October 10, 2016
A new drug compound pushes artificial blood closer to the clinic
Platelets prevent blood loss by adhering to and thus clotting blood vessels. In the latest issue of Stem Cells Translational Medicine, researchers at the Center for iPS Cell Research and Application, Kyoto University, report a new molecule that enhances the adhesion of platelets prepared from human iPS cells. The scientists expect this compound to help bring artificial platelets to the clinic in the next few years.
Platelet transfusion is crucial for a number of diseases and surgical interventions, and most platelet supplies depend on human donors. Aging populations are causing a demand for platelets that is not being matched by the donor supply. Professor Koji Eto and his team are therefore using iPS cells to prepare an alternative platelet source. "Platelets from human donors must be used within a few days," says Eto, "but our iPS cell technology provides a consistent supply."
Effective platelets must express a specific receptor in order to function properly. Eto explains that the receptor "GPIba keeps platelets attached to the injured blood vessel," to cause coagulation. During the generation of platelets in the lab using iPS cell technology, specific enzymes are known to degrade, or shed, GPIba, resulting in suboptimal platelet performance. It turns out a number of enzymes can contribute to the shedding, but Eto's team show that inhibiting just one significantly improves platelet performance. "Many of the enzymes that shed GPIba have multiple roles that should not be inhibited. But we found inactivating ADAM17 gave best results," he said. Indeed, platelets transfused into mice showed better coagulation effects when treated with an ADAM17 inhibitor, a molecule identified as KP-457.
The discovery of KP-457 is but one key step to recapitulate human platelets in the lab. Eto and his team are seeking more chemicals that enhance the platelet phenotype so that platelets from human donors can be completely replaced with those made from iPS cells.