Pig von Willebrand Factor triggers abnormal human platelet clumping

Pig von Willebrand Factor (vWF) interacts abnormally with human platelet receptors, causing spontaneous platelet aggregation and activation within the transplanted pig organ's vasculature. In a normal human organ, vWF mediates controlled platelet adhesion at sites of vascular injury. But pig vWF binds human platelet GPIb receptors with different affinity and kinetics, causing platelets to clump in the absence of injury. This leads to consumption of the recipient's platelets (thrombocytopenia), formation of microthrombi throughout the graft, and progressive ischemic damage to the transplanted organ. The clinical consequence is consumptive coagulopathy: the patient's blood loses its ability to clot normally because clotting factors are being used up inside the graft, creating a dual risk of organ failure from microthrombi and systemic bleeding from factor depletion. Gene editing to modify pig vWF or knock it out entirely would compromise the pig's own hemostasis during development and surgery, so researchers are trying to replace pig vWF with human vWF transgenes, but achieving physiologically appropriate expression levels in the right vascular beds remains unsolved.