Novel Cell Therapy Strategy Against Sepsis: Engineered Exosomes from Non-Stem Cell Sources

Sepsis has long been acknowledged as a major cause of death in the intensive care units, primarily stemming from an exaggerated immune response to pathogen invasion. Exosomes from mesenchymal stem cells (MSCs) have emerged as potential novel treatment options with robust anti-inflammatory, antioxidant and anti-apoptosis properties by assisting the body in managing the excessive complications of the immune system. Recently, there has been increasing attention on the role of microRNAs in mitigating adverse reactions during sepsis. Our previous studies have confirmed the crucial role of the let-7i-5p microRNA in mediating the therapeutic effects of exosomes from human placenta MSCs (i.e., hpMSC exosomes) on mitigating organ injuries caused by lipopolysaccharide (LPS) in mice. However, one major obstacle to the clinical application of stem cell-based therapies is the limited source of stem cells.
To overcome this obstacle, we developed a novel cell therapy strategy, employing engineered exosomes from non-stem cell sources. We have successfully developed an engineered RAW264.7 cells that overexpress the let-7i-5p microRNA. The isolated exosomes from these engineered RAW264.7 cells (i.e., engineered exosomes) have been confirmed to be rich in hsa-let-7i-5p. To further elucidate their therapeutic effects against sepsis, we proposed that engineered exosomes rich in let 7i-5p microRNA may effectively alleviate lung damage in sepsis, similar to hpMSC exosomes.
Adult male C57BL/6J mice were treated with LPS (25 mg/kg, intraperitoneally; LPS group), LPS plus engineered exosomes (1 x 109 particles/mouse, intraperitoneally; LPS+En-Exo group), or LPS plus hpMSC exosomes (1 x 108 particles/mouse, intraperitoneally; LPS+hPMSC-Exo group). We observed that engineered exosomes improved survival rates after exposure to LPS (LPS+En-Exo versus LPS: 91.7% versus 50%, p = 0.015) and performed better than the LPS+hPMSC-Exo group (91.7% versus 66.7%). Additionally, similar to hpMSC exosomes, engineered exosomes alleviated the adverse effects of LPS on lung function (decreases in tidal volume, peak inspiratory flow, and end-expiratory flow; increase in airway resistance) and lung histology (increases in lung injury score and tissue water content) (all p < 0.05). Also similar to hpMSC exosomes, engineered exosomes mitigated the effects of LPS on upregulating inflammation (activation of nuclear factor-κB, hypoxia-inducible factor-1α, and macrophage M1 phase polarization; upregulation of tumor necrosis factor-α, interleukin-1β, interleukin-6, and interleukin-10), oxidation (increase in lipid peroxidation), and apoptosis (increase in DNA fragmentation) in lung tissues (all p < 0.05). These findings collectively demonstrate that engineered exosomes rich in let7i-5p microRNA, similar to hpMSC exosomes, can alleviate sepsis in mice, and the mechanisms may involve their effects on mitigating crucial mechanisms of inflammation, oxidation, and apoptosis.
In conclusion, engineered exosomes from non-stem cell sources can serve as a viable alternative to exosomes from MSCs in the treatment of sepsis.