ability to cross biological barriers, efficiently deliver bioactive cargos or evade immune recognition. Furthermore, we discuss the potential roles for EVs in diagnostics and theranostics, and highlight the challenges that still need to be overcome before EVs can be applied to routine clinical practice

Recombinant phosphatidylserine-binding nanobodies for targeting of extracellular vesicles to tumor cells : a plug-and-play approach

Extracellular vesicles (EVs) are increasingly being recognized as candidate drug delivery systems due to their ability to functionally transfer biological cargo between cells. However, manipulation of targeting properties of EVs through engineering of the producer cells can be challenging and time-consuming. As a novel approach to confer tumor targeting properties to isolated EVs, we generated recombinant fusion proteins of nanobodies against the epidermal growth factor receptor (EGFR) fused to phosphatidylserine (PS)-binding domains of lactadherin (C1C2). C1C2-nanobody fusion proteins were expressed in HEK293 cells and isolated from culture medium with near-complete purity as determined by SDS-PAGE. Fusion proteins specifically bound PS and showed no affinity for other common EV membrane lipids. Furthermore, C1C2 fused to anti-EGFR nanobodies (EGa1-C1C2) bound EGFR with high affinity and competed with binding of its natural ligand EGF, as opposed to C1C2 fused to non-targeting control nanobodies (R2-C1C2). Both proteins readily self-associated onto membranes of EVs derived from erythrocytes and Neuro2A cells without affecting EV size and integrity. EV-bound R2-C1C2 did not influence EV-cell interactions, whereas EV-bound EGa1-C1C2 dose-dependently enhanced specific binding and uptake of EVs by EGFR-overexpressing tumor cells. In conclusion, we developed a novel strategy to efficiently and universally confer tumor targeting properties to PS-exposing EVs after their isolation, without affecting EV characteristics, circumventing the need to modify EV-secreting cells. This strategy may also be employed to decorate EVs with other moieties, including imaging probes or therapeutic proteins

Display of GPI-anchored anti-EGFR nanobodies on extracellular vesicles promotes tumour cell targeting

BACKGROUND: Extracellular vesicles (EVs) are attractive candidate drug delivery systems due to their ability to functionally transport biological cargo to recipient cells. However, the apparent lack of target cell specificity of exogenously administered EVs limits their therapeutic applicability. In this study, we propose a novel method to equip EVs with targeting properties, in order to improve their interaction with tumour cells. METHODS: EV producing cells were transfected with vectors encoding for anti-epidermal growth factor receptor (EGFR) nanobodies, which served as targeting ligands for tumour cells, fused to glycosylphosphatidylinositol (GPI) anchor signal peptides derived from decay-accelerating factor (DAF). EVs were isolated using ultrafiltration/size-exclusion liquid chromatography and characterized using western blotting, Nanoparticle Tracking Analysis, and electron microscopy. EV-tumour cell interactions were analyzed under static conditions using flow cytometry and under flow conditions using a live-cell fluorescence microscopy-coupled perfusion system. RESULTS: EV analysis showed that GPI-linked nanobodies were successfully displayed on EV surfaces and were highly enriched in EVs compared with parent cells. Display of GPI-linked nanobodies on EVs did not alter general EV characteristics (i.e. morphology, size distribution and protein marker expression), but greatly improved EV binding to tumour cells dependent on EGFR density under static conditions. Moreover, nanobody-displaying EVs showed a significantly improved cell association to EGFR-expressing tumour cells under flow conditions. CONCLUSIONS: We show that nanobodies can be anchored on the surface of EVs via GPI, which alters their cell targeting behaviour. Furthermore, this study highlights GPI-anchoring as a new tool in the EV toolbox, which may be applied for EV display of a variety of proteins, such as antibodies, reporter proteins and signaling molecules

Liposomal prednisolone inhibits tumor growth in a spontaneous mouse mammary carcinoma model

Cancers are abundantly infiltrated by inflammatory cells that are modulated by tumor cells to secrete mediators fostering tumor cell survival and proliferation. Therefore, agents that interfere with inflammatory signaling molecules or specific immune cell populations have been investigated as anticancer drugs. Corticosteroids are highly potent anti-inflammatory drugs, whose activity is intensified when targeted by nanocarrier systems. Liposome-targeted corticosteroids have been shown to inhibit tumor growth in different syngeneic murine tumor models as well as human xenograft mouse models, which is attributed to a switch in the tumor microenvironment from a pro-inflammatory to an anti-inflammatory state. Despite the recognized value of implantation tumor models in preclinical research, the “acute” inflammation induced by inoculation of tumor cells together with the exponential tumor growth in a relatively short period of time does not resemble slow progressive human disease that develops in situ. Therefore, in this study, the antitumor effect of liposomal corticosteroids was investigated in a clinically more relevant setting of transgenic mice developing spontaneous breast carcinomas. Here we show that liposomal prednisolone phosphate inhibits the growth of spontaneous breast carcinoma. Interestingly, the liposomal prednisolone was significantly more active than free drug. At 72 h after injection of the liposomal formulation, 3 μg prednisolone per gram of tumor tissue was recovered whereas no drug could be recovered after injection of the free agent. This indicates that, despite etiological and morphological differences between implanted and spontaneous tumor models, EPR-mediated accumulation of drug occurs to similar extent in this spontaneous mammary carcinoma model as in the syngeneic tumor models. Finally, we analyzed miRNA profiles in the MMTV/neu model and showed that the top 10 of miRNAs in the MMTV/neu tumor consisted of miRNAs with a known involvement in breast carcinoma proliferation and metastasis. The only exception was the appearance of miR-146b, a known inflammation-regulating miRNA species, after liposomal prednisolone treatment

