Model representing the mechanism of TFPI action on HSCs. (A) Higher CD26 activity in GPC3^−/− BM leads to lower maintenance of HSPCs, which leads to their entry into cell cycle and mobilization leading to increased circulating HSPCs. (B) TFPI through binding with GPC3 inhibits CD26 activity, enabling HSPCs to respond to the concentration gradient of CXCL12 thereby affecting HSPC homing into the BM positively.