Fig. 1

An “endothelialized” microfluidic system coupled with a microengineered pneumatic valve that induces a vascular “injury” functions as a comprehensive in vitro mechanical injury bleeding model. a Our microfluidic-based bleeding device is constructed from b three polydimethylsiloxane layers: a vascular layer comprised of a vascular channel and outlet channel, a valve layer, and a valve actuator layer. c First, endothelial cells are cultured to confluence in the vascular channel while the pneumatic valve is in the closed position (left). When the valve layer is pulled down by negative pressure in valve actuator channel (pull) and mechanical fluidic pressure (push) is applied through outlet channel, the vascular channel is disrupted and endothelial injury is mechanically induced (middle). Blood is perfused while the valve is maintained in the open position and flows through the vascular channel (horizontal) as well as the newly created “bleeding” wound channel, which leads to the outlet channel (right). d A computational fluid dynamic COMSOL simulation shows initial wall shear stresses when the mechanical injury is introduced. e Our in vitro microcvasculature mechanical injury model enables real-time visualization of the entire hemostatic process. Confluent endothelial cells (stained via a plasma membrane stain—blue) are disrupted when the valve opens and “bleeding” occurs through the injury site. Immediately, platelets (stained via CD41—red) begin to adhere at the injury site (red arrow) followed by fibrinogen/fibrin accumulation (fluorescent tagged fibrinogen, green) until finally hemostasis is achieved. All scale bars = 50 µm