Extracellular vesicles and Duchenne muscular dystrophy pathology: Modulators of disease progression

Generalizable anchor aptamer strategy for loading nucleic acid therapeutics on exosomes

Clinical deployment of oligonucleotides requires delivery technologies that improve stability, target tissue accumulation and cellular internalization. Exosomes show potential as ideal delivery vehicles. However, an affordable generalizable system for efficient loading of oligonucleotides on exosomes remain lacking. Here, we identified an Exosomal Anchor DNA Aptamer (EAA) via SELEX against exosomes immobilized with our proprietary CP05 peptides. EAA shows high binding affinity to different exosomes and enables efficient loading of nucleic acid drugs on exosomes. Serum stability of thrombin inhibitor NU172 was prolonged by exosome-loading, resulting in increased blood flow after injury in vivo. Importantly, Duchenne Muscular Dystrophy PMO can be readily loaded on exosomes via EAA (EXOEAA-PMO). EXOEAA-PMO elicited significantly greater muscle cell uptake, tissue accumulation and dystrophin expression than PMO in vitro and in vivo. Systemic administration of EXOEAA-PMO elicited therapeutic levels of dystrophin restoration and functional improvements in mdx mice. Altogether, our study demonstrates that EAA enables efficient loading of different nucleic acid drugs on exosomes, thus providing an easy and generalizable strategy for loading nucleic acid therapeutics on exosomes.

Challenges and Considerations of Preclinical Development for iPSC-Based Myogenic Cell Therapy

Cell therapies derived from induced pluripotent stem cells (iPSCs) offer a promising avenue in the field of regenerative medicine due to iPSCs' expandability, immune compatibility, and pluripotent potential. An increasing number of preclinical and clinical trials have been carried out, exploring the application of iPSC-based therapies for challenging diseases, such as muscular dystrophies. The unique syncytial nature of skeletal muscle allows stem/progenitor cells to integrate, forming new myonuclei and restoring the expression of genes affected by myopathies. This characteristic makes genome-editing techniques especially attractive in these therapies. With genetic modification and iPSC lineage specification methodologies, immune-compatible healthy iPSC-derived muscle cells can be manufactured to reverse the progression of muscle diseases or facilitate tissue regeneration. Despite this exciting advancement, much of the development of iPSC-based therapies for muscle diseases and tissue regeneration is limited to academic settings, with no successful clinical translation reported. The unknown differentiation process in vivo, potential tumorigenicity, and epigenetic abnormality of transplanted cells are preventing their clinical application. In this review, we give an overview on preclinical development of iPSC-derived myogenic cell transplantation therapies including processes related to iPSC-derived myogenic cells such as differentiation, scaling-up, delivery, and cGMP compliance. And we discuss the potential challenges of each step of clinical translation. Additionally, preclinical model systems for testing myogenic cells intended for clinical applications are described.

Molecular regulation of myocyte fusion

Myocyte fusion is a pivotal process in the development and regeneration of skeletal muscle. Failure during fusion can lead to a range of developmental as well as pathological consequences. This review aims to comprehensively explore the intricate processes underlying myocyte fusion, from the molecular to tissue scale. We shed light on key players, such as the muscle-specific fusogens - Myomaker and Myomixer, in addition to some lesser studied molecules contributing to myocyte fusion. Conserved across vertebrates, Myomaker and Myomixer play a crucial role in driving the merger of plasma membranes of fusing myocytes, ensuring the formation of functional muscle syncytia. Our multiscale approach also delves into broader cell and tissue dynamics that orchestrate the timing and positioning of fusion events. In addition, we explore the relevance of muscle fusogens to human health and disease. Mutations in fusogen genes have been linked to congenital myopathies, providing unique insights into the molecular basis of muscle diseases. We conclude with a discussion on potential therapeutic avenues that may emerge from manipulating the myocyte fusion process to remediate skeletal muscle disorders.

