Macrophage-Derived Exosomes Promote Lung Fibroblast Activation in Response to Cigarette Smoke

<bold>Background:</bold> Exosomes (Exo) are extracellular vesicles that are released from cells and shuttle molecular cargo to promote effective signaling between cells. Under pathological conditions, such as cigarette smoke (CS) exposure and COPD, alveolar macrophages (AM) can release Exo leading to the activation and proliferation of structural cells crucial in COPD- and CS-induced remodeling such as lung fibroblasts (LF). <bold>Aims:</bold> We characterized AM-derived Exo and their effects on LF in response to CS. <bold>Methods:</bold> AM-derived Exo treated (Exo-CS) or not (Exo-CTL) with CS were characterized by western blot, nanoparticle tracking and electron microscope analyses, and their proteomic content was analyzed by liquid chromatography tandem mass spectrometry. LF were treated with Exo-CS and Exo-CTL to measure LF contraction, migration, invasion, and proliferation. <bold>Results:</bold> Exo were identified by the presence of Exo-positive markers (CD63, CD81) and the absence of Exo-negative marker (Calnexin). Exo-CS vs. Exo-CTL were characterized by increases in proteins crucial in extracellular matrix deposition (ECM) and airway remodeling, such as Alpha 2-HS Glycoprotein (AHSG), Protein phosphatase 2, regulatory subunit A, alpha (PPP2R1A), and matrix metalloproteinase-3 (MMP3). Exo-CS vs. Exo-CTL significantly increased LF proliferative, contraction, migration, and invasion properties. Fibroblast identity and proliferation markers such as Vimentin, ki-67+, FAP and ITGb1 were upregulated in LF+Exo-CS vs. LF+Exo-CTL. <bold>Conclusions:</bold> Exo released by CS-exposed AM are able to induce LF contraction, migration, invasion, and proliferation properties responsible for the ECM deposition observed in COPD. These findings pave the way for future therapies targeting Exo in the context of lung inflammation induced by CS and COPD.