Background: Thrombocytopenic patients often experience ‘spontaneous’ bleeding events, where no obvious cause of bleeding can be found. These events range in severity from petechiae to intracranial haemorrhage. Recently, studies in mice have suggested that this bleeding may be due to inflammation. Upon transmigration, neutrophils create small holes in the endothelium and underlying extracellular matrix (ECM), which platelets would normally plug to prevent red blood cell (RBC) leakage. Although these mouse studies have been very informative, a human in vitro model may have more relevance to thrombocytopenic patients.

Aims: To develop a humanized 3D organ-on-a-chip model of inflammation-associated haemostasis.

Methods: Mimetas Organoplates were used to culture human endothelial vessels against physiologically relevant ECM components. Platelets, neutrophils, and RBCs isolated from human whole blood were perfused through TNF-α-stimulated endothelial vessels and their dynamics studied.

Results: Confluent endothelial vessels formed against Geltrex ECM with a small amount of collagen I incorporated. Stimulation of vessels with TNF-α induced transmigration of neutrophils into the ECM. Red blood cells leaked at sites of neutrophil transmigration in stimulated chips, indicative of inflammation-associated bleeding. Washed platelets prevented this bleeding, consistent with mouse models.

Conclusions: We successfully developed a 3D human endothelial vessel model which supported perfusion of isolated primary human neutrophils, platelets, and red blood cells and recapitulates inflammation-associated bleeding. We will further use this model to investigate how platelets prevent bleeding at inflammatory sites.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/a-3d-in-vitro-model-of-inflammation-associated-bleeding/