Understanding stenosis-induced platelet aggregation on a chip by high-speed optical imaging

Vascular stenosis is a pathological hallmark of atherosclerosis, the leading cause of cardiovascular diseases such as stroke and myocardial infarction. While stenosis-induced thrombus formation has been extensively studied using in vivo and in vitro vascular models, the transient and dynamic process of platelet aggregation remains unclear due to the lack of analytical tools with both high spatial and temporal resolution. Here we report spatiotemporally resolved observation of shear-induced platelet aggregation using an in vitro microfluidic stenosis model and an optical time-stretch imaging system. Specifically, we characterized the size, shape, and population of platelet aggregates at single-cell resolution every 20 min in the presence of different agonists in a 3D stenosis model. Our results indicate a significant enhancement in platelet aggregation when both stenosis and an agonist were present, thus suggesting a synergistic effect of atherogenic blood flow disturbance and circulating factors on platelet activation. In particular, platelets activated by thrombin receptor activator peptide 6 (TRAP-6) led to a broad-sized distribution of platelet aggregates with significantly large aggregates (>240 µm2 in area). These findings are expected to deepen our understanding of the mechanism behind stenosis-induced platelet aggregation and pave the way for development of better antithrombotic therapeutics.