Human atrial extracellular vesicles suppress NLRP3 inflammasome activation and profibrotic signaling in a patient-specific iPSC model of postoperative atrial fibrillation.

BACKGROUND

Postoperative atrial fibrillation (AF) remains a common and morbid complication of cardiac surgery, driven by inflammation and fibrosis for which targeted therapies are limited. Conventional antiarrhythmic and anticoagulant strategies have little impact on its incidence or recurrence. We previously demonstrated that a single intracardiac injection of extracellular vesicles (EVs) derived from human heart explant-derived cells prevents postoperative AF in preclinical models. The present study aimed to elucidate the mechanisms underlying this protective effect in human cells.

METHODS

Induced pluripotent stem cells (iPSCs) were generated from circulating mononuclear cells obtained from cardiac surgery patients at high and low risk for postoperative AF, then differentiated into atrial fibroblasts. These cells were compared with primary human atrial fibroblasts isolated from surgical tissue. Clinical-grade cardiac EVs were manufactured from heart explant-derived cells and characterized for size, surface markers, and microRNA cargo. Both iPSC-derived and primary fibroblasts were exposed to inflammatory (IL-6, TGF-β1, lipopolysaccharide) and fibrotic stimuli, with or without EV treatment. Inflammasome activation and cytokine secretion were assessed by transcript and protein analyses.

RESULTS

iPSC-derived and primary atrial fibroblasts exhibited comparable antigenic and functional profiles and efficiently internalized cardiac EVs. EV treatment markedly suppressed activation of the NLRP3 inflammasome following lipopolysaccharide and nigericin stimulation, resulting in reduced secretion of Caspase-1, IL-1β, and IL-18 and corresponding transcript downregulation. EVs also attenuated IL-6 and TGF-β1 induced fibroblast proliferation, confirming their anti-inflammatory and antifibrotic effects across cell sources and patient risk groups.

CONCLUSIONS

This study establishes a patient-specific human cellular model of cardiac fibrosis, a key determinant of postoperative AF, and identifies heart-derived EVs as potent suppressors of inflammasome activation and profibrotic signaling. These findings provide mechanistic insight into the anti-inflammatory and antifibrotic actions of cardiac EVs and support their further development as a cell-free biologic for the prevention of postoperative AF.