A kaleidoscopic view of extracellular vesicles in lysosomal storage disorders

Modulating binding affinity of aptamer-based loading constructs enhances extracellular vesicle-mediated CRISPR/Cas9 delivery

The CRISPR/Cas9 toolbox consists of modular nucleases that can be employed to efficiently modify genomic sequences with high specificity. However, delivery of the large Cas9-sgRNA ribonucleoprotein (RNP) complexes remains challenging due to their immunogenicity, size, and overall negative charge. An approach to overcome these limitations is the use of extracellular vesicles (EVs) as intracellular delivery vehicles. EVs exhibit the natural ability to carry and deliver RNA and proteins across biological barriers, and can be engineered to load and deliver a variety of biotherapeutic molecules. Previous studies have shown that efficient EV-mediated cargo delivery does not only require active loading strategies, but also benefits from strategies to release cargo from the EV membrane. Here, we load Cas9 RNP complexes into EVs by expressing sgRNAs containing MS2 aptamers (MS2-sgRNAs), alongside Cas9 and a fusion protein of CD63 and tandem MS2 coat proteins (MCPs). We demonstrate that efficient Cas9 RNP delivery can also be facilitated by modulating the binding affinity between MS2 aptamers and the MCPs. To study the effect of altering the binding affinity between the MS2 hairpin and the MCP on Cas9 RNP delivery, various mutations affecting the binding affinity were made in both the interacting MS2-hairpin and the RNA-binding domain of the MCPs. Comparing Cas9 RNP delivery of the modulated MS2-sgRNAs revealed that adapting binding affinity highly affects functional RNP delivery. Mutations resulting in high affinity did not facilitate efficient RNP delivery unless combined with a photo-inducible release strategy, showing that cargo release was a limiting factor in RNP delivery. Mutations that decreased affinity resolved this issue, resulting in Cas9 RNP delivery without the requirement of additional release strategies. However, further decreasing affinity resulted in decreased Cas9 gene-editing efficiency due to decreased levels of Cas9 RNP loading into EVs. A similar effect on functional delivery was seen after modification of the RNA-binding domain of the MCPs. Our results demonstrate that EVs are capable of functional Cas9-sgRNA complex delivery, and that modulation of binding affinity can be used to increase efficient functional delivery with non-covalent loading constructs, without the need for additional engineering strategies for cargo release.

Exploring the potential of bacterial-derived EVs for targeted enzyme replacement therapy: mechanisms, applications, and future directions

Extracellular vesicles (EVs) are membrane-bound vesicles produced by cells which promote intercellular communication by delivering different contents such as DNA, RNA, and proteins. These vesicles, nano-sized and released into the extracellular space, are present everywhere under both normal and pathological conditions. Probiotic-derived EVs can serve as nanocarriers for therapeutic cargo, particularly in enzyme replacement therapy (ERT). Traditional ERT for lysosomal storage diseases (LSDs) faces significant challenges, including the inability of enzymes to cross the blood-brain barrier (BBB) and their susceptibility to degradation. Studies show EVs can transport enzyme cargoes across the BBB, accurately delivering them to tissues affected by LSDs. Probiotic EVs also possess immunomodulatory properties, providing therapeutic benefits in inflammatory conditions. However, their potential for delivering deficient enzymes in LSDs remains unclear. This review discusses using probiotic EVs in ERT for targeted enzyme delivery to treat LSDs more efficiently than other exosomes. This novel strategy minimizes off-target delivery and enhances immunomodulatory effects, making it more advantageous than live probiotic bacteria. Probiotic EVs show promise for therapeutic approaches, especially in treating LSDs and inflammatory diseases, by modulating immune responses and delivering enzymes across biological barriers like the BBB. Future research should optimize production, engineer targeted therapies, and confirm safety and efficacy through clinical trials. Expanding studies to include diverse probiotic strains could uncover new therapeutic applications, enhancing their versatility and effectiveness.

Small extracellular vesicles from the human endothelial cell line EA.hy 926 exert a self-cell activation and modulate DENV-2 genome replication and infection in naïve endothelial cells

Extracellular vesicles (EVs) play crucial roles in cell signaling and communication, transporting molecules that convey a message to target cells. During infectious diseases, EVs can also carry viral molecules that may contribute to viral spread, as previously reported for dengue virus (DENV). EVs from infected endothelial cells (EC) may harbor viral segments and various sets of molecules that could contribute to endothelial dysfunction during severe dengue. However, the effect of these EVs on non-infected EC (NIC) remain unknown. We characterized the EVs produced by the human EC line EA.hy 926 infected with DENV-2 and assessed their functional impact on polarized NIC. Results showed that infection induced an increased in the quantity of produced EVs, which differentially carried proteins mainly involved in proteosome activity, along with a peptide of the NS5 viral protein. Additionally, all types of Y-RNAs were found, accompanied by a set of differentially loaded microRNAs (miRs) that could regulate DENV genome. Pre-treatment of polarized NIC with small EVs (sEVs) from infected EC before DENV-2 infection caused EC activation, a decrease in viral genome replication, and a protective effect against barrier disruption during the first 24h post-infection, suggesting that sEVs could be important in the pathology or resolution of DENV and a promising therapeutic tool for infectious diseases.