Isolation of small extracellular vesicles from regenerating muscle tissue using Tangential Flow Filtration and Size Exclusion Chromatography

We have recently made the strikingly discovery that upon a muscle injury, Wnt7a is upregulated and secreted from new regenerating myofibers on the surface of exosomes to elicit its myogenerative response distally. Despite recent advances in extracellular vesicle (EVs) isolation from diverse tissues, there is still a lack of specific methodology to purify EVs from muscle tissue. To eliminate contamination with non-EV secreted proteins and cytoplasmic fragments, which are typically found when using classical methodology, such as ultracentrifugation, we adapted a protocol combining Tangential Flow Filtration (TFF) and Size Exclusion Chromatography (SEC). We found that this approach allows simultaneous purification of Wnt7a, bound to EVs (retentate fraction) and free non-EV Wnt7a (permeate fraction). Here we described this optimized protocol designed to specifically isolate EVs from hind limb muscle explants, without cross-contamination with other sources of non-EV bounded proteins. The first step of the protocol is to remove large EVs with sequential centrifugation. Extracellular vesicles are then concentrated and washed in exchange buffer by TFF. Lastly, SEC is performed to remove any soluble protein traces remaining after TFF. Overall, this procedure can be used to isolate EVs from conditioned media or biofluid that contains EVs derived from any cell type or tissue, improving reproducibility, efficiency, and purity of EVs preparations. Our purification protocol results in high purity EVs that maintain structural integrity and thus fully compatible with in vitro and in vivo bioactivity and analytic assays.

Unraveling the Multifaceted Roles of Extracellular Vesicles: Insights into Biology, Pharmacology, and Pharmaceutical Applications for Drug Delivery

Extracellular vesicles (EVs) are nanoparticles released from various cell types that have emerged as powerful new therapeutic option for a variety of diseases. EVs are involved in the transmission of biological signals between cells and in the regulation of a variety of biological processes, highlighting them as potential novel targets/platforms for therapeutics intervention and/or delivery. Therefore, it is necessary to investigate new aspects of EVs' biogenesis, biodistribution, metabolism, and excretion as well as safety/compatibility of both unmodified and engineered EVs upon administration in different pharmaceutical dosage forms and delivery systems. In this review, we summarize the current knowledge of essential physiological and pathological roles of EVs in different organs and organ systems. We provide an overview regarding application of EVs as therapeutic targets, therapeutics, and drug delivery platforms. We also explore various approaches implemented over the years to improve the dosage of specific EV products for different administration routes.

Involvement of extracellular vesicles in the progression, diagnosis, treatment, and prevention of whole-body ionizing radiation-induced immune dysfunction

Acute radiation syndrome (ARS) develops after exposure to high doses of ionizing radiation and features immune suppression and organ failure. Currently, there are no diagnostics to identify the occurrence or severity of exposure and there are limited treatments and preventative strategies to mitigate ARS. Extracellular vesicles (EVs) are mediators of intercellular communication that contribute to immune dysfunction across many diseases. We investigated if EV cargo can identify whole body irradiation (WBIR) exposure and if EVs promote ARS immune dysfunction. We hypothesized that beneficial EVs derived from mesenchymal stem cells (MSC-EVs) would blunt ARS immune dysfunction and might serve as prophylactic radioprotectants. Mice received WBIR (2 or 9 Gy) with assessment of EVs at 3 and 7 days after exposure. LC-MS/MS proteomic analysis of WBIR-EVs found dose-related changes as well as candidate proteins that were increased with both doses and timepoints (34 total) such as Thromboxane-A Synthase and lymphocyte cytosolic protein 2. Suprabasin and Sarcalumenin were increased only after 9 Gy suggesting these proteins may indicate high dose/lethal exposure. Analysis of EV miRNAs identified miR-376 and miR-136, which were increased up to 200- and 60-fold respectively by both doses of WBIR and select miRNAs such as miR-1839 and miR-664 were increased only with 9 Gy. WBIR-EVs (9 Gy) were biologically active and blunted immune responses to LPS in RAW264.7 macrophages, inhibiting canonical signaling pathways associated with wound healing and phagosome formation. When given 3 days after exposure, MSC-EVs slightly modified immune gene expression changes in the spleens of mice in response to WBIR and in a combined radiation plus burn injury exposure (RCI). MSC-EVs normalized the expression of certain key immune genes such as NFκBia and Cxcr4 (WBIR), Map4k1, Ccr9 and Cxcl12 (RCI) and lowered plasma TNFα cytokine levels after RCI. When given prophylactically (24 and 3 hours before exposure), MSC-EVs prolonged survival to the 9 Gy lethal exposure. Thus, EVs are important participants in ARS. EV cargo might be used to diagnose WBIR exposure, and MSC-EVs might serve as radioprotectants to blunt the impact of toxic radiation exposure.