A specially engineered cell-derived therapy may offer a new way to control the dangerous inflammation associated with cytokine storms, according to research from the University of Osaka and collaborating institutions. In experiments involving mice, the treatment sharply reduced lung inflammation and lowered the production of inflammatory cytokines after acute respiratory distress syndrome was induced. The approach uses microscopic biological particles known as extracellular vesicles, which researchers modified with an enzyme to redirect their activity toward damaged lung tissue.
Cytokine storms occur when the immune system responds to infection or tissue injury with an uncontrolled surge of signaling proteins. Cytokines normally coordinate immune defenses, but excessive production can damage the body’s own organs. In severe respiratory disease, this response can increase the permeability of blood vessels, flood the lungs with fluid, impair oxygen exchange, and trigger widespread complications such as abnormal clotting, liver injury, and organ failure. The phenomenon was widely recognized during the COVID-19 pandemic, but it can also accompany sepsis, pneumonia, autoimmune disorders, and other inflammatory conditions.
The new treatment is based on extracellular vesicles, nanoscale membrane-bound particles released by cells. These vesicles transport proteins, messenger RNAs, lipids, and other molecular signals between cells, allowing them to influence immune activity and tissue repair. Previous studies have investigated vesicles derived from mesenchymal stem cells as potential anti-inflammatory agents. However, the Osaka-led research team found that vesicles originating from liver cells could exert a stronger protective effect in inflammatory disease models. The investigators then sought to enhance their biological activity through an enzymatic reaction.
They treated the liver-cell-derived vesicles with secreted phospholipase A2, or sPLA2, an enzyme that modifies membrane phospholipids. This process produced what the researchers call sPLA2-reacted extracellular vesicles, abbreviated SPLEVs. Phospholipase enzymes can release or remodel lipid molecules from cell membranes, and some of the resulting lipids function as potent signaling mediators. By altering the molecular composition of the vesicle surface, the treatment appeared to change how the particles interacted with tissues after administration.
The researchers injected SPLEVs into mice modeling acute respiratory distress syndrome and then examined the animals’ lungs and inflammatory profiles. Compared with untreated animals and those receiving unmodified extracellular vesicles, mice treated with SPLEVs showed substantially less pulmonary inflammation. Their lungs contained fewer infiltrating immune cells, while levels of cytokines associated with severe inflammation were considerably lower. These findings suggest that the modified vesicles did not simply suppress immunity throughout the body; instead, they may have interrupted the inflammatory process at the injured respiratory surface.
One of the most notable observations was the difference in tissue targeting. Untreated extracellular vesicles tended to interact with macrophages, immune cells that can amplify inflammation when activated by infection or tissue injury. SPLEVs, by contrast, appeared to preferentially associate with the epithelial lining of the lungs. These epithelial cells form the barrier between the airways and the bloodstream and are among the first tissues to suffer during acute respiratory inflammation. Direct delivery of vesicle-associated signals to these cells may help preserve barrier function while reducing the molecular cues that attract additional immune cells.
Further analysis indicated that SPLEVs stimulated lung epithelial cells to produce large quantities of tissue-protective lipids. The researchers describe this response as a “lipid counterstorm,” a biological process that counteracts the destructive signals of a cytokine storm. Among the molecules that increased after SPLEV treatment were lysophosphatidylglycerols, a class of bioactive lipids derived from membrane components. These molecules may influence epithelial repair, inflammatory signaling, and the behavior of immune cells, although the precise mechanisms linking them to the observed protection remain under investigation.
The apparent benefits were not limited to the respiratory model. In additional mouse experiments involving inflammatory diseases, SPLEVs produced favorable effects in models associated with sepsis, abnormal coagulation, liver injury, colitis, and pneumonia. The breadth of these results suggests that the vesicles may act through fundamental pathways shared by multiple inflammatory disorders rather than through a mechanism specific to one pathogen. Nevertheless, the evidence remains preclinical. The experiments were conducted in animals, and the safety, optimal dosing, manufacturing requirements, and effectiveness of SPLEVs in people have not yet been established.
The researchers believe that the lipid response identified in the study could eventually support the development of cell-free artificial SPLEVs. Instead of producing vesicles from living cells for every treatment, scientists might one day manufacture synthetic particles carrying selected protective lipids or molecular signals. Such an approach could make the therapy more consistent, less expensive, and easier to scale. For now, the findings provide a mechanistic explanation for how enzymatically modified extracellular vesicles can redirect the body’s response to severe inflammation: rather than merely dampening the immune system, they may help damaged tissues generate their own protective counter-signals.
Article Title: sPLA2-reacted extracellular vesicles (SPLEVs) as a therapeutic modality for cytokine storm syndromes
Web References: https://doi.org/10.1126/sciadv.adr9135
References: Science Advances, DOI: 10.1126/sciadv.adr9135
Image Credits: Ai Kotani
Keywords: cytokine storm, extracellular vesicles, SPLEVs, sPLA2, lung inflammation, acute respiratory distress syndrome, lipid signaling, lysophosphatidylglycerols, epithelial cells, inflammation, sepsis, pneumonia
