Engineering Extracellular Vesicles for Heart, Lung, Blood, and Sleep Diseases Workshop

On September 16–17, 2021, the National Heart, Lung, and Blood Institute convened a workshop, “Engineering Extracellular Vesicles for Heart, Lung, Blood, and Sleep (HLBS) Diseases,” to explore the utility of endogenous and synthetically and/or biologically engineered extracellular vesicles (EVs) for the diagnosis, treatment, and prognosis of heart, lung, blood, and sleep (HLBS) diseases, with a multidisciplinary approach. The workshop brought together basic, translational, and clinical scientists, and included a representative from the U.S. Food and Drug Administration (FDA) to identify the critical knowledge gaps, regulatory challenges, and research opportunities for human application of EVs.

Background

EVs are a heterogeneous group of small lipid membrane vesicles (e.g., exosomes, microvesicles, apoptotic bodies) that are naturally released by diverse cells to mediate cell-cell or inter-organ communication at paracrine and systemic levels, and have been implicated in both tissue homeostasis and disease development and progression. Natural properties of EVs, such as biocompatibility, low immunogenicity, immune priming, homing/targeting, cargo diversity and capacity, relative longevity in circulation, and ability to cross blood-brain barriers make them attractive as potential therapeutic agents or drug delivery vehicles. Emerging evidence suggests that EVs can be engineered to fine-tune their tropism and enhance their efficacy or can be customized to enable a range of therapeutic applications, including vaccination and delivery of anti-cancer drugs. Despite the growing enthusiasm in research into the active roles of EVs in biology and disease, there is a gap in knowledge and technology for utilization of engineered EVs as a means to treat or cure HLBS diseases.

The workshop is relevant to NHLBI’s goals to “Understand Human Biology, Reduce Human Disease,” and “Advance Translational Research.” It is responsive to NHLBI Strategic Vision Objectives 1-4.

Workshop goals

1. Identify critical knowledge gaps and new research opportunities with multidisciplinary approaches in the field of EVs.
2. Explore the utility of engineered EVs for the diagnosis, treatment, and prognosis of HLBS diseases.

Discussions

Presentations and discussions focused on four thematic areas: EV biology, engineering the EV cargo and membrane for therapeutics, EVs as diagnostic and prognostic biomarkers, and regulatory aspects of EVs as therapeutics.

Overarching Goals: Workshop participants identified three overarching prospective milestones for the next decade:

1. Gain fundamental insights into the mechanism of action of EVs by addressing heterogeneity of EVs; cargo quantity and content; specificity of targeting; and unknown critical quality attributes (CQA) including particle size distribution, composition, as well as complete elements of cargo.
2. Advance applied technology by addressing analytic complexity, short half-life, unknowns of delivery, dosing, and PK/PD.
3. Improve clinical scale-up by addressing reproducibility and manufacturing SOPs and key controls including source control, process control, and product testing.

Gaps and Opportunities: Workshop participants identified the following gaps and opportunities to guide future research:

Engineering the membrane of EVs

• Development of technologies to measure and analyze EV content, fusion, and uptake.
• Exploring the potential utility of surface engineering to alter biophysical, functional, and pharmacologic properties of EVs.
• Engineering delivery vehicles for EVs: improving stability, reproducibility, tropism, and release kinetics with added complexity.
• Controlling EV consistency particularly with scaling up and manufacturing.
• Building on lessons learned from lipid nanoparticle technology: adapted in vivo, high throughput technology to screen for engineered EVs with best attributes.
• Characterization of the optimal cell types that can be used for large-scale generation of EVs. Are mesenchymal stem cells a good option to generate EVs for therapeutic purposes?
• Using leukocyte or erythrocyte-extracted membranes for designing EVs that may mimic the ability of leukocytes to adhere to vasculature.

Engineering the cargo of EVs

• Challenges and opportunities in primary cell-derived EVs vs. synthetic EVs. Pros and cons of using one over the other based on type and stage of disease.
• Use of engineered tissues for improved generation of EVs.
• Engineering environment for delivery of EVs and improving deliverability of EVs.
• Choosing the optimal dose for cargo in EVs and the strategy for dosing of EVs based on EV concentration vs. total cargo vs. size distribution of EVs.
• Using animal models to identify and understand the specificity of EVs. Understanding model applicability and importance of stressors in regulating EV content and function.

EVs in diagnosis and prognosis

• Learning from context-dependent biological mechanisms of EVs.
• Exploiting endogenous mechanisms of EV generation.
• What is the influence of EVs on their microenvironment? What health outcome endpoints should be examined in studies?
• Are stem cells special recipients of EVs? What are the implications and opportunities of EVs for regenerative medicine?
• Importance of cell source of EV isolation on health outcomes.
• Opportunity to better characterize EV sub-populations.
• Using novel technologies to identify cell-specific EVs for increased specificity for diagnosis and prognosis as well as clinical outcomes or care.
• Using novel technologies to generate nanoparticle-based EVs for improved reproducibility and scalability.

Publication Plans

The meeting participants are developing a workshop report, outlining the meeting’s main objectives, knowledge gaps, and future research opportunities that were identified at the workshop, for publication in a peer-reviewed journal.