In-vitro and in-silico evidence for oxidative stress as drivers for RDW

Abstract Red blood cell distribution width (RDW) is a biomarker associated with a variety of clinical outcomes. While anemia and subclinical inflammation have been posed as underlying pathophysiology, it is unclear what mechanisms underlie these assocations. Hence, we aimed to unravel the mechanisms in silico using a large clinical dataset and validate our findings in vitro. We retrieved complete blood counts (CBC) from 1,403,663 measurements from the Utrecht Patient Oriented Database, to model RDW using gradient boosting regression. We performed (sex-stratified) analyses in patients with anemia, patients younger/older than 50 and validation across platforms and care settings. We then validated our hypothesis regarding oxidative stress using an in vitro approach. Only percentage microcytic (pMIC) and macrocytic (pMAC) erythrocytes and mean corpuscular volume were most important in modelling RDW (RMSE = 0.40, R2 = 0.96). Subgroup analyses and validation confirmed our findings. In vitro induction of oxidative stress underscored our results, namely increased RDW and decreased erythrocyte volume, yet no vesiculation was observed. We found that erythrocyte size, especially pMIC, is most informative in predicting RDW, but no role for anemia or inflammation. Oxidative stress affecting the size of the erythrocytes may play a role in the association between RDW and clinical outcomes

The fluid membrane determines mechanics of erythrocyte extracellular vesicles and is softened in hereditary spherocytosis

Extracellular vesicles (EVs) are widely studied regarding their role in cell-to-cell communication and disease, as well as for applications as biomarkers or drug delivery vehicles. EVs contain membrane and intraluminal proteins, affecting their structure and thereby likely their functioning. Here, we use atomic force microscopy for mechanical characterization of erythrocyte, or red blood cell (RBC), EVs from healthy individuals and from patients with hereditary spherocytosis (HS) due to ankyrin deficiency. While these EVs are packed with proteins, their response to indentation resembles that of fluid liposomes lacking proteins. The bending modulus of RBC EVs of healthy donors is ~15 kbT, similar to the RBC membrane. Surprisingly, whereas RBCs become more rigid in HS, patient EVs have a significantly (~40%) lower bending modulus than donor EVs. These results shed light on the mechanism and effects of EV budding and might explain the reported increase in vesiculation of RBCs in HS patients

Liposomal prednisolone inhibits tumor growth in a spontaneous mouse mammary carcinoma model

Cancers are abundantly infiltrated by inflammatory cells that are modulated by tumor cells to secrete mediators fostering tumor cell survival and proliferation. Therefore, agents that interfere with inflammatory signaling molecules or specific immune cell populations have been investigated as anticancer drugs. Corticosteroids are highly potent anti-inflammatory drugs, whose activity is intensified when targeted by nanocarrier systems. Liposome-targeted corticosteroids have been shown to inhibit tumor growth in different syngeneic murine tumor models as well as human xenograft mouse models, which is attributed to a switch in the tumor microenvironment from a pro-inflammatory to an anti-inflammatory state. Despite the recognized value of implantation tumor models in preclinical research, the “acute” inflammation induced by inoculation of tumor cells together with the exponential tumor growth in a relatively short period of time does not resemble slow progressive human disease that develops in situ. Therefore, in this study, the antitumor effect of liposomal corticosteroids was investigated in a clinically more relevant setting of transgenic mice developing spontaneous breast carcinomas. Here we show that liposomal prednisolone phosphate inhibits the growth of spontaneous breast carcinoma. Interestingly, the liposomal prednisolone was significantly more active than free drug. At 72 h after injection of the liposomal formulation, 3 μg prednisolone per gram of tumor tissue was recovered whereas no drug could be recovered after injection of the free agent. This indicates that, despite etiological and morphological differences between implanted and spontaneous tumor models, EPR-mediated accumulation of drug occurs to similar extent in this spontaneous mammary carcinoma model as in the syngeneic tumor models. Finally, we analyzed miRNA profiles in the MMTV/neu model and showed that the top 10 of miRNAs in the MMTV/neu tumor consisted of miRNAs with a known involvement in breast carcinoma proliferation and metastasis. The only exception was the appearance of miR-146b, a known inflammation-regulating miRNA species, after liposomal prednisolone treatment

Interfering with endolysosomal trafficking enhances release of bioactive exosomes

Exosomes are cell-derived extracellular vesicles of 30-150 nm in size and are involved in intercellular communication. Because of their bioactive cargo, consisting of proteins, RNA and lipids, and their natural ability to deliver these biomolecules to recipient cells, exosomes are increasingly being studied as novel drug delivery vehicles or as cell-free approaches to regenerative medicine. However, one of the major hurdles for clinical translation of therapeutic strategies based on exosomes is their low yield when produced under standard culture conditions. Exosomes are vesicles of endocytic origin and are released when multivesicular endosomes fuse with the plasma membrane. Here, we demonstrate that interfering with endolysosomal trafficking significantly increases exosome release. Furthermore, these exosomes retain their regenerative bioactivity as demonstrated by pro-survival and angiogenesis assays using both cardiomyocytes and endothelial cells. These results may be employed to increase exosome production for studying biological functions or to improve clinical translation of exosome-based therapeutics