Small extracellular vesicles (sEVs) are nanosized, lipid-bound particles that mediate intercellular communication through the transfer of proteins, lipids, and nucleic acids1. They are released by all cell types and are present in virtually all biological fluids, where they function as key carriers of bioactive cargo, including peptides and micro ribonucleic acids (RNAs)2. Their cargo is selectively sorted, enabling precise delivery of specific signals3, and their vesicular structure allows them to bypass the typical gradient and dilution constraints of freely secreted factors by delivering concentrated molecular payloads over long distances4. Although EVs from biofluids (e.g., plasma, serum, and saliva) provide a convenient snapshot of systemic signaling, they represent a highly mixed population originating from many tissues5. This makes it challenging to determine which organ is producing a specific biological signal or how EV communication is regulated at the tissue level. Because circulating EVs are pooled together, tissue-specific changes can be diluted or masked, limiting the ability to identify the true source of signals6.
Skeletal muscle (SkM) and bone marrow (BM) are major metabolically and functionally active tissues with distinct cellular compositions and signaling roles7,8. Both tissues may release EV populations enriched with unique, tissue-specific cargo; however, these signals can be easily overshadowed in plasma by EVs from high-turnover tissues such as immune cells8,9. Directly isolating EVs from muscle or BM increases sensitivity and enables detection of subtle, tissue-specific adaptations that may not be observable in circulation. Tissue-derived EVs therefore provide essential complementary information, revealing when a specific organ releases EVs, how long those signals persist, and which adaptations are acute versus chronic. Despite increasing interest in EVs, most established isolation methods have been developed for biofluids (e.g., plasma and serum) or cell culture systems. In these contexts, EVs can be obtained with relatively high yield and minimal structural disruption. However, isolating EVs directly from solid tissues such as SkM and BM presents notable technical challenges. These tissues are structurally complex and heterogeneous, requiring mechanical or enzymatic dissociation steps that can introduce artifacts, including high levels of soluble proteins, organelle fragments, and non-vesicular nanoparticles, making it difficult to achieve high-purity EV preparations.
Another major challenge in tissue-derived EV isolation is the lack of standardized workflows for fraction definition and separation10. Differential centrifugation alone often results in co-isolation of protein aggregates and large vesicles, while ultracentrifugation-based methods, although widely used, can lead to vesicle aggregation, deformation, and variable recovery depending on rotor type and experimental conditions. Density gradient approaches improve purity but are time-intensive, low-throughput, and difficult to standardize across laboratories11. Consequently, there is currently no widely adopted, reproducible method optimized for isolating small EVs from solid tissues with high purity and consistent yield10.
Size-exclusion chromatography (SEC) has emerged as a promising alternative for EV isolation because it separates particles based on size without subjecting vesicles to high centrifugal forces. SEC enables efficient separation of small EVs from soluble proteins and low-molecular-weight contaminants while preserving vesicle integrity and biological function. Importantly, SEC allows for clear definition of elution fractions, enabling reproducible identification of EV-enriched fractions and improved consistency across experiments12. However, SEC workflows require careful optimization for tissue-derived samples, particularly with respect to upstream tissue processing, debris removal, and fraction collection. To address these limitations, we developed a reproducible and standardized protocol for isolating sEVs from SkM and BM. This method integrates controlled enzymatic digestion for fibrous tissues, differential centrifugation for debris removal, and SEC-based purification to isolate high-purity vesicles. The workflow is specifically optimized to minimize contamination from intracellular components while preserving vesicle integrity and enabling consistent recovery from low-yield tissues.
This protocol fills a critical methodological gap by providing a practical and scalable approach for isolating tissue-derived sEVs with defined fractionation and validated purity, achieved through nanoparticle tracking analysis (NTA), Western blotting of canonical EV markers, electron microscopy for morphological assessment, and single-particle EV analysis using antibody capture, interferometric sizing, and multichannel fluorescence imaging. It is particularly well suited for studies requiring tissue-specific EV analysis, where biofluid-derived vesicles are insufficient to resolve the cellular origin of signals. Researchers should use this method when the goal is to obtain high-purity sEVs from solid tissues with minimal contamination and preserved vesicle integrity. In contrast, ultracentrifugation-based methods may be preferred for high-yield applications where purity is less critical, and density gradient approaches may be selected when isolating specific EV subpopulations despite lower throughput. Together, this protocol provides a standardized framework for the isolation and characterization of tissue-derived sEVs, enabling reproducible downstream molecular, biochemical, and functional analyses.